U.S. patent application number 15/116934 was filed with the patent office on 2017-06-15 for ejector cycle heat recovery refrigerant separator.
This patent application is currently assigned to Carrier Corporation. The applicant listed for this patent is Carrier Corporation. Invention is credited to Alexander Lifson, Zuojun Shi, Parmesh Verma.
Application Number | 20170167767 15/116934 |
Document ID | / |
Family ID | 52464625 |
Filed Date | 2017-06-15 |
United States Patent
Application |
20170167767 |
Kind Code |
A1 |
Shi; Zuojun ; et
al. |
June 15, 2017 |
Ejector Cycle Heat Recovery Refrigerant Separator
Abstract
A system (170; 300; 400) comprising a compressor (22). A heat
rejection heat exchanger (30; 420) is coupled to the compressor to
receive refrigerant compressed by the compressor. A separator (180)
has: a vessel (181); an inlet (50) coupled to the heat rejection
heat exchanger to receive refrigerant; a first outlet (54) in
communication with a headspace of the vessel; and a second outlet
(52, 52') in communication with a lower portion of the vessel. The
system has a heat exchanger (182; 220; 220'; 220''; 220''') for
transferring heat from refrigerant passing from a heat rejection
heat exchanger to liquid refrigerant in the separator.
Inventors: |
Shi; Zuojun; (Marcellus,
NY) ; Verma; Parmesh; (South Windsor, CT) ;
Lifson; Alexander; (Manlius, NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Carrier Corporation |
Jupiter |
FL |
US |
|
|
Assignee: |
Carrier Corporation
Jupiter
FL
|
Family ID: |
52464625 |
Appl. No.: |
15/116934 |
Filed: |
February 3, 2015 |
PCT Filed: |
February 3, 2015 |
PCT NO: |
PCT/US15/14159 |
371 Date: |
August 5, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61936781 |
Feb 6, 2014 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F25B 40/00 20130101;
F25B 1/00 20130101; F25B 1/10 20130101; F25B 9/008 20130101; F25B
9/08 20130101; F25B 41/00 20130101; F25B 2341/0012 20130101; F25B
43/00 20130101; F25B 2341/066 20130101; F25B 43/006 20130101; F25B
2400/23 20130101; F25B 2309/06 20130101 |
International
Class: |
F25B 43/00 20060101
F25B043/00; F25B 1/00 20060101 F25B001/00; F25B 9/08 20060101
F25B009/08 |
Claims
1. A system (170; 300; 400) comprising: a compressor (22); a heat
rejection heat exchanger (30; 420) coupled to the compressor to
receive refrigerant compressed by the compressor; a separator (180)
having: a vessel (181); an inlet (50) coupled to the heat rejection
heat exchanger to receive refrigerant; a first outlet (54) in
communication with a headspace of the vessel; a second outlet (52,
52') in communication with a lower portion of the vessel; a heat
absorption heat exchanger (64); and means (182; 220; 220'; 220'';
220''') for transferring heat from refrigerant passing from the
heat rejection heat exchanger to liquid refrigerant in the
separator.
2. The system of claim 1 further comprising: an expansion device
(38; 330; 430) between the heat rejection heat exchanger and the
separator inlet.
3. The system of claim 2 wherein the expansion device is: an
ejector (38) having: a primary inlet (40) coupled to the heat
rejection heat exchanger to receive refrigerant; a secondary inlet
(42); and an outlet (44) coupled to the separator inlet.
4. The system of claim 3 wherein the ejector secondary inlet is
coupled to receive refrigerant from the separator second outlet by
an additional expansion device (70) and the heat rejection heat
exchanger.
5. The system of claim 3 wherein the separator first outlet is
coupled to a suction port (24) of the compressor.
6. The system of claim 2 wherein the expansion device is: an
expansion valve (330; 430).
7. The system of claim 6 further comprising: a pump (320) coupling
the separator second outlet to an inlet (66) of the heat absorption
heat exchanger.
8. The system of claim 7 wherein: a flowpath through the pump
merges with a flowpath through the expansion valve at a junction
(312) upstream of the inlet (66) of the heat absorption heat
exchanger.
9. The system of claim 1 wherein the separator first outlet is
coupled to the compressor.
10. The system of claim 9 wherein the separator first outlet is
coupled to a suction port (24) of the compressor.
11. The system of claim 9 wherein the outlet is coupled to an
interstage of the compressor.
12. The system of claim 9 wherein the compressor is the high
pressure stage (22B) of a two-stage system.
13. The system of claim 9 wherein the separator is configured to:
provide mainly liquid refrigerant to an expansion device upstream
of the heat absorption heat exchanger; and provide mainly vapor
refrigerant to the suction port of the compressor.
14. The system of claim 1 wherein: refrigerant comprises at least
50% carbon dioxide, by weight.
15. A method for operating the system of claim 1 comprising running
the compressor in a first mode wherein: the refrigerant is
compressed in the compressor; refrigerant received from the
compressor by the heat rejection heat exchanger rejects heat in the
heat rejection heat exchanger to produce initially cooled
refrigerant; the initially cooled refrigerant passes through the
expansion device; an outlet flow of refrigerant from the expansion
device passes to the separator to separate said liquid refrigerant
from refrigerant vapor; said heat is transferred from said
refrigerant passing from the heat rejection heat exchanger to said
liquid refrigerant.
16. A refrigerant separator comprising: a vessel (181); an inlet
(50); a first outlet (54) in communication with a headspace of the
vessel; a second outlet (52;52') in communication with a lower
portion of the vessel; and a heat exchanger (182) having: an inlet
(186); an outlet (188); and a portion through the lower portion of
the vessel.
17. The system of claim 16 wherein the heat exchanger comprises: an
upstream spiral leg and a downstream straight leg.
18. A system comprising the refrigerant separator of claim 16 and
further comprising: a compressor (22); a heat rejection heat
exchanger (30; 420) coupled to the compressor to receive
refrigerant compressed by the compressor; and an ejector (38)
having: a primary inlet (40) coupled to the heat rejection heat
exchanger to receive refrigerant; a secondary inlet (42); and an
outlet (44) coupled to the separator inlet.
19. The system of claim 1, wherein the means comprises a heat
exchanger (182) having: an inlet (186); an outlet (188); and a
portion through the lower portion of the vessel.
20. The system of claim 19 the heat exchanger comprises: an
upstream spiral leg and a downstream straight leg.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] Benefit is claimed of U.S. Patent Application Ser. No.
61/936,781, filed Feb. 6, 2014, and entitled "Ejector Cycle Heat
Recovery Refrigerant Separator", the disclosure of which is
incorporated by reference herein in its entirety as if set forth at
length.
BACKGROUND
[0002] The present disclosure relates to refrigeration. More
particularly, it relates to ejector refrigeration systems.
[0003] Early proposals for ejector refrigeration systems are found
in U.S. Pat. No. 1,836,318 and U.S. Pat. No. 3,277,660. FIG. 2
shows one basic example of an ejector refrigeration system 20 drawn
from US Patent Application Publication 2013/0111934 (the '934
publication) the disclosure of which is incorporated in its
entirety herein as is set forth at length. The system includes a
compressor 22 having an inlet (suction port) 24 and an outlet
(discharge port) 26. The compressor and other system components are
positioned along a refrigerant circuit or flowpath 27 and connected
via various conduits (lines). A discharge line 28 extends from the
outlet 26 to the inlet 32 of a heat exchanger (a heat rejection
heat exchanger in a normal mode of system operation (e.g., a
condenser or gas cooler)) 30. A line 36 extends from the outlet 34
of the heat rejection heat exchanger 30 to a primary inlet (liquid
or supercritical or two-phase inlet) 40 of an ejector 38. The
ejector 38 also has a secondary inlet (saturated or superheated
vapor or two-phase inlet) 42 and an outlet 44. A line 46 extends
from the ejector outlet 44 to an inlet 50 of a separator 48. The
separator has a liquid outlet 52 and a gas outlet 54. A suction
line 56 extends from the gas outlet 54 to the compressor suction
port 24. The lines 28, 36, 46, 56, and components therebetween
define a primary loop 60 of the refrigerant circuit 27. A secondary
loop 62 of the refrigerant circuit 27 includes a heat exchanger 64
(in a normal operational mode being a heat absorption heat
exchanger (e.g., evaporator)). The evaporator 64 includes an inlet
66 and an outlet 68 along the secondary loop 62 and expansion
device 70 is positioned in a line 72 which extends between the
separator liquid outlet 52 and the evaporator inlet 66. An ejector
secondary inlet line 74 extends from the evaporator outlet 68 to
the ejector secondary inlet 42.
[0004] In the normal mode of operation, gaseous refrigerant is
drawn by the compressor 22 through the suction line 56 and inlet 24
and compressed and discharged from the discharge port 26 into the
discharge line 28. In the heat rejection heat exchanger, the
refrigerant loses/rejects heat to a heat transfer fluid (e.g.,
fan-forced air or water or other liquid). Cooled refrigerant exits
the heat rejection heat exchanger via the outlet 34 and enters the
ejector primary inlet 40 via the line 36.
[0005] The exemplary ejector 38 (FIG. 3) is formed as the
combination of a motive (primary) nozzle 100 nested within an outer
member 102. The primary inlet 40 is the inlet to the motive nozzle
100. The outlet 44 is the outlet of the outer member 102. The
primary refrigerant flow 103 enters the inlet 40 and then passes
into a convergent section 104 of the motive nozzle 100. It then
passes through a throat section 106 and an expansion (divergent)
section 108 through an outlet 110 of the motive nozzle 100. The
motive nozzle 100 accelerates the flow 103 and decreases the
pressure of the flow. The secondary inlet 42 forms an inlet of the
outer member 102. The pressure reduction caused to the primary flow
by the motive nozzle helps draw the secondary flow 112 into the
outer member. The outer member includes a mixer having a convergent
section 114 and an elongate throat or mixing section 116. The outer
member also has a divergent section or diffuser 118 downstream of
the elongate throat or mixing section 116. The motive nozzle outlet
110 is positioned within the secondary nozzle convergent section
114. As the flow 103 exits the outlet 110, it begins to mix with
the flow 112 with further mixing occurring through the mixing
section 116 which provides a mixing zone. In operation, the primary
flow 103 may typically be supercritical upon entering the ejector
and subcritical upon exiting the motive nozzle. The secondary flow
112 is gaseous (or a mixture of gas with a smaller amount of
liquid) upon entering the secondary inlet port 42. The resulting
combined flow 120 is a liquid/vapor mixture and decelerates and
recovers pressure in the diffuser 118 while remaining a mixture.
Upon entering the separator, the flow 120 is separated back into
the flows 103 and 112. The flow 103 passes as a gas through the
compressor suction line as discussed above. The flow 112 passes as
a liquid to the expansion valve 70. The flow 112 may be expanded by
the valve 70 (e.g., to a low quality (two-phase with small amount
of vapor)) and passed to the evaporator 64. Within the evaporator
64, the refrigerant absorbs heat from a heat transfer fluid (e.g.,
from a fan-forced air flow or water or other liquid) and is
discharged from the outlet 68 to the line 74 as the aforementioned
gas.
[0006] Use of an ejector serves to recover pressure/work. Work
recovered from the expansion process is used to compress the
gaseous refrigerant prior to entering the compressor. Accordingly,
the pressure ratio of the compressor (and thus the power
consumption) may be reduced for a given desired evaporator
pressure. The quality of refrigerant entering the evaporator may
also be reduced. Thus, the refrigeration effect per unit mass flow
may be increased (relative to the non-ejector system). The
distribution of fluid entering the evaporator is improved (thereby
improving evaporator performance). Because the evaporator does not
directly feed the compressor, the evaporator is not required to
produce superheated refrigerant outflow. The use of an ejector
cycle may thus allow reduction or elimination of the superheated
zone of the evaporator. This may allow the evaporator to operate in
a two-phase state which provides a higher heat transfer performance
(e.g., facilitating reduction in the evaporator size for a given
capability).
[0007] The exemplary ejector may be a fixed geometry ejector or may
be a controllable ejector. FIG. 2 shows controllability provided by
a needle valve 130 having a needle 132 and an actuator 134. The
actuator 134 shifts a tip portion 136 of the needle into and out of
the throat section 106 of the motive nozzle 100 to modulate flow
through the motive nozzle and, in turn, the ejector overall.
Exemplary actuators 134 are electric (e.g., solenoid or the like).
The actuator 134 may be coupled to and controlled by a controller
140 which may receive user inputs from an input device 142 (e.g.,
switches, keyboard, or the like) and sensors (not shown). The
controller 140 may be coupled to the actuator and other
controllable system components (e.g., valves, the compressor motor,
and the like) via control lines 144 (e.g., hardwired or wireless
communication paths). The controller may include one or more:
processors; memory (e.g., for storing program information for
execution by the processor to perform the operational methods and
for storing data used or generated by the program(s)); and hardware
interface devices (e.g., ports) for interfacing with input/output
devices and controllable system components.
[0008] The system features a suction line heat exchanger 92 having
a leg 94 (heat absorption leg) along the suction line between the
separator gas outlet and the compressor inlet. The leg 94 is in
heat exchange relationship with a leg 96 (heat rejection leg) in
the heat rejection heat exchanger outlet line between the heat
rejection heat exchanger outlet and the ejector primary inlet.
SUMMARY
[0009] One aspect of the disclosure involves a system comprising a
compressor. A heat rejection heat exchanger is coupled to the
compressor to receive refrigerant compressed by the compressor. A
separator has: a vessel; an inlet coupled to the heat rejection
heat exchanger to receive refrigerant; a first outlet in
communication with a headspace of the vessel; and a second outlet
in communication with a lower portion of the vessel. The system has
means for transferring heat from refrigerant passing from a heat
rejection heat exchanger to liquid refrigerant in the
separator.
[0010] A further embodiment may additionally and/or alternatively
include an expansion device between the heat rejection heat
exchanger and the separator inlet.
[0011] A further embodiment may additionally and/or alternatively
include the expansion device being an ejector having: a primary
inlet coupled to the heat rejection heat exchanger to receive
refrigerant; a secondary inlet; and an outlet coupled to the
separator inlet.
[0012] A further embodiment may additionally and/or alternatively
include the ejector secondary inlet being coupled to receive
refrigerant from the separator second outlet by an additional
expansion device and the heat rejection heat exchanger.
[0013] A further embodiment may additionally and/or alternatively
include the separator first outlet being coupled to a suction port
of the compressor.
[0014] A further embodiment may additionally and/or alternatively
include the expansion device being an expansion valve.
[0015] A further embodiment may additionally and/or alternatively
include a pump coupling the separator second outlet to an inlet of
the heat absorption heat exchanger.
[0016] A further embodiment may additionally and/or alternatively
include a flowpath through the pump merging with a flowpath through
the expansion valve at a junction upstream of the inlet of the heat
absorption heat exchanger.
[0017] A further embodiment may additionally and/or alternatively
include the separator first outlet being coupled to the
compressor.
[0018] A further embodiment may additionally and/or alternatively
include the separator first outlet being coupled to a suction port
of the compressor.
[0019] A further embodiment may additionally and/or alternatively
include the outlet being coupled to an interstage of the
compressor.
[0020] A further embodiment may additionally and/or alternatively
include the compressor being the high pressure stage of a two-stage
system.
[0021] A further embodiment may additionally and/or alternatively
include the separator being configured to: provide mainly liquid
refrigerant to an expansion device upstream of the heat absorption
heat exchanger; and provide mainly vapor refrigerant to the suction
port of the compressor.
[0022] A further embodiment may additionally and/or alternatively
include the refrigerant comprises at least 50% carbon dioxide, by
weight.
[0023] Another aspect of the disclosure involves a method for
operating the system comprising running the compressor in a first
mode wherein: the refrigerant is compressed in the compressor;
refrigerant received from the compressor by the heat rejection heat
exchanger rejects heat in the heat rejection heat exchanger to
produce initially cooled refrigerant; the initially cooled
refrigerant passes through the expansion device; an outlet flow of
refrigerant from the expansion device passes to the separator to
separate said liquid refrigerant from refrigerant vapor; said heat
is transferred from said refrigerant passing from the heat
rejection heat exchanger to said liquid refrigerant.
[0024] Another aspect of the disclosure involves a refrigerant
separator comprising: a vessel; an inlet; a first outlet in
communication with a headspace of the vessel; a second outlet in
communication with a lower portion of the vessel; and a heat
exchanger. The heat exchanger has: an inlet; an outlet; and a
portion through the lower portion of the vessel
[0025] A further embodiment may additionally and/or alternatively
include the heat exchanger having an upstream spiral leg and a
downstream straight leg.
[0026] The details of one or more embodiments are set forth in the
accompanying drawings and the description below. Other features,
objects, and advantages will be apparent from the description and
drawings, and from the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] FIG. 1 is a schematic view of a first ejector refrigeration
system.
[0028] FIG. 2 is a schematic view of a prior art ejector
refrigeration system.
[0029] FIG. 3 is an axial sectional view of an ejector
[0030] FIG. 4 is a schematic view of a second non-ejector
refrigeration system.
[0031] FIG. 5 is a schematic view of a third non-ejector
refrigeration system.
[0032] FIG. 6 is a partially schematic vertical sectional/cutaway
view of a heat exchange separator.
[0033] FIG. 7 is a partially schematic vertical sectional/cutaway
view of another heat exchange separator.
[0034] FIG. 8 is a partially schematic vertical sectional/cutaway
view of another heat exchange separator.
[0035] FIG. 9 is a partially schematic vertical sectional/cutaway
view of another heat exchange separator.
[0036] Like reference numbers and designations in the various
drawings indicate like elements.
DETAILED DESCRIPTION
[0037] FIG. 1 shows an ejector cycle vapor compression
(refrigeration) system 170. The system 170 may be made as a
modification of the system 20 or of another system or as an
original manufacture/configuration. In the exemplary embodiment,
like components which may be preserved from the system 20 are shown
with like reference numerals. Operation may be similar to that of
the system 20 except as discussed below with the controller 140
controlling operation responsive to inputs from various temperature
sensors and pressure sensors.
[0038] The FIG. 1 embodiment replaces the FIG. 2 separator 48 and
suction line heat exchanger 92 with a combined separator and heat
exchanger 180 having a vessel 181. The heat exchanger 180 has a
conventional main inlet 50 coupled to the line 46 from the ejector
outlet 44. A conventional liquid outlet 52 and vapor outlet 54 are
also provided. FIG. 1 further shows a surface 58 of a body of
liquid refrigerant in the lower portion of the vessel 181 with
vapor in a headspace thereabove. The unit 180, however, is in heat
exchange relationship with refrigerant passing along the line 36
from the outlet 34 of the heat rejection heat exchanger 30 to the
primary inlet 40 of the ejector. The heat exchanger portion of 180
is shown as 182 having a leg 184 extending between an inlet 186 and
an outlet 188 in heat exchange relation with refrigerant in the
unit interior.
[0039] In normal operation, refrigerant passing along the primary
flowpath through line 36 passes into the heat exchanger 182 via
inlet 186 and rejects heat to the accumulated refrigerant. A
portion of the leg 184 (e.g., a lower portion) extends low on the
unit 180 to be immersed in liquid refrigerant below the surface 58.
This immersion allows the greatest rejection of heat from the
primary flowpath before entering the ejector inlet.
[0040] Whereas the separator 48 of FIG. 2 or the combined separator
and heat exchanger 180 deliver essentially pure vapor from their
vapor outlets 54, and essentially pure liquid from their liquid
outlets 52, the '934 publication discloses that it may be desirable
to replace one or both of these flows with a slightly mixed state
flow.
[0041] For example, by feeding a two-phase mixture into the
compressor, the discharge temperature of the compressor can be
reduced if desired (thus extending the compressor system operating
range). Feeding a suction line heat exchanger (SLHX) and/or
compressor with small amount liquid are also expected to improve
both SLHX and compressor efficiency. Exemplary refrigerant is
delivered as 85-99% quality (vapor mass flow percentage), more
narrowly, 90-98% or 94-98%. The power required for compression of a
vapor increases which increased suction enthalpy. For hermetic
compressors the refrigerant vapor is used to cool the motor. For
example, in many compressors, the suction flow is first passed over
the motor before entering the compression chamber (raising the
temperature of refrigerant reaching the compression chamber). By
supplying a small amount of liquid in the vapor of the suction
flow, the motor can be cooled while reducing the temperature
increase of the refrigerant as it passes over the motor.
Furthermore, some compressors are tolerant of small amounts of
liquid entering the suction chamber. If the compression process is
begun with some liquid, the refrigerant will remain cooler than it
otherwise would, and less power is required for the compression
process. This is especially beneficial with refrigerants that
exhibit a large degree of heating during compression, such as
CO.sub.2. The negative side of providing liquid refrigerant to the
compressor is that the liquid is no longer available for producing
cooling in the evaporator 64. The optimum choice of quality
provided to line 56 is determined by the specific characteristics
of the system to balance these considerations.
[0042] A small amount of liquid refrigerant can also be used to
improve the performance of a SLHX. SLHXs are typically of
counter-flow design. The total heat transfer is limited by the
fluid side that has the minimum product of flow rate and specific
heat. For a refrigeration system SLHX with pure vapor on the cold
side and pure liquid on the hot side, the cold-side vapor is
limiting. However, a small amount of liquid provided to the
cold-side effectively increases its specific heat. Thus more heat
may be transferred from the same SLHX, or conversely, for the same
heat transfer a smaller heat exchanger may be used if a small
amount of liquid is added to the vapor.
[0043] Also by feeding a two-phase mixture to the expansion valve
upstream of the evaporator one can precisely control the system
capacity, which can prevent unnecessary system shutdowns (comfort
and improved reliability) and improve temperature control. This may
help improve refrigerant distribution in the evaporator manifold
and further improve evaporator performance Exemplary refrigerant is
delivered as 1-10% quality (vapor mass flow percentage), more
narrowly 2-6%. Direct expansion evaporators typically have poor
heat transfer in the very low and very high quality ranges. For
these evaporator designs providing higher quality may improve the
heat transfer coefficient at the entrance region of the evaporator
(where quality is the lowest).
[0044] Thus, the separator/heat exchanger 180 may have means for
providing at least one of the 1-10% quality refrigerant to the heat
absorption heat exchanger and the 90-99% quality refrigerant to at
least one of the compressor and, at present, a suction line heat
exchanger.
[0045] Examples of such means involving configuration of tubes and
their inlets is disclosed in the '934 publication.
[0046] The controller may control an operation in response to input
from a plurality of sensors such as temperature sensors and
pressure sensors. A first exemplary pair of these sensors 600 (self
heat sensor) and 602 (regular sensor) is shown in the suction line
56 between the outlet 186 and the suction port 24 of FIG. 1. A
second exemplary pair 604, 606 is shown along the line 74
downstream of the evaporator and upstream of the ejector secondary
inlet in FIG. 1. An alternative method is to use the measured
discharge superheat and, through known calibration of the
compressor isotropic efficiency, have the controller determine the
suction quality condition. This may be determined via a discharge
superheat sensor 610 in the discharge line at the exit of the
compressor. This may be a relatively cost effective method for
measuring the quality of refrigerant discharged from the outlet
186. A third variation involves a superheat sensor 614 (FIG. 1)
within the compressor downstream of the motor.
[0047] FIG. 4 shows use of the separator/heat exchanger 180 in an
ejector-less system 300. An expansion device 330 (e.g., similar to
the expansion device 70) replaces the ejector and has an inlet
along the line 36 downstream of the heat exchanger 182 (e.g., the
heat exchanger outlet 188 is coupled to the inlet of the expansion
device 330 via an appropriate conduit). The outlet of the expansion
device 330 feeds the inlet 66 of the heat rejection heat exchanger
64 flow from the outlet 68 of the heat rejection heat exchanger 64
passes to the separator/heat exchanger inlet 50. Liquid refrigerant
from the outlet 52 is passed to the inlet 66 of the heat rejection
heat exchanger via a conduit 310 defining a flowpath extending to a
junction 312 with the line 36 and its flowpath. A pump 320 having
an inlet 322 and an outlet 324 is located along the lines or
conduit 310 so as to pump the liquid refrigerant to create an open
loop flow via the line 310, through the heat rejection heat
exchanger 64, and returning to the separator inlet 50. The
exemplary pump 320 is a centrifugal pump driven by an electric
motor.
[0048] Operation of the pump 320 and expansion valve 330 may be
under the control of the controller 140. For example, expansion
valve 330 may be an electronic expansion valve (EXV) or may be a
thermal expansion valve (TXV) controlled by superheat at inlet port
of compressor at pipe 56. Pump 320 may be controlled in response to
superheat of inlet port of compressor at pipe 56 or refrigerant
liquid level 58 in the phase separator. For example, as long as
superheat is less than a threshold such as 0.5.degree. C., or
refrigerant liquid level is at least at a threshold such as 3/4 of
the separator height, the controller will run the pump to pump
refrigerant liquid back to the evaporator. A check valve 326
downstream of the pump serves to prevent refrigerant flow back to
the pump.
[0049] FIG. 5 shows a second ejector-less system 400 utilizing the
separator/heat exchanger 180. There is a two-stage compressor 22
having stages 22A and 22B. This may alternatively represent two
separate compressors 22A and 22B. The discharge port 26B of the
second stage connects to a discharge line to in turn feed a heat
exchanger 420 before entering the heat exchanger 182 and feeding
back into the inlet 50 of the separator/heat exchanger 180. In the
exemplary implementation, an expansion device 430 is in the line
between the heat exchanger 182 and the inlet 150. The exemplary
expansion device 430 is a high pressure expansion valve such as an
EXV. The high pressure expansion valve serves to convert
supercritical refrigerant (e.g., CO.sub.2) to a two-phase
state.
[0050] The refrigerant from the liquid outlet 52 passes through the
expansion device 70 and the heat rejection heat exchanger 64 to
return to the inlet 24A of the low pressure compressor or stage
22A. A vapor line from the outlet line 54 may extend to the inlet
24B of the high pressure compressor or stage 22B.
[0051] FIG. 5 shows an economizer valve 440 (allowing an economizer
mode when open) and a one-way check valve 442 located between the
outlet 54 and the inlet 24B to prevent reverse low pressure flow
back into the separator/heat exchanger through the outlet 54. The
outlet 26A of the first compressor or stage 22A is connected to a
heat exchanger 450. The exemplary heat exchangers 420 and 450 are
refrigerant-air heat exchangers integrated in a unit 452 where a
fan (not shown) drives an airflow across the heat exchanger 420
then the heat exchanger 450 so as to reject heat to the
environment. 420 is upstream along the airflow because it is
desirable that this receive the coldest air to determine downstream
conditions along the refrigerant flowpath. Alternative
configurations may involve separate airflows across the two heat
exchangers 420 and 450.
[0052] A line from the outlet of the heat exchanger 450 extends
back to a suction location of the high pressure compressor or stage
22B. Thus, in some operational modes, flows may merge from the
outlet 54 and the first stage to feed the second stage. FIG. 5 also
shows a bypass 460 between the suction location of the first
compressor and the suction location of the second compressor. The
bypass line through which flow is controlled by a valve 470. The
exemplary valve 470 is an unload bypass valve and is used to bypass
refrigerant around the first stage compressor 22A when the loading
requirement is low (and the first stage is shut off).
[0053] FIG. 6 shows one example of the heat exchanger as a twisted
spiral tube heat exchanger 220 having an upstream spiral leg 222
extending downward and a downstream straight leg 224 extending
upward within the spiral.
[0054] FIG. 6 also shows various optional variations on the basic
separator structure. The separator has an inlet tube 230 extending
to an outlet end 232 to deliver refrigerant toward an interior
sidewall surface of the vessel to be deflected with liquid
descending into the accumulation in the lower portion 59 and thus
avoid/limit foaming. Also well up in the headspace (shown even
higher than the outlet end 232 is the inlet end 242 of an outlet
conduit 240. the exemplary outlet conduit 240 is a J-tube having a
lower end portion or turn 244 near the bottom of the vessel. near
the bottom of the lower end 244, the conduit includes an aperture
or orifice 246 which serves as an oil pickup to entrain oil into
vapor flow through the conduit 240. In an exemplary embodiment, an
upper extreme of the orifice is below a lower extreme of the outlet
52 so as to keep a level of any oil accumulation below the outlet
52 to limit/prevent oil flow out the outlet 52.
[0055] An exemplary spacing of the outlet lower end above the
orifice upper end is at least 2 mm (e.g., 2 mm to 10 mm, or at
least 5 mm). In an exemplary embodiment, a lower extreme of the
heat exchanger is above an upper extreme of the outlet 52 so as to
keep the surface level 58 of liquid refrigerant sufficiently above
the outlet 52 to limit/prevent vapor flow out the outlet 52 (e.g.,
the heat exchanger will not be able to boil off refrigerant below
its lower end). An exemplary spacing of the heat exchanger lower
end above the outlet upper end is at least 5 mm (e.g., 5 mm to 20
mm, or at least 10 mm while still in a lower half or third or
quarter or fifth of the vessel interior height). An alternative
outlet location 52' at the bottom of the vessel is shown in broken
lines.
[0056] FIG. 7 shows an alternative variation otherwise similar to
FIG. 6 but where the downstream leg 224' of the heat exchanger 220'
is aside rather than within the spiral upstream leg 222'.
[0057] FIG. 8 shows an alternative variation otherwise similar to
FIG. 6 but where the upstream leg 222'' and downstream leg 224'' of
the heat exchanger 220'' are legs of a U-tube and the tube is
finned to enhance heat transfer. Fins may be plate fins or one or
more helical fins.
[0058] FIG. 9 shows an alternative variation otherwise similar to
FIG. 8 but where the U portion of the heat exchanger 220''' tube
along its legs 222'', 224''' and base has a heli-enhanced deformed
sidewall (e.g., double helix outward deformation shown).
[0059] The system may be fabricated from conventional components
using conventional techniques appropriate for the particular
intended uses.
[0060] Although an embodiment is described above in detail, such
description is not intended for limiting the scope of the present
disclosure. It will be understood that various modifications may be
made without departing from the spirit and scope of the disclosure.
For example, when implemented in the remanufacturing of an existing
system or the reengineering of an existing system configuration,
details of the existing configuration may influence or dictate
details of any particular implementation. Accordingly, other
embodiments are within the scope of the following claims.
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