U.S. patent application number 17/334163 was filed with the patent office on 2021-12-23 for lubricant management for an hvacr system.
The applicant listed for this patent is TRANE INTERNATIONAL INC.. Invention is credited to Benjamin Elias Dingel, Jon P. Hartfield.
Application Number | 20210396436 17/334163 |
Document ID | / |
Family ID | 1000005841636 |
Filed Date | 2021-12-23 |
United States Patent
Application |
20210396436 |
Kind Code |
A1 |
Hartfield; Jon P. ; et
al. |
December 23, 2021 |
LUBRICANT MANAGEMENT FOR AN HVACR SYSTEM
Abstract
Systems and methods for lubricant management of a compressor in
an HVACR system are disclosed. A heat transfer circuit can utilize
a working fluid to provide heating or cooling includes a compressor
for compressing the working fluid and a heat source configured to
increase a suction temperature of the working fluid entering the
compressor. One or more lubricant rheological properties in a
compressor system based on measurements taken at or near a bearing
cavity of the compressor are determinable. A lubricant reservoir
can be in thermal communication with a discharge flow path of the
compressor. An internal heat exchanger can be disposed within a
compressor for improving viscosity of the lubricant to be cycled
back into the compressor. A heater can be located on a fluid line
between a lubricant separator and a lubricant inlet. Condenser fans
can be controlled.
Inventors: |
Hartfield; Jon P.; (La
Crosse, WI) ; Dingel; Benjamin Elias; (La Crosse,
WI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TRANE INTERNATIONAL INC. |
Davidson |
NC |
US |
|
|
Family ID: |
1000005841636 |
Appl. No.: |
17/334163 |
Filed: |
May 28, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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PCT/US2019/063839 |
Nov 29, 2019 |
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17334163 |
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62773904 |
Nov 30, 2018 |
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62773918 |
Nov 30, 2018 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F25B 43/02 20130101;
F25B 2700/21151 20130101; F25B 2339/0242 20130101; F25B 31/004
20130101; F25B 1/047 20130101; F25B 39/02 20130101 |
International
Class: |
F25B 43/02 20060101
F25B043/02; F25B 1/047 20060101 F25B001/047; F25B 31/00 20060101
F25B031/00; F25B 39/02 20060101 F25B039/02 |
Claims
1. A heat transfer circuit, comprising: a compressor for
compressing a working fluid; a condenser for cooling the working
fluid; an expansion device for expanding the working fluid; an
evaporator for providing a first heating of the working fluid
flowing through the evaporator, the first heating being a heat
exchange between the working fluid and a process fluid flowing
through the evaporator, a flow path of the working fluid extending
from the compressor through the condenser, the expansion device,
the evaporator, and back to the compressor, the flow path including
a suction stream disposed after the first heating and before the
compressor; and a heat source, the suction stream including the
heat source and the heat source configured to provide a second
heating of the working fluid.
2. The heat transfer circuit of claim 1, wherein the heat source is
disposed within the evaporator.
3. The heat transfer circuit of claim 2, wherein the heat source is
an electric heater.
4. The heat transfer circuit of claim 2, wherein the evaporator
includes a first set of heat exchanger tubes through which the
process fluid flows, and the working fluid flowing past the first
set of tubes undergoing the first heating, and the heat source is a
second set of heat exchanger tubes in the evaporator, the second
heating of the working fluid being a heat exchange between the
working fluid flowing past the second set of heat exchange tubes
and a third fluid flowing through the second set of heat exchanger
tubes.
5. The heat transfer circuit of claim 4, wherein the third fluid is
a portion of the compressed working fluid discharged by the
compressor before the compressed working fluid flows through the
expansion device.
6. The heat transfer circuit of claim 4, wherein the third fluid is
the same type of fluid as the process fluid.
7. The heat transfer circuit of claim 4, wherein a second process
fluid flows through the condenser and absorbs heat from the working
fluid to provide the cooling of the working fluid, and the third
fluid includes a portion of the second process fluid.
8. The heat transfer circuit of claim 1, the heat source is
disposed in the suction stream between the evaporator and the
compressor.
9. The heat transfer circuit of claim 8, wherein the heat source is
an electric heater.
10. The heat transfer circuit of claim 8, wherein the heat source
is a heat exchanger including a first side and a second side, the
working fluid heated by the heat source flowing through the first
side, a third fluid flowing through the second side, and the second
heating of the working fluid being a heat exchange between the
third fluid and the working fluid.
11. The heat transfer circuit of claim 10, wherein the third fluid
is a portion of the compressed working fluid discharged by the
compressor before the compressed working fluid flows through the
expansion device.
12. The heat transfer circuit of claim 10, wherein the third fluid
is the same type of fluid as the process fluid.
13. The heat transfer circuit of claim 10, wherein a second process
fluid flows through the condenser and absorbs heat from the working
fluid to provide the cooling of the working fluid, and the third
fluid includes a portion of the second process fluid.
14. The heat transfer circuit of claim 8, further comprising: a
suction pipe extending to a suction inlet of the compressor, the
suction stream including the suction pipe, wherein the heat source
extends along an outside of the suction pipe.
15. The heat transfer circuit of claim 1, further comprising: a
controller configured to control heat provided by the heat source
to the working fluid based on a suction temperature of the working
fluid entering the compressor.
16. The heat transfer circuit of claim 1, wherein the heat source
is configured to increase superheat of the working fluid entering a
suction inlet of the compressor.
17. A method of operating a heat transfer circuit, the heat
transfer circuit including a compressor, a condenser, an expansion
device, an evaporator, a heat source, and a working fluid flowing
through the heat transfer circuit, the method comprising:
compressing the working fluid with the compressor; cooling the
working fluid compressed by the compressor with the condenser;
expanding the working fluid cooled by the condenser with the
expansion device; heating the working fluid expanded by the
expansion device in the evaporator with a process fluid, the
working fluid absorbing heat from the process fluid; and heating
the working fluid heated by the process fluid with the heat source,
the working fluid heated with the heat source as the working fluid
flows through a suction stream, the suction stream including the
heat source and disposed after a location at which the working
fluid is heated by the process fluid and before the compressor.
18. The method of claim 17, wherein heating the working fluid with
the heat source includes heating the working fluid flowing from the
evaporator to the compressor.
19. The method of claim 17, wherein heating the working fluid with
the heat source includes increasing superheat of the working fluid
entering a suction inlet of the compressor.
20. The method of claim 17, further comprising: directing the
working fluid from an inlet of the evaporator, past a first set of
heat exchanger tubes in the evaporator through which the first
fluid flows, past the heat source, and to an outlet of the
evaporator in this order, wherein the suction stream includes a
portion of the evaporator located after the first set of heat
exchanger tubes.
21. The method of claim 17, further comprising: directing at least
a portion of the compressed working fluid discharged by the
compressor, which has not been expanded by the expansion device,
through a first side of the heat source, wherein heating the
working fluid heated by the process fluid with the heat source
includes directing the working fluid heated by the heat source
through a second side of the heat source.
22-41. (canceled)
Description
FIELD
[0001] This disclosure relates generally to a heating, ventilation,
air conditioning, and refrigeration (HVACR) system. More
specifically, this disclosure relates to lubricant management for a
compressor in an HVACR system.
BACKGROUND
[0002] A heating, ventilation, air conditioning, and refrigeration
(HVACR) system generally includes a compressor. Compressors, such
as, but not limited to, screw compressors and scroll compressors,
utilize bearings to support a rotating shaft. The bearings
generally include a lubricant system. If the bearings are not
properly lubricated, the bearings, and ultimately the compressor,
may fail prior to an expected lifetime of the bearing.
SUMMARY
[0003] This disclosure relates generally to a heating, ventilation,
air conditioning, and refrigeration (HVACR) system. More
specifically, this disclosure relates to lubricant management for a
compressor in an HVACR system.
[0004] In an embodiment, a heat transfer circuit that utilizes a
working fluid to provide heating or cooling includes a compressor
for compressing the working fluid and a heat source configured to
increase a suction temperature of the working fluid entering the
compressor.
[0005] In an embodiment, one or more lubricant rheological
properties in a compressor system based on measurements taken at or
near a bearing cavity of the compressor are determinable. The
measurements may include a viscometer reading, a refractive index,
a bearing cavity pressure and a bearing cavity temperature, or a
bearing cavity temperature and a suction pressure of the
compressor.
[0006] In an embodiment, a lubricant reservoir is in thermal
communication with a discharge flow path of the compressor.
[0007] In an embodiment, an internal heat exchanger is disposed
within a compressor for improving viscosity of the lubricant to be
cycled back into the compressor.
[0008] In an embodiment, compressor systems condition lubricant to
allow operation of the compressor under an increased variety of
operating conditions while maintaining bearing reliability. The
compressor systems can include a heater located on a fluid line
between a lubricant separator and a lubricant inlet.
[0009] In an embodiment, a method and system for controlling
condenser fans in a heating, ventilation, and air conditioning
(HVAC) system are provided.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] References are made to the accompanying drawings that form a
part of this disclosure, and which illustrate embodiments in which
the systems and methods described in this specification can be
practiced.
[0011] FIG. 1 shows a system diagram of a compressor system,
according to an embodiment.
[0012] FIG. 2 shows a system diagram of a compressor system,
according to an embodiment.
[0013] FIG. 3 shows a flow chart of a method, according to an
embodiment.
[0014] FIG. 4 is a front view of a bearing cover of a compressor
according to an embodiment.
[0015] FIG. 5 is a section view of a compressor according to an
embodiment.
[0016] FIG. 6 is a flow chart of a method of operating a compressor
according to an embodiment.
[0017] FIG. 7 is a schematic view of an HVAC system that can employ
fan control, according to one embodiment.
[0018] FIG. 8 illustrates a fan control system, according to one
embodiment.
[0019] FIG. 9 is a flow chart of a method on fan control, according
to one embodiment.
[0020] FIG. 10 shows a relationship between the system pressure
differential and the ambient temperature, according to one
embodiment
[0021] FIG. 11 is a schematic diagram of a heat transfer circuit,
according to an embodiment.
[0022] FIG. 12 is a schematic diagram of a heat transfer circuit,
according to an embodiment.
[0023] FIG. 13 is a schematic diagram of a heat transfer circuit,
according to an embodiment.
[0024] FIG. 14 is a schematic diagram of a heat transfer circuit,
according to an embodiment.
[0025] FIG. 15 is a diagram showing a flow of working fluid through
an evaporator.
[0026] FIG. 16 is a block diagram of a method of operating a heat
transfer circuit.
[0027] FIG. 17 is a schematic diagram of a refrigerant circuit,
according to an embodiment.
[0028] FIG. 18 is a side sectional view of a compressor for a vapor
compression system (e.g., the refrigerant circuit of FIG. 17),
according to an embodiment.
[0029] FIG. 19 is a side sectional view of a compressor for a vapor
compression system (e.g., the refrigerant circuit of FIG. 17),
according to an embodiment.
[0030] FIG. 20 illustrates a schematic view of an embodiment of a
refrigeration system.
[0031] FIG. 21 illustrates a schematic view of another embodiment
of a refrigeration system.
[0032] FIG. 22 illustrates an example of a screw compressor, with
which the embodiments as disclosed herein can be practiced.
[0033] FIG. 23 illustrates an example of an internal heat exchanger
utilizing passages drilled or casted in the bottom wall of the
bearing housing of a screw compressor, according to an
embodiment.
[0034] FIG. 24 illustrates another example of an internal heat
exchanger utilizing surface passages milled on an interface surface
of the bearing housing of a screw compressor, according to an
embodiment.
[0035] FIG. 25 illustrates a circuit including a suction-line heat
exchanger according to an embodiment.
[0036] FIG. 26A illustrates a perspective view of a suction-line
heat exchanger according to an embodiment.
[0037] FIG. 26B illustrates a side view of a suction-line heat
exchanger according to the embodiment shown in FIG. 26A.
[0038] FIG. 27 illustrates a heat exchanger baffle of a
suction-line heat exchanger according to an embodiment.
DETAILED DESCRIPTION
[0039] This disclosure relates generally to a heating, ventilation,
air conditioning, and refrigeration (HVACR) system. More
specifically, this disclosure relates to lubricant management for a
compressor in an HVACR system.
[0040] Environmental impacts of HVACR refrigerants are a growing
concern. For example, since 2011, the European Union has been
phasing out refrigerants with a global warming potential (GWP) of
more than, for example, 150 in some refrigeration systems.
Environmentally-suitable HVACR refrigerants, with suitable
properties such as density, vapor pressure, heat of vaporization,
and suitable chemical properties, which satisfy the requirements
regarding safety and environment impacts, such as the European
Union standard discussed above, can be utilized for HVACR systems.
The environmentally-suitable HVACR refrigerants are nonflammable or
mildly flammable, non-ozone depleting, energy efficient, low in
toxicity, compatible with materials of construction, and are
chemically stable over the life of the equipment.
[0041] Current refrigerants, such as R134a or the like, may have
relatively higher GWPs. For example, R134a has a GWP of 1,430. As a
result, replacement refrigerants such as, but not limited to,
R1234ze, R513A, and the like, are being implemented in HVACR
systems.
[0042] In utilizing newer refrigerant compositions such as, but not
limited to, R1234ze and R513A, various problems may arise as a
result of the different properties of the refrigerant compared to
prior refrigerants such as R134a. In general, refrigerants with
lower GWPs such as R1234ze, R513A, and the like may be carried over
into the lubricant. In some instances, the replacement refrigerants
are relatively more likely to dissolve into the lubricant than the
current refrigerants, resulting in a higher concentration of
refrigerant within the lubricant (e.g., lubricant dilution).
[0043] As a result, portions of an operating map for a compressor
of the HVACR system may suffer from higher lubricant dilution and
limited bearing viscosity due to low discharge superheat. In some
instances, the occurrence of higher lubricant dilution and limited
bearing viscosity may be more significant when the variable speed
compressor operates at relatively lower speeds. Higher lubricant
dilution and limited bearing viscosity can result in, for example,
a shortened lifetime for the bearings and ultimately compressor
failures. In some instances, utilizing the R134A replacement
refrigerants may require a replacement of the mechanical components
(e.g., bearings or the like) in the compressor.
[0044] In other instances, controlling a variable speed compressor
to maximize efficiency can also result in lubricant dilution
problems, even when utilizing the current refrigerants such as
R134a.
[0045] In general, lubricants utilized with R134a replacement
refrigerants suffer the higher lubricant dilution problem. The
lubricants can include any suitable lubricant which is miscible
with the selected replacement refrigerant.
[0046] In general, higher lubricant dilution may occur when
discharge superheat becomes relatively low. For example, higher
lubricant dilution can occur when the discharge superheat is below
at or about 8.degree. C.
[0047] Compressor System Having Isolated Heated Lubricant Flow
(FIGS. 1-3)
[0048] This disclosure is directed to compressor systems where
bearing lubricant flow is isolated and heated prior to being
provided to the bearings, for example by a heater such as an
electric heater or by heat exchange with heat scavenged from other
compressor components.
[0049] Modern refrigerants may be more soluble in lubricants, and
the dissolved refrigerant may compromise the effectiveness of the
lubricant. Heat can be used to drive out the dissolved refrigerant
from the lubricant, conditioning the lubricant. By conditioning
lubricant for use at the compressor bearings, compressor systems
according to embodiments increase the extent to which refrigerant
can be separated from lubricant, and thus improve lubricant quality
(e.g. the mass fraction of the refrigerant dissolved in the
lubricant). The improved lubricant quality allows operation at
combinations of speed and capacity that may not otherwise allow for
sufficient lubrication of the bearings. Compressor systems
according to embodiments thus can use a greater portion of the
operating map defined by combinations of compressor speed and
capacity, and are capable of delivering improved efficiency by
utilizing more of the operating map of the compressor that
ordinarily may not provide sufficient heat for effective separation
of lubricant and refrigerant.
[0050] A compressor system embodiment includes a compressor having
a suction port, a discharge port, and a lubricant inlet. The
compressor system embodiment includes a lubricant storage. The
compressor system embodiment includes a fluid line, wherein the
fluid line allows fluid communication between the lubricant storage
and the lubricant inlet. The compressor system embodiment also
includes a heat supply, thermally coupled to the fluid line. The
lubricant storage may be a lubricant sump, a lubricant tank, or the
like. The lubricant sump may be part of a lubricant separator
located downstream of the discharge port of the compressor.
[0051] In an embodiment, the heat supply is an electric heater
thermally coupled to the fluid line.
[0052] In an embodiment, the heat supply is a heat scavenger. The
heat scavenger is thermally coupled to the fluid line. In an
embodiment, the heat scavenger is thermally coupled to a lubricant
separator. In an embodiment, the compressor system further includes
a discharge line connected to the discharge port of the compressor,
and the heat scavenger is thermally coupled to the discharge line.
In an embodiment, the compressor system further includes a
discharge muffler connected to the discharge port of the
compressor, and the heat scavenger is thermally coupled to the
discharge muffler. In an embodiment, the compressor system further
includes a condenser and the heat scavenger is thermally coupled to
the condenser. In an embodiment, the compressor system further
includes a discharge housing and the heat scavenger transfers heat
from the discharge housing to the fluid line.
[0053] In an embodiment, the compressor system further includes a
second heat supply. In an embodiment, the first heat supply is an
electric heater and the second heat supply is a heat scavenger.
[0054] In an embodiment, the compressor system further includes a
controller connected to the heat supply. In an embodiment, the
compressor system further includes a flow control device that is
connected to the controller. In an embodiment, the controller
controls operation of the heat supply and the flow control device
based on operational parameters of the compressor. In an
embodiment, the operational parameters of the compressor are a
saturated suction temperature of the compressor, a saturated
discharge temperature of the compressor, and/or compressor speed.
The operational parameters may reflect, for example, a temperature
of the lubricant affecting, for example, the quantity of the
refrigerant dissolved in the lubricant and/or the viscosity of the
lubricant.
[0055] A method embodiment includes separating a lubricant from a
discharge of the compressor, directing the lubricant into a fluid
line, heating the lubricant using a heat source thermally coupled
to the fluid line, and after heating the lubricant, directing the
lubricant to a lubricant inlet of the compressor.
[0056] In an embodiment, the heat source includes a component that
sources heat separate from the compressor, such as for example an
electric heater. In an embodiment, the heat source includes a heat
scavenger thermally coupled to the fluid line and also thermally
coupled to the compressor system at a location separate from the
fluid line.
[0057] In an embodiment, the method further includes restricting
the flow of lubricant, and determining, using a processor, a
lubricant volume and a lubricant temperature, where restricting the
flow of the lubricant is controlled based on the determined
lubricant volume and heating the lubricant is based on the
determined lubricant temperature.
[0058] In an embodiment, the lubricant volume and the lubricant
temperature are determined by the processor based on an operating
map of the compressor.
[0059] FIG. 1 shows a system diagram of a compressor system 1100
according to an embodiment. Compressor system 1100 includes a
compressor 1102. Compressor 1102 has suction port 1104, discharge
port 1106, and lubricant inlet 1108. A discharge line 1110 is
connected to discharge port 1106. Discharge line 1110 extends to
lubricant separator 1112. A fluid line 1114 connects the lubricant
separator 1112 to the lubricant inlet 1108 of compressor 1102.
Lubricant separator 1112 is connected to lubricant storage 1132.
Heater 1116 is thermally coupled to fluid line 1114. Fluid line
1114 may include a flow control device 1118. The heater 1116 and/or
the flow control device 1118 may be connected to a controller
1120.
[0060] Compressor 1102 is a compressor connected to a refrigeration
circuit. Compressor 1102 compresses a fluid received at suction
port 1104, and expels the compressed fluid at discharge port 1106.
The compressor 1102 may be, for example, a screw compressor, where
compression chambers are formed and a fluid such as a refrigerant
are compressed by the rotation of two rotors and the engagement of
lobes on each of the rotors. Compressor 1102 may include one or
more bearings receiving lubricant taken in at lubricant inlet 1108.
The bearings may, for example, support and allow the rotation of
components of the compressor such as the rotors of a screw
compressor.
[0061] Compressor 1102 is part of a refrigeration circuit also
including condenser 1122, an expansion device 1124, for example and
expansion valve, and an evaporator 1126.
[0062] Compressor 1102 includes suction port 1104. Suction port
1104 is a port located on compressor 1102 where the fluid to be
compressed enters the compressor. In an embodiment, one or more
sensors 1128 may be located at the suction port 1104 to measure
parameters including, for example, the temperature and the pressure
of the fluid at the suction port 1104.
[0063] Compressor 1102 also includes discharge port 1106. Discharge
port 1106 is where compressed fluid exits the compressor 1102. The
fluid exiting discharge port 1106 includes both the fluid such as
refrigerant and also lubricant from the bearings of compressor
1102. Fluid exits discharge port 1106 into discharge line 1110. The
fluid at discharge port 1106 is at a higher temperature and
pressure than the fluid entering compressor 1102 at suction port
1104. One or more sensors 1130 may be located at the discharge port
1106 to measure parameters including pressure and/or temperature of
the fluid as it exits the compressor 1102. In an embodiment,
sensors 1130 may be located within the compressor 1102 between
suction port 1104 and discharge port 1106.
[0064] Compressor 1102 further includes lubricant inlet 1108.
Lubricant inlet 1108 directs lubricant into a bearing cavity 1134
of compressor 1102, which contains one or more bearings 1136. The
lubricant inlet may be, for example, a port on a bearing cover or a
housing of the compressor 1102 extending into a bearing cavity 1134
receiving lubricant from the lubricant inlet 1108.
[0065] Discharge line 1110 is a fluid line extending from discharge
port 1106 of compressor 1102. Discharge line 1110 conveys fluid
from the discharge port of the compressor to the refrigeration
circuit in which compressor 1102 is incorporated. The fluid
discharged at discharge port 1106 and conveyed by discharge line
1110 includes a fluid such as a refrigerant used in the
refrigeration circuit and further includes lubricant from the
bearings and bearing cavity of the compressor 1102.
[0066] Lubricant separator 1112 is located along discharge line
1110. Lubricant separator 1112 separates lubricant from the flow of
fluid discharged from the compressor, allowing the refrigerant to
continue through a refrigeration circuit, for example, a condenser,
an expansion device, for example an expansion valve, and an
evaporator, while removing a significant portion of the lubricant
from the flow discharged by the compressor. Lubricant separator
1112 may include, for example, a filter configured to allow passage
of refrigerant while trapping lubricant in the discharge flow of
the compressor. Lubricant separator may be located between
discharge port 1106 of the compressor 1102 and the condenser 1122
of the refrigeration circuit of compressor system 1100.
[0067] Lubricant storage 1132 stores lubricant to be provided to
compressor 1102. In an embodiment, lubricant storage 1132 is a sump
connected to lubricant separator 1112. In an embodiment, lubricant
storage 1132 is a lubricant tank or the like. In an embodiment, the
lubricant trapped by lubricant separator 1112 collects, for example
in a pool included in the lubricant storage 1132. In an embodiment,
this pool is connected to fluid line 1114 via a port. In an
embodiment, lubricant storage 1132 is integrated into lubricant
separator 1112. In an embodiment, lubricant storage 1132 is
separate from lubricant separator 1112.
[0068] Fluid line 1114 is a fluid line providing fluid
communication between lubricant storage 132 and lubricant inlet
1108 of the compressor 1102. In the embodiment shown in FIG. 1,
fluid line 1114 allows lubricant recovered at lubricant separator
1112 and stored in lubricant storage 1132 to be conveyed to the
bearing cavities and/or bearings of compressor 1102.
[0069] Heater 1116 is located along fluid line 1114. Heater 1116 is
thermally coupled to the fluid line 1114 such that heat produced by
heater 1116 is transferred to fluid line 1114 and the contents of
fluid line 1114. The heater 1116 may be thermally coupled to fluid
line 1114 by, for example, surrounding the fluid line 1114, having
a heating element wrapped around or embedded in the fluid line
1114, or the like. In an embodiment, heater 1116 is an electric
heater. In an embodiment, heater 1116 is an electromagnetic
induction heater.
[0070] Flow control device 1118 may be located along fluid line
1114 and configured to govern the flow of fluid through fluid line
1114. In an embodiment, flow control device 1118 may be, but is not
limited to, a controllable valve. Flow control device 1118 may be
used to limit the quantity of lubricant flowing through fluid line
1114. In an embodiment, flow control device 1118 is upstream where
heater 1116 is thermally coupled to fluid line 1114, with respect
to the direction of flow of lubricant from lubricant storage 1132
to lubricant inlet 1108. In an embodiment, flow control device 1118
allows lubricant to be heated to a higher temperature by heater
1116 by reducing the volume of flow that absorbs heat provided by
heater 1116. In an embodiment, the flow control device 1118 is a
pump.
[0071] Controller 1120 may be connected to heater 1116 and/or flow
control device 1118. Controller 1120 may receive compressor
operational information relevant to lubrication requirements and/or
lubricant quality. The compressor operational information may
include one or more of, for example, the speed the compressor 1102
is operated at, the capacity the compressor 1102 is operated at, a
saturated suction temperature, saturated discharge temperature or
the like. In an embodiment, the controller 1120 determines a
lubricant volume and/or a lubricant quality target based on the
compressor operational information. The determined lubricant volume
may be used to control the flow control device 1118. The determined
lubricant volume and/or the lubricant quality target may be used to
determine an amount of heat to be added to the lubricant by heater
1116. In an embodiment, controller 1120 directs operation of heater
1116, for example, by setting the heater 1116 to supply a
particular quantity of heat to fluid line 1114, operating the
heater 1116 at a particular temperature or setting, or activating
and deactivating the heater 1116.
[0072] FIG. 2 shows a system diagram of a compressor system 1200
according to an embodiment. Compressor system 1200 includes
compressor 1102 having suction port 1104, discharge port 1106, and
lubricant inlet 1108, discharge line 1110, lubricant separator
1112, lubricant storage 1132, fluid line 1114, and flow control
device 1118 as shown in FIG. 1 and described above. The embodiment
shown in FIG. 2 includes a heat scavenger 1202 that is thermally
coupled to a section of the compressor system 1200 and to the fluid
line 1114. In an embodiment, a discharge muffler 1204 is fluidly
connected to the discharge port 1106 of the compressor 1102. In an
embodiment, a condenser 1206 is located downstream of the
compressor. Compressor 1102 and condenser 1206 are part of a
refrigeration circuit also including expansion device 1124 and
evaporator 1126. In an embodiment, the compressor 1102 has a
discharge housing 1208 surrounding the discharge port 1106. In an
embodiment, controller 1210 is connected to the flow control device
1118 and the heat scavenger 1202. In an embodiment, a temperature
sensor 1212 is included in compressor system 1200. The temperature
sensor 1212 may be connected to the controller 1210 and the heat
scavenger 1202.
[0073] Heat scavenger 1202 thermally couples a portion of fluid
line 1114 to at least one other part of the compressor system 1200.
Heat scavenger 1202 thermally couples fluid line 1114 to another
part of compressor system 1200. The other part of compressor system
1200 is a part that is typically at a higher temperature than the
fluid line 1114, such that the thermal coupling transfers heat to
the fluid line 1114 and heats lubricant traveling therein. The
other part of the compressor system 1200 may be, for example, the
discharge line 1110, discharge muffler 1204, condenser 1206, or
discharge housing 1208. The heat scavenger 1202 may include, for
example, a heat-absorbing element located on, in, or at the
location on the compressor system 1200 where heat is to be
collected. Heat scavenger 1202 may include one or more
heat-conducting elements 1214 extending from the heat-absorbing
element to the fluid line 1114. The one or more heat-conducting
elements 1214 may provide the thermal coupling of the
heat-absorbing element of heat scavenger 1202 to the fluid line
1114.
[0074] In an embodiment, both a heater 1116 as described above and
shown in FIG. 1 and a heat scavenger 1202 as shown in FIG. 2 are
included in a compressor system. In this embodiment, both the
heater 1116 and the heat scavenger 1202 are thermally coupled to
the fluid line 1114. In this embodiment, both the heater 1116 and
the heat scavenger 1202 provide heat to the lubricant carried in
fluid line 1114. In an embodiment, the heater 1116 is downstream of
the heat scavenger 1202 with respect to a flow of lubricant through
the fluid line 1114. In an embodiment, the heater 1116 and/or heat
scavenger 1202 are downstream of flow control device 1118 with
respect to a flow of lubricant through the fluid line 1114.
[0075] In an embodiment, the heat-absorbing element of heat
scavenger 1202 is located on the surface of the discharge line
1110. In an embodiment, the heat-absorbing element of heat
scavenger 1202 is located within the discharge line 1110 such that
the flow of fluid discharged from compressor 1102 into discharge
line 1110 passes over the heat-absorbing element.
[0076] In an embodiment, a discharge muffler 1204 is fluidly
connected to the discharge port 1106 of the compressor 1102. The
discharge muffler 1204 may be located between discharge port 1106
and discharge line 1110, or along discharge line 1110. The
discharge muffler is a muffler configured to reduce pulsation
and/or vibration resulting from the operation and discharge of the
compressor. The discharge muffler receives compressed fluid from
the compressor and acts to reduce pulsation and/or vibration
resulting from the operation of compressor 1102. In an embodiment,
the discharge muffler 1204 reduces pulsation and vibration by
separating the discharge line 1110 from the rest of the
refrigeration circuit by having a gap between a part of the
discharge muffler 1204 directly mechanically connected to discharge
line 1110 and the remainder of the refrigeration circuit. In an
embodiment, the discharge muffler 1204 reduces pulsation and/or
vibration by directing the discharged fluid through a series of
baffles, or other such feature. In an embodiment, multiple such
structures are used to reduce pulsation and/or vibration via their
combined effects. In an embodiment, the discharge muffler 1204 is
upstream of the lubricant separator 1112 with respect to the flow
of fluid discharged from compressor 1102. By receiving fluid at or
near where it is discharged from the compressor 1102, the discharge
muffler 1204 receives the fluid of the refrigerant circuit in a
heated, compressed state. During operation of the compressor 1102,
the discharge muffler 1204, or fluid traveling through the
discharge muffler 1204, is typically at a temperature that is
higher than the temperature of fluid line 1114 or fluid located
within fluid line 1114.
[0077] In an embodiment, the heat-absorbing element of heat
scavenger 1202 is located on the surface of the discharge muffler
1204.
[0078] In an embodiment, the heat-absorbing element of heat
scavenger 1202 is located within the discharge muffler 1204 such
that the flow of fluid discharged from compressor 1102 into
discharge muffler 1204 passes over the heat-absorbing element.
[0079] In an embodiment, a condenser 1206 is located downstream of
the compressor 1102. Condenser 1206 is a component of the
refrigeration circuit where the fluid compressed by compressor 1102
rejects heat. In an embodiment, the condenser 1206 is downstream of
lubricant separator 1112 with respect to the flow of fluid
discharged from compressor 1102. Condenser 1206 receives the
refrigerant in a heated and compressed state, while fluid line
1114, downstream of the lubricant separator 1112 may be isolated
from the heated refrigerant. Therefore, during operation of the
compressor system 1200, the condenser 1206 may be at a temperature
that is higher than the temperature of fluid line 1114 or fluid
located within fluid line 1114. In an embodiment, the
heat-absorbing element of heat scavenger 1202 is located on the
surface of the condenser 1206. In an embodiment, the heat-absorbing
element of heat scavenger 1202 is located within the condenser 1206
such that the flow of fluid within condenser 1206 passes over the
heat-absorbing element.
[0080] In an embodiment, the compressor 1102 has a discharge
housing 1208 surrounding the discharge port 1106. Discharge housing
1208 is a portion of the housing of compressor 1102 that is at or
near the discharge port. The heat produced when operating the
compressor and heat from the compressed fluid itself are absorbed
by discharge housing 1208. When compressor 1102 is in operation,
discharge housing 1208 is typically at a temperature higher than
discharge line 1114 or fluid located inside discharge line 1114. In
an embodiment, the heat-absorbing element of heat scavenger 1202 is
located on the surface of the discharge housing 1208.
[0081] Controller 1210 is connected to flow control device 1118. In
an embodiment, controller 1210 is connected to temperature sensor
1212 and is configured to receive temperature data from temperature
sensor 1212. Controller 1210 is configured to control flow control
device 1118 to determine an amount of lubricant to provide to the
compressor 1102 based on, for example, the operating conditions of
compressor 1102, such as the speed or capacity of the compressor,
and the temperature data from temperature sensor 1212. In an
embodiment, controller 1210 determines a temperature to achieve a
lubricant quality target based on the operating conditions of
compressor 1102. In an embodiment, the lubricant quality target is
a temperature of the lubricant. In this embodiment, controller 1210
determines a volume of lubricant that can be heated to the
determined temperature by the heat scavenger 1202, based on the
temperature data. In an embodiment, controller 1210 directs flow
control device 1118 to open or constrict to allow a flow of
lubricant through fluid line 1114 that provides the determined
volume of lubricant. In an embodiment where heat scavenger 1202 is
thermally coupled to more than one part of compressor system 1200
aside from fluid line 1114, the controller may determine whether to
isolate the heat scavenger 1202 from one or more of the parts of
the compressor system 1200. Isolation of heat scavenger 1202 from
other components of compressor system 1200 may be based on the flow
allowed through flow control device 1118. Isolation of heat
scavenger 1202 from other components of the compressor system 1200
may be based on the temperature of the parts of the compressor
system 1200 aside from fluid line 1114, to ensure lubricant is at
the desired temperature at lubricant inlet 1108. In an embodiment
where there is both a heat scavenger 1202 and a heater 1116, the
controller 1210 may determine a required quantity of lubricant
flow. When the required volume of lubricant flow exceeds the volume
of lubricant that can be heated to the determined temperature by
the heat scavenger 1202 alone, as determined based on the
temperature data, the controller 1210 directs operation of the
heater 1116 to heat the lubricant to the determined temperature,
while directing the flow control device to open or constrict such
that the volume of flow through fluid line 1114 is at least the
determined required quantity of lubricant. In an embodiment, the
controller 1210 may determine the volume of flow through fluid line
1114 based on a speed at which the compressor system 1200 is being
operated.
[0082] One or more temperature sensors 1212 obtain temperature data
at the one or more parts of the compressor system that heat
scavenger 1202 is thermally coupled to via the one or more
heat-conducting elements 1214. Temperature sensor 1212 may be
located, for example, on the heat scavenger 1202 or at any or all
of the one or more parts of compressor system 1200, other than
fluid line 1114, that it is thermally coupled to. Multiple
temperature sensors according to 1212 may be included in
embodiments of compressor system 1200. Examples of these other
parts of the compressor system 1200 include the discharge line
1110, discharge muffler 1204, condenser 1206, or discharge housing
1208. Temperature sensor 1212 provides temperature data regarding
the heat scavenger 1202 itself or the sources of heat recovered and
transferred by the heat scavenger 1202 to the fluid line 1114. The
temperature data from temperature sensor 1212 may be supplied to
controller 1210. The temperature data supplied to controller 1210
may be used, for example, to estimate the amount of heat that the
heat scavenger 202 can provide to fluid in the fluid line 1114.
Temperature sensor 1212 may be, for example a thermistor, a
thermocouple, a semiconductor-based temperature sensor or any other
suitable temperature measurement apparatus capable of measuring
temperatures within the range of typical temperatures of the part
of the compressor system 1200 or the heat scavenger 1202, for
example temperatures from at or about 0 to at or about 100.degree.
F. at suction and from at or about 60 to at or about 250.degree. F.
at discharge of the compressor system 1200.
[0083] FIG. 3 shows a flow chart of a method 1300 according to an
embodiment. Method 1300 optionally includes separating a lubricant
from a discharge of a compressor 1302. Method 1300 includes
directing the lubricant from a lubricant storage into a fluid line
1304, restricting the flow of the lubricant in the fluid line using
a flow control device 1306, heating the lubricant using a heat
source thermally coupled to the fluid line 1308, and directing the
lubricant to a lubricant inlet of the compressor after it has been
heated 1310.
[0084] In an embodiment, lubricant is separated from a discharge of
a compressor 1302. The compressor, such as compressor 1102,
discharges compressed gas at a discharge port, such as discharge
port 1106. The compressed gas further includes lubricant, such as
lubricant from the bearings and bearing cavity of the compressor.
The lubricant may be separated from the gas discharged by the
compressor by, for example, a lubricant separator such as lubricant
separator 1112. The lubricant may be stored following separation
from the discharge of the compressor 1302, for example in a
lubricant storage such as lubricant storage 1132.
[0085] The lubricant is directed from lubricant storage into a
fluid line 1304. The lubricant storage, such as lubricant storage
1132, where the lubricant is stored prior to being provided to
compressor 1302, may include an outlet directing the lubricant into
the fluid line, such as fluid line 1114. The fluid line is a line
providing fluid communication between and a lubricant inlet of the
compressor, such as lubricant inlet 1108 of compressor 1102.
[0086] In an embodiment, the flow of the lubricant in the fluid
line may optionally be restricted using a flow control device 1306.
The flow control device may be flow control device 1118 as
described above. The flow rate may be restricted based on, for
example, an amount of lubricant required by the bearings of the
compressor and/or the heating capacity of the heat source or heat
sources that are used to heat the lubricant 1308. In an embodiment,
the amount of flow may be restricted based on the heat available
from the heat source, for example the heating capacity of an
electric heater and/or the temperature of a compressor system
element thermally coupled to a heat scavenger 1202.
[0087] The lubricant is heated using a heat source thermally
coupled to the fluid line 1308. In an embodiment, the heat source
is a heater such as heater 1116. In an embodiment, the heat source
is a heat scavenger such as heat scavenger 1202 thermally coupled
to another section of the compressor system. In an embodiment, the
lubricant is heated by both a heater such as heater 1116 and a heat
scavenger such as heat scavenger 1202.
[0088] The heating of the lubricant 1308 may be governed by a
controller, such as controller 1120 or controller 1210. The heat
added to the lubricant during heating of the lubricant 1308 or the
final temperature of the lubricant at the end of heating 1308 may
be determined by the controller based on, for example, the speed
and/or discharge temperature of the compressor. In an embodiment,
the amount of heat added to the lubricant may be varied based on
the volume of the lubricant flow following the restriction at 1306.
In an embodiment, the controller controls the temperature of the
lubricant entering the lubricant inlet of the compressor by
controlling the volume of lubricant that flows through flow control
device 1118.
[0089] The lubricant is directed to a lubricant inlet of the
compressor after it has been heated 1310. The lubricant may be
conveyed by the fluid line, such as fluid line 1114, to a lubricant
inlet such as lubricant inlet 1108, where it enters the compressor.
In an embodiment, the lubricant inlet provides the lubricant to a
bearing cavity of the compressor, where the lubricant lubricates
one or more bearings supporting one or more rotating parts of the
compressor, such as the rotors of a screw compressor.
[0090] Aspects:
[0091] Any of aspects 1-15 may be combined with any of aspects
16-20. It is understood that any of aspects 1-20 can be combined
with any other aspects recited herein.
[0092] Aspect 1. A compressor system, comprising: a compressor
having a suction port, a discharge port, and a lubricant inlet; a
lubricant storage; a fluid line, wherein the fluid line allows
fluid communication between the lubricant storage and the lubricant
inlet; and a heat supply, thermally coupled to the fluid line.
[0093] Aspect 2. The compressor system according to aspect 1,
wherein the heat supply is an electric heater.
[0094] Aspect 3. The compressor system according to aspect 1,
wherein the heat supply is a heat scavenger.
[0095] Aspect 4. The compressor system according to aspect 3,
wherein the heat scavenger is thermally coupled to a lubricant
separator.
[0096] Aspect 5. The compressor system according to any of aspects
3-4, further comprising a discharge line connected to the discharge
port of the compressor, and wherein the heat scavenger is thermally
coupled to the discharge line.
[0097] Aspect 6. The compressor system according to any of aspects
3-5, further comprising a discharge muffler connected to the
discharge port of the compressor, and wherein the heat scavenger is
thermally coupled to the discharge muffler.
[0098] Aspect 7. The compressor system according to any of aspects
3-6, further comprising a condenser and wherein the heat scavenger
is thermally coupled to the condenser.
[0099] Aspect 8. The compressor system according to any of aspects
3-7, wherein the compressor further comprises a discharge housing
and the heat scavenger transfers heat from the discharge housing to
the fluid line.
[0100] Aspect 9. The compressor system according to any of aspects
1-8, further comprising a second heat supply.
[0101] Aspect 10. The compressor system according to any of aspects
1-9 further comprising a lubricant separator located downstream of
the discharge port of the compressor, and wherein the lubricant
storage is a lubricant sump of the lubricant separator.
[0102] Aspect 11. The compressor system according to any of aspects
1-10, wherein the fluid line includes a flow control device.
[0103] Aspect 12. The compressor system according to any of aspects
1-11, further comprising a controller connected to the heat
supply.
[0104] Aspect 13. The compressor system according to aspect 12,
further comprising a flow control device, and wherein the
controller is connected to the flow control device.
[0105] Aspect 14. The compressor system according to aspect 13,
wherein the controller controls operation of the heat supply and
the flow control device based on operational parameters of the
compressor.
[0106] Aspect 15. The compressor system according to aspect 14,
wherein the operational parameters of the compressor comprise one
or more of a saturated suction temperature, a suction pressure, a
suction temperature, a discharge temperature, a saturated discharge
temperature, a discharge pressure, and a compressor speed.
[0107] Aspect 16. A method of operating a compressor system,
comprising: directing a lubricant from a lubricant storage into a
fluid line; heating the lubricant using a heat source thermally
coupled to the fluid line; and after heating the lubricant,
directing the lubricant to a lubricant inlet of a compressor.
[0108] Aspect 17. The method according to aspect 16, wherein the
heat source includes an electric heater.
[0109] Aspect 18. The method according to any of aspects 16-17,
wherein the heat source includes a heat scavenger thermally coupled
to the compressor system at a location separate from the fluid
line.
[0110] Aspect 19. The method according to any of aspects 16-18,
further comprising: determining, using a processor, a lubricant
volume and a lubricant temperature; and restricting the flow of the
lubricant based on the determined lubricant volume, and wherein
heating the lubricant is based on the determined lubricant
temperature.
[0111] Aspect 20. The method according to aspect 19, wherein the
lubricant volume and the lubricant temperature are determined by
the processor based on an operating map of the compressor.
[0112] Compressor systems condition lubricant to allow the
operation of the compressor under an increased variety of
conditions while maintaining bearing reliability. The compressor
systems include a heater located on a fluid line between a
lubricant separator and a lubricant inlet. The heater may be an
electric heater, or a heat scavenger transferring heat from other
parts of the compressor system to the fluid in the fluid line. A
flow control device may control the amount of lubricant passing
through the fluid line, reducing a lubricant pressure and/or flow
rate, increasing the effectiveness of adding heat to the
lubricant.
[0113] Compressor Bearing Protection Using Measured Or Estimated
Rheological Properties to Control Chiller (FIGS. 4-6)
[0114] This disclosure is directed to methods and systems for the
measurement of lubricant rheological properties in compressors used
in chillers, particularly determining a direct measure of lubricant
rheological properties based on measurements at or near the bearing
cavity, and operation of compressors based on the determined
lubricant rheological properties.
[0115] Proper lubrication of a bearing requires that the lubricant
have sufficient rheological properties, including viscosity. The
rheological properties may indicate whether a lubricant is properly
lubricating the bearing. The rheological properties may be
presented as a viscosity ratio such as kappa, the ratio of the
applied viscosity to a rated viscosity, or lambda, a ratio of
lubricant film thickness to surface asperity height in the bearing.
When determining kappa values, for example, the rated viscosity may
vary depending on operational parameters such as a speed of a
compressor including the bearing. Currently, lubricant quality
(i.e. a mass fraction of lubricant vs. dissolved refrigerant) is
typically estimated using a discharge superheat (DSH) measurement
of the difference between a saturation temperature and the
temperature in the discharge line, and this estimated lubricant
quality is in turn used in place of rheological properties when
controlling a compressor. Target DSH measurements are used when
controlling compressor operations to account for lubricant quality
and device longevity and safety. The use of a direct measure of
lubricant rheological properties such as a kappa value improves
accuracy over approaches that instead use proxies or correlated
values such as DSH and lubricant quality. Further, DSH measurements
capture lubricant quality at the lubricant separator, but the
lubricant is in use at the bearings, which may be at different
conditions and thus the behavior of the lubricant may deviate from
what can be predicted based on DSH. Measurement of lubricant
rheological properties at or near the bearing cavity provide more
accurate assessments of bearing lubrication and allow bearing
lubrication to be properly assessed in systems including lubricant
preparation or enrichment devices downstream from the lubricant
separator with respect to the bearings. This allows a greater
portion of the operating map for the compressor to be utilized, due
to the improved understanding of bearing lubrication.
[0116] Using rheological properties expressed as a viscosity ratio
such as a kappa value to assess lubrication at the bearing allows
factors such as compressor speed, which affects the sufficiency of
rheological properties, to be accounted for. This further improves
the accuracy and precision of compressor operation in parts of the
operating map typically associated with poor lubrication at partial
loads, such as lower compressor speeds, or operations at lower
ambient temperatures. Improving the extent to which the full
operating map of a compressor is used allows improved efficiency to
be realized in systems including the compressor, such as chillers.
Improving the accuracy and precision of bearing lubrication
assessments also provides the ability to use a broader variety of
refrigerants, even ones that may have increased solubility in the
lubricant used with the compressor and that thus may require more
heat to be driven out of the lubricant.
[0117] A method embodiment for operating a compressor system
including a lubricant separator includes measuring one or more
parameters of a lubricant via one or more sensors within a bearing
cavity of the compressor and using the one or more parameters to
determine one or more lubricant rheological properties. In an
embodiment, the one or more rheological properties include a kappa
value of the lubricant.
[0118] In an embodiment, the one or more parameters include a
bearing cavity temperature and a bearing cavity pressure. In an
embodiment, the one or more parameters include a bearing cavity
temperature and a suction pressure, modified according to a
transfer function. In an embodiment, the one or more parameters
include a refractive index of the lubricant. In an embodiment, the
one or more parameters include a viscometer reading for the
lubricant.
[0119] In an embodiment, the speed of the compressor is adjusted
based on the one or more lubricant rheological properties. In an
embodiment, the capacity of the compressor is adjusted based on the
one or more lubricant rheological properties. In an embodiment, a
heater is in thermal communication with a flow path of the
lubricant from the lubricant separator to the bearing cavity.
[0120] A compressor system embodiment includes a compressor
including a suction port and a bearing cavity, one or more sensors
inside the bearing cavity and configured to measure one or more
parameters of a lubricant, a lubricant separator, and a controller
configured to receive the one or more parameters of the lubricant
and determine one or more lubricant rheological properties.
[0121] In an embodiment, in the compressor system, the one or more
parameters include a temperature in the bearing cavity and a
pressure inside the bearing cavity. In an embodiment, in the
compressor system, the one or more parameters include a refractive
index of the lubricant inside the bearing cavity. In an embodiment,
in the compressor system, the one or more parameters include the
temperature inside the bearing cavity, and a suction pressure
measured by a sensor at the suction port, and the processor is
configured to adjust the suction pressure according to a transfer
function when determining the one or more lubricant rheological
properties.
[0122] In an embodiment, the controller is configured to determine
an adjusted speed of the compressor based on the one or more
lubricant rheological properties and direct operation of the
compressor at the adjusted speed.
[0123] In an embodiment, the controller is configured to determine
an adjusted capacity for the compressor based on the one or more
lubricant rheological properties, and direct operation of the
compressor at the adjusted capacity.
[0124] In an embodiment, the compressor system further includes a
lubricant heater in thermal communication with a flow path of the
lubricant from the lubricant separator to the bearing cavity, and
wherein the controller is configured to direct operation of the
lubricant heater based on the one or more lubricant rheological
properties.
[0125] The rheological properties of a lubricant are flow
properties of the lubricant, including, for example, one or more of
the viscosity of the lubricant, the viscosity-pressure relationship
of the lubricant, and the like. One or more of the rheological
properties may be determined as a function of one or more of a
lubricant viscosity reading, a lubricant refractive index,
temperature, and pressure. The temperature and pressure may be
direct measurements at a location where rheological properties are
to be determined, such as within a bearing cavity, or may be
measurements taken at another location and transformed, for example
via a transfer function. The rheological properties may define
whether the bearing has sufficient lubrication to operate at
sufficient levels of reliability or longevity.
[0126] The one or more rheological properties may be presented as a
ratio, such as a viscosity ratio. The viscosity ratio may include
the measured rheological properties and minimum thresholds or
preferred values for rheological properties of lubricants at a
particular bearing. In an embodiment, the viscosity ratio is a
kappa value, a ratio of the applied viscosity of the lubricant over
the rated viscosity for the bearing. The rated viscosity may be
based on, for example, reliability and/or longevity data for a
bearing. The rated viscosity may vary based on operational
parameters at the bearing, such as a speed of rotation at the
bearing.
[0127] In an embodiment, the rheological properties and rated
viscosity with respect to obtaining the kappa value may be
determined based on elasto-hydrodynamic lubrication (EHL) or
hydrodynamic lubrication. Whether EHL or hydrodynamic lubrication
methods are used may be determined based on the type of bearing,
for example using EHL for lubricant used with roller bearings.
[0128] In an embodiment, the viscosity ratio may be a lambda value,
a ratio of the oil film thickness compared to a surface asperity
height in the lubricated bearing.
[0129] FIG. 4 is a front view of bearing cover 2102 of compressor
2100 according to an embodiment. In an embodiment, bearing cover
2102 includes temperature probe aperture 2104 and pressure probe
aperture 2106.
[0130] Compressor 2100 may be, for example, a screw compressor. In
an embodiment, compressor 2100 is a variable volume ratio
compressor. Compressor 2100 includes a bearing cavity, which is
enclosed at an end by bearing cover 2102. In an embodiment,
compressor 2100 is a scroll compressor. In an embodiment,
compressor 2100 is a centrifugal compressor.
[0131] Bearing cover 2102 is a cover located at an end of a bearing
cavity of compressor 2100. Bearing cover 2102 encloses the bearing
cavity, in which there are bearings allowing rotation of the rotors
of the compressor.
[0132] Temperature probe aperture 2104 is an opening extending
through bearing cover 2102 and allowing at least a portion of a
temperature sensor to be located within the bearing cavity. The
temperature sensor may be, for example, a thermistor, a
thermocouple, a semiconductor-based temperature sensor or any other
suitable temperature measurement apparatus capable of measuring the
range of typical temperatures of the bearing cavity. The
temperature sensor protruding through the temperature probe
aperture 2104 into the bearing cavity allows a temperature within
the bearing cavity to be measured directly.
[0133] In an embodiment, compressor 2100 may include two or more
temperature probe apertures 2104. Each bearing included in the
compressor may have different speeds of rotation and/or local
temperatures, for example in a screw compressor, the female rotor
may have a slower speed of rotation than the male rotor. Lubricant
rheological property requirements and lubricant rheological
properties may vary locally even for bearings all located within
the bearing cavity of compressor 2100, for example due to
differences in speed of rotation at each bearing. In an embodiment,
one temperature probe aperture 2104 may be provided for each
bearing included in the bearing cavity of compressor 2100. For
example, temperature measurements may be taken at or near each of
the male and female rotors of compressor 2100 when compressor 2100
is a crew compressor.
[0134] Pressure probe aperture 2106 is an opening extending through
bearing cover 2102 and allowing at least a portion of a pressure
sensor to be located within the bearing cavity. The portion of the
pressure sensor may be a probe of the sensor, configured to receive
pressure and produce an output representative of the pressure at or
within the bearing cavity. The pressure sensor may, for example,
include a force collector, and may be a piezoresistive, capacitive,
electromagnetic, or other such sensor capable of measuring
pressures within the ranges typically occurring within the bearing
cavity. The pressure probe aperture 2106 allows the pressure sensor
to directly measure the pressure within the bearing cavity.
[0135] FIG. 5 is a section view of a portion of a heating,
ventilation, air conditioning and refrigeration (HVACR) system 2200
including compressor 2202. Compressor 2202 includes compressor
housing 2204 and rotors 2206 and 2208, with rotors 2206 and 2208
disposed in a space within compressor housing 2204. Rotor 2206 and
2208 are supported at one end by bearings 2214, 2216 that are
located in bearing cavity 2210. Compressor housing 2204, the rotors
2206, 2208 and bearing cover 2212 define bearing cavity 2210.
Discharge from the compressor 2202 continues through the HVACR
system 2200 to lubricant separator 2218, where lubricant is
captured and recirculated to bearing cavity 2210. Lubricant heater
2220 may be located along the path carrying lubricant from the
lubricant separator 2218 or a lubricant sump, tank, or reservoir to
the bearing cavity 2210. HVACR system 2200 may include a controller
2222 and one or more lubricant condition sensors 2224.
[0136] HVACR system 2200 is a system including a compressor circuit
for heating and/or cooling a fluid. HVACR system 2200 may be, for
example, included in a water chiller, a heat recovery system, an
ice manufacturing system, or the like. HVACR system 2200 includes a
compressor circuit including compressor 2202, condenser 2230,
expansion device (e.g. an expansion valve) 2232, and evaporator
2234.
[0137] In an embodiment, compressor 2202 is a screw compressor that
compresses a refrigerant used in HVACR system 2200. Compressor 2202
includes bearings and allows mixing of lubricant for the bearings
with the refrigerant it compresses. Compressor 2202 includes a
suction port 2238 where the refrigerant enters the compressor 2202
and a discharge port 2240 where compressed refrigerant exits the
compressor 2202.
[0138] Compressor housing 2204 has a suction port 2238 where gas
enters and a discharge port 2240 where gas leaves the compressor
housing. Compressor housing 2204 defines a space including cavities
accommodating rotors 2206 and 2208. Compressor housing 2204 is
configured to, in combination with grooves and lobes of the rotors
2206 and 2208, define compression chambers as the rotors 2206 and
2208 are rotated.
[0139] Rotors 2206, 2208 are located within the space defined by
compressor housing 2204. Rotors 2206, 2208, may be disposed in
respective cavities within compressor housing 2204. The rotors are
rotated when operating compressor 2202, and lobes of the rotors
2206 and 2208, combined with the compressor housing, direct
refrigerant from the suction port 2238 of the compressor 2202 and
compress the refrigerant as it is moved towards the discharge port
2240 of compressor 2202. In an embodiment, rotors 2206 and 2208
have corresponding mated lobes configured to form compression
chambers when the rotors 2206, 2208 are rotated. In an embodiment,
rotor 2206 is a male rotor and rotor 2208 is a female rotor. In an
embodiment, one of the rotors, such as rotor 2206, includes a shaft
2228 that is driven by a motor 2236 to rotate the rotors 2206 and
2208 when the compressor 2202 is in operation. Rotors 2206 and 2208
each have a first end opposite the end where shaft 2228 extends
from rotor 2206. The first ends of each of rotors 2206 and 2208 are
supported by bearings 2214, 2216.
[0140] Bearing cavity 2210 is a space defined by rotors 2206 and
2208, compressor housing 2204 and bearing cover 2212. The bearing
cavity 2210 contains bearings 2214 and 2216. A lubricant may be
located within the bearing cavity 2210, particularly at bearings
2214, 2216, to lubricate the bearings. The bearing cavity may
receive the lubricant from, for example, a lubricant separator
2218. A fluid pathway from lubricant separator 2218 to bearing
cavity 2210 may include or be in contact with, for example, a
heater.
[0141] Bearing cover 2212 encloses an end of compressor housing
2204. Bearing cover 2212, along with compressor housing 2204 and
rotors 2206 and 2208 defines bearing cavity 2210. Bearing cover
2212 may include one or more apertures, such as temperature probe
aperture 2104 and pressure probe aperture 2106 described above and
shown in FIG. 4, through which sensors may be introduced into
bearing cavity 2210. In an embodiment, bearing cover 2212 includes
a refractive index probe aperture. In an embodiment, bearing cover
2212 includes an aperture through which lubricant in bearing cavity
can be introduced into a refractive index sensor.
[0142] Bearing 2214 supports an end 2242 of rotor 2206, and bearing
2216 supports an end 2244 of rotor 2208. Bearings 2214 and 2216 may
be located at the ends of rotors 2206 and 2208 towards the
discharge end of compressor 2202. Bearings 2214 and 2216 allow the
respective rotors 2206, 2208 to rotate when the compressor 2202 is
operated. Bearings 2214 and 2216 are lubricated by a lubricant
present within bearing cavity 2210. Bearings 2214 and 2216 may be,
for example, mechanical bearings such as ball bearings, roller
bearings, or the like. Compressor 2202 may further include bearings
2246 and 2248 at the suction end of rotors 2206 and 2208,
respectively. Bearings 2246 and 2248 may receive lubricant from a
common source with bearings 2214 and 2216.
[0143] Lubricant separator 2218 is located downstream of the
discharge port 2240 of compressor 2202. Lubricant separator 2218
removes lubricant from the flow of refrigerant discharged by
compressor 2202 and returns the lubricant to bearing cavity 2210.
Lubricant separator 2218 may include a lubricant sump. In an
embodiment, lubricant separator 2218 includes a lubricant sump and
lubricant heater 2220 thermally coupled to the lubricant sump.
[0144] Lubricant heater 2220 is located at the lubricant sump of
lubricant separator 2218 or along the lubricant flow path between
lubricant separator 2218 and the bearing cavity 2210. Lubricant
heater 2220 may be, for example, an electric heater. Lubricant
heater 2220 may be a system or waste heat collector thermally
coupled to another part of the HVACR system 2200. Lubricant heater
2220 may be controlled based on the lubricant rheological
properties within the bearing cavity 2210, for example via
controller 2222. In an embodiment, lubricant heater 2220 is located
at or within lubricant separator 2218.
[0145] In an embodiment, other lubricant conditioning devices may
be between lubricant separator 2218 and bearing cavity 2212 in
place of or in addition to lubricant heater 2220. The lubricant
conditioning devices may include, for example, a filter, an
expansion valve or an orifice configured to reduce a pressure of
the lubricant, or the like.
[0146] In an embodiment, the HVACR system 2200 may include
controller 2222. Controller 2222 is configured to receive data from
one or more sensors 2224. Controller 2222 is configured to
determine, based on at least one output of the one or more sensors
2224, one or more lubricant rheological properties. In an
embodiment, controller 2222 is further configured to control
operation of the compressor 2202 based on the one or more lubricant
rheological properties.
[0147] The one or more sensors 2224 may be at least partially
disposed within bearing cavity 2210. The one or more sensors 2224
may include a refractive index sensor, a viscometer, a temperature
sensor, and/or a pressure sensor. Each of the one or more sensors
may have at least a portion, such as a probe, protruding into
bearing cavity 2210 through an aperture in bearing cover 2212. In
an embodiment, the sensor is located entirely within bearing cavity
2210, and a connection to the controller 2222 extends through an
aperture in the bearing cover 2212.
[0148] In an embodiment, the one or more lubricant rheological
properties determined by controller 2222 include a viscosity ratio,
for example a kappa value. The kappa value is the viscosity ratio
of the applied viscosity of the lubricant over the rated viscosity
for that lubricant. The kappa ratio may be reflective of the
surface separation at a rolling contact such as the bearings 2214,
2216, 2246, and/or 2248. In an embodiment, the applied viscosity
used to determine kappa is determined based on the bearing cavity
temperature and pressure measured by sensors 2224. The bearing
cavity temperature and pressure may be used, for example, to
determine a lubricant/refrigerant mass fraction of the lubricant
being provided to the bearing, which may then be used to determine
the applied viscosity. The bearing cavity temperature and pressure
may be used to determine the applied viscosity directly based on
the known properties of the lubricant and the refrigerant. In an
embodiment, the applied viscosity used to determine kappa is
determined based a refractive index of the lubricant measured by
sensors 2224. The refractive index may be used, for example, to
determine the lubricant/refrigerant mass fraction, which may then
be used to determine the applied viscosity. The pressure,
viscosity, and temperature properties of the lubricant and also of
the refrigerant may be used when determining the applied viscosity
then used to determine Kappa. In an embodiment, the viscosity ratio
is a function of parameters including, for example compressor
speed, bearing cavity pressure, bearing cavity pressure,
refrigerant properties, lubricant properties, lubricant quality
(i.e. lubricant and refrigerant mass fractions) and bearing size.
In an embodiment, the applied viscosity used to determine Kappa is
determined directly using a viscometer, and the following function
to determine Kappa:
Kappa = Viscometer .times. .times. cSt 4 .times. 5 .times. 0
.times. 0 * ( ( R .times. P .times. M - 0 . 5 ) * ( Bearing .times.
.times. Mean .times. .times. Diameter - 0 . 5 ) ##EQU00001##
[0149] In an embodiment, a sensor 2226 may be located at the
suction 2238 of compressor 2202. Sensor 2226 may be, for example a
temperature sensor or a pressure sensor. Sensor 2226 may be
connected to controller 2222. In an embodiment where sensor 2226 is
a temperature sensor, the saturated suction temperature of
compressor 2202 may be adjusted by controller 2222 according to a
transfer function and the adjusted value used in determining the
lubricant rheological properties. In an embodiment where sensor
2226 is a pressure sensor, suction pressure measured by sensor 2226
may be used by controller 2222 to determine a value for bearing
cavity pressure to use when determining lubricant rheological
properties.
[0150] FIG. 6 is a flow chart of a method 2300 of operating a
chiller according to an embodiment. Lubrication rheological
property parameters are obtained 2302. The lubrication rheological
property parameters are used to determine one or more lubricant
rheological properties 2304. In an embodiment, the one or more
lubricant rheological properties are used to determine an updated
compressor operational profile 2306. The compressor is then
operated in accordance with the updated compressor operational
profile 2308. In an embodiment, a device affecting lubricant
rheological properties is operated based on the determined one or
more lubricant rheological properties 2310.
[0151] One or more lubrication rheological property parameters are
obtained 2302 at or near the bearing cavity, such as bearing cavity
2210 described above and shown in FIG. 5. In an embodiment, the one
or more lubrication rheological property parameters are a pressure,
measured by a pressure sensor located in the bearing cavity, and a
temperature, measured by a temperature sensor located in the
bearing cavity. In an embodiment, the one or more lubrication
rheological property parameters include a refractive index of the
lubricant. In this embodiment, the refractive index may be obtained
by a sensor located within a bearing cavity, evaluating a sample of
the lubricant within the bearing cavity. In an embodiment, the one
or more lubrication rheological property parameters include a
viscometer reading of the lubricant. The one or more lubrication
rheological property parameters may be measured at locations
outside the bearing cavity but proximate to the bearing cavity with
respect to a flow of refrigerant through a compressor circuit. The
locations outside the bearing cavity may include, for example, the
suction port of the compressor, one or more points within the
compressor but separate from the bearings, or between the discharge
of the compressor and the lubricant separator. In an embodiment,
the one or more lubrication rheological property parameters are a
suction pressure measured at the suction port of the compressor and
a bearing cavity temperature. In an embodiment, the lubrication
rheological property parameters are a suction pressure of the
compressor measured at the suction port of the compressor and a
bearing cavity temperature. In an embodiment, a function using a
saturated suction temperature, saturated discharge temperature,
discharge temperature, and compressor speed may be used to
determine a value corresponding to the bearing cavity temperature,
which can be used to determine the lubricant rheological properties
when combined with suction pressure.
[0152] The one or more lubrication rheological property parameters
are used to determine one or more lubrication rheological
properties 2304. A processor may be used to determine the
lubrication rheological properties. In an embodiment, the
lubrication rheological properties include viscosity ratio, for
example a kappa value. The kappa value is the viscosity ratio of
the lubricant, a ratio of the actual viscosity to the rated
viscosity for the lubricant. The larger the kappa value is, the
better the lubricant is performing. The kappa value of lubricant
may need to exceed certain thresholds based on the operational
state of the compressor, such as the speed at which the compressor
is operating. The kappa value may be determined by a function using
the one or more lubrication rheological property parameters. In an
embodiment, the one or more rheological properties may be a lambda
value, a ratio of oil film thickness to a surface asperity height
of the bearing. In an embodiment, the lubrication rheological
properties may be used to determine a compressor component life
expectancy.
[0153] The one or more lubrication rheological properties may be
used to determine an updated compressor operational profile 2306.
The updated compressor operational profile may include one or more
of a position of a valve, a minimum speed for the compressor, or
the like. The updated compressor operational profile 2306 may be
determined, for example, based on a lookup table of permissible
compressor operation, such as capacity and/or speed at given values
of lubricant rheological properties. In an embodiment, the updated
compressor operational profile determined at 2306 may be a change
to the minimum speed of the compressor. In an embodiment, the
change to the minimum speed of the compressor may be periodic
changes to minimum speed. In an embodiment, the minimum speed may
be increased at or near a minimum threshold value for the
lubrication rheological properties. In an embodiment, the one or
more rheological properties may include a viscosity ratio that is a
function of parameters including compressor speed, and that
viscosity ratio function may be used to determine a speed included
in the updated compressor operational profile. In an embodiment,
the relationship between the lubrication rheological properties and
speed used to determine the minimum speed may be the following
formula:
Kappa = Applied .times. .times. Viscosity 4 .times. 5 .times. 0
.times. 0 * ( ( R .times. P .times. M - 0 . 5 ) * ( Bearing .times.
.times. Mean .times. .times. Diameter - 0 . 5 ) ##EQU00002##
[0154] The compressor may then be operated according to the updated
compressor operational profile 2308. Operating the compressor
according to the updated compressor operational profile may
include, for example, operating the compressor at a particular
speed or capacity. In an embodiment, operating the compressor at a
particular speed may be performed by controlling a variable speed
drive (VSD) of the compressor. In an embodiment, operating the
compressor at the particular capacity may be performed by
controlling the position of an expansion device, such as an
electronic expansion valve (EXV). In an embodiment, the oil return
from an evaporator may be controlled based on the lubricant
rheological properties. In an embodiment, the oil return from an
evaporator may be reduced in amount when lubricant rheological
properties indicate insufficient lubrication. In an embodiment, the
timing of oil return from an evaporator may be accelerated when one
or more lubricant rheological properties are above a threshold, and
slowed when one or more lubricant rheological properties are at or
near the threshold.
[0155] In an embodiment, operating the compressor according to the
updated compressor operational profile may include regular sampling
or continuous monitoring of the lubricant rheological properties,
and when one or more lubricant rheological properties satisfy a
threshold, a predetermined pressure differential may be used for
the current load point of the compressor. The predetermined
pressure differential may be a standard operating pressure for the
compressor, based on an efficiency curve for that compressor.
[0156] In an embodiment, a device affecting lubricant rheological
properties may be operated based on the determined lubricant
rheological properties 2310. In an embodiment, the device affecting
lubricant rheological properties is a heater, thermally coupled to
at least part of the flow path of the lubricant from an oil
separator to the bearing cavity. In an embodiment, the heater is an
electric heater. In an embodiment, the heater is a system or waste
heat collector thermally coupled to another part of the HVACR
system. The operation of the device affecting lubricant rheological
properties may be controlled based on, for example, whether one or
more lubricant rheological properties satisfy a threshold value. In
an embodiment, the device affecting lubricant quality is a
controllable expansion valve or orifice, configured to reduce the
pressure of the lubricant by a controlled amount. In an embodiment,
the device affecting lubricant quality is a drive (e.g. variable
speed drive) and/or a motor that may provide heat to gas in the
compressor system.
[0157] Determining lubricant rheological properties at or near the
bearing cavity, instead of using more remote or indirect
measurements of lubrication, can allow more efficient use of
lubricant enrichment devices such as heaters and can improve the
amount of the operational map that can be used during compressor
operations. This can allow improved efficiency for compressor
operations, for example in variable volume ratio compressors, and
under conditions where lubricant rheological properties may be
insufficient, such as low ambient temperatures or at low compressor
speeds.
[0158] Aspects:
[0159] Any of aspects 1-9 can be combined with any of aspects
10-18. It is understood that any of aspects 1-18 can be combined
with any other aspects recited herein.
[0160] Aspect 1. A method for operating a compressor system
including a lubricant separator, comprising: measuring one or more
parameters of a lubricant via one or more sensors within a bearing
cavity of the compressor; and determining one or more lubricant
rheological properties based on the one or more parameters.
[0161] Aspect 2. The method according to aspect 1, wherein the one
or more parameters include a bearing cavity temperature.
[0162] Aspect 3. The method according to aspect 2, wherein the one
or more parameters further includes a bearing cavity pressure.
[0163] Aspect 4. The method according to aspect 2, further
comprising measuring a suction pressure of the compressor, and
wherein determining the one or more lubricant rheological
properties is based on the one or more parameters and the suction
pressure, and determining the one or more lubricant rheological
properties comprises applying a predetermined transfer function to
the suction pressure of the compressor.
[0164] Aspect 5. The method according to any of aspects 1-4,
wherein the one or more parameters include a refractive index of
the lubricant.
[0165] Aspect 6. The method according to any of aspects 1-5,
wherein the one or more lubricant rheological properties include a
kappa value of the lubricant.
[0166] Aspect 7. The method according to any of aspects 1-6,
further comprising determining, via the controller, an adjusted
speed of the compressor based on the one or more lubricant
rheological properties; and operating the compressor at the
adjusted speed.
[0167] Aspect 8. The method according to any of aspects 1-7,
further comprising determining, using the controller, an adjusted
capacity for the compressor based on the one or more lubricant
rheological properties, and operating the compressor at the
adjusted capacity.
[0168] Aspect 9. The method according to any of aspects 1-8,
further comprising operating a heater based on the one or more
lubricant rheological properties, wherein the heater is in thermal
communication with a flow path of the lubricant from the lubricant
separator to the bearing cavity.
[0169] Aspect 10. A compressor system, comprising: a compressor,
including a suction port and a bearing cavity; one or more sensors
located inside the bearing cavity and configured to measure one or
more parameters of a lubricant; and a processor, configured to
receive the one or more parameters of the lubricant from the one or
more sensors and to determine one or more lubricant rheological
properties.
[0170] Aspect 11. The compressor system according to aspect 10,
wherein the one or more parameters include a temperature of the
bearing cavity and a pressure within the bearing cavity.
[0171] Aspect 12. The compressor system according to any of aspects
10-11, wherein the one or more parameters include a refractive
index of the lubricant inside the bearing cavity
[0172] Aspect 13. The compressor system according to any of aspects
10-12, wherein the one or more lubricant rheological properties
include a kappa value of the lubricant.
[0173] Aspect 14. The compressor system according to any of aspects
10-13, further comprising a sensor measuring a suction pressure of
the compressor, and wherein the processor is configured to
determine the one or more lubricant rheological properties based on
a bearing cavity temperature and the suction pressure.
[0174] Aspect 15. The compressor system according to any of aspects
10-14, wherein the controller is configured to determine an
adjusted speed of the compressor based on the one or more lubricant
rheological properties and direct operation of the compressor at
the adjusted speed.
[0175] Aspect 16. The compressor system according to any of aspects
10-15, wherein the controller is configured to determine an
adjusted capacity for the compressor based on the one or more
lubricant rheological properties, and direct operation of the
compressor at the adjusted capacity.
[0176] Aspect 17. The compressor system according to any of aspects
10-16, further comprising a lubricant heater in thermal
communication with a flow path of the lubricant from the lubricant
separator to the bearing cavity, and wherein the controller is
configured to direct operation of the lubricant heater based on the
one or more lubricant rheological properties.
[0177] Aspect 18. The compressor system according to any of aspects
10-17, wherein the one or more sensors include a viscometer and the
one or more parameters include a viscosity of the lubricant.
[0178] This disclosure is directed to determining one or more
lubricant rheological properties in a compressor system based on
measurements taken at or near a bearing cavity of the compressor.
The measurements may include a viscometer reading, a refractive
index, a bearing cavity pressure and a bearing cavity temperature,
or a bearing cavity temperature and a suction pressure of the
compressor. The one or more lubricant rheological properties may be
used to adjust compressor operations including compressor capacity
and/or compressor speed. The one or more lubricant rheological
properties may be used to control one or more lubricant rheological
property management devices such as a heater and/or an expansion
valve.
[0179] Methods and Systems for Fan Control Based on Lubricant
Characteristics (FIGS. 7-10)
[0180] At many operating conditions, a chiller may not be operating
at full load. For chillers that have variable speed fan(s) and/or
fans with a multiple number of fan stages or discrete steps, and
that have variable speed or variable load compressor(s) and/or
multiple fixed speed compressors that can be staged on/off, a fan
speed based on chiller operating condition can be obtained via fan
control in the HVAC systems to achieve target power consumption
(e.g., power optimization) in the chiller at various unloaded
conditions, i.e. conditions not at full load or conditions at
partial load.
[0181] The HVACR system includes a heat transfer circuit to heat or
cool a process fluid (e.g., air, water and/or glycol, or the like).
A working fluid flows through the heat transfer circuit and is
utilized to heat or cool the process fluid. In an embodiment, the
working fluid includes one or more refrigerants. There has been
recent movement (e.g., the Kigali Amendment to the Montreal
Protocol, the Paris Agreement, United States' Significant New
Alternatives Policy ("SNAP")) to limit the types of refrigerants
utilized in HVACR systems as concern about environmental impact
(e.g., ozone depletion, global warming impact) has increased. In
particular, the movement has been to replace ozone depleting
refrigerants (e.g., chlorofluorocarbons (CFCs),
hydrochlorofluorocarbons (HCFCs), or the like) and high global
warming potential refrigerants with refrigerants that have a lower
environmental impact.
[0182] The replacement refrigerants are non-ozone depleting,
flammable or non-flammable, energy efficient, compatible with the
materials of the heat transfer circuit and its equipment, low in
toxicity, and chemically stable over the life of the equipment of
the heat transfer circuit. For example, previous refrigerants
having relatively higher GWPs such as R134a or the like, are being
replaced with refrigerants such as, but not limited to, R1234ze
(e.g., R1234ze(E)), R513A, and the like.
[0183] The heat transfer circuit includes a compressor that
compresses the working fluid. Lubricant is supplied to the
compressor to provide lubrication for its moving parts. A lubricant
may include one or more types of lubricants. For example, a
lubricant be, but is not limited to, polyolester (POE) oils, or the
like. The lubricant is discharged from the compressor with the
working fluid. Thus, the working fluid discharged from the
compressor contains lubricant. In some heat transfer circuits, the
lubricant is also separated from the working fluid and the
separated lubricant is circulated back to the compressor. In other
heat transfer circuits, the lubricant is circulated with the
working fluid and is then supplied through a suction inlet of the
compressor as part of the working fluid. The working fluid may also
include one or more additional components other than lubricant(s)
and refrigerant(s). For example, an additional component may be,
but is not limited to, impurities, refrigeration system additives,
tracers, ultraviolet ("UV") dyes, and/or solubilizing agents.
[0184] Various issues may arise with the use of the
newer/replacement refrigerants due to having different properties
relative to previous refrigerants such as R134a. For example, newer
refrigerants with lower GWPs such as R1234ze (e.g., R1234ze(E)),
R513A, and the like are more soluble in the lubricant relative to
previous refrigerants such as R134a due to their chemical
structures. Accordingly, the lubricant provided back to the
compressor contains a higher concentration of refrigerant. The
higher concentration of refrigerant decreases the viscosity of the
lubricant, which reduces the amount of lubrication ("lubricity")
provided by the lubricant. In particular, when a compressor is
operated at certain operating conditions, the lubricant provided to
the bearings of the compressor may not provide adequate lubricity
due to the concentration of refrigerant in the lubricant being too
high. The compressor might be operated to avoid operation
conditions where lubricity of the lubricant becomes an issue.
However, this may result in being unable to use certain areas of
the operating map of a compressor that may be efficient for a
desired operation of the compressor (e.g., desired flow rate of
working fluid discharged by a compressor, a desired pressure for
the discharged working fluid, or the like).
[0185] Lubricant (e.g., oil and/or oil/refrigerant mixture)
characteristics include, for example, lubricant quality (e.g. the
mass fraction of the refrigerant dissolved in the lubricant),
lubricant viscosity, and lubricant kappa value. Lubricant
characteristics concern can be greater with more efficient
compressor(s). As the compressor becomes more efficient, at a low
ambient temperature with low compressor load, the discharge
superheat can be relatively low. Low discharge superheat can result
in less than sufficient lubricant characteristics such as lubricant
quality. Lubricant characteristics such as lubricant quality can be
a function of discharge superheat. The embodiments described herein
can determine a less efficient chiller operation which makes the
compressor work a little harder (less efficient) for the same load,
increases the discharge superheat, and achieves target lubricant
characteristics.
[0186] In an embodiment, a method of controlling condenser fans in
an HVAC system is provided. The method includes obtaining, by a
controller, a measurement of a measureable parameter of the HVAC
system. The method also includes determining, by the controller, a
differential pressure between a condenser and an evaporator based
on the measurement and a predetermined threshold (e.g., a threshold
for the discharge superheat). The method further includes
outputting, by the controller, a fan speed suitable to achieve the
differential pressure determined. Also the method includes
controlling one or more condenser fans based on an output of the
fan speed to obtain a fan capacity suitable to control the one or
more condenser fans, such that power of the HVAC system is managed
through a power consumed by a compressor and the one or more
condenser fans. The measureable parameter is indicative of
lubricant characteristics.
[0187] In an embodiment, an HVAC system is provided. The system
includes a compressor, an evaporator fluidly connected to the
compressor, a condenser fluidly connected to the compressor, and a
controller. The condenser includes one or more condenser fans. The
controller is operatively connected to a device to measure a
measureable parameter of the HVAC system, is configured to obtain a
measurement of the measureable parameter, and is operatively
connected to the condenser including the one or more condenser
fans. The controller is also configured to determine a differential
pressure between the condenser and the evaporator based on the
measurement and a predetermined threshold. The controller is
further configured to determine a fan speed suitable to achieve the
differential pressure determined. Also the controller is configured
to operate the one or more condenser fans based on an output of the
fan speed to obtain a fan capacity suitable to control the one or
more condenser fans, such that the power of the HVAC system is
managed through power consumed by the compressor and the one or
more condenser fans. The measureable parameter is indicative of
lubricant characteristics.
[0188] Other features and aspects will become apparent by
consideration of the following detailed description and
accompanying drawings.
[0189] This disclosure relates generally to fan control for HVAC
systems. More specifically, the disclosure relates to methods and
systems for controlling fan(s) to achieve a balance between
compressor(s) and fan(s) for target lubricant characteristics for
HVAC system(s). "Target" lubricant characteristics refer to, for
example, a lubricity of the lubricant provided to the compressor
where the compressor can operate at the full operating map with
such lubricant having the lubricity. It will be appreciated that
"target" lubricant characteristics can refer to one or more of the
lubricant characteristics that exceeds the minimum requirement for
operation. It will also be appreciated that "target" lubricant
characteristics can refer to an optimal lubricant characteristic.
It will also be appreciated that "target" efficiency of the chiller
can refer to an optimal efficiency of the chiller. The "target"
efficiency of the chiller can be achieved by, for example,
determining a fan speed to minimize total power consumption at the
chiller capacity by using the compressor load and the ambient
temperature.
[0190] For chillers that have variable speed fan(s) and/or fans
with a multiple number of fan stages or discrete steps, and that
have variable speed or variable load compressor(s) and/or multiple
fixed speed compressors that can be staged on/off, a fan speed
based on chiller operating condition can be obtained via fan
control in the HVAC systems to achieve target power consumption
(e.g., power optimization) in the chiller at various unloaded
conditions, i.e. conditions not at full load or conditions at
partial load. U.S. Pat. No. 9,810,469, which is incorporated herein
by reference in its entirety, describes a fan speed control system
to determine a fan speed to minimize total power consumption at the
chiller capacity, based on various operating conditions of
compressor load and ambient air temperature.
[0191] In one embodiment, lubricant characteristics can be a
function of discharge superheat. Lubricant characteristics
concern(s) can be greater with more efficient compressor(s). As the
compressor becomes more efficient, at a low ambient temperature
with low or partial compressor load, the discharge superheat can be
relatively low. Higher compressor efficiency can result in lower
discharge superheat. Low discharge superheat can result in less
than sufficient lubricant characteristics. The embodiments
described herein can determine a less efficient chiller operation
which makes the compressor work a little harder (less efficient)
for the same load, increases the discharge superheat, and achieves
target lubricant characteristics. High lubricant characteristics
(such as target or better than target lubricant characteristics)
can ensure a long lifecycle of the compressor. It will be
appreciated that the chemistry of which type of refrigerant is
used, and/or which type of lubricant is used can determine the
sensitivity of the lubricant characteristics when the discharge
superheat changes.
[0192] FIG. 7 shows a schematic view of a chiller in an HVAC system
to control fan(s). FIG. 7 shows one embodiment of a chiller (such
as an air cooled chiller) that has a compressor 3001, an evaporator
3003, a condenser 3004 with air coil 3005 and fans 3008, and a
control unit 3002 and panel 3007. It will be appreciated that the
compressor 3001 can be a variable speed compressor or a variable
load compressor and/or one of the multiple fixed speed compressors
that can be staged on/off, and that the fans 3008 can be variable
speed fan(s) and/or fan(s) with a multiple number of fan stages or
discrete steps. The condenser 3004 and its air coil 3005 in the
embodiment shown are one example of an air cooled condenser,
however it will be appreciated that the specific condenser
3004/coil 3005 combination shown is merely exemplary. The chiller
can be considered a single unit within the HVAC system and be
supported by a frame 3006 for example. It will be appreciated that
the specific configuration shown in FIG. 7 is merely exemplary, as
other chiller designs, layouts, and specific configurations may be
employed. For example, the chiller of FIG. 7 can be a chiller with
"W" shaped coils; however, it will be appreciated that other coil
types may be used, such as for example multiple "V" shaped coils or
more than one circuit employing multiple compressors, evaporators,
condensers. Generally, the methods and systems to control fan can
be employed in any type of chiller with variable speed fan(s)
and/or with fan(s) that have a multiple number of fan stages or
discrete steps and variable speed (or variable load) compressor(s)
and/or multiple fixed speed compressors that can be staged
on/off.
[0193] FIG. 8 illustrates fan control 3200 that can include devices
to detect, obtain, or otherwise determine the inputs needed for a
controller to determine the appropriate output to control fan(s).
In one embodiment, a device 3205 is used to measure a measureable
parameter (e.g., temperature, pressure) of an HVAC system. The
device 3205 communicates the measurement to a controller 3210. The
controller 3210 uses the measurement to obtain a superheat (e.g.,
the discharge superheat). The controller 3210 can control the
fan(s) 3215 based on the obtained superheat and target lubricant
characteristics (e.g., the predetermined lubricity of the lubricant
where the compressor can operate at the full operating map with
such lubricant, or predetermined discharge superheat because
lubricant characteristics can be a function of discharge
superheat). The device 3205 can periodically update the
measurements taken as needed and/or desired, such as automatically,
during/after an operation change or changing conditions of the
chiller, and/or manually. It will be appreciated that the
controller 3210 can use the most recent measurement data available
unless otherwise specified.
[0194] The controller 3210 can be implemented into, for example,
control unit 3002 and panel 3007 in FIG. 7. It will be appreciated
that the control unit 3002, such as shown in the chiller of FIG. 7,
generally can include a processor (not shown), a memory (not
shown), and optionally a clock (not shown) and an input/output
(I/O) interface (not shown), and the control unit 3002 can be
configured to receive data as input from various components within
an HVAC system, such as the components shown in FIG. 7 and FIG. 8,
and can also send command signals as output to various components
within the HVAC system.
[0195] In one embodiment, superheat can be defined as a difference
between the actual temperature of the refrigerant vapor and the
saturation temperature (boiling point) of the refrigerant at the
same measuring location. In one embodiment, the saturation
temperature (boiling point) of the refrigerant can be obtained by
measuring a pressure (e.g., discharge pressure or suction pressure)
of the refrigerant by using, for example, a pressure sensor, a
gauge, and then converting the measured pressure to a temperature
(saturation temperature). In an embodiment, the device 3205 can
include a pressure sensor, a gauge, or the like to measure the
pressure. The device 3205 can also include a temperature sensor to
measure the actual temperature of the refrigerant vapor. In one
embodiment, discharge superheat is the superheat obtained at the
compressor discharge side (e.g., in the lubricant separator, or in
the bearing cavity), which is the measured actual temperature of
the refrigerant vapor minus the obtained saturation temperature
(boiling point) of the refrigerant at the same measuring location
at the compressor discharge side.
[0196] In one embodiment, lubricant characteristics can be a
function of discharge superheat. Perceived low lubricant
characteristics (such as less than sufficient lubricant quality)
correspond to a low discharge superheat value. When the controller
3210 determines that the obtained discharge superheat drops below a
predetermined value (which corresponds to the perceived low
lubricant characteristics), the controller 3210 can determine a
first differential pressure (.DELTA.Pdiff) between a condenser and
an evaporator (or between a compressor suction side and a
compressor discharge side) to achieve target lubricant
characteristics.
[0197] In one embodiment, the controller 3210 can determine a
second differential pressure (.DELTA.Pdiff) between a condenser and
an evaporator (or between a compressor suction side and a
compressor discharge side), based on a measured ambient air
temperature and an obtained present load on the compressor, to
achieve a target (e.g., optimal) efficiency of the chiller by, for
example, balancing the power requirements of the compressor(s) and
the fan(s).
[0198] It will be appreciated that the first differential pressure
is to achieve target lubricant characteristics, and the second
differential pressure is to achieve target efficiency of the
chiller. Both the first differential pressure and the second
differential pressure are used to determine corresponding fan speed
(and/or compressor speed) to achieve the target lubricant
characteristics or the target efficiency. It will also be
appreciated that at a low or partial load (where efficiency is not
as important), the compressor might not generate enough superheat
to keep the target lubricant characteristics. In an embodiment,
when the discharge superheat drops below a predetermined value
(which corresponds to the perceived low lubricant characteristics),
the controller 3210 can determine the first differential pressure
to make the compressor work harder (corresponding to a slower fan
speed) than when the compressor works under the second differential
pressure, so that the superheat (and lubricant characteristics)
increases (giving up efficiency). When the discharge superheat is
at or above the predetermined value (indicative of target lubricant
characteristics), the controller 3210 can determine the second
differential pressure to make the compressor work more efficiently
(corresponding to a faster fan speed) than when the compressor
works under the first differential pressure, to achieve the target
efficiency (in such case, the superheat (and lubricant
characteristics such as lubricant quality) can decrease).
[0199] The ambient air temperature can be measured by, for example,
a temperature sensor (not shown). The temperature sensor can
communicate the ambient temperature measurement to the controller
3210. The present load on the compressor can be determined based on
a compressor's running speed, which in some examples may be
expressed as a percentage of rated speed for a particular
compressor frame size, e.g. relative to the compressor full speed
configured limit. A device (not shown) can measure and communicate
for example, the percentage of rated speed of the compressor to the
controller 3210. It will be appreciated that, depending on the
method of unloading of the compressor, mechanical unloader position
sensor(s) may be considered to obtain the compressor load, e.g.
compressor speed. In other embodiments, compressor load, e.g.
compressor speed, could also be estimated indirectly such as for
example by a change in evaporator water temperature obtained by the
controller through use of for example temperature sensor(s).
[0200] In operation, the controller 3210 can determine the second
differential pressure between a condenser and an evaporator, based
on a measured ambient air temperature and an obtained present load
on the compressor, to achieve target efficiency of the chiller. If
the controller 3210 determines that an obtained discharge superheat
drops below a predetermined value, the controller 3210 can
determine a first differential pressure between the condenser and
the evaporator to achieve target lubricant characteristics. It will
be appreciated that the first differential pressure can be set to a
value greater than the second differential pressure. With a larger
differential pressure, the chiller is less efficient--the
compressor works harder (less efficient) for the same load, the
discharge superheat is thus increased, and target lubricant
characteristics can be achieved. When the differential pressure is
larger, typically the compressor speed is higher (for variable
speed compressors), and the fan speed is lower for the same load.
In another embodiment, for a larger differential pressure when a
variable load compressor is used, an unloader can be used to change
(e.g., increase) the load of the compressor; and the fan speed can
be decreased.
[0201] If the controller 3210 determines that an obtained discharge
superheat is no less than the predetermined value, the controller
3210 can determine and/or set the first differential pressure to be
the same as the second differential pressure. In such a case, both
the target lubricant characteristics and the target efficiency of
the chiller can be achieved.
[0202] It will be appreciated that the controller 3210 can use
lubricant viscosity and/or lubricant kappa value instead of (or in
addition to) discharge superheat, to determine the first
differential pressure.
[0203] In one embodiment, the discharge superheat (and/or lubricant
viscosity and/or lubricant kappa value) can be an integral of the
discharge superheat (and/or lubricant viscosity and/or lubricant
kappa value) over a predetermined period of time to track how far
the discharge superheat (and/or lubricant viscosity and/or
lubricant kappa value) is below the predetermined value over time.
If the integral exceeds a certain value, the controller 3210 can
set the first differential pressure to a value greater than the
second differential pressure, to achieve target lubricant
characteristics. If the integral decreases to or below the certain
value, the controller 3210 can set the first differential pressure
to be the same as the second differential pressure to also achieve
efficiency of the chiller.
[0204] It will be appreciated that the target differential pressure
(e.g., the first differential pressure or the second differential
pressure) can be added to the suction pressure from the compressor
to obtain a target discharge pressure of the compressor. As the
fans may change speed to reach a target discharge pressure of the
compressor, the unit capacity, e.g. of the chiller, can also change
to a new compressor speed. The new compressor speed can then in
turn change the output target differential pressure across the
compressor. The chilled water temperature control then drives the
chiller to the appropriate chiller capacity.
[0205] In one embodiment, the fan control can determine the fan
speed to achieve target lubricant characteristics by using the
discharge superheat to obtain the output target differential
pressure (the first differential pressure). The fan control can
also determine the fan speed to minimize total power consumption at
that unit capacity by using the compressor load and the ambient
temperature to obtain the output target differential pressure (the
second differential pressure).
[0206] The output target differential pressure (the first or second
differential pressure) in turn can be used to determine the
appropriate fan capacity, e.g. based on the resulting fan speed
that can (1) meet the target lubricant characteristics (when the
first differential pressure is used), or (2) minimize total power
consumption at that unit capacity, for example the relative power
consumed by the compressor and by the fans (when the second
differential pressure is used).
[0207] It will be appreciated that compressor speed in rpm can be
commanded by the controller, e.g. 3210, in response to, for
example, the chiller water temperature control loop of a water
chiller. In the methods and systems described herein, differential
pressure can be the controller output parameter, and discharge
superheat (for the first differential pressure) can be the input
parameter used to obtain the output parameter. In the methods and
systems described herein, differential pressure can be the
controller output parameter, and compressor load and/or ambient
temperature (for the second differential pressure) can be the input
parameter used to obtain the output parameter.
[0208] It will be appreciated that the use of target differential
pressure is just one example of a control parameter obtained from
the input parameter, and is not meant to be limiting. It will be
appreciated that the input parameter(s) could be used to output fan
speed directly, rather than using them to first obtain the target
differential pressure.
[0209] In some embodiments, the controller 3210 may employ a high
pressure avoidance control to control fan capacity in multi-stages
such as for example, when the condensing temperature approaches the
condenser pressure limit, fan capacity can be added in discrete
fixed speed fan stages in systems using variable speed fan(s)
and/or fan(s) with a multiple number of fan stages or discrete
steps.
[0210] FIG. 9 is a flow chart of one embodiment of a method 3300 of
fan control. The method 3300 of controlling condenser fans in an
HVAC system includes obtaining a measurement of a measureable
parameter 3305. The measureable parameter can be one or more of a
discharge superheat, a viscosity of lubricant used in the HVAC
system, or a kappa value of the lubricant. With a controller, a
target differential pressure between a condenser and an evaporator
can be determined 3310, which can be based on, for example, the
measureable parameter (such as the discharge superheat) and a
predetermined threshold. If the measurement is less than the
predetermined threshold, the controller can set the differential
pressure (the first differential pressure) to a value greater than
a second differential pressure between the condenser and the
evaporator, to achieve target lubricant characteristics. In one
embodiment, the second differential pressure can be based on a
measured ambient air temperature and an obtained present load on
the compressor. If the measurement is no less than the
predetermined threshold, the controller can set the differential
pressure (the first differential pressure) to be equal to a second
differential pressure between the condenser and the evaporator.
[0211] With the controller, a condenser fan speed suitable to
achieve a fan capacity can be outputted 3315 and that is suitable
to achieve the target differential pressure determined. One or more
variable speed fans can be controlled 3320 based on the output of
condenser fan speed to achieve the fan capacity. It will be
appreciated that the fans may be fans with a multiple number of fan
stages or discrete steps, or a combination of variable speed fan(s)
and fan(s) with a multiple number of fan stages or discrete steps.
In an embodiment, when fixed speed fan(s) with a multiple number of
fan stages or discrete steps are used, for example, to drop the
amount of airflows, some fan(s) can be turned off; to increase the
amount of airflows, more fan(s) can be turned on.
[0212] Using a system with such a control method, the differential
pressure target can be varied based on the measureable parameter
(such as the discharge superheat) to determine the fan speed, which
can achieve target lubricant characteristics. At part load and full
load operation conditions, the control can determine the fan speed
to obtain efficiencies in the circuit to allow trade-offs between
condenser fan power (which can increase to keep system differential
pressure relatively low) and compressor power (which can increase
when system differential pressure increases). In an embodiment, the
objective is to achieve balance between compressor speed (or load)
and the fan speed (or staging) to provide target efficiency (e.g.,
for the overall chiller performance or compressor performance) for
a given capacity. In such embodiment, the discharge superheat
generated by the compressor might not be high enough to achieve
target lubricant characteristics. As a result, the control of the
compressor speed (or load) and the fan speed (or staging) is moved
from target efficiency to target lubricant characteristics to
increase the discharge superheat (by e.g. making the compressor to
work harder or less efficient for the same load and/or by lowering
the fan speed).
[0213] It will be appreciated that a differential pressure (e.g.,
the second differential pressure) based on, for example, the
compressor load and the ambient temperature, can be used to achieve
target efficiency of the chiller. A differential pressure (e.g.,
the first differential pressure) based on, for example, a desired
discharge superheat (or lubricant viscosity, or lubricant kappa
value) can be used to achieve target lubricant characteristics.
Moving from target efficiency to target lubricant characteristics
can increase the discharge superheat (and thus the lubricant
characteristics) but the efficiency of the chiller can be lower
(compared with target efficiency).
[0214] It will also be appreciated that in an operation map for fan
control to achieve target efficiency, the fan control (e.g., fan
speed control) can be a function of the compressor speed/load and
the ambient temperature. It will be appreciated that the fan
control to achieve target chiller efficiency works better around
minimum compressor speed (for example, 1400 rpm) than at other
compressor speed. It will further be appreciated that to achieve
target lubricant characteristics, in the corresponding areas of the
operating map, discharge superheat can be raised by utilizing fan
control to target higher differential pressures. The higher
pressure differential results in the compressor doing more work for
the same operating point (e.g., in the operating map) providing a
higher discharge superheat value and thus higher lubricant
characteristics.
[0215] Testing and/or simulation show that in one embodiment, for a
screw compressor in an air cooled chiller, from a baseline
configuration, when the power consumption of the chiller increases
about 33.5% (e.g., the fan speed decreases 32% and the compressor
speed increases about 4%), the discharge superheat gains about one
degree (Fahrenheit). Testing and/or simulation also show that in
one embodiment, for a screw compressor in an air cooled chiller,
from a baseline configuration, when the power consumption of the
chiller increases about 68% (e.g., the fan speed decreases 43% and
the compressor speed increases about 8%), the discharge superheat
gains about four degrees (Fahrenheit). In an embodiment, the
baseline configuration is based on the chiller operating at target
efficiency (e.g., optimal efficiency achieved by determining a fan
speed by minimizing total (e.g., compressor and fan) power
consumption at a certain operating load and/or capacity of the
chiller).
[0216] FIG. 10 shows a relationship between the system pressure
differential and the ambient temperature, according to one
embodiment. In FIG. 10, the vertical coordinate is the system
pressure differential (unit psid), and the horizontal coordinate is
the ambient temperature. The solid line represents a fan control
curve to achieve the maximum unit efficiency (but the lubricant
characteristics (such as lubricant quality) are low because of,
e.g., low discharge superheat). The dotted lines represent fan
control curves to achieve lower (and/or further lower) unit
efficiency (compared with the maximum unit efficiency) but the
lubricant characteristics are improved (and/or further improved)
because of, e.g., increased discharge superheat.
[0217] It will be appreciated that as soon as the fan control is
changed from target lubricant characteristics control to target
efficiency control, the dotted lines transition/merge into the
solid line. It will be appreciated that lubricant characteristics
can be a function of discharge superheat. For any given saturated
discharge temperature, the lubricant characteristics improve as the
discharge superheat improves/increases.
[0218] With regard to the foregoing description, it is to be
understood that changes may be made in detail, without departing
from the scope of the present invention. It is intended that the
specification and depicted embodiments are to be considered
exemplary only, with a true scope and spirit of the invention being
indicated by the broad meaning of the claims.
[0219] Aspects:
[0220] Any of aspects 1-7 can be combined with any of aspects 8-14.
It is understood that any of aspects 1-14 can be combined with any
other aspects recited herein.
[0221] Aspect 1. A method of controlling condenser fans in a
heating, ventilation, and air conditioning (HVAC) system,
comprising: obtaining, by a controller, a measurement of a
measureable parameter of the HVAC system; determining, by the
controller, a differential pressure between a condenser and an
evaporator based on the measurement and a predetermined threshold;
outputting, by the controller, a fan speed suitable to achieve the
differential pressure determined; and controlling one or more
condenser fans based on an output of the fan speed to obtain a fan
capacity suitable to control the one or more condenser fans, such
that power of the HVAC system is managed through a power consumed
by a compressor and the one or more condenser fans, wherein the
measureable parameter is indicative of lubricant
characteristics.
[0222] Aspect 2. The method of aspect 1, wherein the measureable
parameter is one of a discharge superheat of the compressor, a
viscosity of lubricant used in the HVAC system, or a kappa value of
the lubricant.
[0223] Aspect 3. The method of aspect 1 or aspect 2, wherein the
compressor is a variable speed compressor or a variable load
compressor.
[0224] Aspect 4. The method of any one of aspects 1-3, wherein the
one or more condenser fans are variable speed fans or fans with fan
stages.
[0225] Aspect 5. The method of any one of aspects 1-4, wherein the
measurement is an integral of measured values of the measureable
parameter over a predetermined period of time.
[0226] Aspect 6. The method of any one of aspects 1-5, further
comprising: determining a second differential pressure between the
condenser and the evaporator based on a measured ambient air
temperature and an obtained present load on the compressor, wherein
if the measurement is less than the predetermined threshold, the
differential pressure is set to greater than the second
differential pressure.
[0227] Aspect 7. The method of any one of aspects 1-6, further
comprising: determining a second differential pressure between the
condenser and the evaporator based on a measured ambient air
temperature and an obtained present load on the compressor, wherein
if the measurement is no less than the predetermined threshold, the
differential pressure is set to the second differential
pressure.
[0228] Aspect 8. A heating, ventilation, and air conditioning
(HVAC) system, comprising: a compressor; an evaporator fluidly
connected to the compressor; a condenser fluidly connected to the
compressor; the condenser including one or more condenser fans; a
controller operatively connected to a device to measure a
measureable parameter of the HVAC system, configured to obtain a
measurement of the measureable parameter, and operatively connected
to the condenser including the one or more condenser fans; the
controller configured to determine a differential pressure between
the condenser and the evaporator based on the measurement and a
predetermined threshold, the controller configured to determine of
a fan speed suitable to achieve the differential pressure
determined, and the controller configured to operate the one or
more condenser fans based on an output of the fan speed to obtain a
fan capacity suitable to control the one or more condenser fans,
such that the power of the HVAC system is managed through power
consumed by the compressor and the one or more condenser fans,
wherein the measureable parameter is indicative of lubricant
characteristics.
[0229] Aspect 9. The system of aspect 8, wherein the measureable
parameter is one of a discharge superheat of the compressor, a
viscosity of lubricant used in the HVAC system, or a kappa value of
the lubricant.
[0230] Aspect 10. The system of aspect 8 or aspect 9, wherein the
compressor is a variable speed compressor or a variable load
compressor.
[0231] Aspect 11. The system of any one of aspects 8-10, wherein
the one or more condenser fans are variable speed fans or fans with
fan stages.
[0232] Aspect 12. The system of any one of aspects 8-11, wherein
the measurement is an integral of measured values of the
measureable parameter over a predetermined period of time.
[0233] Aspect 13. The system of any one of aspects 8-12, wherein if
the measurement is less than the predetermined threshold, the
differential pressure is set to greater than a second differential
pressure between the condenser and the evaporator, the second
differential pressure is based on a measured ambient air
temperature and an obtained present load on the compressor.
[0234] Aspect 14. The system of any one of aspects 8-13, wherein if
the measurement is no less than the predetermined threshold, the
differential pressure is set to a second differential pressure
between the condenser and the evaporator, the second differential
pressure is based on a measured ambient air temperature and an
obtained present load on the compressor.
[0235] Methods and systems for controlling condenser fans in a
heating, ventilation, and air conditioning (HVAC) system are
provided. The method includes obtaining, by a controller, a
measurement of a measureable parameter of the HVAC system. The
method also includes determining, by the controller, a differential
pressure between a condenser and an evaporator based on the
measurement and a predetermined threshold. The method further
includes outputting, by the controller, a fan speed suitable to
achieve the differential pressure determined. Also the method
includes controlling one or more condenser fans based on an output
of the fan speed to obtain a fan capacity suitable to control the
one or more condenser fans, such that power of the HVAC system is
managed through a power consumed by a compressor and the one or
more condenser fans.
[0236] Heat Transfer Circuit with Increased Compressor Suction
Heat, and Operating Method Thereof (FIGS. 11-16)
[0237] AN HVACR system can include a heat transfer circuit
configured to heat or cool a process fluid (e.g., air, water and/or
glycol, or the like). A working fluid is circulated through the
heat transfer circuit. The heat transfer circuit includes a
compressor for compressing the working fluid. The working fluid and
process fluid separately flow through a heat exchanger to cool or
heat the process fluid. The heat exchanger may be a condenser or an
evaporator.
[0238] The working fluid is heated by a first heating that occurs
due to heat exchange between the working fluid and the process
fluid. A flow path of the working fluid through the heat transfer
circuit includes a suction stream. The suction stream extends from
a location where a first heating occurs to the suction inlet of the
compressor. The suction stream includes a heat source. The heat
source is configured to heat the working fluid flowing through the
suction stream. The heat source provides a second heating of the
working fluid after the first heating.
[0239] In an embodiment, the working fluid includes one or more
refrigerants.
[0240] In an embodiment, the heat source is disposed after the
evaporator and before the compressor. The heat source heats the
working fluid within the suction stream as it flows from the
evaporator to the compressor.
[0241] In an embodiment, the heat source is located in the
evaporator. The heat source is located between the location of the
first heating and the outlet of the evaporator. The heat source
heats the working fluid after it has been heated by the process
fluid and before it exits the evaporator.
[0242] In an embodiment, high temperature compressed working fluid
is discharged by the compressor and utilized by the heat source to
provide the heat for the second heating. The heat source is
configured so that at least a portion of the compressed working
fluid flows through the heat source. Working fluid in the suction
stream is heated as it flows through the heat source and absorbs
heat from the compressed working fluid also flowing through the
heat source. The heat source is configured to utilize the
compressed working fluid to heat the working fluid of the suction
stream.
[0243] In an embodiment, a method of operating a heat transfer
circuit includes heating a working fluid with a process fluid in an
evaporator. The method also includes heating the working fluid with
a heat source after the working fluid has been heated by the
process fluid.
[0244] A heating, ventilation, air conditioning, and refrigeration
system ("HVACR") is generally configured to heat and/or cool an
enclosed space (e.g., an interior space of a commercial building or
a residential building, an interior space of a refrigerated
transport unit, or the like). The HVACR system includes a heat
transfer circuit to heat or cool a process fluid (e.g., air, water
and/or glycol, or the like). A working fluid flows through the heat
transfer circuit and is utilized to heat or cool the process fluid.
In an embodiment, the working fluid includes one or more
refrigerants. The working fluid may heat and/or cool a process
fluid directly or indirectly. For example, indirect heating and/or
cooling may include the working fluid heating and/or cooling an
intermediate fluid (e.g., air, water and/or glycol, or the like),
and then the heated/cooled intermediate fluid heating and/or
cooling the process fluid.
[0245] There has been recent movement (e.g., the Kigali Amendment
to the Montreal Protocol, the Paris Agreement, United States'
Significant New Alternatives Policy ("SNAP")) to limit the types of
refrigerants utilized in HVACR systems as concern about
environmental impact (e.g., ozone depletion, global warming impact)
has increased. In particular, the movement has been to replace
ozone depleting refrigerants (e.g., chlorofluorocarbons (CFCs),
hydrochlorofluorocarbons (HCFCs), or the like) and high global
warming potential refrigerants with refrigerants that have a lower
environmental impact.
[0246] The replacement refrigerants are non-ozone depleting,
flammable or non-flammable, energy efficient, compatible with the
materials of the heat transfer circuit and its equipment, low in
toxicity, and chemically stable over the life of the equipment of
the heat transfer circuit. For example, previous refrigerants
having relatively higher GWPs such as R134a or the like, are being
replaced with refrigerants such as, but not limited to, R1234ze
(e.g., R1234ze(E)), R513A, and the like.
[0247] The heat transfer circuit includes a compressor that
compresses the working fluid. Lubricant is supplied to the
compressor to provide lubrication for its moving parts. A lubricant
may include one or more types of lubricants. For example, a
lubricant may be, but is not limited to, one or more polyolester
(POE) oils, mineral oils, or the like. The lubricant is discharged
from the compressor with the working fluid. Thus, the working fluid
discharged from the compressor contains lubricant. In some heat
transfer circuits, the lubricant is also separated from the working
fluid and the separated lubricant is circulated back to the
compressor. In other heat transfer circuits, the lubricant is
circulated with the working fluid and is then supplied through a
suction inlet of the compressor as part of the working fluid. The
working fluid may also include one or more additional components
other than lubricant(s) and refrigerant(s). For example, an
additional component may be, but is not limited to, impurities,
refrigeration system additives, tracers, ultraviolet ("UV") dyes,
and/or solubilizing agents.
[0248] Various issues may arise with the use of newer/replacement
refrigerants due to having different properties relative to
previous refrigerants such as R134a. For example, newer
refrigerants with lower GWPs such as R1234ze (e.g., R1234ze(E)),
R513A, and the like may be more soluble in the lubricant relative
to previous refrigerants such as R134a due to their chemical
structures. Accordingly, the lubricant provided back to the
compressor contains a higher concentration of refrigerant. The
higher concentration of refrigerant decreases the viscosity of the
lubricant, which reduces the amount of lubrication ("lubricity")
provided by the lubricant. In particular, when a compressor is
operated at certain operating conditions, the lubricant provided to
the bearings of the compressor may not provide adequate lubricity
due to the concentration of refrigerant in the lubricant being too
high. The compressor might be operated to avoid operation
conditions where lubricity of the lubricant becomes an issue.
However, this may result in being unable to use significant areas
of the operating map of a compressor that are most efficient for a
desired operation of the compressor (e.g., desired flow rate of
working fluid discharged by a compressor, a desired pressure for
the discharged working fluid, or the like). As such, the
incorporation and use of newer/replacement refrigerants may result
in compressors being operated in a less efficient manner to avoid
lubrication issues. Embodiments described herein are directed to
heat transfer circuits and methods of operating a heat transfer
circuit that help reduce and/or avoid such lubrication issues
without having to avoid specific operating conditions of a
compressor due to, for example, the use of newer/replacement
refrigerants.
[0249] FIG. 11 is a schematic diagram of a heat transfer circuit
4001 according to an embodiment. In an embodiment, the heat
transfer circuit 4001 may be employed in an HVACR system. The heat
transfer circuit 4001 includes a compressor 4010, a condenser 4020,
an expansion device 4030, an evaporator 4040, and a heat source
4050. Optionally, the heat transfer circuit 4001 may also include a
lubricant separator 4060 as shown in FIG. 11. In an embodiment, the
heat transfer circuit 4001 can be modified to include additional
components such as, for example, an economizer heat exchanger, one
or more flow control devices, a receiver tank, a dryer, a
suction-liquid heat exchanger, or the like.
[0250] The components of the heat transfer circuit 4001 are fluidly
connected. The heat transfer circuit 4001 can be configured as a
cooling system (e.g., a fluid chiller of an HVACR system, an air
conditioning system, or the like) that can be operated in a cooling
mode, or the heat transfer circuit 4001 may be configured to
operate as a heat pump system that can run in a cooling mode or a
heating mode.
[0251] A working fluid flows through the heat transfer circuit
4001. The flow path of the working fluid through the heat transfer
circuit 4001 extends from the compressor 4010 through the lubricant
separator 4060, the condenser 4020, the expansion device 4030, the
evaporator 4040, the heat source 4050, and back to the compressor
4010. The working fluid includes one or more refrigerants with a
lower environmental impact and may include one or more additional
components as discussed above. Dotted lines are provided in the
Figures to indicate fluid flows through the heat exchangers (e.g.,
condenser 4020, evaporator 4040), and should be understood as not
specifying specific flow paths for the fluid flows through the heat
exchangers. Dashed and dotted lines are provided in the Figures to
illustrate electronic communications between different features.
For example, a dashed dotted line extends between a temperature
sensor 4080 and a controller 4070 as the controller 4070 receives
temperatures readings from the temperature sensor 4080. For
example, a dashed dotted line extends from the controller 4070 to
the heat source 4050 as the controller 4070 can provide energy
and/or electronically control the heat source 4050 in an
embodiment.
[0252] Working fluid in a lower pressure gaseous state is drawn
into the suction inlet 4012 of the compressor 4010. In an
embodiment, the compressor 4010 is a screw compressor or a scroll
compressor. A screw compressor utilizes one or more rotating screws
to compress a gas. Trapped spaces are formed along the blades of
the screw(s) as the screw rotates. As the screw(s) rotate, a
trapped space is moved along a length of the screw and becomes
smaller. Gas in the trapped space is compressed as the trapped
space becomes smaller. The trapped space eventually rotates along
an opening and is released as compressed gas. A scroll compressor
includes at least one pair of scrolls. Each scroll includes a
baseplate and a wrap, and the wraps of the pair of scrolls are
intermeshed. One or both of the scrolls are moved such that the
scrolls orbit/rotate relative to each other. As the scrolls
orbit/rotate relative to each other, a trapped space between the
intermeshed wraps and the baseplates is moved along the intermeshed
wraps in a clockwise or counter-clockwise direction and becomes
smaller. The gas in the trapped space is compressed as the trapped
space becomes smaller. The trapped space eventually reaches an
outlet located along a diameter or central location of the
baseplates and is released as compressed gas.
[0253] In an embodiment, the lubricant for the bearings 4016 of the
compressor 4010 may be provided with the working fluid via the
suction inlet 4012 of the compressor 4010. In such an embodiment,
the compressor 4010 may also be a different type of compressor than
a screw or scroll compressor.
[0254] The working fluid is compressed as it flows from the suction
inlet 4012 to an outlet 4014 of the compressor 4010. The
compression of the working fluid in the compressor 4010 also
increases the temperature of the working fluid. Thus, the
compressed working fluid discharged from the outlet 4014 of the
compressor has a higher temperature. The compressor 4010 utilizes a
lubricant to lubricate its moving parts (e.g., rotor, bearings
4016). Lubricant mixes with the working fluid flowing through the
compressor 4010 such that the compressed working fluid discharged
from the compressor 4010 contains lubricant.
[0255] In an embodiment, the high pressure and temperature working
fluid flows from the outlet 4014 of compressor 4010 to the
lubricant separator 4060. The working fluid discharged from the
compressor 4010 includes a gaseous portion and a liquid portion.
The gaseous portion of the working fluid contains gaseous
refrigerant. The gaseous portion of the working fluid may also
contain entrained lubricant. The liquid portion contains lubricant
and refrigerant dissolved in the lubricant. The gaseous and liquid
portions of the working fluid may also include one or more
additional components, respectively, as discussed above. The
lubricant separator 4060 is configured to physically separate the
gaseous working fluid from the liquid lubricant. A primary
lubricant flow path 4062 fluidly connects the lubricant separator
4060 to the compressor 4010. The liquid lubricant is separated in
the lubricant separator 4060. The separated liquid lubricant then
flows back to the compressor 4010 from the lubricant separator 4060
through the primary lubricant flow path 4062. In an embodiment, the
separated lubricant is provided to the bearings 4016 of the
compressor 4010.
[0256] The higher pressure and temperature gaseous working fluid
flows from the lubricant separator 4060 to and through the
condenser 4020. A first process fluid PF.sub.1 also separately
flows through the condenser 4020. The condenser 4020 is a heat
exchanger that allows the working fluid and the first process fluid
PF.sub.1 to be in a heat transfer relationship within the condenser
4020 without physically mixing. As the working fluid and first
process fluid PF.sub.1 flow through the condenser 4020, the working
fluid is cooled by the first process fluid PF.sub.1. The process
fluid PF.sub.1 is heated by the working fluid and exits the
condenser 4020 at a higher temperature. In an embodiment, the first
process fluid PF.sub.1 may be air, water and/or glycol, or the like
that is suitable for absorbing and transferring heat from the
working fluid and the heat transfer circuit 4001. For example, the
first process fluid PF.sub.1 may be ambient air circulated from an
outside atmosphere, water to be heated as hot water, or a fluid for
transferring heat from the heat transfer circuit 4001. The working
fluid becomes liquid or mostly liquid as it is cooled in the
condenser 4020.
[0257] The liquid/gas working fluid flows from the condenser 4020
to the expansion device 4030. The expansion device 4030 allows the
working fluid to expand. The expansion causes the working fluid to
significantly decrease in temperature. In an embodiment, the
expansion device 4030 may be an expansion valve, expansion plate,
expansion vessel, orifice, the like, or other such types of
expansion mechanisms. It should be appreciated that the expansion
device 4030 may be any type of expander used in the field for
expanding a working fluid causing the working fluid to decrease in
temperature.
[0258] The lower temperature gaseous/liquid working fluid then
flows from the expansion device 4030 to and through the evaporator
4040. A second process fluid PF.sub.2 also flows through the
evaporator 4040 separately from the working fluid. The evaporator
4040 is a heat exchanger that allows the working fluid and the
second process fluid PF.sub.2 to be in a heat transfer relationship
within the evaporator 4040 without physically mixing. As the
working fluid and second process fluid PF.sub.2 flow through the
evaporator 4040, the working fluid absorbs heat from the second
process fluid PF.sub.2 cooling the second process fluid PF.sub.2.
In an embodiment, the evaporator 4040 may be a flooded evaporator
as described below with respect to FIG. 15. In an embodiment, the
working fluid exiting the evaporator 4040 may be at or about its
saturation temperature.
[0259] In an embodiment, the second process fluid PF.sub.2 is air
cooled by the HVACR system and ventilated to the enclosed space to
be conditioned. In an embodiment, the second process fluid PF.sub.2
may be an intermediate fluid (e.g., water, heat transfer fluid, or
the like) and the cooled second process fluid PF.sub.2 may then be
utilized by the HVACR system to cool air. The working fluid is
mostly gaseous as it exits the evaporator 4040.
[0260] In some embodiments, lubricant that was entrained in gaseous
working fluid exiting the lubricant separator 4060 is later
separated due to the temperature and/or pressure changes of the
working fluid as it flows to and/or through the evaporator 4040.
This separated lubricant may flow to a bottom of the evaporator
4040. In an embodiment, an optional secondary lubricant flow path
4064 may fluidly connect the evaporator 4040 to the compressor 4010
and allow the liquid lubricant in the evaporator 4040 to flow back
to the compressor 4010.
[0261] The mostly gaseous working fluid flows from the evaporator
4040 to and through the heat source 4050. The heat source 4050
further heats the working fluid. The heat source 4050 heats the
working fluid to increase the superheat of the working fluid.
Superheat is a measure of the temperature change relative to the
temperature at which the working fluid evaporates at a set pressure
(e.g.,
T(P.sub.x).sub.superheat=T(P.sub.x).sub.Actual-T(P.sub.x).sub.Saturation)-
. For example, increasing superheat of the working fluid is an
increase in the temperature of the working fluid to above the
saturation temperature at which the refrigerant(s) of the working
fluid change state from a liquid to vapor.
[0262] In an embodiment, the heat source 4050 in FIG. 11 is an
electrical heat source that generates heat from supplied
electricity. A suction pipe 4018 extends from outlet of the
evaporator 4040 to the suction inlet 4012 of the compressor 4010.
In an embodiment, the suction pipe 4018 may include one or more
sections or portions (i.e. not be a single continuous length of
pipe). In an embodiment, the heat source 4050 contacts an outside
surface of the suction pipe 4018. In such an embodiment, the heat
source 4050 may be wrapped around the suction pipe 4018. In an
embodiment, the heat source 4050 may be located within the suction
pipe 4018. The heat source 4050 being disposed outside of the
suction pipe 4018 may be advantageous as the heat source 4050 is
not located in the flow path of the working fluid and can avoid
causing a pressure drop.
[0263] The flow path of the working fluid through the heat circuit
4001 includes a suction stream. The suction stream is disposed
after the location where the working fluid is heated by the second
process fluid PF.sub.2 and before the compressor 4010. In an
embodiment, the suction stream extends from a location after where
the working fluid is heated by the second process fluid PF.sub.2 to
the suction inlet 4012 of the compressor 4010. In an embodiment,
the suction stream extends from the evaporator 4040 to the suction
inlet 4012 of the compressor 4010. In FIG. 11, the suction stream
includes the heat source 4050 and the suction pipe 4018. In an
embodiment, the heat transfer circuit 4001 may include additional
components (one or more pipes, flow control device(s), a receiver
tank, a dryer, or the like) disposed between the evaporator 4040
and the compressor 4010. In such an embodiment, the suction stream
may also include such additional components. The heat source 4050
is configured to provide heat to and increase the temperature of
the working fluid flowing through the suction stream (i.e. increase
the suction temperature T.sub.1).
[0264] The temperature of the working fluid entering the compressor
4010 ("suction temperature T.sub.1") is increased by the heat
source 4050. The heat source 4050 increases the temperature of the
working fluid as it flows through the suction stream. The increase
of the suction temperature T.sub.1 causes an increase in a
temperature T.sub.2 of the compressor 4010 itself and the
temperature T.sub.3 of the working fluid exiting the compressor
4010 ("discharge temperature T.sub.3").
[0265] As discussed above, the working fluid discharged from the
compressor 4010 includes liquid lubricant. The lubricant is
circulated back to the compressor 4060. In FIG. 11, the lubricant
is separated in the lubricant separator 4060 and separately
circulated back to the compressor 4010 (e.g., through primary
lubricant flow path 4062). However, the heat transfer circuit 4001
in an embodiment may not include the lubricant separator 4060. In
an embodiment, the lubricant may be configured to be circulated
back to the compressor 4010 as part of the working fluid without
being separated with a lubricant separator 4060. In such an
embodiment, the lubricant may enter through the suction inlet 4012
of the compressor 4010 as part of the working fluid.
[0266] As discussed above, the lubricant may contain dissolved
refrigerant that decreases the lubricity of the lubricant, which
has a negative impact on the efficiency of the compressor 4010 and
the heat transfer circuit 4001. Additionally, the separated
lubricant is at a higher pressure after the lubricant separator
4060 in FIG. 11. As discussed above, the working fluid is
compressed as it flows through the compressor 4010 from the suction
inlet 4012 to the outlet 4014. For example, the working fluid has
its highest pressure at the outlet 4014 of the compressor 4010. The
lubricant may be provided to the compressor 4010 at a location
before the outlet 4014. Accordingly, the lubricant undergoes a
pressure drop as it goes from a higher pressure to a lower
pressure. The pressure drop liberates at least some of the
refrigerant dissolved in the lubricant. The liberation of the
refrigerant in the lubricant allows the refrigerant to expand and
thereby cool the lubricant. This temperature decrease of the
lubricant further decreases the lubricity of the lubricant,
reducing and/or countering the increased lubricity caused by the
lubricant having a lower concentration of refrigerant.
[0267] The increase in the temperature T.sub.2 of the compressor
4010 increases the temperature of the lubricant flowing through the
compressor 4010. This can reduce and/or counter the temperature
decrease caused by the refrigerant being liberated due to the
pressure drop. Accordingly, the lubricant has a decreased
concentration of refrigerant due to the pressure drop while no
longer having a reduced temperature due to the liberation of
refrigerant caused by the pressure drop. This advantageously
reduces and/or prevents the lowered lubricity caused by dissolved
refrigerant while also reducing and/or preventing a temperature
decreased that also decreases the lubricity of the lubricant.
[0268] The concentration of refrigerant in the lubricant separated
in the lubricant separator 4060 is based on temperature and
pressure. A higher temperature causes a lower concentration of
refrigerant to be dissolved in the lubricant. Thus, an increase in
the discharge temperature T.sub.3 of the working fluid results in
the separated lubricant having a lower concentration of
refrigerant. The increased discharge temperature T.sub.3 causes the
separated lubricant supplied back to the compressor 4010 from the
lubricant separator 4060 to advantageously have an increased
viscosity and lubricity due to its lower concentration of
refrigerant.
[0269] The heat transfer circuit 4001 includes a circuit controller
4070 that controls the heat output of the heat source 4050. In an
embodiment, the circuit controller 4070 controls a heat output of
the heat source 4050 based on at least one of the suction
temperature T.sub.1, the discharge temperature T.sub.3, and/or a
temperature of the second process fluid PF.sub.2 after the passing
through the evaporator 4040 ("second process fluid exit temperature
T.sub.4"). In an embodiment, a desired temperature for the second
process fluid exit temperature T.sub.4 may be at or about
10.degree. F. to at or about 75.degree. F. In an embodiment, a
desired temperature for the second process fluid exit temperature
T.sub.4 may be at or about 44.degree. F. In an embodiment, the
circuit controller 4070 may be an HVACR controller for controlling
operation of the HVACR system.
[0270] In an embodiment, the circuit controller 4070 may control
the heat provided by the heat source 4050 to the working fluid so
that the suction temperature T.sub.1 is within a desired
temperature range. In an embodiment, the heat transfer circuit 1
may be configured so that the working fluid entering the suction
inlet 4012 contains the lubricant for lubricating the compressor
4010. For example, a desired temperature range for the suction
temperature T.sub.1 in an embodiment may be based on one or more of
a chemical degradation temperature of the lubricant, a minimum
efficiency for the compressor 4010, and/or the concentration of
lubricant in the liquid portion of the working fluid entering the
suction inlet 4012. In an embodiment, the desired temperature for
the suction inlet temperature T.sub.1 may be at or about 0.degree.
F. to at or about 70.degree. F. In an embodiment, the desired
temperature for the suction inlet temperature T.sub.1 may be at or
about 40.degree. F. In an embodiment, the superheat of the working
fluid entering the compressor 4010 may be at least 6.degree. F.
(e.g., T.sub.1-T.sub.sat.gtoreq.6.degree. F.). In an embodiment,
the superheat of the working fluid entering the compressor 4010 may
at or about 6.degree. F. to at or about 15.degree. F. (e.g.,
15.degree. F..gtoreq.(T.sub.1-T.sub.sat).gtoreq.6.degree. F.).
[0271] In an embodiment, the circuit controller 4070 may control
the heat output of the heat source 4050 so that the discharge
temperature T.sub.3 is within a desired temperature range. For
example, a desired temperature range for the discharge temperature
T.sub.3 may be based on one or more of a chemical degradation
temperature of the lubricant, a minimum efficiency for the
compressor 4010, and/or a concentration of the lubricant in the
liquid portion of the working fluid discharged from the compressor
4010. In an embodiment, a desired temperature for the discharge
temperature T.sub.3 may be at or about 60.degree. F. to at or about
180.degree. F. In an embodiment, a desired temperature for the
discharge temperature T.sub.3 may be at or about 125.degree. F. In
an embodiment, the discharge temperature T.sub.3 may be controlled
so that the separated lubricant provided to the bearings 4016 has a
lubricant concentration of 70% or greater.
[0272] The circuit controller 4070 in FIG. 11 utilizes a sensor
4080 to detect the suction inlet temperature T.sub.1, a sensor 4082
to detect the discharge temperature T.sub.3, a sensor 4084 to
detect the second process fluid exit temperature T.sub.4, and a
sensor 4086 to detect the temperature T.sub.2 of the compressor
4010. In an embodiment, the heat transfer circuit 4001 may include
one or more sensors (e.g., sensor 4080, sensor 4082, sensor 4084,
sensor 4086, or the like) as suitable and/or desired for
controlling the heat source 4050 to provide the desired amount of
heat to the working fluid as discussed above.
[0273] FIG. 12 is a schematic diagram of a heat transfer circuit
4100 according to an embodiment. In an embodiment, the heat
transfer circuit 4100 may be employed in an HVACR system. The heat
transfer circuit 4100 is similar to the heat transfer circuit 4001
in FIG. 11, except with respect to a heat source 4150 and the flow
of working fluid between the lubricant separator 4160 and the
condenser 4120. For example, the heat transfer circuit 4100
includes a compressor 4110, the optional lubricant separator 4160,
the condenser 4120, an expansion device 4130, and an evaporator
4140. The condenser 4120 utilizes a first process fluid PF.sub.1 to
cool the working fluid, and the evaporator 4140 utilizes the
working fluid to cool a second process fluid PF.sub.2 similar to
the heat transfer circuit 4001 in FIG. 11. In an embodiment, the
evaporator 4140 may be a flooded evaporator as described below with
respect to FIG. 15. In an embodiment, the working fluid exiting the
evaporator 4140 may be at or about its saturation temperature.
[0274] The heat source 4150 is configured to increase the suction
temperature T.sub.1 of the working fluid entering the compressor
4110 similar to the heat source 450 in FIG. 11. As shown in FIG.
12, the heat source 4150 is a heat exchanger with a first side 4152
and a second side 4154. It should be understood that "side" refers
to a separate flow passageway through the heat source 4150, and not
to a particular physical orientation. Fluids in the first side 4152
and second side 4154 of the heat source 4150 exchange heat but do
not mix. Working fluid from the evaporator 4140 flows to the heat
source 4150, through the first side 4152, and from the heat source
4150 to the compressor 4110. A first passageway 4156 and second
passageway 4158 extend from opposite ends of the second side 4154.
A portion of the compressed working fluid exiting the lubricant
separator 4160 flows into the first passageway 4156, through the
second side 4154 of the heat source 4150, through the second
passageway 4158, and to the condenser 4120. A second portion of the
compressed working fluid exits the lubricant separator 4160, flows
past the first and second passageways 4156, 4158, and to the
condenser 4120. The end 4159 of the second passageway 4158 opposite
to the heat source 4150 is fluidly connected downstream of the end
4157 of the first passageway 4156 opposite to the heat source
4150.
[0275] In FIG. 12, the first passageway 4156 and second passageway
4158 are connected between the lubricant separator 4160 and the
condenser 4120. However, the first passageway 4156 and/or the
second passageway 4158 in an embodiment may be connected at a
different location than shown in FIG. 12. In an embodiment, the
first passageway 4156 may be connected between the compressor 4110
and the expansion device 4130. In an embodiment, the first
passageway 4156 may be connected between the compressor 4110 and
the lubricant separator 4160. In another embodiment, the first
passageway 4156 may be connected between the condenser 4120 and the
expansion device 4130. In such an embodiment, a portion of the
compressed working fluid discharged from the compressor 4110 would
flow from the lubricant separator 4160, through the condenser 4120,
through the heat source 4150, then enter then expansion device
4130.
[0276] In an embodiment, the second passageway 4158 may be
connected at a different location. In an embodiment, the second
passageway 4158 may be connected between the condenser 4120 and the
expansion device 4130. In an embodiment, the second passageway 4158
may be connected between the expansion device 4130 and the
evaporator 4140, and may include a second expansion device to
provide an expansion to the working fluid flowing through the
second passageway 4158 similar to the expansion device 4130. In an
embodiment, the portion of compressed working fluid may flow from
the heat source 4050, through the second expansion device, and to
the evaporator 4140, bypassing the expansion device 4130. In such
embodiments, the compressed working fluid flowing through the heat
source 4050 may bypass one or both of the condenser 4120 and the
expansion device 4130.
[0277] As discussed above, the working fluid increases in
temperature as the working fluid is compressed in the compressor
4110. Accordingly, the working fluid discharged from the compressor
4110 has a higher temperature and pressure. The heat source 4150
utilizes the higher temperature compressed working fluid to heat
the working fluid flowing from the evaporator 4140 to the
compressor 4110. Utilizing the compressed working fluid in the heat
source 4150 may be advantageous as the heat source 4150 does not
require additional heat (e.g., heat generated from electricity,
heat provided by an external process fluid or fluid circuit) to be
added to the heat transfer circuit 4100.
[0278] The heat transfer circuit 4100 includes a circuit controller
4170. A control valve 4155 regulates the flow rate of the
compressed working fluid through the second side 4154 of the heat
source 4150. The circuit controller 4170 controls the heat provided
to the working fluid flowing through the first side 4152 of the
heat source 4150 using the control valve 4155. In an embodiment,
the circuit controller 4170 may be an HVACR controller of the HVACR
system.
[0279] The amount of heat provided to the working fluid flowing
through the heat source 4150 may be controlled in a similar manner
as discussed regarding the heat source 4050 in FIG. 11. For
example, the circuit controller 4170 may control the amount of heat
provided to the working fluid flowing through the first side 4152
of the heat source 4150 based on at least one of the suction
temperature T.sub.1, the discharge temperature T.sub.3, and/or the
second process fluid exit temperature T.sub.4. In an embodiment,
the heat transfer circuit 4100 may include one or more sensors
(e.g., sensor 4180, sensor 4182, sensor 4184, sensor 4186, and the
like) as suitable and/or desired for the heat source 150 to provide
the desired amount of heat to the working fluid as discussed
above.
[0280] The heat source 4150 in FIG. 12 is an active system.
However, it should be appreciated that the heat source 4150 in FIG.
12 may be configured as a passive system. In an embodiment, heat
transfer circuit 4100 may be configured so that the working fluid
exits the evaporator 4140 within a set temperature range, and the
flow rate of compressed working fluid through the heat source 4150
is a set amount or within a set range so that the working fluid
reaches a desired temperature (e.g., suction temperature T.sub.1 is
above a desired temperature) as discussed above.
[0281] The heat source 4150 in FIG. 12 utilizes the compressed
working fluid. However, it should be appreciated that the heat
source 4150 may utilize a different fluid to heat the working fluid
flowing through the first side 4152 instead of the compressed
working fluid. In an embodiment, the heat source 4150 may utilize
the first process fluid PF.sub.1, the second process fluid
PF.sub.2, or a third process fluid (e.g., hot air, hot water, or
the like) that flows through the second side 4154 to heat the
working fluid. In an embodiment, a portion of the second process
fluid PF.sub.2, before entering the evaporator 4140, may flow
through the second side 4154 of the heat source 4150 instead of the
compressed working fluid. The portion of the second process fluid
PF.sub.2 may then flow through the evaporator 4140 or bypass the
evaporator 4140 before joining the rest of the second process fluid
PF.sub.2. In another embodiment, the first process fluid PF.sub.1
(or a portion of the first process fluid PF.sub.1) after being
heated in the condenser 120 may flow through the second side 4154
of the heat source 4150 instead of the compressed working
fluid.
[0282] In FIG. 12, the lubricant is separated in the lubricant
separator 4160 and separately circulated back to the compressor
4110. However, the heat transfer circuit 4100 in an embodiment may
not include the lubricant separator 4160. In an embodiment, the
lubricant may be configured to be circulated back to the compressor
4010 as part of the working fluid without being separated with a
lubricant separator 4060. In such an embodiment, the lubricant may
enter through the suction inlet 4012 of the compressor 4010 as part
of the working fluid.
[0283] The flow path of the working fluid through the heat circuit
4100 includes a suction stream. The suction stream is disposed
after the location where the working fluid is heated by the second
process fluid PF.sub.2 and before the compressor 4110. In an
embodiment, the suction stream extends from a location after where
the working fluid is heated by the second process fluid PF.sub.2 to
the suction inlet 4112 of the compressor 4110. In an embodiment,
the suction stream extends from the evaporator 4140 to the suction
inlet 4112 of compressor 4110. In FIG. 12, the suction stream
includes the heat source 4150, the pipe that fluidly connects the
evaporator 4140 to the heat source 4150, and the suction pipe that
fluidly connects the heat source 4150 to the suction inlet 4112 of
the compressor 4110. In an embodiment, the heat transfer circuit
4100 may include additional components (one or more pipes, flow
control device(s), a receiver tank, a dryer, or the like) disposed
between the evaporator 4140 and the compressor 4110. In such an
embodiment, the suction stream may also include such additional
components. The heat source 4150 is configured to provide heat to
and increase the temperature of the working fluid flowing through
the suction stream (i.e. increase the suction temperature
T.sub.1).
[0284] FIG. 13 is a schematic diagram of a heat transfer circuit
4200 according to an embodiment. In an embodiment, the heat
transfer circuit 4200 may be employed in an HVACR system. The heat
transfer circuit 4200 is similar to the heat transfer circuit 4100
in FIG. 12, except with respect to fluid utilized by the heat
source 4250 for heating the working fluid. For example, the heat
transfer circuit includes a compressor 4210, an optional lubricant
separator 4260, a condenser 4220, an expansion device 4230, an
evaporator 4240, and a circuit controller 4270.
[0285] Similar to the heat transfer circuit 4100, the flow path of
the working fluid through the heat circuit 4100 includes a suction
stream. The suction stream is disposed after the location where the
working fluid is heated by the second process fluid PF.sub.2 in the
evaporator 240 and before the compressor 4110. The suction stream
includes the heat source 4250. The heat source 4250 is disposed in
the suction stream between the evaporator 4240 and the compressor
4210. The heat source 4250 is configured to heat the gaseous or
mostly gaseous working fluid as it flows from the evaporator 4240
to the compressor 4210.
[0286] The heat source 4250 is a heat exchanger that includes a
first side 4252 and a second side 4254. The working fluid from the
evaporator 4240 flows to the heat source 4250, through the first
side 4252, and from the heat source 4250 to the compressor 4210.
The heat source 4250 is fluidly connected to a secondary cooling
circuit 4290. In an embodiment, the secondary cooling circuit 4290
may be for cooling electronics. For example, the electronics may be
the electronics of the compressor 4210 or an HVACR system of the
heat circuit 4200. The secondary cooling circuit 4290 utilizes a
working fluid to provide cooling. The working fluid provides
cooling by absorbing heat. The working fluid of the secondary
cooling circuit 4290 is provided to the heat source 4250 as a third
process fluid. In an embodiment, the third process fluid may be
and/or include air, water, refrigerant(s), or the like. The third
process fluid has an elevated temperature as it absorbs heat to
provide cooling in the secondary cooling circuit 4290. The third
process fluid having a temperature sufficient for superheating the
working fluid flowing through the heat source 4250.
[0287] A first passageway 4256 and a second passageway 4258 extend
from opposite ends of the second side 4254 and fluidly connect the
second side 4254 of the heat source 4250 to the secondary cooling
circuit 4290. The third fluid flows from secondary cooling circuit
4290 into the first passageway 4256, through the second side 4254
of the heat source 4250, through the second passageway 4258, and
back to secondary cooling circuit 4290. As similarly discussed
above regarding the heat source 4150 in FIG. 12, the third fluid
flowing through the second side 4254 is configured to superheat the
gaseous or mostly gaseous working fluid as it flows through the
heat source 4250.
[0288] The heat transfer circuit 4200 may include a control valve
4255 regulates the flow rate of the third fluid through the second
side 4254 of the heat source 4250. In a similar manner as discussed
above regarding the circuit controller 4170 in FIG. 12, the circuit
controller 4270 may control the heat provided to the working fluid
flowing through the first side 4252 of the heat source 4250 using
the control valve 4255. In an embodiment, the circuit controller
4270 may be an HVACR controller of the HVACR system. In another
embodiment, the heat transfer circuit 4200 may be a passive system
as similar discussed above and may not include/utilize the control
valve 4255.
[0289] FIG. 14 is a schematic diagram of a heat transfer circuit
4300 according to an embodiment. In an embodiment, the heat
transfer circuit 4300 may be employed in an HVACR system. The heat
transfer circuit 4300 is similar to the heat transfer circuit 4100
in FIG. 12, except with respect to the heat source 4350. For
example, the heat transfer circuit 4300 includes a compressor 4310,
an optional lubricant separator 4360, a condenser 4320, an
expansion device 4330, and an evaporator 4340.
[0290] The evaporator 4340 includes an inlet 4342 and an outlet
4344. FIG. 15 shows a diagram of the flow of the working fluid
through the evaporator 4340 in an embodiment. The working fluid
from the expansion device 4330 enters the evaporator 4340 through
the inlet 4342 and exits the evaporator 4340 through the outlet
4344. FIG. 15 illustrates an exemplary flow path FP of the working
fluid through the evaporator 4340. The working fluid flows from the
inlet 4342 of the evaporator 4340, past a set of heat exchanger
tubes 4346, past the heat source 4350, and then to the outlet 4344
of evaporator 4340. The heat exchanger tubes 4346 are configured to
evaporate the liquid working fluid. The heat source 4350 is
configured to provide additional heat to the evaporated (or mostly
evaporated) working fluid to superheat the working fluid. In an
embodiment, the evaporator 4340 may be a flooded heat exchanger. In
such an embodiment, the liquid working fluid pools in the bottom of
the evaporator 4340, and some of the heat exchanger tubes 4346
extend through the pool of liquid working fluid. For example, as
shown in FIG. 15, an upper surface 4353 of the pooled working fluid
in the evaporator 4340 may be above all of the heat exchanger tubes
4346. During operation, location of the upper surface 4353 (e.g.,
level) of the pooled working fluid may vary. For example, the upper
surface 4353 may lower such that some of the heat exchanger tubes
4346 are not submerged in the pooled liquid working fluid.
[0291] The second process fluid PF.sub.2 flows through the heat
exchanger tubes 4346. The second process fluid PF.sub.2 is
configured to heat the pooled liquid working fluid in the
evaporator 4340 and continuously evaporate the liquid working
fluid. Once evaporated, the working fluid flows towards the outlet
4344. In an embodiment, the heat exchanger tubes 4346 are
configured to heat the working fluid to at or about its saturation
temperature as the heat exchanger tubes 4346 provide a sufficient
amount of heat to evaporate the liquid working fluid.
[0292] As shown in FIG. 15, the heat source 4350 in an embodiment
is another set of heat exchanger tubes 4351. The first passageway
4356 is fluidly connected to the inlets of the heat exchanger tubes
4351 and the second passageway 4358 is fluidly connected to the
outlets of the heat exchanger tubes 4351. The passageways 4356,
4358 allow a portion of the compressed working discharged by the
compressor 4310 to pass through the heat exchanger tubes 4351
before the compressed working fluid flows to the condenser 4320 and
the expansion device 4330.
[0293] The process fluid PF.sub.2 flows through the heat exchanger
tubes 4346. The compressed working fluid flows through the next set
of heat exchanger tubes 4351. In an embodiment, the set of heat
exchanger tubes 4351 are spaced apart from the set of heat
exchanger tubes 4346. For example, as shown in FIG. 15, a space
(e.g., an open space) may be provided between the set of heat
exchanger tubes 4346 and the set of heat exchanger tubes 4351 along
the flow path 4351 of the working fluid. The working fluid is
heated as it flows past the heat exchanger tubes 4346 and absorbs
heat from the flowing process fluid PF.sub.2. The heat exchanger
tubes 4346 configured to evaporate the liquid working fluid. The
heated working fluid is then heated further as it flows past the
heat exchanger tubes 4351 and absorbs heat from the compressed
working fluid. The heat exchanger tubes 4351 are configured to heat
the gaseous or mostly gaseous working fluid. For example, the heat
exchanger tubes 4351 are configured to be above the upper surface
4353 of the working fluid (e.g., not be submerged in liquid working
fluid) during normal operation of the evaporator 4340.
[0294] As shown in FIG. 14, the heat transfer circuit 4300 includes
a circuit controller 4370. The amount of heat provided by the heat
source 4350 to the working fluid flowing past the heat exchanger
tubes 4351 is controlled by the circuit controller 370 in a similar
manner as discussed above regarding the heat source 4050 in FIG.
11. For example, the circuit controller 4370 may control the amount
of heat provided by the heat source 4350 to the working fluid
flowing past the heat exchanger tubes 4351 based on at least one of
the suction temperature T.sub.1, the discharge temperature T.sub.3,
and/or the second process fluid exit temperature T.sub.4. The
circuit controller 4370 controls the heat provided by the heat
source 4350 using the control valve 4355 to adjust the flow rate of
compressed working fluid through the heat exchange tubes 4351.
[0295] As shown in FIG. 14, the evaporator 4340 includes a
temperature sensor 4388. The temperature sensor 4388 is configured
to detect a temperature of the working fluid as it exits the
evaporator 4340 ("evaporator outlet temperature T.sub.5"). The heat
transfer circuit 4300 in FIG. 14 does not include any components
that heat or cool the working fluid between the evaporator 4340 and
the compressor 4310. Accordingly, the suction temperature T.sub.1
would be the same as the evaporator outlet temperature T.sub.5, and
the sensor 4388 may be for detecting the suction temperature
T.sub.1 instead of sensor 4380. In an embodiment, the heat transfer
circuit 4300 may include one or more sensors (e.g., sensor 4380,
sensor 4382, sensor 4384, sensor 4386, sensor 4388, or the like) as
suitable and/or desired for controlling the heat source 4350 to
generate the desired heat output as discussed above.
[0296] The heat source 4350 in the heat transfer circuit 4300 is an
active system. However, it should be appreciated that the heat
transfer circuit 4300 and the heat source 4350 may be configured to
be a passive system as similarly discussed above regarding the heat
transfer circuit 4100 in FIG. 12. In such an embodiment, circuit
controller 4370 may not actively operate the heat output of the
heat source 4350.
[0297] In an embodiment, the passageways 4356, 4358 are connected
to the flow path of the working fluid between the lubricant
separator 4360 and the condenser 4320. However, one or both of the
passageways 4356, 4358 may be connected at a different location
than shown in FIG. 14 as similarly discussed above regarding the
passageways 4156, 4158 in FIG. 12. In an embodiment, the
passageways 4356, 4358 are connected after the compressor 4310 and
before the expansion device 4330.
[0298] The heat source 4350 in FIGS. 14 and 15 is the heat
exchanger tubes 4351 through which the compressed working fluid
flows. However, the hot fluid flowing through the heat source 4350
in an embodiment may be the first process fluid PF.sub.1, the
second process fluid PF.sub.2, or a third process fluid (e.g., hot
water, hot air, fluid from a secondary cooling circuit, or the
like) instead of the compressed working fluid as similarly
discussed above regarding the heat source 4150 in FIG. 12 and the
heat source 4250 in FIG. 13. In such an embodiment, the first
passageway 4356 and the second passageway 4358 would not be fluidly
connected to the flow path of the working fluid.
[0299] Different steams of fluid flow through heat exchanger tubes
4346 and the heat exchanger tubes 4351. In an embodiment, the
streams of fluid flowing through the heat exchanger tubes 4346 and
the heat exchanger tubes 4351 may be the same type of fluid. In an
embodiment, the type of fluid flowing through the heat exchanger
tubes 4351 may be the second process fluid PF.sub.2 instead of
compressed working fluid. A main stream of second process fluid
PF.sub.2 is supplied from a source (e.g., a duct system of an
HVACR, an intermediate heat exchange circuit, or the like) (not
shown) to the heat circuit 4300. For example, a portion of the main
stream of second process fluid PF.sub.2 branches off and flows
through the heat exchanger tubes 4351 of the heat source 4350. The
remaining portion of the main stream of second process fluid
PF.sub.2 flows through the heat exchanger tubes 4346. The portion
of the main stream of second process fluid PF.sub.2 may rejoin the
remaining portion of the main stream after the remaining portion
has flowed through the heat exchanger tubes 4346. Alternatively,
the portion of the main stream of second process fluid PF.sub.2 may
rejoin the remaining portion of the main stream before the heat
exchanger tubes 4346, such that both portions flow through the heat
exchanger tubes 4346. In another example, the main stream of the
second process fluid PF.sub.2 flows through the heat exchanger
tubes 4351 and then flows through the heat exchanger tubes
4346.
[0300] In another embodiment, the type of fluid flowing through the
heat exchanger tubes 4351 may be the first process fluid PF.sub.1
instead of compressed working fluid. The first process fluid
PF.sub.1 flowing through the condenser 4320 is heated by the
compressed working fluid. For example, after the first process
fluid PF.sub.1 flows through the condenser 4320, at least a portion
of the heated first process fluid PF.sub.1 flows through the heat
exchanger tubes 4351 of the heat source 4350. The first process
fluid PF.sub.1 being utilized to transfer heat from the compressed
working fluid to the working fluid flowing past the heat exchanger
tubes 4351.
[0301] In another embodiment, the type of fluid flowing through the
heat exchanger tubes 4351 may be a third process fluid instead of
the compressed working fluid. For example, the third process fluid
may be hot air, hot water, working fluid, or the like. In an
embodiment, the third process fluid may be the fluid for a
secondary cooling circuit as similarly discussed in FIG. 13 (e.g.,
secondary cooling circuit 4290). For example, the third process
fluid of the secondary cooling loop may be a fluid utilized for
transferring heat (e.g., air, water and/or glycol, or the like that
is suitable for absorbing and transferring heat) or a working fluid
that is expanded to provide cooling (e.g., a fluid including one or
more refrigerants).
[0302] In another embodiment, the heat source 4350 may be an
electric heater similar to the heat source 4050 in FIG. 11. In such
an embodiment, the heat source 4350 utilizes supplied electricity
to generate the heat provided to the passing working fluid instead
of utilizing a hot fluid (e.g., the compressed working fluid, the
third process fluid). For example, the circuit controller 4370 in
such an embodiment may control the amount of heat provided by the
heat source 4350 to the passing working fluid by controlling the
amount of electricity supplied to the heat source 4350.
[0303] The flow path of the working fluid through the heat circuit
4300 includes a suction stream. The suction stream is disposed
after the location where the working fluid is heated by the second
process fluid PF.sub.2 flowing through the heat exchanger tubes
4346 and before the compressor 4310. In an embodiment, the suction
stream extends from after the location where the working fluid is
heated by the second process fluid PF.sub.2 to the suction inlet
4312 of the compressor 4310. In an embodiment, the suction stream
extends from the heat exchanger tubes 4346 to the suction inlet
4312 of the compressor 4310. In FIG. 14, the suction stream
includes the heat source 4350, the portion of the evaporator 4340
after the heat exchanger tubes 4346, and the suction pipe that
fluidly connects the evaporator 4340 to the suction inlet 4312 of
the compressor 4310. In an embodiment, the heat transfer circuit
300 may include additional components (one or more pipes, flow
control device(s), a receiver tank, a dryer, or the like) disposed
between the evaporator 4340 and the compressor 4310. In such an
embodiment, the suction stream would also include such additional
components. The heat source 4350 is configured to provide heat to
and increase the temperature of the working fluid as it flows
through the suction stream (i.e. increase the suction temperature
T.sub.1).
[0304] In FIG. 14, the lubricant is separated in the lubricant
separator 4360 and separately circulated back to the compressor
4310. However, the heat transfer circuit 300 in an embodiment may
not include the lubricant separator 4360. In an embodiment, the
lubricant may be configured to be circulated back to the compressor
4310 as part of the working fluid without being separated with a
lubricant separator 4360. In such an embodiment, the lubricant may
enter through the suction inlet 4312 of the compressor 4310 as part
of the working fluid.
[0305] FIG. 16 is a block diagram of a method of operating a heat
transfer circuit 400. For example, the method 4400 may be for
operating the heat transfer circuit 4001 in FIG. 11, the heat
transfer circuit 4100 in FIG. 12, and/or the heat transfer circuit
4300 in FIG. 14. In an embodiment, the heat transfer circuit is
employed in an HVACR system. The method 4400 starts at 4410.
[0306] At 4410, a compressor (e.g., compressor 4010, 4110, 4310) is
operated to compress a working fluid. The temperature of the
working fluid increases as it is compressed in the compressor. The
compressed working fluid discharged from the compressor contains
lubricant. In an embodiment, the lubricant is circulated to the
compressor separately from the working fluid and mixes with the
working fluid as it passes through the compressor. In such an
embodiment, the method 4400 proceeds to optional 4420. At optional
4420, a liquid lubricant is separated from the working fluid by a
lubricant separator (e.g., lubricant separator 4060, 4160, 4360).
The separated liquid lubricant in some cases contains a
concentration of refrigerant that has been dissolved in the liquid
lubricant. The separated liquid lubricant is then circulated back
to the compressor from the lubricant separator. A stream of working
fluid, which may contain entrained lubricant, is also discharged
from the lubricant separator. The method 4400 then proceeds to
4430.
[0307] In another embodiment, the lubricant is circulated with the
working fluid to a suction inlet (e.g., suction inlet 4012 in FIG.
11) of the compressor without being separated with a lubricant
separator (e.g., lubricant separator 4060, 40160, 4360). In such an
embodiment, the method 4400 proceeds from 4410 to 4430 and does not
include optional 4420.
[0308] At 4430, the compressed working fluid is cooled as it flows
through a condenser (e.g., condenser 4020, 4120, 4320). The
compressed working fluid is cooled by a first process fluid (e.g.,
first process fluid PF.sub.1 in FIG. 11, 12, or 14) that separately
flows through the condenser. The working fluid is partially or
entirely condensed as it is cooled in the condenser. The method
4400 then proceeds to 4440.
[0309] At 4440, the working fluid from the condenser is expanded by
an expansion device (e.g., expansion device 4030, 4130, 4330). The
expansion device allows the working fluid to suddenly expand. The
expansion causes the working fluid to significantly decrease in
temperature. The method 4400 then proceeds to 4450.
[0310] At 4450, the expanded working fluid from the expansion
device is heated in an evaporator (e.g., evaporator 4040,
evaporator 4140, evaporator 4340). A second process fluid (e.g.,
second process fluid PF.sub.2 in FIG. 11, 12, or 14) flows through
the evaporator separately from the working fluid. The working fluid
absorbs heat from the second process fluid and is heated as it
flows through the evaporator. The second process fluid being cooled
by the working fluid as it flows through the evaporator. The method
4400 then proceeds to 4460.
[0311] At 4460, a heat source (e.g., heat source 4050, heat source
4150, heat source 4350) heats the working fluid after it has been
heated by the second process fluid. The heating by the heat source
increases the suction temperature (e.g., suction temperature
T.sub.1) of the working fluid as it enters the compressor. The
increase in suction temperature decreases the concentration of
dissolved refrigerant in the lubricant provided to the compressor.
In an embodiment, suction stream includes the heat source. The
suction stream is disposed after the location where the working
fluid is heated by the second process fluid and before the
compressor. In an embodiment, the suction stream extends from a
location after where the working fluid is heated by the second
process fluid to a suction inlet (e.g., suction inlet 4012, suction
inlet 4112, suction inlet 4312) of the compressor. In an
embodiment, the heat source heats the working fluid as it flows
from the evaporator to the compressor. In such an embodiment, the
suction stream may include a suction pipe that connects the suction
inlet of the compressor to at least one of the heat source and the
evaporator. In another embodiment, the heat source is located
within the evaporator and heats the working fluid as to flows
through the evaporator after being heated by the second process
fluid. In such an embodiment, suction stream may include the
portion of the evaporator that is after the heat exchanger tubes of
the evaporator through which the second process fluid flows (e.g.,
heat exchanger tubes 4346).
[0312] In an embodiment, the method 4400 may be modified based on
the heat transfer circuit 4001, heat transfer circuit 4100, heat
transfer circuit 4200, and/or heat transfer circuit 4300 as shown
in FIGS. 11-14 and as described above. For example, the method 4400
in an embodiment may include directing hot fluid (e.g., compressed
working fluid, the first process fluid PF.sub.1, the second process
fluid PF.sub.2, a third process fluid) through the heat source as
similarly described for the heat source 4150 in FIG. 12, the heat
source 4250 in FIG. 13, and the heat source 4350 in FIGS. 13 and
14.
[0313] Aspects:
[0314] Any of aspects 1-12 can be combined with any of aspects
13-17. It is understood that any of aspects 1-17 can be combined
with any other aspects recited herein.
[0315] Aspect 1. A heat transfer circuit, comprising: a compressor
for compressing a working fluid; a condenser for cooling the
working fluid; an expansion device for expanding the working fluid;
an evaporator for providing a first heating of the working fluid
flowing through the evaporator, the first heating being a heat
exchange between the working fluid and a process fluid flowing
through the evaporator, a flow path of the working fluid extending
from the compressor through the condenser, the expansion device,
the evaporator, and back to the compressor, the flow path including
a suction stream disposed after the first heating and before the
compressor; and a heat source, the suction stream including the
heat source and the heat source configured to provide a second
heating of the working fluid.
[0316] Aspect 2. The heat transfer circuit of aspect 1, wherein the
heat source is an electric heater.
[0317] Aspect 3. The heat transfer circuit of either one of aspects
1 and 2, wherein the heat source is disposed within the
evaporator.
[0318] Aspect 4. The heat transfer circuit of either one of aspects
1 and 3, wherein the evaporator includes a first set of heat
exchanger tubes through which the process fluid flows, and the
working fluid flowing past the first set of tubes undergoing the
first heating, and the heat source is a second set of heat
exchanger tubes in the evaporator, the second heating of the
working fluid being a heat exchange between the working fluid
flowing past the second set of heat exchange tubes and a third
fluid flowing through the second set of heat exchanger tubes.
[0319] Aspect 5. The heat transfer circuit of either one of aspects
1 and 2, the heat source is disposed in the suction stream between
the evaporator and the compressor.
[0320] Aspect 6. The heat transfer circuit of either one of aspects
1 and 5, wherein the heat source is a heat exchanger including a
first side and a second side, the working fluid heated by the heat
source flowing through the first side, a third fluid flowing
through the second side, and the second heating of the working
fluid being a heat exchange between the third fluid and the working
fluid.
[0321] Aspect 7. The heat transfer circuit of either one aspects 4
and 6, wherein the third fluid is a portion of the compressed
working fluid discharged by the compressor before the compressed
working fluid flows through the expansion device.
[0322] Aspect 8. The heat transfer circuit of either one of aspects
4 and 6, wherein the third fluid is the same type of fluid as the
process fluid.
[0323] Aspect 9. The heat transfer circuit of either one of aspects
4 and 6, wherein a second process fluid flows through the condenser
and absorbs heat from the working fluid to provide the cooling of
the working fluid, and the third fluid includes a portion of the
second process fluid.
[0324] Aspect 10. The heat transfer circuit of either one of
aspects 1, 2, 5, and 6, further comprising: a suction pipe
extending to a suction inlet of the compressor, the suction stream
including the suction pipe, wherein the heat source extends along
an outside of the suction pipe.
[0325] Aspect 11. The heat transfer circuit of any one of aspects
1-10, further comprising: a controller configured to control heat
provided by the heat source to the working fluid based on a suction
temperature of the working fluid entering the compressor.
[0326] Aspect 12. The heat transfer circuit of any one of aspects
1-11, wherein the heat source is configured to increase superheat
of the working fluid entering a suction inlet of the
compressor.
[0327] Aspect 13. A method of operating a heat transfer circuit to
cool a first process fluid, the heat transfer circuit including a
compressor, a condenser, an expansion device, an evaporator, a heat
source, and a working fluid flowing through the heat transfer
circuit, the method comprising: compressing the working fluid with
the compressor; cooling the working fluid compressed by the
compressor with the condenser; expanding the working fluid cooled
by the condenser with the expansion device; heating the working
fluid expanded by the expansion device in the evaporator with a
process fluid, the working fluid absorbing heat from the process
fluid; and heating the working fluid heated by the process fluid
with the heat source, the working fluid heated with the heat source
as the working fluid flows through a suction stream, the suction
stream including the heat source and disposed after a location at
which the working fluid is heated by the process fluid and before
the compressor.
[0328] Aspect 14. The method of aspect 13, wherein heating the
working fluid with the heat source includes heating the working
fluid flowing from the evaporator to the compressor.
[0329] Aspect 15. The method of either one of aspects 13 and 14,
wherein heating the working fluid with the heat source includes
increasing superheat of the working fluid entering a suction inlet
of the compressor.
[0330] Aspect 16. The method of any one of aspects 13-15, further
comprising: directing the working fluid from an inlet of the
evaporator, past a first set of heat exchanger tubes in the
evaporator through which the first fluid flows, past the heat
source, and to an outlet of the evaporator in this order, wherein
the suction stream includes a portion of the evaporator located
after the first set of heat exchanger tubes.
[0331] Aspect 17. The method of any one of aspects 13-15, further
comprising: directing at least a portion of the compressed working
fluid discharged by the compressor, which has not been expanded by
the expansion device, through a first side of the heat source,
wherein heating the working fluid heated by the process fluid with
the heat source includes directing the working fluid heated by the
heat source through a second side of the heat source.
[0332] A heat transfer circuit that utilizes a working fluid to
provide heating or cooling. The heat transfer circuit includes a
compressor for compressing the working fluid and a heat source
configured to increase a suction temperature of the working fluid
entering the compressor. A flow path of the working fluid through
the heat transfer circuit includes a suction stream. The suction
stream is disposed after a location at which the working fluid is
heated by a process fluid and before the compressor. The suction
stream includes the heat source. A method for operating a heat
transfer circuit includes heating a working fluid with a process
fluid, and further heating the working fluid heated by the process
fluid with a heat source.
[0333] Lubricant Management for an HVACR System (FIGS. 17-19)
[0334] This disclosure relates generally to a heating, ventilation,
air conditioning, and refrigeration (HVACR) system. More
specifically, this disclosure relates to lubricant management for a
compressor in an HVACR system.
[0335] A heating, ventilation, air conditioning, and refrigeration
(HVACR) system includes a refrigerant circuit. The refrigerant
circuit includes a compressor, lubricant source, a condenser, an
expansion device, and an evaporator fluidly connected. One or more
sensors are included for determining a pressure and a temperature.
The compressor includes a plurality of bearings and a suction port.
A lubricant reservoir is fluidly connected to the lubricant source,
the plurality of bearings, and the suction port. The lubricant
reservoir is configured to receive a lubricant-refrigerant mixture.
The lubricant reservoir is in thermal communication with a
discharge flow path of the compressor.
[0336] A heating, ventilation, air conditioning, and refrigeration
(HVACR) system is also disclosed. The HVACR system includes a
refrigerant circuit. The refrigerant circuit includes a compressor
including a plurality of bearings and a suction port, a lubricant
source, a condenser, an expansion device, and an evaporator fluidly
connected. One or more sensors are included for determining a
pressure and a temperature. The plurality of bearings include
discharge side bearings and suction side bearings. The plurality of
bearings are fluidly connected to the lubricant source and
configured to receive a lubricant mixture from the lubricant
source. The discharge side bearings are fluidly connected to the
suction port.
[0337] Environmental impacts of HVACR refrigerants are a growing
concern. For example, since 2011, the European Union has been
phasing out refrigerants with a global warming potential (GWP) of
more than, for example, 150 in some refrigeration systems.
Environmentally-suitable HVACR refrigerants, with suitable
properties such as density, vapor pressure, heat of vaporization,
and suitable chemical properties, which satisfy the requirements
regarding safety and environment impacts, such as the European
Union standard discussed above, can be utilized for HVACR systems.
The environmentally-suitable HVACR refrigerants are nonflammable or
mildly flammable, non-ozone depleting, energy efficient, low in
toxicity, compatible with materials of construction, and are
chemically stable over the life of the equipment.
[0338] Current refrigerants, such as R134a or the like, may have
relatively higher GWPs. For example, R134a has a GWP of 1,430. As a
result, replacement refrigerants such as, but not limited to,
R1234ze, R513A, and the like, are being implemented in HVACR
systems.
[0339] In utilizing newer refrigerant compositions such as, but not
limited to, R1234ze and R513A, various problems may arise as a
result of the different properties of the refrigerant compared to
prior refrigerants such as R134a. In general, refrigerants with
lower GWPs such as R1234ze, R513A, and the like may be carried over
into the lubricant. In some instances, the replacement refrigerants
are relatively more likely to dissolve into the lubricant than the
current refrigerants, resulting in a higher concentration of
refrigerant within the lubricant (e.g., lubricant dilution).
[0340] As a result, portions of an operating map for a compressor
of the HVACR system may suffer from higher lubricant dilution and
limited bearing viscosity due to low discharge superheat. In some
instances, the occurrence of higher lubricant dilution and limited
bearing viscosity may be more significant when the variable speed
compressor operates at relatively lower speeds. Higher lubricant
dilution and limited bearing viscosity can result in, for example,
a shortened lifetime for the bearings and ultimately compressor
failures. In some instances, utilizing the R134A replacement
refrigerants may require a replacement of the mechanical components
(e.g., bearings or the like) in the compressor.
[0341] In other instances, controlling a variable speed compressor
to maximize efficiency can also result in lubricant dilution
problems, even when utilizing the current refrigerants such as
R134a.
[0342] In general, lubricants utilized with R134a replacement
refrigerants suffer the higher lubricant dilution problem. The
lubricants can include any suitable lubricant which is miscible
with the selected replacement refrigerant.
[0343] In general, higher lubricant dilution may occur when
discharge superheat becomes relatively low. For example, higher
lubricant dilution can occur when the discharge superheat is below
at or about 8.degree. C.
[0344] FIG. 17 is a schematic diagram of a refrigerant circuit
5010, according to an embodiment. The refrigerant circuit 5010
generally includes a compressor 5015, a condenser 5020, an
expansion device 5025, an evaporator 5030, and a lubricant source
5060.
[0345] The refrigerant circuit 5010 is an example and can be
modified to include additional components. For example, in an
embodiment, the refrigerant circuit 5010 can include other
components such as, but not limited to, an economizer heat
exchanger, one or more flow control devices, a receiver tank, a
dryer, a suction-liquid heat exchanger, or the like.
[0346] The refrigerant circuit 5010 can generally be applied in a
variety of systems used to control an environmental condition
(e.g., temperature, humidity, air quality, or the like) in a space
(generally referred to as a conditioned space). Examples of such
systems include, but are not limited to, HVACR systems, transport
refrigeration systems, or the like.
[0347] The compressor 5015, condenser 5020, expansion device 5025,
and evaporator 5030 are fluidly connected via refrigerant lines
5035, 5040, 5045. In an embodiment, the refrigerant lines 5035,
5040, and 5045 can alternatively be referred to as the refrigerant
conduits 5035, 5040, and 5045, or the like.
[0348] In an embodiment, the refrigerant circuit 5010 can be
configured to be a cooling system (e.g., an air conditioning
system) capable of operating in a cooling mode. In an embodiment,
the refrigerant circuit 5010 can be configured to be a heat pump
system that can operate in both a cooling mode and a
heating/defrost mode.
[0349] The refrigerant circuit 5010 can operate according to
generally known principles. The refrigerant circuit 5010 can be
configured to heat or cool a gaseous process fluid (e.g., a heat
transfer medium or fluid such as, but not limited to, air or the
like), in which case the refrigerant circuit 5010 may be generally
representative of an air conditioner or heat pump.
[0350] In operation, the compressor 5015 compresses a working fluid
(e.g., a heat transfer fluid such as a refrigerant or the like)
from a relatively lower pressure gas (e.g., suction pressure) to a
relatively higher-pressure gas (e.g., discharge pressure). In an
embodiment, the compressor 5015 can be a positive displacement
compressor. In an embodiment, the positive displacement compressor
can be a screw compressor, a scroll compressor, a reciprocating
compressor, or the like. In an embodiment, the compressor 5015 can
be a centrifugal compressor.
[0351] The relatively higher-pressure gas is also at a relatively
higher temperature, which is discharged from the compressor 5015
and flows through refrigerant line 5035 to the condenser 5020. The
working fluid flows through the condenser 5010 and rejects heat to
a process fluid (e.g., water, air, or the like), thereby cooling
the working fluid. The cooled working fluid, which is now in a
liquid form, flows to the expansion device 5025 via the refrigerant
line 5040. The expansion device 5025 reduces the pressure of the
working fluid. As a result, a portion of the working fluid is
converted to a gaseous form. The working fluid, which is now in a
mixed liquid and gaseous form flows to the evaporator 5030 via the
refrigerant line 5040. The working fluid flows through the
evaporator 5030 and absorbs heat from a process fluid (e.g., water,
air, or the like), heating the working fluid, and converting it to
a gaseous form. The gaseous working fluid then returns to the
compressor 5015 via the refrigerant line 5045. The above-described
process continues while the refrigerant circuit is operating, for
example, in a cooling mode (e.g., while the compressor 15 is
enabled).
[0352] In the illustrated embodiment, the refrigerant circuit 5010
can include a lubricant source 5060 disposed between the compressor
5015 and the condenser 5020. In the illustrated embodiment, the
lubricant source 5060 can be a lubricant separator. It will be
appreciated that a particular location for the lubricant source
5060 can vary within the principles of this disclosure. For
example, in an embodiment, the lubricant source 5060 could
alternatively be a location at or near the evaporator 5030.
[0353] The lubricant source 5060 is fluidly connected to a
discharge of the compressor 5015 via the refrigerant line 5035. The
lubricant source 5060 is fluidly connected to the compressor 5015
to provide lubricant to various components of the compressor 5015
(e.g., bearings, rotors, or the like) via lubricant return line
5055A and optionally via a second lubricant return line 5055B. It
will be appreciated that the number of lubricant return lines
5055A, 5055B can be selected based on, for example, which
components of the compressor are being provided with lubricant.
[0354] A controller 5050 is included in the system. The controller
5050 can be used to control one or more aspects of the refrigerant
circuit 5010. For example, in embodiments disclosed in accordance
with FIGS. 18 and 19 below, the controller 5050 can be used to
selectively control a state of a flow control device (e.g., a valve
or the like) to control lubricant flow within the refrigerant
circuit 5010. The controller 5050 can be in electronic
communication with the flow control device and one or more sensors
5065 to determine one or more operating conditions (e.g.,
temperature, pressure, or the like) of the compressor 5015 and its
components (e.g., bearings, rotors, or the like). In an embodiment,
the controller 5050 can monitor a pressure and temperature of the
lubricant using the one or more sensors 5065. The controller 5050
will use the measured pressure and temperature to selectively
manage the lubricant flow rate (e.g., to the bearings, the rotors,
or the like) to achieve a desired lubricant viscosity. In an
embodiment, the pressure may be measured in a bearing cavity or
inferred from a suction pressure or suction saturation temperature.
In an embodiment, the temperature may be measured at the bearings
or in a lubricant reservoir.
[0355] FIG. 18 is a side sectional view of a compressor 5015 for a
vapor compression system (e.g., the refrigerant circuit 5010 of
FIG. 17), according to an embodiment.
[0356] In an embodiment, the compressor 5015 is a screw compressor.
The screw compressor 5015 includes a rotor housing 5100 and an
electric motor housing 5105. The rotor housing 5100 includes a
suction port 5110 and a discharge port 5115. Rotors 5120a, 5120b
are intermeshed and are disposed at least partially within the
rotor housing 5100. The screw compressor 5015 can operate in
accordance with generally known principles to compress a working
fluid received via the suction port 5110 and to be output via the
discharge port 5115.
[0357] The motor housing 5105 houses a motor 5125, according to an
embodiment. The motor housing 5105 may be integral to the rotor
housing 5100. The electric motor 5125 can drive the intermeshed
rotors 4120a, 4120b.
[0358] The motor housing 4105 includes the electric motor 4125. The
motor housing 4105 further includes a stator 5140 and a rotor 5145.
The rotor 5145 rotates a shaft which is also connected to the rotor
5120b. An airgap 5130 is formed between the stator 5140 and the
rotor 5145. In the embodiment illustrated in FIG. 18, the electric
motor 5125 can be provided with a portion of the working fluid
(e.g., a heat transfer fluid such as refrigerant or the like) which
flows through the airgap 5130 of the electric motor 5125, in a flow
direction which is generally from right to left with respect to the
figure, and is provided to the suction port 5110. In an embodiment,
the working fluid can be in a gaseous form. It will be appreciated
that a gaseous form of the working fluid may include a portion that
is in liquid form, but the gaseous form includes a relatively
higher portion of the working fluid in the gaseous form than the
liquid form.
[0359] A bearing housing 5135 contains discharge side bearings
5150. Suction side bearings 5155 are disposed within the rotor
housing 5100. A combination of the discharge side bearings 5150 and
the suction side bearings 5155 support the rotors 5120a, 5120b. The
discharge side bearings 5150 and the suction side bearings 5155 can
be provided with a lubricant for lubricating the discharge side
bearings 5150 and the suction side bearings 5155. In an embodiment,
the discharge side bearings 5150 can include radial bearings and
thrust bearings. In an embodiment, a bearing may be configured to
accommodate both thrust and radial loads.
[0360] In an embodiment, the discharge side bearings 5150 in the
bearing housing 5135 are maintained at a pressure that is lower
than a discharge pressure of the compressor 5015. In an embodiment,
the discharge side bearings 5150 in the bearing housing 5135 are
maintained at a pressure that is at or about a suction pressure of
the compressor 5015. In an embodiment, the suction side bearings
5155 are also at or about the suction pressure of the compressor
5015.
[0361] In the illustrated embodiment, a lubricant reservoir 5160 is
disposed at a location that thermally communicates with the
compressor 5015. In an embodiment, the lubricant reservoir 5160 can
alternatively be referred to as a lubricant still or a lubricant
sump. In an embodiment, the entire lubricant reservoir 5160 or a
portion of the lubricant reservoir 5160 can be disposed within the
rotor housing 5100. In an embodiment, the lubricant reservoir 5160
can be placed at a location that is relatively closer to the
discharge port 5115 than the suction port 5110. As a result, the
lubricant reservoir 5160 can receive more heat generated through
the compression process than if located relatively closer to the
suction port 5110. The thermal communication with the discharge
flow path of the compressor 5015 can include a location at which
the lubricant reservoir 5160 can receive heat generated from the
compression process. The discharge flow path can include, for
example, a rotor housing of the compressor 5015, a bearing housing
of the compressor 5015, a muffler of the compressor 5015, a
discharge conduit of the compressor 5015, an oil separator, a
condenser, or the like. In an embodiment, the lubricant reservoir
5160 can be in thermal communication with another heat generating
component of the HVACR system such as, but not limited to, a
variable frequency drive controller, an electric fan motor, or the
like.
[0362] In an embodiment, a total volume of the lubricant reservoir
5160 can be less than a typical low-side lubricant sump in prior
systems. In the illustrated embodiment, the lubricant reservoir
5160 is disposed on a top (with respect to the page) of the
compressor 5015. The placement can enable fluid flow from the
lubricant reservoir 5160 to the compressor 5015 via gravity. As a
result, in an embodiment, the lubricant reservoir 5160 does not
include a pump. This can, for example, reduce a cost and complexity
of the system relative to prior systems which generally utilize a
pump to move lubricant.
[0363] In an embodiment, the lubricant reservoir 5160 can be placed
at or near the lubricant source 5060 so that the fluid in the
lubricant reservoir 5160 can receive heat from the higher
temperature working fluid at the location of the lubricant source
5060.
[0364] The lubricant reservoir 5160 is fluidly connected to the
lubricant source 5060. In operation, the lubricant reservoir 5160
can receive lubricant as separated from the lubricant source 5060.
Even though the lubricant reservoir 5160 is downstream of the
lubricant source 5060, the lubricant can include a mixture of
lubricant and refrigerant.
[0365] An expansion device 5165 is disposed at a location between
the lubricant source 5060 and the lubricant reservoir 5160. The
expansion device 5165 can be, for example, a fixed or variable
orifice that induces a pressure drop in the lubricant being
received from the lubricant source 5060. In an embodiment, the
expansion device 5165 can be an electronic expansion device or the
like.
[0366] Inducing the pressure drop also reduces a temperature of the
lubricant mixture. The mixed refrigerant and lubricant mixture
received in the lubricant reservoir 5160 can be heated due to
thermal communication with a discharge flow path of the compressor
5015. The thermal communication with the discharge flow path of the
compressor 5015 can include a location at which the lubricant
reservoir 5160 can receive heat generated from the compression
process. The discharge flow path can include, for example, a rotor
housing of the compressor 5015, a bearing housing of the compressor
5015, a muffler of the compressor 5015, a discharge conduit of the
compressor 5015, an oil separator, a condenser, or the like. The
heat can cause the refrigerant in the refrigerant and lubricant
mixture to boil off to the gaseous state. In an embodiment, an
electric resistance heater could be included, although the electric
resistance heater may reduce performance of the compressor
5015.
[0367] A conduit 5170 is fluidly connected to a top portion of the
lubricant reservoir 5160 so that the gaseous refrigerant boiling
from the refrigerant and lubricant mixture can be returned to the
suction port 5110 of the compressor 5015.
[0368] The conduit 5170 includes a flow control device 5175. In an
embodiment, the flow control device 5175 can be, for example, a
fixed orifice. The flow control device 5175 in such an embodiment
can limit an overall flowrate of the refrigerant flowing from the
lubricant reservoir 5160 to the suction port 5110. In an
embodiment, the orifice can be variable. In such an embodiment, a
size of the orifice can be controlled to control an amount of flow
through the conduit 5170 to the suction port 5110.
[0369] In an embodiment, the flow control device 5175 can be a
valve. In such an embodiment, the flow control device 5175 can have
a plurality of states (e.g., an open state, a closed state, one or
more intermediate states). The state of the flow control device
5175 can be selectively controlled using a controller (e.g.,
controller 5050, FIG. 17) to control an amount of flow through the
conduit 5170.
[0370] A second conduit 5180 is fluidly connected to a bottom
portion of the lubricant reservoir 5160. The second conduit 5180 is
fluidly connected to the discharge side bearings 150 and the
suction side bearings 5155. The second conduit 180 is disposed at a
location of the lubricant reservoir 5160 via which a lubricant
(e.g., in a liquid or substantially liquid state) can flow via, for
example, gravity. The lubricant can then be provided to the
discharge side bearings 5150 and the suction side bearings
5155.
[0371] The flow control device 5175 in the conduit 5170 can be
designed so that a flowrate of the lubricant in the conduit 5180 is
controlled. For example, to increase a lubricant flow to the
discharge side bearings 5150 and the suction side bearings 5155,
the flow control device 175 can be placed into the closed state by
the controller 5050. As a result, a pressure in the lubricant
reservoir 5160 can increase, thereby resulting in an increased flow
of lubricant through the conduit 5180.
[0372] The flow control device 5175 can be selectively controlled
based on, for example, a temperature as sensed in the bearing
housing 5150.
[0373] During operation of the compressor, the discharge side
bearings 5150 and the suction side bearings 5155 generate heat.
With focus on the discharge side bearings 5150, when the heat is
generated during operation, the lubricant pool is heated. In an
embodiment, the discharge side bearings 5150 can be a flooded
bearing design in which drag of the discharge side bearings 5150 in
the lubricant pool can generate heat. The heat can raise a
temperature of the lubricant in the cavity of the discharge side
bearings. As the heat increases, lubricant viscosity increases for
a period of time until the heat becomes excessive, at which point
the lubricant viscosity drops. As discussed above, the lubricant
received from the lubricant source 5060 can include a mixture of
lubricant and refrigerant. As a result, when the lubricant pool is
heated, refrigerant may be boiled off from the mixture.
[0374] When the temperature increases to a threshold limit,
indicating that additional lubricant is desired, the controller
5050 can place the flow control device 5175 in the closed state,
thereby increasing flow of lubricant from the lubricant reservoir
5160 to the discharge side bearings 5150 and the suction side
bearings 5155.
[0375] When the temperature is within the threshold limit,
indicating that additional lubricant is not needed, the controller
5050 can place the flow control device in the open state, thereby
decreasing flow of lubricant from the lubricant reservoir 5160 to
the discharge side bearings 5150 and the suction side bearings
5155.
[0376] In an embodiment, the flow control device 5175 can include
an intermediate state in which some flow is permitted (e.g.,
between the open and the closed state). In such an embodiment, the
controller 5050 can vary the position of the flow control device
5175 to maintain the sensed temperature within a desired operating
range.
[0377] In an embodiment, by controlling the pressure in the
lubricant reservoir 5160 to maintain a selected lubricant flowrate
to the discharge side bearings 5150 and the suction side bearings
5155, the lubricant reservoir 5160 may generally be considered to
be at a medium pressure that is between the suction pressure and
the discharge pressure of the compressor 5015.
[0378] FIG. 19 is a side sectional view of a compressor 5015 for a
vapor compression system (e.g., the refrigerant circuit 5010 of
FIG. 17), according to an embodiment.
[0379] For simplicity of this Specification, aspects of FIG. 19
which have previously been described with respect to FIG. 18 will
not be described in additional detail. Such aspects are labeled
with the same reference numbers as FIG. 18.
[0380] In FIG. 19, the lubricant reservoir 5160 is not present.
Instead, the discharge side bearings 5150 are fluidly connected to
the suction port 5110. Connecting the discharge side bearings 5150
with the suction port 5110 enables refrigerant gas to be returned
from the discharge side bearings 5150 to the suction stream. As a
result, refrigerant gas can be removed from the cavity in which the
discharge side bearings 5150 are located.
[0381] In operation, lubricant is provided to the discharge side
bearings 5150 and the suction side bearings 5155 via the conduit
5180. A pool of lubricant is formed within the cavity in which the
discharge side bearings 5150 and the suction side bearings 5155 are
located.
[0382] As discussed above regarding FIG. 18, during operation of
the compressor, the discharge side bearings 5150 and the suction
side bearings 5155 generate heat. With focus on the discharge side
bearings 5150, when the heat is generated during operation, the
lubricant pool is heated. As discussed above, the lubricant
received from the lubricant source 5060 can include a mixture of
lubricant and refrigerant. As a result, when the lubricant pool is
heated, refrigerant may be boiled off from the mixture. The gaseous
refrigerant can be removed from the cavity via conduit 5200 and
lubricant can be removed via conduit 5205. The conduit 5200 is
fluidly connected to the cavity containing the discharge side
bearings 5150 and to the suction port 5110. The conduit 5205 is
also fluidly connected to the cavity containing the discharge side
bearings 5150 and to the suction port 5110. As illustrated, an
inlet of the conduit 5200 is disposed at a location on a top side
of the cavity (e.g., above a depth of the lubricant pool in the
cavity) so that gaseous refrigerant can be removed and the inlet of
the conduit 5205 is disposed at a location on a lower side of the
cavity (e.g., below a depth of the lubricant pool in the cavity) so
that liquid lubricant can be removed.
[0383] The conduit 5200 can include a flow control device 5210
which can be selectively controlled to enable, disable, or limit
the amount of refrigerant being pulled from the discharge side
bearings 5150 and provided to the suction port 5110. In an
embodiment, the conduit 200 can be sized to restrict a flow of
fluid therethrough to a predetermined flowrate. When the flow
control device 5210 is closed, a pressure in the bearing cavity
increases. As the pressure increases, a flow of lubricant from the
lubricant source 5060 decreases. If the temperature in the cavity
approaches an upper limit, the flow through conduit 5200 can be
enabled, allowing gaseous refrigerant to leave the cavity and
increasing a flow of lubricant from the lubricant source 5060,
which should reduce a temperature of the discharge side bearings
50150,
[0384] The conduit 5205 can include a flow control device 5215. In
an embodiment, the flow control device 5215 can be a restriction,
such as a fixed orifice. In an embodiment, the flow control device
5215 can alternatively be selectively controllable to, for example,
vary a flow through the conduit 5205. In such an embodiment, the
flow control device 5215 can be a valve or the like.
[0385] In operation, the controller (e.g., controller 5050 in FIG.
17) can be used to monitor a temperature of the lubricant for the
discharge side bearings 5150 (e.g., using one or more sensors
5065). If the temperature of the lubricant increases beyond a
threshold limit, additional lubricant can be provided to the
discharge side bearings 5150. If the temperature decreases below a
threshold limit, additional lubricant can be prevented from being
provided.
[0386] Aspects:
[0387] Any of aspects 1-9 can be combined with any one of aspects
10-17. It is understood that any of aspects 1-17 can be combined
with any other aspects recited herein.
[0388] Aspect 1. A heating, ventilation, air conditioning, and
refrigeration (HVACR) system, comprising: a refrigerant circuit,
including: a compressor including a plurality of bearings and a
suction port, a lubricant source, a condenser, an expansion device,
and an evaporator fluidly connected; one or more sensors for
determining a pressure and a temperature; and a lubricant reservoir
fluidly connected to the lubricant source, the plurality of
bearings, and the suction port, the lubricant reservoir configured
to receive a lubricant-refrigerant mixture, wherein the lubricant
reservoir is in thermal communication with a discharge flow path of
the compressor.
[0389] Aspect 2. The HVACR system of aspect 1, further comprising a
flow control device disposed between the lubricant reservoir and
the suction port.
[0390] Aspect 3. The HVACR system of aspect 2, wherein the flow
control device is one of an orifice and an electronically
controlled valve.
[0391] Aspect 4. The HVACR system of any one of aspects 1-3,
wherein the lubricant reservoir is fluidly connected to the
plurality of bearings at a location configured to provide a
lubricant to the plurality of bearings.
[0392] Aspect 5. The HVACR system of any one of aspects 1-4,
wherein the lubricant reservoir is fluidly connected to the suction
port at a location configured to provide a gaseous refrigerant to
the suction port.
[0393] Aspect 6. The HVACR system of any one of aspects 1-5,
wherein a pressure within the lubricant reservoir is between a
suction pressure of the compressor and a discharge pressure of the
compressor.
[0394] Aspect 7. The HVACR system of any one of aspects 1-6,
wherein a conduit fluidly connecting the lubricant reservoir and
the suction port is sized to restrict a flow of fluid therethrough
to a predetermined flowrate.
[0395] Aspect 8. The HVACR system of any one of aspects 1-7,
wherein the compressor is a screw compressor.
[0396] Aspect 9. The HVACR system of any one of aspects 1-8,
wherein the lubricant source is a lubricant separator.
[0397] Aspect 10. A heating, ventilation, air conditioning, and
refrigeration (HVACR) system, comprising: a refrigerant circuit,
including: a compressor including a plurality of bearings and a
suction port, a lubricant source, a condenser, an expansion device,
and an evaporator fluidly connected; one or more sensors for
determining a pressure and a temperature; and wherein the plurality
of bearings include a discharge side bearing and a suction side
bearing, the plurality of bearings fluidly connected to the
lubricant source and configured to receive a lubricant mixture from
the lubricant source, and wherein the discharge side bearing is
fluidly connected to the suction port.
[0398] Aspect 11. The HVACR system of aspect 10, further comprising
a flow control device disposed between the discharge side bearing
and the suction port.
[0399] Aspect 12. The HVACR system of aspect 11, wherein the flow
control device is one of an orifice and an electronically
controlled valve.
[0400] Aspect 13. The HVACR system of any one of aspects 10-12,
wherein the lubricant mixture includes a lubricant and a
refrigerant.
[0401] Aspect 14. The HVACR system of any one of aspects 10-13,
wherein the fluid connection between the discharge side bearing and
the suction port is disposed at a location configured to provide a
gaseous refrigerant to the suction port.
[0402] Aspect 15. The HVACR system of any one of aspects 10-14,
wherein a conduit fluidly connecting the discharge side bearing and
the suction port is sized to restrict a flow of fluid therethrough
to a predetermined flowrate.
[0403] Aspect 16. The HVACR system of any one of aspects 10-15,
wherein the compressor is a screw compressor.
[0404] Aspect 17. The HVACR system of any one of aspects 10-16,
wherein the lubricant source is a lubricant separator.
[0405] A heating, ventilation, air conditioning, and refrigeration
(HVACR) system includes a refrigerant circuit. The refrigerant
circuit includes a compressor, a lubricant source, a condenser, an
expansion device, and an evaporator fluidly connected. The
compressor includes a plurality of bearings and a suction port. A
lubricant reservoir is fluidly connected to the lubricant source,
the plurality of bearings, and the suction port. The lubricant
reservoir is configured to receive a lubricant-refrigerant mixture.
The lubricant reservoir is in thermal communication with a
discharge flow path of the compressor.
[0406] Heat Exchanger in Compressor Housing and Method for
Degassing Compressor Lubricant (FIGS. 20-24)
[0407] The disclosure relates to an internal heat exchanger within
a compressor, a system, and a method for improving viscosity of a
lubricant to be recycled back into the compressor for reuse.
[0408] The internal heat exchanger is in fluid communication with
the compressor, for example cavities of bearings of the compressor.
The internal heat exchanger can utilize system heat in the
compressor to drive refrigerant out of the lubricant to be recycled
back into the compressor. In an embodiment, the lubricant is
oil.
[0409] The internal heat exchanger can include a single or a
plurality of passages. The passage(s), in part or as a whole, can
be provided or formed within a component of the compressor or on a
surface of a component of the compressor. In an embodiment, the
passage(s), in part or as a whole, can extend within a component of
the compressor. In an embodiment, the passage(s), in part or as a
whole, can be integrated into a component of the compressor. In an
embodiment, the passage(s), in part or as a whole can be formed
onto or into a surface of a component of the compressor. The
surface can include, but not limited to, an interface surface or a
face of the component.
[0410] The component can be, but not limited to, a bearing housing
cover, bearing housing, rotor housing, motor housing, muffler of
the compressor.
[0411] The passage(s), in part or as a whole, can be a machined
passage(s) or passage(s).
[0412] In an embodiment, the passage(s), in part or as a whole, can
be manufactured through a process including but not limited to
drilling, casting, etching, milling, welding, or retrofitting,
combinations thereof, or the like.
[0413] In an embodiment, the passage(s), in part or as a whole, can
be casted or drilled within a wall of a casting of a bearing
housing cover, bearing housing, rotor housing, motor housing, or
muffler of the compressor. Thereby, the casting can utilize system
heat to remove refrigerant from the lubricant returning to the
compressor.
[0414] In an embodiment, the passage(s), in part or as a whole, can
be milled on a surface including but not limited to an interface
surface or face of a bearing housing cover, bearing housing, rotor
housing, motor housing, or muffler of the compressor.
[0415] The passage(s), in part or as a whole, can adopt any type of
suitable flow configuration including but not limited to
serpentine, straight, and curved flow configurations.
[0416] The passage(s), in part or as a whole, can be configured
into any type of flow arrangements including but not limited to a
single-pass or multi-pass passage. In an embodiment, the
single-pass or multi-pass passage can be serpentine single-pass or
serpentine multi-pass passages.
[0417] In an embodiment, the compressor is a screw compressor. In
an embodiment, the compressor is a scroll compressor. In an
embodiment, the compressor is a reciprocating compressor. In an
embodiment, the compressor is a centrifugal compressor.
[0418] The system in an embodiment can be an HVACR system including
a compressor having an internal heat exchanger. The HVACR system
can include a lubricant source. In an embodiment, the lubricant
source may be a lubricant separator. The lubricant separator can
receive compressed refrigerant discharged from the screw
compressor, and then separate a lubricant from compressed gaseous
refrigerant.
[0419] In an embodiment, the HVACR system can further include a
pressure-reducing device. The pressure-reducing device can receive
lubricant separated by the lubricant separator and then reduce
pressure of the lubricant so that at least a portion of the
refrigerant in the lubricant evaporates. The pressure-reducing
device then directs the lubricant to the internal heat exchanger
for improving a viscosity of the lubricant. In an embodiment, the
pressure-reducing device is disposed within the compressor. In an
embodiment, the pressure-reducing device is separate (e.g.,
physically separate) from the compressor. In an embodiment, the
pressure-reducing device can be an expansion device of the HVACR
system.
[0420] In an embodiment, a method for improving viscosity of
lubricant to a compressor includes reducing a pressure of a
lubricant containing refrigerant by a pressure-reducing device; and
heating the lubricant containing refrigerant in an internal heat
exchanger of the compressor.
[0421] The compressor can be, but is not limited to, a screw,
scroll, reciprocating, or centrifugal compressor.
[0422] In an embodiment, the compressor can include male and female
rotors that can be supported by bearings such as, for example,
radial and axial bearings at a discharge end of the compressor. The
rotors can be enclosed within a rotor and motor housing, and the
bearings can be enclosed and/or supported by a bearing housing
assembly. The bearing housing assembly can include a bearing
housing and bearing cover. The bearing housing assembly can be, for
example, positioned at the axial end of the rotor housing. The
bearing cover can be attached to the bearing housing to form an
enclosed space.
[0423] During operation, the male and female rotors of the
compressor can rotate in opposite direction and mesh with each
other. The meshing rotors draw refrigerant vapor and force the
refrigerant vapor moving along the rotors. As the refrigerant vapor
progresses, the refrigerant vapor is compressed with higher
temperature as the volume space between the rotors decreases. The
compressed refrigerant vapor can be discharged out of the
compressor with high heat and pressure through a discharge
port.
[0424] In an embodiment, the compressor can include intermeshing
scrolls, a bearing, a motor, and housings. The intermeshing scrolls
can include an orbiting scroll member and a fixed scroll member. An
orbiting motion of the orbiting scroll member relative to the fixed
scroll member creates pockets that trap refrigerant gas. The pocket
becomes increasingly smaller as the refrigerant gas moves toward a
center of the fixed scroll member, and thereby the refrigerant gas
is compressed and pressurized, accompanied by an increasing
temperature. The compressed refrigerant reaches the highest
pressure and temperature at the center of the fixed iron scroll
member and then is discharged through a discharge port.
[0425] In an embodiment, the compressor can include a muffler.
[0426] The compressor can be used to compress working fluids, such
as for example refrigerant vapor.
[0427] The compressor can be provided with lubricant, which is used
to lubricate, seal, and protect running surfaces of a component,
for example bearings, within the compressor. During operation of
the compressor, some lubricant in the compressor is mixed with
refrigerant such that the lubricant leaving the compressor contains
an amount of refrigerant. This may cause, for example, inadequate
supply of lubricant to the compressor. In an HVACR system, the
lubricant discharged from the compressor can be circulated back
into the compressor such as cavities of the bearings to maintain an
adequate supply of the lubricant.
[0428] In an embodiment, a lubricant separator can be provided
upstream or downstream of the compressor to separate the lubricant
from the refrigerant discharged from the compressor. However, the
lubricant separated from the lubricant separator can contain an
appreciable amount of refrigerant, as the refrigerant may dissolve
in the lubricant. This may lower purity of the lubricant and in
turn reduce, for example, viscosity of the lubricant. Low viscosity
can cause insufficient lubrication, sealing, and/or protection of
the running surfaces within the compressor.
[0429] Generally, a desirable viscosity range for a lubricant may
vary with regard to the type of compressor and/or operation of the
compressor. A lubricant used in a compressor in an HVACR system may
have a peak viscosity at a temperature higher than a saturation
temperature of the refrigerant.
[0430] Removing refrigerant dissolved in the lubricant can improve
the viscosity of the lubricant to be recycled back into the
compressor. This can be achieved by reducing pressure of the
lubricant and heating the lubricant.
[0431] By reducing the pressure of the lubricant, a portion of the
refrigerant contained in the lubricant can evaporate due to the
loss of pressure. The evaporation of the refrigerant may lower the
temperature of the lubricant.
[0432] By adding heat to the lubricant whose pressure and
temperature have been reduced, another portion of refrigerant can
be boiled from the lubricant. Thereby, the viscosity of the
lubricant can be further improved. Generally, if the pressure and
temperature of a lubricant containing refrigerant is lowered, for
example, by a pressure reducer, and subsequently heat is added to
the lubricant, refrigerant can be removed from the
lubricant-refrigerant mixture.
[0433] By combining the processes of reducing the pressure of a
lubricant and adding heat to the lubricant, the viscosity of the
lubricant can be improved to a desirable level.
[0434] The process of reducing pressure can be performed by any
suitable pressure-reducing device known in the art that has a
mechanism for reducing pressure. The pressure-reducing device can
including but not limited to an expander, pressure reducer,
pressure regulator, orifice, expansion valve, or the like. In an
embodiment, the pressure-reducing device can be a dedicated device.
In an embodiment, the pressure-reducing device can be an expansion
device of a refrigerant circuit of an HVACR system.
[0435] The process of adding heat to the lubricant can be
implemented by creating an internal heat exchanger within a
compressor so that the system heat can be utilized to boil off
refrigerant from the lubricant.
[0436] The term "boil off," as used in this Specification, means
that refrigerant contained in a lubricant is driven out of the
lubricant by heat.
[0437] The term "system heat," as used in this Specification, means
heat generated by the compressor due to compressing a working fluid
such as, for example, refrigerant. In an embodiment, system heat
can include heat from a motor driving the compressor.
[0438] The internal heat exchanger can include a single or a
plurality of passages. The passage(s), in part or as a whole, can
be provided or formed on a surface or within a body of a component
of the compressor. The component can be used to transfer system
heat to boil off refrigerant from the lubricant returning to the
compressor.
[0439] In an embodiment, the passage(s), in part or as a whole, can
extend within a body of a component of the compressor. In an
embodiment, the passage(s), in part or as a whole, can be
integrated into a body, for example a wall, of a component of the
compressor.
[0440] In an embodiment, the passage(s), in part or as a whole, can
be extended onto a surface of a component of the compressor. In an
embodiment, the internal heat exchanger, in part or as a whole, can
be integrated onto or into a surface of a component of the
compressor. The surface can include an interface surface or
non-interface surface. The interface surface in an embodiment can
be a machined surface between mating parts such as bearing housing
to rotor housing. A non-interface surface in an embodiment can have
a cover and bolts. In an embodiment, the surface can be a face of
the component. The "face" means any flat surface of a component of
the compressor.
[0441] The component of the compressor can be any part of the
compressor that can accommodate the passage(s) of the internal heat
exchanger and can transfer sufficient system heat. In an
embodiment, the component can be a part exposed to discharge
temperature. In an embodiment, the component can be a part whose
temperature is greater than a suction temperature of the
compressor. In an embodiment, the component can be a part near or
close to the discharge port of compressor. In an embodiment, the
component of the compressor can include but not limited to a
bearing housing cover, bearing housing, rotor housing, motor
housing, and/or muffler.
[0442] In an embodiment, the passage(s) of the internal heat
exchanger, in part or as a whole, can be provided within a casting
of a bearing housing cover, bearing housing, rotor housing, motor
housing, or muffler of the compressor. The casting of the bearing
housing, rotor housing, motor housing, or muffler of the compressor
can accommodate the passage(s) and transfer system heat. In an
embodiment, the passage(s), in part or as a whole, extend within a
bottom of the casting of the bearing housing, rotor housing, or
motor housing.
[0443] In an embodiment, the passage(s), in part or as a whole, can
be provided onto a surface of a bearing cover, bearing housing,
rotor housing, motor housing, or a muffler of the compressor. In an
embodiment, the passage(s), in part or as a whole, can extend on an
interface of the casting of a bearing housing, rotor housing, motor
housing, or muffler of the compressor. In an embodiment, the
passage(s), in part or as a whole, can be provided on a face of the
casting of the bearing housing cover, bearing housing, rotor
housing, motor housing, or muffler of the compressor.
[0444] The passage(s), in part or as a whole, can be machined
passages(s).
[0445] The passage(s), in part or as a whole, can be formed by any
suitable means including but not limited to casting, etching,
drilling, milling, retrofitting, welding, or a combination
thereof.
[0446] In an embodiment, the passage(s), in part or as a whole,
can, but not limited to, be casted within the bearing housing,
rotor housing, motor housing, or muffler of the compressor. In an
embodiment, the passage(s), in part or as a whole, is drilled
hole(s) within the casting of the bearing housing, bearing cover,
rotor housing, motor housing, or muffler of the compressor. In an
embodiment, the passage(s), in part or as a whole, can be milled on
a surface of the bearing housing cover, bearing housing, rotor
housing, motor housing, or muffler of the compressor.
[0447] The bearing housing can be disposed at or near the discharge
end where the compressed hot refrigerant is discharged. In some
circumstances, for example, the temperature of the casting of the
bearing housing may be higher than those of the rotor housing and
the motor housing.
[0448] The passage(s) of the internal heat exchanger can be
configured to any type of flow arrangements. In an embodiment, the
internal heat exchanger can be configured to include a single-pass
or multi-pass passage. In an embodiment, the internal heat
exchanger can be configured to include multiple parallel
single-pass passages.
[0449] The passage(s), in part or as a whole, can adopt any
suitable configuration, such as geometry and shape, that can
transfer sufficient system heat to the lubricant flowing therein.
The configuration can include but not limited to serpentine,
straight, and/or curved configurations. In an embodiment, the
passage(s) can be configured to form one or more serpentine
single-pass passages. In an embodiment, the passage(s) can be
configured to form one or more serpentine multi-pass passages, so
that the lubricant can flow back and forth for multiple times to
increase the heat transfer efficiency.
[0450] The compressor can be a component of a system. In an
embodiment, the system can be an HVACR system. The HVACR system can
include a lubricant source and a pressure-reducing device, in
addition to a compressor containing the internal heat exchanger. In
an embodiment, the lubricant source can be a lubricant separator.
The lubricant separator can receive compressed refrigerant
discharged from the compressor, and then separate lubricant from
gaseous compressed refrigerant. The pressure-reducing device can
reduce pressure of the lubricant received from the lubricant
separator so that at least a portion of the refrigerant in the
lubricant evaporates due to loss of pressure. The lubricant can be
routed to the internal heat exchanger for further improvement of
viscosity. Thus, the lubricant separator, pressure-reducing device,
and internal heat exchanger can constitute a pathway for refining
the lubricant to be cycled back to the compressor.
[0451] The lubricant separator can be disposed upstream or
downstream of the compressor. In an embodiment, the lubricant
separator is fluidly disposed between the compressor and the
condenser. In an embodiment, the lubricant separator is disposed
upstream of the compressor.
[0452] The lubricant separator can be any suitable device known in
the art that has a mechanism for separating lubricant from
refrigerant. In an embodiment, the lubricant separator can be an
oil tank or reservoir. The lubricant separator can be a dedicated
or non-dedicated device. In an embodiment, an oil reservoir is
deposed upstream of the compressor for separating lubricant from
refrigerant. In an embodiment, an evaporator of a refrigerant
circuit of an HVACR system can function as a non-dedicated
lubricant separator.
[0453] The pressure-reducing device can be disposed within the
compressor or outside of the compressor. In an embodiment, the
pressure-reducing device is disposed within the compressor. In an
embodiment, the pressure-reducing device is disposed outside of the
compressor.
[0454] The pressure-reducing device can include, but is not limited
to, a pressure regulator or expansion device. In an embodiment, the
pressure-reducing device is an orifice. In an embodiment, the
pressure-reducing device can be an expander such as, for example,
an expansion valve. In an embodiment, the pressure-reducing device
can be an expansion device of the refrigerant circuit of the HVACR
system.
[0455] A method, which uses the internal heat exchanger, the
compressor, or the system for improving the viscosity of a
lubricant to be cycled back into the compressor, can include
reducing a pressure of a lubricant containing refrigerant by a
pressure-reducing device and heating the lubricant containing
refrigerant in the internal heat exchanger of the compressor with
system heat to obtain a refined lubricant.
[0456] In an embodiment, the method can further include directing a
refrigerant-lubricant mixture discharged from the compressor to a
lubricant separator.
[0457] In an embodiment, the method can further include directing a
lubricant containing refrigerant from the lubricant separator to a
pressure-reducing device.
[0458] In an embodiment, the method can further include directing a
lubricant containing refrigerant from the pressure-reducing device
to the internal heat exchanger of the compressor.
[0459] In an embodiment, the method can further include directing a
lubricant from the internal heat exchanger to cavities of bearings
of the compressor.
[0460] The internal heat exchanger, system, and method herein can
improve viscosity of the lubricant returning to a compressor to a
desirable level without use of a sump. A sump is a device that can
receive both the lubricant separated from the lubricant separator
and a hot lubricant directly from the compressor, for example the
bearings. The hot lubricant heats the lubricant separated from the
lubricant separator in the sump, and as such a portion of
refrigerant in the lubricant can be boiled off. However, the sump
can increase the complexity and cost of the system.
[0461] FIG. 20 illustrates a schematic view of a refrigeration
system 6001, with which the embodiments as disclosed herein can be
practiced. The refrigeration system 6001 provides benefits for
improving viscosity of the lubricant returning to a compressor by
utilizing system heat generated in the compressor. The lubricant
may be cycled to, for example, lubricate, seal, and cool moving
surfaces within the compressor 6100.
[0462] Referring to FIG. 20, the refrigeration system 6001 can
include a compressor 6100, a lubricant separator 6200, a condenser
6300, an expansion device 6400, and an evaporator 6500. In an
embodiment, the lubricant separator 6200 may not be present or can
be included at a different location of the refrigeration system
6001. The compressor 6100 can include bearings 6102, rotors 6104,
an internal heat exchanger 6106, and a pressure-reducing device
6108. The internal heat exchanger 6106 is disposed within the
compressor 6100. The internal heat exchanger 6106 is in fluid
communication with cavities of the bearings 6102 and with the
pressure-reducing device 6108. The pressure-reducing device 6108 is
further in fluid communication with the lubricant separator 6200.
The lubricant separator 6200 is further in fluid communication with
the compressor 6100 and the condenser 6300. The lubricant separator
6200, the pressure-reducing device 6108, and the internal heat
exchanger 6106 can constitute a return pathway to circulate the
lubricant back to the compressor 6100.
[0463] In operation, the compressor 6100 compresses gaseous
refrigerant. The compressed gaseous refrigerant is discharged
together with lubricant as a high-pressure refrigerant-lubricant
mixture. The compressor 6100 then delivers the high-pressure
superheated refrigerant-lubricant mixture through a line 6010 to
the lubricant separator 6200. The lubricant separator 6200
separates the lubricant from the compressed gaseous refrigerant at
high pressure. In an embodiment, the lubricant separator 6200 can
include an oil reservoir. The lubricant, even after separation, may
contain an appreciable amount of refrigerant, which can lower
viscosity of the lubricant. As a result, the lubricant may not have
sufficient viscosity to lubricate the running surfaces of the
compressor 6100 including the bearings 6102.
[0464] If the lubricant from the lubricant separator 6200 at high
pressure is directly circulated into the bearings 6102 at low
pressure, a proportion of the refrigerant may evaporate from the
lubricant. However, this would not increase viscosity of the
lubricant to a sufficient level.
[0465] In the embodiment illustrated by FIG. 20, the viscosity of
the lubricant returning the compressor 6100 can be improved by both
reducing pressure and increasing temperature of the lubricant.
[0466] The lubricant from the lubricant separator 6200 enters the
pressure-reducing device 6108 through passage 6016. The
pressure-reducing device 6108 lowers the pressure of the lubricant,
and a proportion of refrigerant in the lubricant evaporates due to
loss of pressure. The evaporation of refrigerant also reduces
temperature of the lubricant. In an embodiment, the
pressure-reducing device 6108 is an orifice. In an embodiment, the
pressure-reducing device 6108 can be an expansion valve. In an
embodiment, the pressure-reducing device 6108 can be expander.
[0467] After pressure reduction, the lubricant from the
pressure-reducing device 6108 enters the internal heat exchanger
6106 through line 6020. The internal heat exchanger 106 can utilize
system heat generated in the compressor 6100 to increase
temperature of the lubricant, so that an additional proportion of
refrigerant can be driven out of the lubricant to further improve
viscosity. In an embodiment, the internal heat exchanger 6106
absorbs the system heat in the compressor 6100 to boil off
refrigerant contained in the lubricant. In an embodiment, the
pressure-reducing device 6108 is configured to reduce the pressure
of the lubricant as much as possible.
[0468] The internal heat exchanger 6106 can be integrated with a
component within the compressor 6100. The internal heat exchanger
6106 can include passage(s) where the lubricant flows. The
passage(s) of the internal heat exchanger 6106, in part or as a
whole, can be integrated for example within or on a surface of the
bearing housing assembly, rotor housing, motor housing, or muffler
of the compressor 6100.
[0469] The passage(s) of the internal heat exchanger 6106, in part
or as a whole, can be machined passage(s). In an embodiment, the
passage(s), in part or as a whole, can be drilled in a bottom of
the bearing housing, rotor housing, or motor housing of the
compressor 6100. In an embodiment, the passage(s), in part or as a
whole, can be casted in a bottom of the bearing housing, rotor
housing, or motor housing of the compressor 6100.
[0470] In an embodiment, the passage(s) of the internal heat
exchanger 6106 can be milled on a surface, for example an interface
surface, within the compressor 6100. In an embodiment, the
passage(s) can be milled on an interface surface of the bearing
housing, rotor housing, motor housing, or muffler of the compressor
6100.
[0471] In an embodiment, the flow rates of the lubricant in the
heat exchanger 6106 and/or the pressure-reducing device 6108 can be
controlled to optimize heat transfer to the lubricant and/or
pressure reduction of the lubricant, achieving an excellent
performance in degassing and raising temperature. In an embodiment,
the flow rates can be controlled by using a solenoid valve or other
regulating valve or flow control method. In an embodiment, the flow
rates could be controlled by logic defined by compressor operating
parameters to optimize the flow and heat transfer.
[0472] The lubricant can be optionally further heated by mixing
with a hot lubricant from the compressor 6100 such as the bearing
6102 and the rotor 6104. In an embodiment, the hot lubricant from
the compressor 6100 flows through line 6021 and enters into passage
6022 to further vaporize the refrigerant in the lubricant, before
the lubricant returns to the compressor 6100.
[0473] The fluid entering cavities of the bearings 6102 includes
gaseous refrigerant and a refined lubricant. The refined lubricant
is a liquid. The fluid to enter the cavities of the bearings 6102
is a two-phase fluid. Both the refined lubricant and the gaseous
refrigerant can enter into the cavities of the bearings 6102. In an
embodiment, the gaseous refrigerant is separated from the refined
lubricant by, for example, an internal lubricant separator, so that
the refined lubricant enters into the cavities of the bearings
6102. The gaseous refrigerant separated from the refined lubricant
merges with refrigerant from the evaporator 6500 through line 6024.
In an embodiment, the line 6024 is provided with a flow regulator
6023 to direct flow of the gaseous refrigerant separated from the
refined lubricant.
[0474] The compressed high-pressure gaseous refrigerant separated
from the lubricant separator 6200 enters the condenser 6300 through
passage 6014. In the condenser 6300, the compressed high-pressure
gaseous refrigerant is cooled and condenses into a liquid phase.
The refrigerant then passes an expansion device 6400 and enters the
evaporator 6500 through lines 6018 and 6019. The liquid refrigerant
in the evaporator 6500 evaporates into a gaseous phase. The gaseous
refrigerant then enters the compressor 6100 through passage
6026.
[0475] FIG. 21 illustrates another schematic view of a
refrigeration system 6002, with which the embodiments as disclosed
herein can be practiced.
[0476] Referring to FIG. 21, the compressor 6100 compresses a
gaseous refrigerant. The compressed gaseous refrigerant is
discharged from the compressor 6100 together with an appreciable
amount of lubricant, forming a compressed high-pressure
refrigerant-lubricant mixture. The compressor 6100 then delivers
the compressed high-pressure refrigerant-lubricant mixture through
a line 6010 to the condenser 6300. The compressed high-pressure
refrigerant-lubricant mixture gets cooled in the condenser 6300,
and gaseous refrigerant in this mixture is transformed into liquid
refrigerant. The condenser 6300 then delivers the
refrigerant-lubricant mixture to an expansion device 6400 and the
evaporator 6500 through lines 6018 and 6019. The expansion device
6400 reduces the pressure of the refrigerant-lubricant mixture, so
that the liquid refrigerant evaporates into a gaseous phase in
evaporator 6500, which cools the air flowing through the evaporator
6500. In an embodiment, the lubricant, which is in liquid form, and
some residual liquid refrigerant settle down in the evaporator
6500, forming a lubricant-refrigerant mixture. In an embodiment,
the expansion device 6400 reduces the pressure of the lubricant
discharged from the compressor 6100. This lubricant-refrigerant
mixture is then delivered to an optional pressure-reducing device
6108 through line 6016 to further lower the pressure of the
lubricant-refrigerant mixture. As such, an additional proportion of
the refrigerant may flash out of the lubricant-refrigerant mixture
due to reduction of the pressure, which may also further reduce the
temperature of the lubricant-refrigerant. In an embodiment, a pump
type device is provided at, for example, the line 6016 to drive the
lubricant-refrigerant mixture toward the internal heat exchanger
6106. The pump type device can be any types of pumper know in the
art that has a mechanism for pumping the lubricant-refrigerant
mixture. The lubricant-refrigerant mixture is then delivered to the
internal heat exchanger 6106 through passage 6020. The heat
exchanger 6106 further boils off refrigerant from the
lubricant-refrigerant mixture to obtain a refined lubricant with
sufficient viscosity for lubricating and sealing running surfaces
within the compressor 6100.
[0477] The refined lubricant can be optionally further heated by
mixing with hot lubricant from the compressor 6100 such as the
bearing 6102 and the rotor 6104. In an embodiment, the hot
lubricant from the compressor 6100 flows through line 6021 and
enters into passage 6022 to further boil off the refrigerant from
the refined lubricant, before the refined lubricant returns to
cavities of the bearings 6102 though the passage 6022.
[0478] Both the gaseous refrigerant and the refined lubricant can
enter into cavities of the bearings 6102 through passage 6022.
[0479] In an embodiment, the gaseous refrigerant is separated from
the refined lubricant, so that the refined lubricant enters into
the bearings of 6102. In an embodiment, the separated gaseous
refrigerant merges with the gaseous refrigerant from the evaporator
6500 through line 6024 and then enters the compressor 6100 through
line 6026 for compression. In an embodiment, the line 6024 is
provided with a flow regulator 6023 directing the flow of the
gaseous refrigerant separated from the refined lubricant.
[0480] FIG. 22 illustrates an example of the compressor 6100, with
which the embodiments as disclosed herein can be practiced.
[0481] Referring to FIG. 22, the compressor 6100 is a screw
compressor and further includes a bearing assembly 6130, a rotor
housing 6140, and a motor housing 6150.
[0482] The bearing assembly 6130 includes a bearing housing 6132
and a bearing cover 6134. The bearing assembly 6130 houses
bearings. The compressed working fluid such as refrigerant can be
discharged through the bearing assembly 6130. The bearing assembly
6130 covers the rotor housing 6140 at the axial end.
[0483] The rotor housing 6140 houses rotors 6142a and 6142b. The
rotor housing may have a suction port 6176 and discharge port 6178.
The suction port 6176 and discharge port 6178 are in fluid
communication with the working chamber 6144. The suction port 6176
and the discharge port 6178 may each be an axial port, a radial
port, or a combination of a radial and an axial port.
[0484] The suction port 6176 may receive the refrigerant at a
suction pressure and a suction temperature. The compressor 6100
compresses the refrigerant as the compressor 6100 communicates the
refrigerant from the suction port 6176 to the discharge port
6178.
[0485] In an embodiment, the motor housing 6150 houses an electric
motor 6152. The electric motor 6152 drives meshed screw rotors
6142a, 6142b. In an embodiment, the motor housing 6150 may be
integral to the rotor housing 6140.
[0486] FIG. 23 illustrates an embodiment of the internal heat
exchanger 6106 including passages drilled or casted within the
bottom wall of the casting of the bearing housing 6132 of a
compressor, according to an embodiment.
[0487] Referring to FIG. 23, the embodiment of the internal heat
exchanger 6106 can include a plurality passages. In an embodiment,
the internal heat exchanger includes seven internal passages
provided within the bottom wall of the casting of the bearing
housing 6132 of a compressor. The seven internal passages are 6410,
6412, 6414, 6416, 6418, 6420, and 6422. The seven internal passages
can be arranged in a parallel manner. It is understood that the
number and the arrangement of the internal passages in the
embodiment of the internal heat exchanger 6106 is exemplary and can
be other number and/or arrangement that can transfer sufficient
system heat for boiling off refrigerant out of lubricant.
[0488] The seven passages can be configured to a serpentine
seven-pass passage by other passages including passages 6413, 6417,
and 6421, with the passage 6410 being an inlet and the passage 6422
being an outlet in an embodiment. The serpentine seven-pass passage
allows the lubricant to flow back and forth seven times to absorb
system heat to remove the refrigerant contained in the lubricant.
As such, the lubricant can become refined with sufficient viscosity
to lubricating and sealing the running surfaces within the
compressor. It is understood that the seven internal passages can
be configured to any other flow configuration without being limited
particular to the serpentine seven-pass passages. In an embodiment,
the seven internal passages 6410, 6412, 6414, 6416, 6418, 6420, and
6422 can be configured to form multiple parallel single-pass
passages.
[0489] The passage 6422 is in fluid communication with passage
6430. The passage 6430 is further in fluid communication with
passage 6435 that is in fluid communication with cavities of the
bearings of the compressor. The passage 6435 can receive a fluid
from the passage 6422 and route the fluid to the cavities of the
bearings 6102 of the compressor.
[0490] A length of each passage is not particularly limited but can
be dependent on a flow rate and temperature rise needed. In an
embodiment, each of the passages 6410, 6412, 6414, 6416, 6418,
6420, and 6422 can have a length of at or about 6020 inches. Thus,
the total length of the serpentine seven-pass passage is at or
about 6140 inches. It is understood that any other suitable length
of passages can be chosen to transfer sufficient heat to boil off
refrigerant out of the lubricant.
[0491] In an embodiment, the passages can be formed by for example
machining. The passages can be manufactured by any suitable means
including but not limited to drilling, casting, etching,
retrofitting, etc.
[0492] The bottom wall of the bearing housing 6132 can have a
sufficient thickness for accommodating the passages. In an
embodiment, the passages, in part or as a whole can be manufactured
by casting holes within the bottom wall of the bearing housing 6132
of the compressor. In an embodiment, the passages, in part or as a
whole, can be manufactured by milling and/or retrofitting in
addition to casting and/or drilling. It is understood that the
above embodiment illustrated by FIG. 23 is merely an example. The
passages can be machined in any suitable location of the bearing
housing, rotor housing, or motor housing of the compressor,
depending on their shape, size, and design, if the location can
accommodate the passages and can provide sufficient system heat to
boil off the refrigerant out of the lubricant.
[0493] FIG. 24 illustrate an embodiment of the internal heat
exchanger 6106 including surface passages 6510 and 6520 provided on
a surface of a bearing housing of a compressor according to an
embodiment.
[0494] Referring to FIG. 24, the embodiment of the internal heat
exchanger 6106 includes passages 6510 and 6520 provided on a
surface of the bearing housing assembly of a compressor. In an
embodiment, the passages 6510 and 6520 are milled on a surface of
the bearing housing of the compressor. In an embodiment, the
passages 6510 and 6520 are provided on an interface surface of the
bearing housing of the compressor. In an embodiment, the interface
can be an interface surface between the bearing housing and the
rotor housing. It is understood that the embodiment of the internal
heat exchange 6106 can include one (1) or more than two (2)
passages.
[0495] The two passages 6510 and 6520 are fluidly connected with
the pressure-reducing device 6108. In an embodiment, the two
passages 6510 and 6520 can further respectively fluidly connected
with passages 6530 and 6540 below the interface surface of the
bearing housing of the compressor. In an embodiment, the passages
6530 and 6540 can be further in fluid communication with cavities
of the bearings of the compressor.
[0496] The passages 6510 and 6520 can have a serpentine shape. The
embodiment of the internal heat exchanger 6106 absorbs the system
heat of the compressor to boil off liquid refrigerant in the
lubricant. As such, the lubricant becomes refined with excellent
viscosity before entering into bearings 6102 of the compressor.
[0497] It is understood that the embodiment illustrated by FIG. 24
is an example. In an embodiment, the passages 6510 and 6520 can be
provided on a surface of the rotor housing, muffler, or motor
housing of the compressor.
[0498] The passages 6510 and 6520 are milled on a surface of the
bearing housing assembly. It is understood that the passages 6510
and 6520 can also be manufactured by any other suitable means such
as for example etching, welding, and the like. In an embodiment,
the passages 6530 and 6540 are drilled within the bearing housing
assembly. It is understood that the passages 6530 and 6540 can also
be manufactured by any other suitable means such as for example
casting.
[0499] Aspects:
[0500] Any of aspects 1-6 can be combined with any of aspects 7-9,
and any of aspects 1-9 can be combined with aspect 10. It is
understood that any of aspects 1-10 can be combined with any other
aspects recited herein.
[0501] Aspect 1. A compressor comprising an internal heat
exchanger, wherein the internal heat exchanger is fluid
communication with bearings of the compressor.
[0502] Aspect 2. The compressor of aspect 1, wherein the internal
heat exchanger is fluidly connected with a pressure-reducing
device.
[0503] Aspect 3. The compressor of aspects 1-2, wherein the
internal heat exchanger includes passages extended within bearing
housing, rotor housing, motor housing, or muffler of the
compressor.
[0504] Aspect 4. The compressor of aspects 1-3, wherein the
internal heat exchanger includes passage(s) provided onto a surface
or interface surface of bearing housing, motor housing, motor
housing, or muffler of the compressor.
[0505] Aspect 5. The compressor of aspects 1-4, wherein the
internal heat exchanger includes passage(s) casted or drilled
within bearing housing, motor housing, motor housing, or muffler of
the compressor.
[0506] Aspect 6. The compressor of aspects 1-4, wherein the
internal heat exchanger includes passage(s) milled on a surface or
interface surface of bearing housing assembly, motor housing, motor
housing, or muffler of the compressor.
[0507] Aspect 7. A heating, ventilation, air conditioning, and
refrigeration (HVACR) system, comprising the compressor of aspects
1-6.
[0508] Aspect 8. The HVACR system of aspect 7, wherein the HVACR
system further comprises a lubricant separator, the lubricant
separator receives fluid discharged from the compressor and
separates lubricant from the fluid.
[0509] Aspect 9. The HVACR system of aspect 8, wherein the
lubricant separator is in fluid communication with a
pressure-reducing device, and the pressure-reducing device is in
fluid communication with the internal heat exchanger.
[0510] Aspect 10. A method form improving viscosity of lubricant
returning to the compressor of aspects 1-9 for reuse, comprising:
reducing a pressure and temperature of a lubricant-refrigerant
mixture by a pressure-reducing device; and heating the
lubricant-refrigerant mixture in an internal heat exchanger of the
compressor, wherein the pressure-reducing device evaporates a
portion of refrigerant out of the lubricant-refrigerant mixture,
the internal heat exchanger absorbs system heat in the compressor
to boil off another portion of refrigerant out of the
lubricant-refrigerant mixture.
[0511] Disclosure relates to an internal heat exchanger within a
compressor, a system, and a method for improving viscosity of the
lubricant to be cycled back into the compressor. The internal heat
exchanger is in fluid communication with a pressure-reducing
device, which receives a lubricant separated from a
refrigerant-lubricant mixture discharged from the compressor. The
pressure-reducing device lowers pressure of the lubricant, causing
a proportion of refrigerant in the lubricant evaporates
concurrently with a temperature drop. The lubricant then flows
through the internal heat exchanger, so that another proportion of
refrigerant in the lubricant can be boiled off to obtain a refined
lubricant. The refined lubricant then enters into cavities of
bearings of the compressor for reuse.
[0512] Suction-Line Heat Exchanger (FIGS. 25-27)
[0513] This disclosure is related to a refrigeration circuit
including a suction line heat exchanger to increase a discharge
superheat of the compressor.
[0514] A suction line heat exchanger can allow relatively hot
liquid leaving a condenser of a refrigeration circuit to exchange
heat with relatively cool gas leaving an evaporator of a
refrigeration circuit. This heat exchange can increase the
temperature of working fluid that is being received at a suction
port of a compressor of the refrigeration circuit. The increased
suction temperature in turn can result in increased discharge
superheat for the discharge of the compressor. Increased discharge
superheat can improve oil separation and recovery and reduce
problems associated with lubricant being dissolved in the
refrigerant, particularly for compressor designs having improved
efficiency and for low global warming potential (low-GWP)
refrigerants such as R1234ze.
[0515] In an embodiment, a refrigeration circuit includes a
compressor, a condenser, an expander, an evaporator, and a suction
line heat exchanger. The suction line heat exchanger is configured
to exchange heat between a liquid side receiving a working fluid as
a liquid leaving the condenser, prior to the expander and a gas
side receiving the working fluid as a gas leaving the evaporator,
prior to the compressor. The liquid side includes a shell and the
gas side includes a plurality of tubes extending through the shell.
The suction line heat exchanger is configured such that a discharge
of the compressor has a discharge superheat of at or about
3.3.degree. C. or more than 3.3.degree. C.
[0516] In an embodiment, the refrigerant circuit further includes a
throttling valve between the plurality of tubes of the suction line
heat exchanger and the compressor.
[0517] In an embodiment, the shell has a length of at or about one
meter and the shell has a diameter of between at or about 200
millimeters (mm) and at or about 220 mm. The plurality of tubes
includes between at or about 55 and at or about 65 tubes, and each
of the plurality of tubes has an interior diameter of between at or
about 15 mm and at or about 18 mm.
[0518] In an embodiment, a pressure drop across the gas side of the
suction line heat exchanger is at or about 10 kPa or less than 10
kPa for refrigerant R1234ze.
[0519] In an embodiment, a temperature of gas leaving the gas side
of the suction line heat exchanger is greater than at or about
1.5.degree. C. greater than a temperature of the gas entering the
gas side of the suction line heat exchanger.
[0520] In an embodiment, the refrigeration circuit further includes
a plurality of baffles within the shell. Each of the baffles
includes a continuous perimeter in contact with an entire inner
diameter of the shell and an open area. In an embodiment, the open
area includes at or about 30% of the area defined by the continuous
perimeter.
[0521] In an embodiment, the shell includes a plurality of
longitudinal baffles each extending a length of the shell and
extending from an inner surface of the shell to one of the
plurality of tubes.
[0522] In an embodiment, a suction line heat exchanger embodiment
includes a liquid side including an inlet connected to a condenser
of a refrigeration circuit, an outlet connected to an expander of
the refrigeration circuit, and a shell defining an internal space.
The suction line heat exchanger also includes a gas side including,
an inlet connected to an evaporator of the refrigeration circuit,
an inlet header connecting the inlet to a plurality of tubes, the
plurality of tubes extending through the internal space from one
end of the shell to an opposing end of the shell, and an outlet
header connecting the plurality of tubes to an outlet. The suction
line heat exchanger is configured to increase a discharge superheat
of a compressor of the refrigeration circuit such that the
discharge superheat is at or about 3.3.degree. C. or more than
3.3.degree. C.
[0523] In an embodiment, the shell has a length of at or about one
meter and the shell has a diameter of between at or about 200
millimeters (mm) and at or about 220 mm. The plurality of tubes
includes between at or about 55 and at or about 65 tubes, and each
of the plurality of tubes has an interior diameter of between at or
about 15 mm and at or about 18 mm.
[0524] In an embodiment, a pressure drop across the gas side of the
suction line heat exchanger is at or about 10 kPa or less than 10
kPa for refrigerant R1234ze.
[0525] In an embodiment, there is a chamfer where each of the tubes
is connected to the inlet header, and a chamfer where each of the
tubes is connected to the outlet header.
[0526] In an embodiment, the suction line heat exchanger further
includes a plurality of baffles within the shell. Each of the
baffles includes a continuous perimeter in contact with an entire
inner diameter of the shell and an open area. In an embodiment, the
open area includes at or about 30% of the area defined by the
continuous perimeter.
[0527] In an embodiment, the shell includes a plurality of
longitudinal baffles each extending a length of the shell and
extending from an inner surface of the shell to one of the
plurality of tubes.
[0528] In an embodiment, a method of increasing superheat of a
refrigerant includes directing relatively hot liquid refrigerant
from a condenser to a suction line heat exchanger; directing
relatively cool gaseous refrigerant from an evaporator to the
suction line heat exchanger; performing heat exchange between the
relatively hot liquid refrigerant and the relatively cool gaseous
refrigerant using the suction line heat exchanger, to increase the
heat of the relatively cool gaseous refrigerant to obtain a heated
gaseous refrigerant; and directing the heated gaseous refrigerant
to a suction port of the compressor, wherein the compressor heats
and pressurizes the heated gaseous refrigerant to obtain a
superheated gaseous refrigerant.
[0529] Improvements to efficiency of compressors may reduce
superheating by the compressor. In turn, this can result in
difficulty in oil separation and increased issues with oil
saturation in a working fluid. A heat exchanger at the suction line
heating working fluid prior to its entry into the compressor can
result in the discharge of the compressor being superheated,
improving oil separation. Further, this can increase the available
portions of the operational map by ensuring sufficient performance
and lubricant separation even at lower capacities.
[0530] FIG. 25 illustrates a circuit including a suction-line heat
exchanger according to an embodiment. The refrigeration circuit
2500 shown in FIG. 25 includes a compressor 2502, a condenser 2504,
a suction line heat exchanger 2506, expansion device 2508,
evaporator 2510, and optional throttling valve 2512.
[0531] Compressor 2502 is a compressor connected to the
refrigeration circuit 2500. The compressor 2502 may be, for
example, a screw compressor, where compression chambers are formed
and a fluid such as a working fluid is compressed by the rotation
of two rotors and the engagement of lobes on each of the rotors.
Compressor 2502 may include one or more lubricated bearings that
may, for example, support and allow the rotation of components of
the compressor such as the rotors of a screw compressor. Compressor
2502 can be, for example, any of the compressor embodiments
described herein. Compressor 2502 has an operational map defining
its range of operation over saturated suction temperatures and
saturated discharge temperatures for the compressor. Compressor
2502 can have a minimum required suction pressure for operation.
The discharge of compressor 2502 can have a discharge superheat of
at least 3.3.degree. C. or at or about 3.3.degree. C. across the
entire operating map within which compressor 2502 is operated
during operation of refrigeration circuit 2500. In an embodiment,
the discharge superheat of the compressor 2502 is in the range from
at or about 3.3.degree. C. to at or about 25.degree. C. In an
embodiment, the compressor 2502 requires a suction pressure in a
range from at or about 1.35 to at or about 5.13 bars.
[0532] Condenser 2504 is located downstream of the compressor 2502.
Condenser 2504 is a component of the refrigeration circuit where
the working fluid compressed by compressor 2502 rejects heat.
Condenser 2504 receives the working fluid in a heated and
compressed state from compressor 2502. Condenser 2504 allows the
heated and compressed working fluid to reject heat.
[0533] Suction line heat exchanger 2506 allows the exchange of heat
between the working fluid leaving condenser 2504, and the working
fluid leaving evaporator 2510. The working fluid leaving condenser
2504 is at a relatively higher temperature than the working fluid
leaving evaporator 2510. The exchange of heat in suction line heat
exchanger 2506 heats the working fluid from evaporator 2510 that
then passes to compressor 2502. The exchange of heat in suction
line heat exchanger 2506 also cools the working fluid from
condenser 2504 that then passes to expansion device 2508. Suction
line heat exchanger 2506 can include a plurality of tubes, a shell
and one or more baffles within the shell, which are detailed below
and shown in FIGS. 26A, 26B, and 27. The suction line heat
exchanger 2506 can be configured to provide subcooling sufficient
to preserve the cooling capacity of the refrigeration circuit 2500
without excessive pressure drop of the working fluid across the
suction line heat exchanger 2506. The subcooling and pressure drop
values may be particular to the design of a particular refrigerant
circuit 2500. In an embodiment, a temperature of gas leaving the
gas side of the suction line heat exchanger 2506 can be in the
range from at or about 0.degree. C. to at or about 20.degree. C. In
an embodiment, the heating of gas in suction line heat exchanger
can result in a discharge superheat of the compressor being
increased by at least 1.5.degree. C. or at or about 1.5.degree. C.
In an embodiment, a subcooling in suction line heat exchanger 2506
can be at least 33 kW or at or about 33 kW.
[0534] Expansion device 2508 is a device configured to expand the
working fluid passing through. The expansion causes the working
fluid to significantly decrease in temperature. In an embodiment,
the expansion device 2508 may be an expander such as an expansion
valve, expansion plate, expansion vessel, orifice, the like, or
other such types of expansion mechanisms. It should be appreciated
that the expansion device 2508 may be any type of expander used in
the field for expanding a working fluid causing the working fluid
to decrease in temperature.
[0535] Evaporator 2510 provides heat exchange between the working
fluid leaving expansion device 2508 and another fluid. In
evaporator 2510, the working fluid absorbs heat from the other
fluid, evaporating the working fluid. Working fluid leaving
evaporator 2510 then travels to suction line heat exchanger
2506.
[0536] Optionally, throttling valve 2512 can be included between
suction line heat exchanger 2506 and compressor 2502. In an
embodiment, throttling valve 2512 is not included in the
refrigeration circuit 2500, and the suction line heat exchanger
2506 may be directly connected to the suction of compressor 2502.
Throttling valve 2512 can control the flow of working fluid into
the suction port of compressor 2502, for example to maintain
suitable pressure between the evaporator 2510 and the suction port
of the compressor 2502.
[0537] FIG. 26A illustrates a perspective view of a suction-line
heat exchanger 2600 according to an embodiment. FIG. 26B
illustrates a side view of the suction-line heat exchanger 2600
according to the embodiment shown in FIG. 26A. In FIG. 26A, the
shell 2602 is omitted such that internal components of the heat
exchanger are visible. In FIG. 26B, the tubes 2608 are omitted from
the sectional view while shell 2602 is included.
[0538] Suction line heat exchanger 2600 includes a shell 2602,
which is shown cut away to allow the interior of suction line heat
exchanger 2600 to be visible. Shell 2602 has an inlet 2604 and an
outlet 2606, and a plurality of tubes 2608 connected to an inlet
header 2610 and an outlet header 2612. The inlet header 2610 is
connected to an inlet 2614 and the outlet header 2612 is connected
to an outlet 2616. Baffles 2618 can be included within shell 2602
and surrounding tubes 2608. Suction line heat exchanger 2600 can
further include longitudinal baffles 2620.
[0539] The suction line heat exchanger 2600 can be configured to
provide subcooling sufficient to preserve the cooling capacity of a
refrigeration circuit and without excessive pressure drop of the
working fluid across the suction line heat exchanger 2600. In an
embodiment, the subcooling provided by suction line heat exchanger
2600 can be at least 33 kW or at or about 33 kW. For example, the
heating of the fluid passing through tubes 2608 can be sufficient
that the discharge superheat of a compressor receiving the fluid is
at least 3.3.degree. C. or at or about 3.3.degree. C., for example,
across the entire operating map of the compressor. In an
embodiment, the suction line heat exchanger 2600 adds at least
1.5.degree. C. or at or about 1.5.degree. C. to the temperature of
gas passing through tubes 2608. In an embodiment, the pressure drop
is such that the fluid leaving the suction line heat exchanger 2600
has a pressure greater than a minimum suction pressure of the
compressor. In an embodiment, a pressure drop for the relatively
cool gas across the suction line heat exchanger 2600 is at or about
10 kPa or less than 10 kPa. This configuration can include
parameters including the number and diameter of tubes 2608, the
length of the shell 2602, features such as a conical inlet and
outlet headers 2610, 2612, chamfering of the inlets to each of the
tubes 2608, and the like.
[0540] Shell 2602 receives working fluid from a first point in a
refrigeration circuit, such as refrigeration circuit 2500 described
above and shown in FIG. 25. In an embodiment, the working fluid
received by and conveyed through shell 2602 is a relatively hot
liquid received from a condenser, such as condenser 2504 discussed
above and shown in FIG. 25. In an embodiment, the length and/or the
diameter of shell 2602 is based on, for example, one or more of the
available space in an HVACR unit, the desired heat exchange at the
suction line heat exchanger 2600, and the temperature, density,
and/or flow rates of the fluids within shell 2602 and tubes 2608,
respectively. In an embodiment, shell 2602 is at or about one meter
in length. In an embodiment, shell 2602 is at or about 1006 mm in
length. In an embodiment, shell 2602 has an exterior diameter of
between at or about 200 mm and at or about 220 mm. In an
embodiment, shell 2602 has an interior diameter of between at or
about 195 mm to 202 mm.
[0541] Shell 2602 has an inlet 2604 and an outlet 2606. Inlet 2604
is an inlet in fluid communication with a hot liquid source such as
a condenser of a refrigerant circuit, such as condenser 2504.
Outlet 2606 allows fluid to exit shell 2602 once it has exchanged
heat with the fluid in the tubes 2608. Outlet 2606 may be in fluid
communication with an expander included in the refrigeration
circuit such as expansion device 2508 described above and shown in
FIG. 25. In an embodiment, shell 2602, inlet 2604 and outlet 2606
form the liquid side of suction line heat exchanger 2600.
[0542] A plurality of tubes 2608 extend through shell 2602. The
tubes 2608 are sealed from the interior of shell 2602 such that
fluid in tubes 2608 cannot mix with fluid within the shell 2602.
The number of tubes can be selected based on the values defining a
sufficient exchange of heat between the fluids, and properties of
the fluids including, for example, their temperature, flow rate,
density, and the like. The size of shell 2602 may be affected by
the number and size of tubes 2608. In an embodiment, suction line
heat exchanger 2600 includes sixty-one tubes 2608. The tubes 2608
may have a length and a diameter selected to allow sufficient heat
exchange within the suction line heat exchanger 2600. In an
embodiment, sufficient heat exchange can be defined based on one or
more of the refrigerant used as the working fluid, such as, for
example, R1234ze, a lubricant used in a compressor connected to the
suction line heat exchanger 2600, the operating map of the
compressor, compressor flow, compressor efficiency, discharge
superheat for portions of the operating map, and the temperatures
of the working fluid in the relatively hot liquid state entering
shell 2602 and the relatively cool gaseous state entering tubes
2608. The tubes 2608 are made of a thermally-conductive material
allowing heat transfer between the fluid in shell 2602 and the
fluid in each of the tubes 2608. In an embodiment, the tubes are
made of copper. In an embodiment, the material of the tubes is
selected based on other parameters such as one or more of the
length of the tubes 2608 and/or the shell 2602, the rates of fluid
flow through the shell 2602 and/or the tubes 2608, the temperatures
of the fluid in each of the shell 2602 and tubes 2608, and the
like, to allow sufficient heat exchange within the suction line
heat exchanger 2600. In an embodiment, the length of each of the
tubes 2608 is the same as the length of shell 2602. In an
embodiment, the length of each of the tubes 2608 is at or about
approximately one meter. In an embodiment, the outer diameter of
each of the tubes 2608 is from at or about 18 mm to at or about 19
mm. In an embodiment, the thickness of the wall of each of the
tubes 2608 is between at or about 2.3 mm and at or about 2.6 mm. In
an embodiment, the interior diameter of each of the tubes 2608 is
between at or about 15.4 mm and at or about 16.7 mm.
[0543] The tubes 2608 are each connected to an inlet header 2610
and also to an outlet header 2612. The inlet header 2610 is
connected to an inlet 2614 and the outlet header 2612 is connected
to an outlet 2616. In an embodiment, the inlet header 2610 is
generally conical and chamfered in shape, having a smaller diameter
at the inlet 2614 and a larger diameter at shell 2602. In an
embodiment, the outlet header 2616 is generally conical and
chamfered in shape, having a smaller diameter at the outlet 2616
and a larger diameter at shell 2606.
[0544] In an embodiment, the working fluid received at inlet header
2610 and divided to flow through the plurality of tubes 2608 is a
relatively cool gas received from an evaporator of a refrigeration
circuit including the suction line heat exchanger 2600. The
relatively cool gas is at a temperature lower than the temperature
of the relatively hot liquid received at and passing through shell
2602. In an embodiment, there is a chamfer where each of the tubes
2608 meets the inlet header 2610, to facilitate flow into each of
the tubes 2608 and reduce pressure drop.
[0545] Outlet header 2612 receives working fluid from tubes 2608 as
a gas that has been heated by heat exchange with the relatively hot
liquid in shell 2602. Each of tubes 2608 joins outlet header 2612,
where the flows from the tubes combine and are conveyed to outlet
2616. In an embodiment, where each of the tubes 2608 joins the
outlet header 2612, the tubes have a chamfered surface expanding
towards outlet header 2612 to facilitate flow from tubes 2608 into
outlet header 2612 and reduce pressure drop.
[0546] The outlet 2616 allows the working fluid that entered at
inlet 2614 and was directed through tubes 2608 to leave the suction
line heat exchanger 2600. In an embodiment, the outlet 2616 is
connected to a suction port of a compressor of a refrigeration
circuit. At outlet 2616, the working fluid has a greater
temperature than it did at inlet 2614 of the suction line heat
exchanger 2600. The relatively heated working fluid can result in
an increased discharge superheat once the working fluid is
compressed by the compressor and discharged, compared to working
fluid in an otherwise equivalent refrigeration circuit lacking
suction line heat exchanger 2600. In an embodiment, tubes 2608,
inlet header 2610, outlet header 2612, inlet 2614, and outlet 2614
form the gas side of suction line heat exchanger 2600.
[0547] Baffles 2618 can be included within shell 2602 and
surrounding tubes 2608. In an embodiment, two baffles 2618 are
located within shell 2602. Baffles 2618 are configured to partially
obstruct and/or redirect flow through the shell 2602. The direction
of flow of fluid through shell 2602 by baffles 2618 can improve the
exchange of heat between the fluid within shell 2602 and the fluid
in tubes 2608. In an embodiment including multiple baffles, the
baffles can each be oriented differently, so that areas allowing
fluid to pass each of the baffles 2618 do not overlap one another
or only partially overlap one another when viewed in the
longitudinal direction of shell 2602. At least a portion of baffles
2618 surround a portion of the tubes 2608 of the suction line heat
exchanger 2600, such that fluid cannot pass between those tubes
2608 and the baffle 218. In an embodiment, the baffles 2618 are
according to the design of baffle 2800 described below and shown in
FIG. 27.
[0548] Longitudinal baffles 2620 can also be provided within shell
2602. Longitudinal baffles 2620 can extend all or less than all of
the length of the interior surface of the shell 2602. Longitudinal
baffles 2620 and baffles 2618 can limit or reduce the amount of
fluid flow bypassing tubes 2608 at the wall of the shell 2602. In
an embodiment, two longitudinal baffles 2620 are provided. In an
embodiment, the longitudinal baffles are at positions within shell
2602 opposing one another. Longitudinal baffles 2620 may pass
through baffles 2618 at notches formed within those baffles.
Longitudinal baffles 2620 can each extend from the inner surface of
shell 2602 to an outer surface of one of the plurality of tubes
2608. In an embodiment, each of the longitudinal baffles 2620
extends from the inner surface of the shell 2602 to the nearest
tube of the plurality of tubes 2608. In an embodiment, longitudinal
baffles 2620 further assist in aligning and positioning the other
components of suction line heat exchanger 2600. While longitudinal
baffles 2620 are shown in a suction line heat exchanger 2600,
longitudinal baffles 2620 can be included in any suitable shell and
tube design heat exchanger.
[0549] FIG. 27 illustrates a heat exchanger baffle 2700 according
to an embodiment. In an embodiment, one or more of the heat
exchanger baffle 2700 can be included in a suction line heat
exchanger such as suction line heat exchanger 2600 described above
and shown in FIGS. 25 and 26.
[0550] The heat exchanger baffle 2700 generally includes a
continuous perimeter 2702 corresponding to the inner shape of the
shell of the heat exchanger, such as shell 2602 described above and
shown in FIGS. 26A and 26B. The heat exchanger baffle 2700 includes
a fluid passage 2704, and channels 2706 corresponding to the size,
shape and position of tubes outside the fluid passage 2702, such as
tubes 2608 described above and shown in FIGS. 26A and 26B. The heat
exchanger baffle 2700 can further include notches 2708 configured
to accommodate longitudinal baffles such as longitudinal baffles
2620 described above and shown in FIGS. 26A and 26 B.
[0551] Continuous perimeter 2702 follows the surface of the shell
of a heat exchanger into which heat exchanger baffle 2700 is
installed. Continuous perimeter 2702 is configured such that it
surrounds all of the tubes of the heat exchanger within the shell,
such as, for example, the entire plurality of tubes 2608 described
above and shown in FIGS. 26A and 26B. Continuous perimeter 2702 can
be configured to match the inner diameter of the shell, such as
shell 2602 described above and shown in FIGS. 26A and 26B.
[0552] Fluid passage 2704 is an opening located within continuous
perimeter 2702 allowing fluid to flow from one side of the baffle
2700 to the other. Fluid passage 2704 can be within the continuous
perimeter 2702 such that it is completely surrounded by portions of
heat exchanger baffle 2700 that obstruct fluid flow. In an
embodiment, fluid passage 2704 has a generally pentagonal shape. In
an embodiment, fluid passage 2704 has rounded corners. In an
embodiment, the perimeter of fluid passage 2704 includes one or
more recesses formed therein corresponding to tubes of the heat
exchanger, such as tubes 2608, that would be intersected by the
perimeter of the fluid passage 2704. In an embodiment, fluid
passage 2704. In an embodiment, the area of fluid passage 2704 is
between at or about 25% and at or about 35% of the area defined by
continuous perimeter 2702. In an embodiment, the area of fluid
passage 2704 is at or about 30% of the area defined by continuous
perimeter 2702.
[0553] Channels 2706 each surround one of the tubes of the heat
exchanger, such as tubes 2608 described above and shown in FIGS.
26A and 26B. In an embodiment, the channels are sized such that
they contact the tubes 2608 and do not provide spaces allowing
fluid flow between the exterior of the tubes 2608 and the heat
exchanger baffle 2700. In an embodiment, the number of channels
2706 can be the number of tubes 2608 outside of the fluid passage
2704.
[0554] Notches 2708 are formed in continuous perimeter 2702 of heat
exchanger baffle 2700 at positions corresponding to where any
longitudinal baffles are located on an inner surface of the shell.
The longitudinal baffles can be, for example, the longitudinal
baffles 2620 described above and shown in FIGS. 26A and 26B. In an
embodiment, the notches 2708 formed in the heat exchanger baffle
2700 can be configured to engage with corresponding notches formed
in the longitudinal baffles.
[0555] Where multiple heat exchanger baffles 2700 are included in a
suction line heat exchanger, the fluid passages 2704 of the heat
exchanger baffles 2700 can be offset from one another such that the
respective fluid passages 2704 are not aligned with one another. In
an embodiment, the fluid passage 2704 of a heat exchanger baffle
2700 is aligned with a portion of the adjacent heat exchanger
baffle that obstructs fluid flow. In an embodiment, the fluid
passages 2704 are opposite one another, for example, having a fluid
passage 2704 of a first baffle towards a bottom of the shell and a
fluid passage 2704 of a second baffle towards the top of the
shell.
[0556] Aspects:
[0557] Any of aspects 1-8 can be combined with any of aspects 9-13
and any of aspects 14 and 15, and any of aspects 9-13 may be
combined with any of aspects 14 and 15. It is understood that any
of aspects 1-15 can be combined with any other aspects recited
herein.
[0558] Aspect 1. A refrigerant circuit, comprising:
a compressor; a condenser; an expander; an evaporator; and a
suction line heat exchanger configured to exchange heat between a
liquid side receiving a working fluid as a liquid leaving the
condenser, prior to the expander and a gas side receiving the
working fluid as a gas leaving the evaporator, prior to the
compressor, wherein the liquid side includes a shell and the gas
side includes a plurality of tubes extending through the shell,
wherein the suction line heat exchanger is configured such that a
discharge of the compressor has a discharge superheat of at or
about 3.3.degree. C. or more than 3.3.degree. C.
[0559] Aspect 2. The refrigerant circuit according to aspect 1,
further comprising a throttling valve between the plurality of
tubes of the suction line heat exchanger and the compressor.
[0560] Aspect 3. The refrigerant circuit according to any of
aspects 1-2, wherein:
the shell has a length of at or about one meter, the shell has a
diameter of between at or about 200 millimeters (mm) and at or
about 220 mm, the plurality of tubes includes between at or about
55 and at or about 65 tubes, and each of the plurality of tubes has
an interior diameter of between at or about 15 mm and at or about
18 mm.
[0561] Aspect 4. The refrigerant circuit according to any of
aspects 1-3, wherein a pressure drop across the gas side of the
suction line heat exchanger is 10 kPa or less for refrigerant
R1234ze.
[0562] Aspect 5. The refrigerant circuit according to any of
aspects 1-4, wherein a temperature of gas leaving the gas side of
the suction line heat exchanger is greater than 1.5.degree. C. or
at or about 1.5.degree. C. greater than a temperature of the gas
entering the gas side of the suction line heat exchanger.
[0563] Aspect 6. The refrigerant circuit according to any of
aspects 1-5, further comprising a plurality of baffles within the
shell, wherein each of the baffles includes a continuous perimeter
in contact with an entire inner diameter of the shell and an open
area.
[0564] Aspect 7. The refrigerant circuit according aspect 6,
wherein the open area comprises at or about 30% of the area defined
by the continuous perimeter.
[0565] Aspect 8. The refrigerant circuit according to any of
aspects 1-7, wherein the shell includes a plurality of longitudinal
baffles each extending a length of the shell and extending from an
inner surface of the shell to one of the plurality of tubes.
[0566] Aspect 9. A suction line heat exchanger comprising:
a liquid side including:
[0567] an inlet connected to a condenser of a refrigeration
circuit;
[0568] an outlet connected to an expander of the refrigeration
circuit; and
[0569] a shell defining an internal space; and
a gas side including:
[0570] an inlet connected to an evaporator of the refrigeration
circuit;
[0571] an inlet header connecting the inlet to a plurality of
tubes, the plurality of tubes extending through the internal space
from one end of the shell to an opposing end of the shell;
[0572] an outlet header connecting the plurality of tubes to an
outlet, wherein the suction line heat exchanger is configured to
increase a discharge superheat of a compressor of the refrigeration
circuit such that the discharge superheat is at or about
3.3.degree. C. or more than 3.3.degree. C.
[0573] Aspect 10. The suction line heat exchanger according to
aspect 9, wherein a pressure drop across the gas side is 10 kPa or
less for refrigerant R1234ze.
[0574] Aspect 11. The suction line heat exchanger according to any
of aspects 9-10, wherein there is a chamfer where each of the tubes
is connected to the inlet header, and a chamfer where each of the
tubes is connected to the outlet header.
[0575] Aspect 12. The suction line heat exchanger according to any
of aspects 9-11, further comprising a plurality of baffles within
the shell, wherein each of the baffles includes a continuous
perimeter in contact with an entire inner diameter of the shell and
an open area, the open area comprises at or about 30% of the area
defined by the continuous perimeter.
[0576] Aspect 13. The suction line heat exchanger according to any
of aspects 9-12, wherein the shell includes a plurality of
longitudinal baffles each extending a length of the shell and
extending from an inner surface of the shell to one of the
plurality of tubes.
[0577] Aspect 14. A method of increasing superheat of a
refrigerant, comprising: directing relatively hot liquid
refrigerant from a condenser to a suction line heat exchanger;
directing relatively cool gaseous refrigerant from an evaporator to
the suction line heat exchanger; performing heat exchange between
the relatively hot liquid refrigerant and the relatively cool
gaseous refrigerant using the suction line heat exchanger, to
increase the heat of the relatively cool gaseous refrigerant to
obtain a heated gaseous refrigerant; and directing the heated
gaseous refrigerant to a suction port of the compressor, wherein
the compressor heats and pressurizes the heated gaseous refrigerant
to obtain a superheated gaseous refrigerant.
[0578] Aspect 15. The method of aspect 14, wherein the refrigerant
is R1234ze.
[0579] The terminology used in this specification is intended to
describe particular embodiments and is not intended to be limiting.
The terms "a," "an," and "the" include the plural forms as well,
unless clearly indicated otherwise. The terms "comprises" and/or
"comprising," when used in this specification, specify the presence
of the stated features, integers, steps, operations, elements,
and/or components, but do not preclude the presence or addition of
one or more other features, integers, steps, operations, elements,
and/or components.
[0580] With regard to the preceding description, it is to be
understood that changes may be made in detail, especially in
matters of the construction materials employed and the shape, size,
and arrangement of parts without departing from the scope of the
present disclosure. This specification and the embodiments
described are exemplary only, with the true scope and spirit of the
disclosure being indicated by the claims that follow.
* * * * *