U.S. patent application number 12/997938 was filed with the patent office on 2011-04-28 for refrigerant system and method of operating the same.
This patent application is currently assigned to CARRIER CORPORATION. Invention is credited to Alexander Lifson, Michael F. Taras.
Application Number | 20110094248 12/997938 |
Document ID | / |
Family ID | 40801471 |
Filed Date | 2011-04-28 |
United States Patent
Application |
20110094248 |
Kind Code |
A1 |
Taras; Michael F. ; et
al. |
April 28, 2011 |
Refrigerant System and Method of Operating the Same
Abstract
The present disclosure provides a refrigerant system that
comprises a compressor, a main refrigerant circuit, an economizer
refrigerant circuit, and a bypass refrigerant circuit. The
refrigerant system further comprises a single refrigerant flow
control device switching between different operational modes to
provide various degree of system unloading in operation. The
present disclosure also provides a method of operating the
refrigerant system.
Inventors: |
Taras; Michael F.;
(Fayetteville, NY) ; Lifson; Alexander; (Manlius,
NY) |
Assignee: |
CARRIER CORPORATION
Farmington
CT
|
Family ID: |
40801471 |
Appl. No.: |
12/997938 |
Filed: |
December 20, 2007 |
PCT Filed: |
December 20, 2007 |
PCT NO: |
PCT/US2007/026044 |
371 Date: |
December 14, 2010 |
Current U.S.
Class: |
62/115 ;
62/196.1; 62/500; 62/513 |
Current CPC
Class: |
F25B 1/10 20130101; F25B
2600/2501 20130101; F25B 2600/0261 20130101; F25B 2400/13 20130101;
F25B 2600/2521 20130101 |
Class at
Publication: |
62/115 ; 62/500;
62/513; 62/196.1 |
International
Class: |
F25B 1/00 20060101
F25B001/00; F25B 1/06 20060101 F25B001/06; F25B 41/00 20060101
F25B041/00; F25B 41/04 20060101 F25B041/04 |
Claims
1. A refrigerant system comprising: a compressor having a suction
port and an intermediate port; a main refrigerant circuit; an
economizer refrigerant circuit; a bypass refrigerant circuit; and a
flow control device, wherein said flow control device comprises: a
first position putting said economizer refrigerant circuit in fluid
communication with at least one of said suction port and said
intermediate port of said compressor, during an economized mode of
operation, and a second position putting said intermediate port of
said compressor and said suction port of said compressor in fluid
communication through said bypass refrigerant circuit, during a
bypass mode of operation.
2. The refrigerant system of claim 1, wherein said flow control
device further has a third position isolating said economizer
refrigerant circuit and said bypass refrigerant circuit from said
main refrigerant circuit, during a normal mode of operation.
3. The refrigerant system of claim 1, further comprising a first
controller in communication with said flow control device.
4. The refrigerant system of claim 3, wherein said first controller
controls the refrigerant system.
5. The refrigerant system of claim 3, wherein said first controller
is in communication with a second controller, wherein said second
controller controls the refrigerant system.
6. The refrigerant system of claim 1, further comprising an
economizer heat exchanger in fluid communication with said
compressor, wherein at least a portion of a refrigerant flowing
through said main refrigerant circuit is diverted through said
economizer refrigerant circuit at a point upstream of said
economizer heat exchanger, during said economized mode of
operation.
7. The refrigerant system of claim 1, further comprising an
economizer heat exchanger in fluid communication with said
compressor, wherein at least a portion of a refrigerant flowing
through said main refrigerant circuit is diverted through said
economizer circuit at a point downstream of said economizer heat
exchanger, during said economized mode of operation.
8. The refrigerant system of claim 1, wherein said flow control
device further has a third position placing said economizer
refrigerant circuit and said bypass refrigerant circuit in fluid
communication with each other, and with said main refrigerant
circuit, during an economized bypass mode of operation.
9. The refrigerant system of claim 1, wherein said flow control
device adjusts proportions of a refrigerant flowing into said
suction port and said intermediate port.
10. The refrigerant system of claim 1, wherein when said flow
control device is in said first position, said economizer
refrigerant circuit is in fluid communication with only one of said
suction port and said intermediate port.
11. The refrigerant system of claim 1, wherein said refrigerant
flow control device adjusts refrigerant flow through either
modulated or pulsed control.
12. The refrigerant system of claim 1, wherein said flow control
device further has a third position, putting said economizer
refrigerant circuit and said bypass refrigerant circuit in fluid
communication.
13. The refrigerant system of claim 12, wherein said flow control
device adjusts proportions of a refrigerant flowing through said
economizer refrigerant circuit and said bypass refrigerant
circuit.
14. The refrigerant system of claim 1, wherein said flow control
device is a rotary type flow control device, or a piston type flow
control device.
15. The refrigerant system of claim 1, wherein said intermediate
port is a single port for accepting economized refrigerant flow
from said economizer refrigerant circuit, and for discharging
bypass refrigerant flow into said bypass refrigerant circuit.
16. The refrigerant system of claim 1, wherein said intermediate
port of said compressor comprises a first port and a second port,
wherein said first port accepts economized refrigerant flow from
said economizer refrigerant circuit, and said second port
discharges bypass refrigerant flow into said bypass refrigerant
circuit.
17. The refrigerant system of claim 1, wherein said flow control
device is a three-way valve.
18. A method of operating a refrigerant system, comprising the
steps of: controlling a refrigerant to flow through a main
refrigerant circuit and an economizer refrigerant circuit, but not
a bypass refrigerant circuit, during an economizer mode of
operation; and controlling said refrigerant to flow through said
main refrigerant circuit and said bypass refrigerant circuit, but
not said economizer refrigerant circuit, during a bypass mode of
operation.
19. The method of claim 18, further comprising: controlling said
refrigerant to flow through said main refrigerant circuit but not
said economizer refrigerant circuit and not said bypass refrigerant
circuit during a normal mode of operation.
20. The method of claim 18, further comprising: controlling said
refrigerant to flow through said main refrigerant circuit, said
economizer refrigerant circuit, and said bypass refrigerant circuit
during an economized bypass mode of operation.
Description
BACKGROUND OF THE DISCLOSURE
[0001] 1. Field of the Disclosure
[0002] This disclosure relates to refrigerant systems. More
particularly, this disclosure relates to refrigerant systems having
economizer circuits and methods of operating such refrigerant
systems.
[0003] 2. Discussion of the Related Art
[0004] Refrigerant systems are utilized to control the temperature
and humidity of air in various environments to be conditioned.
Typically, refrigerant systems include a refrigerant that is
compressed in a compressor and delivered to a heat rejection heat
exchanger. Although, as known, the heat rejection heat exchanger is
a condenser for subcritical applications and a gas cooler for
transcritical applications, for simplicity, it will be referred to
as a condenser throughout the disclosure. In the condenser, heat is
exchanged between outside ambient air (or other cooling media) and
the refrigerant. From the condenser, the refrigerant passes to an
expansion device, in which the refrigerant is expanded to a lower
pressure and temperature, and is then passed through an evaporator.
In the evaporator, heat is exchanged between the refrigerant and
the indoor air, which is delivered into the environment to be
conditioned. When the refrigerant system is in operation, the
evaporator cools the air that is being supplied to the conditioned
environment. In addition, as the temperature of the air is lowered,
usually moisture is also taken out of the air. In this manner, the
humidity level of the air can also be controlled.
[0005] Enhancement of system efficiency is one of the foremost
concerns in the air conditioning and refrigeration industry. One of
the options available to the refrigerant system designer to
increase system efficiency is a so-called economizer cycle. When
the economizer circuit is activated, at least a portion of the
refrigerant flowing from the condenser is tapped and passed through
an economizer expansion device and then to an economizer heat
exchanger. This tapped refrigerant cools a main refrigerant flow
that also passes through the economizer heat exchanger. The tapped
refrigerant leaves the economizer heat exchanger usually in a vapor
state and is injected back into the compressor at an intermediate
compression point. The main refrigerant is additionally cooled
after passing through the economizer heat exchanger and then flown
through a main expansion device and to the evaporator. This main
refrigerant flow will provide a higher capacity and/or efficiency,
due to extra cooling obtained in the economizer heat exchanger. An
economizer circuit thus provides enhanced system performance
characteristics. As also known, there are several economizer
circuit configurations that provide similar enhanced system
operational functionality. For instance, the economizer flow can be
tapped from the main refrigerant flow downstream (instead of
upstream) of the economizer heat exchanger. Also, a flash tank,
essentially representing a 100% effective economizer heat
exchanger, may be utilized instead to provide similar
functionality.
[0006] As known, to increase part-load efficiency, many refrigerant
systems may be equipped with the unloading features. In particular,
one of such unloading options available for economized refrigerant
systems is a bypass unloading, when at least a portion of partially
compressed refrigerant is bypassed from an intermediate compression
point to the compressor suction. It has been determined by the
present disclosure that many current economized refrigerant
systems, and especially the systems incorporating unloading
functionality, require extra refrigerant cycle and control
hardware, which add to the cost and complexity of the refrigerant
systems utilizing such circuits. In addition, it has been
determined by the present disclosure that the cost and complexity
of prior art economized refrigerant systems make it difficult and
expensive to retrofit existing refrigerant systems with economizer
circuits.
[0007] Accordingly, there is a need for refrigerant systems and
methods of operating such systems that will mitigate these and
other disadvantages of currently available economized refrigerant
systems.
SUMMARY OF THE DISCLOSURE
[0008] The present disclosure provides a refrigerant system. The
refrigerant system comprises a compressor having a suction port and
an intermediate port, a main refrigerant circuit, an economizer
refrigerant circuit, a bypass refrigerant circuit, and a
refrigerant flow control device. The refrigerant flow control
device has at least two positions, with a first position providing
fluid communication between the economizer refrigerant circuit and
at least one of the suction compressor port and the intermediate
compressor port, during an economized mode of operation. A second
position provides fluid communication between the intermediate port
and the suction port through the bypass refrigerant circuit, during
a bypass mode of operation. Additionally, the refrigerant flow
control device may have a third position, at least partially
isolating the economizer refrigerant circuit and the bypass
refrigerant circuit from the main refrigerant circuit, during a
normal mode of operation. The compressor may be a single
compression device, or a pair of compressors connected in sequence,
so that the discharge port of the first compression stage is
connected to a suction port of the second compression stage. In the
latter case, the intermediate compressor port is a point on the
refrigerant line connecting the two compression stages.
[0009] The present disclosure also provides a method for operating
a refrigerant system. The method comprises: selectively controlling
a single refrigerant flow control device to provide the refrigerant
flow through the economizer circuit, during an economized mode of
operation of the refrigerant system, and to provide the refrigerant
flow through the bypass circuit, during a bypass mode of operation
of the refrigerant system. The method may include an additional
step of controlling the same refrigerant flow control device to
provide the refrigerant flow through the main refrigeration
circuit, and not through the economizer refrigerant circuit or
bypass refrigerant circuit, during a normal mode of operation of
the refrigerant system.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 shows a schematic drawing of a refrigerant system
according to the present disclosure; and
[0011] FIG. 2 shows a schematic drawing of a second embodiment of a
refrigerant system according to the present disclosure.
DETAILED DESCRIPTION OF THE INVENTION
[0012] Referring to FIG. 1, a refrigerant system 10 according to
the present disclosure is shown. Refrigerant system 10 has a
refrigerant flow control device 12 which is in communication with a
controller 14. Controller 14 may be a main controller for
refrigerant system 10, or a separate auxiliary controller. In one
embodiment, flow control device 12 is a three-way valve and is
controlled by controller 14 to selectively place a main
refrigeration circuit 16 in fluid communication with an economizer
refrigerant circuit 18 or a bypass refrigerant circuit 20. Flow
control device 12 may have an additional position to isolate main
refrigerant circuit 16 from economizer refrigerant circuit 18 and
bypass refrigerant circuit 20.
[0013] Refrigerant flow control device 12 may regulate the flow of
a refrigerant (not shown) through economizer refrigerant circuit 18
and/or bypass refrigerant circuit 20, with either modulated or
pulsed methods of control. Flow control device 12 may also mix
refrigerant flows from the economizer refrigerant circuit 18 and
the bypass refrigerant circuit 20 in various proportions in a
single refrigerant stream.
[0014] Therefore, refrigerant system 10 advantageously has a single
refrigerant flow control device 12 to provide at least two modes of
operation for the refrigerant system 10: an economized mode of
operation and an unloaded mode of operation, unlike currently
available refrigerant systems that require at least two refrigerant
flow control devices. As such, refrigerant flow control device 12
only occupies a single output (not shown) of controller 14, unlike
the two or more outputs required by conventional refrigerant
systems having more than one refrigerant flow control device. Thus,
the refrigerant system 10 of the present disclosure is less complex
and less expensive to implement. Moreover, the present disclosure,
due to the use of a single refrigerant flow control device 12,
allows existing refrigerant systems to be more easily retrofitted
with economizer refrigerant circuit 18 and bypass refrigerant
circuit 20 than currently available equipment.
[0015] Main refrigeration circuit 16 includes a compressor 22, a
condenser 24, a main expansion device 26, and an evaporator 28 in
serial fluid communication with one another. In a normal mode of
operation of refrigerant system 10, controller 14 controls flow
control device 12 to a first position (not shown) such that
refrigerant from main refrigeration circuit 16 is isolated from
both economizer refrigerant circuit 18 and bypass refrigerant
circuit 20. Here, and as is well known to a person of ordinary
skill in the art, compressor 22 drives refrigerant through
discharge refrigerant line 30 to condenser 24, from condenser 24
through liquid refrigerant line 32 to main expansion device 26,
from main expansion device 26 to evaporator 28, and from evaporator
28 through suction refrigerant line 36 and back to compressor 22.
Condenser 24 is in a heat exchange relationship with outside air
38, while evaporator 28 is in a heat exchange relationship with a
fluid to be conditioned 40, such as air delivered to a
climate-controlled space. It should be noted that instead of
outside air 38, other cooling media (such as, for example,
circulating water or a glycol solution) can be used to cool the
refrigerant in condenser 24.
[0016] For refrigerant system 10, the normal mode of operation may
be optional, in addition to an economized and bypass modes of
operation described below. Therefore, refrigerant flow control
device 12 may have an optional position to provide a refrigerant
flow through main refrigeration circuit 16, and to isolate this
main refrigerant circuit 16 from economizer refrigerant circuit 18
and bypass refrigerant circuit 20, during a normal mode of
operation of the refrigerant system 10.
[0017] Also as shown in FIG. 1, refrigerant system 10 comprises
performance-enhancing economizer refrigerant circuit 18. Economizer
refrigerant circuit 18 includes an economizer expansion device 42
and an economizer heat exchanger 44. In an economized mode of
operation, economizer expansion device 42 is in fluid communication
with a liquid refrigerant line 32 of main refrigerant circuit 16
via a tap refrigerant line 46. Further, economizer heat exchanger
44 is in serial fluid communication with expansion device 42, which
is in turn in serial fluid communication with refrigerant flow
control device 12, via an economizer refrigerant line 50. In an
economized mode of operation, flow control device 12 is also
fluidly connected to an intermediate compressor port 56 via an
intermediate pressure refrigerant line 58.
[0018] Flow control device 12 can be controlled to a second
position by controller 14 to place economizer refrigerant circuit
18 in fluid communication with main refrigerant circuit 16, so that
at least a portion of refrigerant in main refrigerant circuit 16
flows through economizer refrigerant circuit 18, and into
intermediate port 56 and/or suction port 54 of the compressor 22.
As shown, the refrigerant flows through a tap refrigerant line 46,
economizer expansion device 42, economizer heat exchanger 44,
economizer refrigerant line 50, and refrigerant flow control device
12 in sequence. When controller 14 controls refrigerant flow
control device 12 such that an economizer refrigerant flow passes
from main refrigerant circuit 16 to economizer circuit 18,
refrigerant system 10 operates in an economized mode, discussed in
further detail below.
[0019] Refrigerant flowing through main refrigerant circuit 16 in
liquid refrigerant line 32 also passes through economizer heat
exchanger 44, and is in heat exchange relationship with refrigerant
in tap refrigerant line 46 of economizer circuit 18. In economized
mode of operation, refrigerant flowing through tap refrigerant line
46 is expanded in economizer expansion device 42 to a lower
pressure and temperature, and used to further cool refrigerant in
main refrigerant circuit 16 to enhance the capacity and efficiency
of refrigerant system 10 as desired. Although the two refrigerant
streams are shown flowing in the same direction for illustration
purposes, in practice, it is advantageous to arrange these flows in
a counterflow configuration.
[0020] In the economized mode of operation, refrigerant flow
control device 12 may be controlled by controller 14 such that
economizer refrigerant line 50 of economizer refrigerant circuit 18
is in serial fluid communication with an intermediate pressure
refrigerant line 58, and/or a bypass refrigerant line 52. In this
manner, refrigerant flows out of flow control device 12, and takes
one or both of two possible paths. The first path is through
intermediate pressure refrigerant line 58 and into intermediate
port 56 of compressor 22. The second path is into bypass
refrigerant line 52, where it combines with the refrigerant flowing
in refrigerant suction line 36 and into suction port 54 of
compressor 22. In this case, in the economizer mode of operation,
flow control device 12 can be selectively controlled so that all of
the refrigerant flowing through economizer refrigerant line 50 of
economizer circuit 18 flows through intermediate pressure
refrigerant line 58 and into intermediate compressor port 56. Flow
control device 12 can also be controlled so that at least a portion
of economizer circuit refrigerant in line 50 can be diverted
through bypass refrigerant line 52. The capability of
simultaneously providing these two refrigerant flows can be
obtained through one of modulating or pulsating techniques. In the
modulation technique, the refrigerant flow control device 12
provides variable size restrictions to the two refrigerant flows,
thus simultaneously changing the hydraulic resistances and
controlling the amount of refrigerant delivered into the suction
and intermediate ports. In the pulse width modulation control,
refrigerant flow control device 12 is rapidly switched from one
economized mode of operation to the other.
[0021] Flow control device 12 can also be controlled to a third
position by controller 14, placing refrigerant system 10 in a
bypass unloaded mode of operation. In this mode of operation,
refrigerant flows out of intermediate port 56 of compressor 22 and
into bypass refrigerant circuit 20, i.e. through intermediate
pressure refrigerant line 58 and bypass refrigerant line 52, before
merging with the refrigerant in suction refrigerant line 36 and
traveling back into suction port 54 of compressor 22. In bypass
unloaded mode of operation, bypass refrigerant circuit 20 is
isolated from economizer refrigerant circuit 18 but is in fluid
communication with main refrigerant circuit 16. Similarly to the
above description, refrigerant flow control device 12 can be
controlled to regulate refrigerant flow by modulation or pulsation
means.
[0022] Refrigerant flow control device 12 can also have a fourth
position, during an economized/bypass mode, which puts the
economizer and bypass circuits in fluid communication with each
other. The economized refrigerant flow from economizer refrigerant
line 50 is combined with the bypass refrigerant flow from
intermediate pressure refrigerant line 58 to be routed to bypass
refrigerant line 52. Various flow combinations can be provided by
precise positioning of refrigerant flow control device 12, as will
be discussed in further detail below.
[0023] Refrigerant line 58 can comprise two separate refrigerant
lines, and intermediate port 56 of compressor 22 can comprise two
separate intermediate ports, so that one of them is used during
economized mode of operation, and the other is used during bypass
unloaded mode of operation. Further, compressor 22 may be a single
compressor unit comprising two sequential compression stages or two
compressors connected in sequence with an intermediate port located
in between the two compressors.
[0024] Refrigerant flow control device 12 can be, for instance, of
piston or rotary type, where controlling an alignment of valve
openings with corresponding refrigerant lines provides a desired
mode of operation for refrigerant system 10.
[0025] The mode of operation most desirable for refrigerant system
10 can depend on the required load on compressor 22, which will be
a function of the ambient temperature and the desired amount of
cooling/dehumidification in the climate-controlled space to be
conditioned. Based on these parameters, controller 14 can
selectively position or adjust refrigerant flow control device 12
accordingly to match the thermal load demands in the conditioned
space. For example, at moderate levels of thermal demands,
controller 14 can position refrigerant flow control device 12 in
the first position as described above, placing refrigerant system
10 in a normal cooling mode of operation. At high levels of thermal
demand in the conditioned space and/or at high ambient
temperatures, controller 14 can position refrigerant flow control
device 12 into the second position described above, placing
refrigerant system 10 in an economized mode of operation. At low
ambient temperatures and/or when there is a low demand for cooling,
refrigerant flow control device 12 can be placed into the third
position, operating refrigerant system 10 in a bypass mode. The
bypass mode can be advantageous in that at least a portion of the
refrigerant in compressor 22 is not compressed fully, thus reducing
the amount of work performed by the compressor and improving
operational efficiency of refrigerant system 10.
[0026] As shown in Table 1 below, various combinations of
operational modes described above provide intermediate levels of
loading and unloading for compressor 22 that allow for refrigerant
system 10 to precisely match thermal load demands in the
climate-controlled space. As stated here above, refrigerant flow
control device 12 and controller 14 should be capable to provide
this functionality. Thus, the present disclosure has advantageously
disclosed a single refrigerant flow control device 12 providing
various combinations of operational modes for refrigerant system 10
at reduced complexity, cost, maintenance and improved
reliability.
[0027] As is shown in Table 1, refrigerant system 10 may have at
least nine different configurations. For example, in configuration
#1, refrigerant system 10 is capable of operating in all of the
four modes described above. In configuration #2, refrigerant system
10 can operate in normal, bypass, and economizer modes only, and so
on. Thus, refrigerant system 10 can be customized to the particular
needs of a customer and application requirements.
TABLE-US-00001 TABLE 1 1 2 3 4 5 6 7 8 9 Normal X X X X X Bypass X
X X X X X Economizer X X X X X X Economizer with Bypass X X X X X X
X
[0028] It should be noted that refrigerant flow control devices
referred to herein as closed include refrigerant flow control
devices such as valves which are substantially closed so as to
prevent meaningful flow therethrough, such that the circuits
containing the valves are substantially inactive, and refrigerant
flow control devices referred to as open include those which are
substantially open so as to allow meaningful flow therethrough,
such that the circuits containing these refrigerant flow control
devices are substantially active.
[0029] It should be recognized that refrigerant system 10 is shown
in FIG. 1, by way of example only, as having tap refrigerant line
46 of economizer circuit 18 selectively taping at least a portion
of refrigerant from liquid refrigerant line 32 of main
refrigeration circuit 16 upstream of the first refrigerant pass
through economizer heat exchanger 44. Of course, it is contemplated
by the present disclosure for economizer circuit 18 to be located
anywhere in main refrigeration circuit 16 as long as economizer
heat exchanger 44 is positioned upstream of main expansion device
26 and downstream of condenser 24. For example, and referring to
FIG. 2, refrigerant system 10 is shown including tap refrigerant
line 46 of economizer circuit 18 selectively taping at least a
portion of refrigerant from liquid refrigerant line 32 of main
refrigeration circuit 16 downstream of the first pass through
economizer heat exchanger 44. As was mentioned above, an economizer
cycle with a flash tank may be equally utilized as well.
[0030] It should be pointed out that many different compressor
types could be used in this invention. For example, scroll, screw,
rotary, or reciprocating compressors can be employed. The
refrigerant systems that utilize this invention can be used in many
different applications, including, but not limited to, air
conditioning systems, heat pump systems, marine container units,
refrigeration truck-trailer units, and supermarket refrigeration
systems.
[0031] While the present disclosure has been described with
reference to one or more exemplary embodiments, it will be
understood by those skilled in the art that various changes may be
made and equivalents may be substituted for elements thereof
without departing from the scope of the present disclosure. In
addition, many modifications may be made to adapt a particular
situation or material to the teachings of the disclosure without
departing from the scope thereof. Therefore, it is intended that
the present disclosure not be limited to the particular
embodiment(s) disclosed as the best mode contemplated, but that the
disclosure will include all embodiments falling within the scope of
the appended claims.
* * * * *