U.S. patent application number 15/965191 was filed with the patent office on 2018-08-30 for refrigerant vapor compression system with intercooler.
The applicant listed for this patent is Carrier Corporation. Invention is credited to Zvonko Asprovski, Suresh Duraisamy, Hans-Joachim Huff, Kursten Lamendola, KeonWoo Lee, Alexander Lifson, Lucy Yi Liu.
Application Number | 20180245821 15/965191 |
Document ID | / |
Family ID | 44625663 |
Filed Date | 2018-08-30 |
United States Patent
Application |
20180245821 |
Kind Code |
A1 |
Huff; Hans-Joachim ; et
al. |
August 30, 2018 |
REFRIGERANT VAPOR COMPRESSION SYSTEM WITH INTERCOOLER
Abstract
A refrigerant vapor compression system includes a compression
device having at least a first compression stage and a second
compression stage arranged in series refrigerant flow relationship;
a first refrigerant heat rejecting heat exchanger disposed
downstream with respect to refrigerant flow of the second
compression stage for passing the refrigerant in heat exchange
relationship with a first secondary fluid; a second refrigerant
heat rejecting heat exchanger disposed downstream with respect to
refrigerant flow of the first refrigerant heat rejecting heat
exchanger for passing the refrigerant in heat exchange relationship
with a second secondary fluid.
Inventors: |
Huff; Hans-Joachim; (Mainz,
DE) ; Lee; KeonWoo; (Manlius, NY) ; Liu; Lucy
Yi; (Fayetteville, NY) ; Duraisamy; Suresh;
(Liverpool, NY) ; Asprovski; Zvonko; (Liverpool,
NY) ; Lamendola; Kursten; (Chittenango, NY) ;
Lifson; Alexander; (Manlius, NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Carrier Corporation |
Palm Beach Gardens |
FL |
US |
|
|
Family ID: |
44625663 |
Appl. No.: |
15/965191 |
Filed: |
April 27, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13581528 |
Aug 28, 2012 |
9989279 |
|
|
PCT/US2011/029936 |
Mar 25, 2011 |
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15965191 |
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61329332 |
Apr 29, 2010 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F25B 2400/072 20130101;
F28D 7/10 20130101; F25B 1/10 20130101; F25B 2400/04 20130101; F25B
2309/061 20130101; F25B 2400/13 20130101 |
International
Class: |
F25B 1/10 20060101
F25B001/10; F28D 7/10 20060101 F28D007/10 |
Claims
1. A refrigerant vapor compression system comprising: a compression
device having at least a first compression stage and a second
compression stage arranged in series refrigerant flow relationship;
a first refrigerant heat rejecting heat exchanger disposed
downstream with respect to refrigerant flow of the second
compression stage for passing the refrigerant in heat exchange
relationship with a first secondary fluid; a second refrigerant
heat rejecting heat exchanger disposed downstream with respect to
refrigerant flow of the first refrigerant heat rejecting heat
exchanger for passing the refrigerant in heat exchange relationship
with a second secondary fluid.
2. The refrigerant vapor compression system as recited in claim 1
wherein the first refrigerant heat rejection heat exchanger
operates at least in part at a refrigerant pressure and refrigerant
temperature in excess of a critical point of the refrigerant.
3. The refrigerant vapor compression system as recited in claim 2
wherein the refrigerant comprises carbon dioxide.
4. The refrigerant vapor compression system as recited in claim 1
wherein the first secondary fluid comprises air and the secondary
fluid comprises at least one of water and glycol.
5. The refrigerant vapor compression system as recited in claim 4
further comprising at least one fan operatively associated with the
first refrigerant heat rejection heat exchanger for moving the flow
of air through the first refrigerant heat rejection heat
exchanger.
6. The refrigerant vapor compression system as recited in claim 4
further comprising a pump operatively associated with the second
refrigerant heat rejection heat exchanger for moving the flow of
the second secondary fluid through the second refrigerant heat
rejection heat exchanger.
7. A refrigerated container for use in transporting perishable
goods including a refrigeration system incorporating the
refrigeration vapor compression system as recited in claim 1.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 13/581,528, filed Aug. 28, 2012, which is a
U.S. National Stage of Patent Application No. PCT/US2011/029936,
filed Mar. 25, 2011, which claims the benefit of and priority to
U.S. Provisional Patent Application No. 61/329,332, filed Apr. 29,
2010, all of which are incorporated herein by reference in their
entirety.
FIELD OF THE INVENTION
[0002] This invention relates generally to refrigerant vapor
compression systems and, more particularly, to improving the energy
efficiency and/or cooling capacity of a refrigerant vapor
compression system incorporating a multi-stage compression device,
for example a two-stage compressor, and more particularly to a
refrigerant vapor compression system incorporating a two-stage
compressor and an intercooler for cooling refrigerant passing
between the compression stages.
BACKGROUND OF THE INVENTION
[0003] Refrigerant vapor compression systems are well known in the
art and commonly used for conditioning air to be supplied to a
climate controlled comfort zone within a residence, office
building, hospital, school, restaurant or other facility.
Refrigerant vapor compression systems are also commonly used in
refrigerating air supplied to display cases, merchandisers, freezer
cabinets, cold rooms or other perishable/frozen product storage
area in commercial establishments. Refrigerant vapor compression
systems are also commonly used in transport refrigeration systems
for refrigerating air supplied to a temperature controlled cargo
space of a truck, trailer, container or the like for transporting
perishable/frozen items by truck, rail, ship or intermodally.
[0004] Refrigerant vapor compression systems used in connection
with transport refrigeration systems are generally subject to more
stringent operating conditions due to the wide range of operating
load conditions and the wide range of outdoor ambient conditions
over which the refrigerant vapor compression system must operate to
maintain product within the cargo space at a desired temperature.
The desired temperature at which the cargo needs to be controlled
can also vary over a wide range depending on the nature of cargo to
be preserved. The refrigerant vapor compression system must not
only have sufficient capacity to rapidly pull down the temperature
of product loaded into the cargo space at ambient temperature, but
also should operate energy efficiently over the entire load range,
including at low load when maintaining a stable product temperature
during transport.
[0005] A typical refrigerant vapor compression system includes a
compression device, a refrigerant heat rejection heat exchanger, a
refrigerant heat absorption heat exchanger, and an expansion device
disposed upstream, with respect to refrigerant flow, of the
refrigerant heat absorption heat exchanger and downstream of the
refrigerant heat rejection heat exchanger. These basic refrigerant
system components are interconnected by refrigerant lines in a
closed refrigerant circuit, arranged in accord with known
refrigerant vapor compression cycles. It is also known practice to
incorporate an economizer into the refrigerant circuit for
increasing the capacity of the refrigerant vapor compression
system. For example, a refrigerant-to-refrigerant heat exchanger or
a flash tank may be incorporated into the refrigerant circuit as an
economizer. The economizer circuit includes a vapor injection line
for conveying refrigerant vapor from the economizer into an
intermediate pressure stage of the compression process.
[0006] Traditionally, most of these refrigerant vapor compression
systems have been operated at subcritical refrigerant pressures.
Refrigerant vapor compression systems operating in the subcritical
range are commonly charged with fluorocarbon refrigerants such as,
but not limited to, hydrochlorofluorocarbons (HCFCs), such as R22,
and more commonly hydrofluorocarbons (HFCs), such as R134a, R410A,
R404A and R407C. However, greater interest is being shown in
"natural" refrigerants, such as carbon dioxide, for use in
refrigeration systems instead of HFC refrigerants. Because carbon
dioxide has a low critical temperature, most refrigerant vapor
compression systems charged with carbon dioxide as the refrigerant
are designed for operation in the transcritical pressure
regime.
[0007] In refrigerant vapor compression systems operating in a
subcritical cycle, both the refrigerant heat rejection heat
exchanger, which functions in a subcritical cycle as a condenser,
and the refrigerant heat absorption heat exchanger, which functions
as an evaporator, operate at refrigerant temperatures and pressures
below the refrigerant's critical point. However, in refrigerant
vapor compression systems operating in a transcritical cycle, the
refrigerant heat rejection heat exchanger operates at a refrigerant
temperature and pressure in excess of the refrigerant's critical
point, while the refrigerant heat absorption heat exchanger, i.e.
the evaporator, operates at a refrigerant temperature and pressure
in the subcritical range. Operating at refrigerant pressure and
refrigerant temperature in excess of the refrigerant's critical
point, the refrigerant heat rejection heat exchanger functions as a
gas cooler rather than as a condenser.
[0008] In multi-stage compression systems it is known that the
operational envelope of the compression device can often be
extended by incorporating a refrigerant to secondary fluid heat
exchanger into the refrigerant circuit between two compression
stages. Commonly referred to as an intercooler, this heat exchanger
provides for passing refrigerant flowing from one compression stage
to another compression stage in heat exchange relationship with a
cooler fluid whereby the refrigerant is cooled. Typically, the
cooler fluid is a secondary fluid and the heat extracted from the
refrigerant is carried away by the secondary fluid. However,
incorporating an intercooler into a refrigerant vapor compression
system in accord with previous practice may not be practical in
some situations, for example due to physical space, weight and
equipment cost considerations. Such considerations are particularly
relevant in transport refrigeration applications where it is
generally desirable to minimize weight, size and cost of the
components of the refrigerant vapor compression system. The higher
refrigerant pressures associated with operation in a transcritical
refrigeration cycle, such as in refrigerant vapor compression
systems using carbon dioxide as the refrigerant, complicates
incorporation of an intercooler into the refrigerant circuit.
SUMMARY OF THE INVENTION
[0009] In an aspect, the refrigerant vapor compression system
includes a compression device a compression device having at least
a first compression stage and a second compression stage arranged
in series refrigerant flow relationship; a first refrigerant heat
rejecting heat exchanger disposed downstream with respect to
refrigerant flow of the second compression stage for passing the
refrigerant in heat exchange relationship with a first secondary
fluid; a second refrigerant heat rejecting heat exchanger disposed
downstream with respect to refrigerant flow of the first
refrigerant heat rejecting heat exchanger for passing the
refrigerant in heat exchange relationship with a second secondary
fluid.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] For a further understanding of the disclosure, reference
will be made to the following detailed description which is to be
read in connection with the accompanying drawing, wherein:
[0011] FIG. 1 is perspective view of a refrigerated container
equipped with a transport refrigeration system;
[0012] FIG. 2 is a schematic illustration of an embodiment of the
refrigerant vapor compression system in accord with an aspect of
the invention;
[0013] FIG. 3 is a schematic illustration of an alternate
embodiment of the refrigerant vapor compression system illustrated
in FIG. 1;
[0014] FIG. 4 is a schematic illustration of an alternate
embodiment of the refrigerant vapor compression system illustrated
in FIG. 1;
[0015] FIG. 5 is a schematic illustration of an embodiment of the
refrigerant vapor compression system in accord with an aspect of
the invention;
[0016] FIG. 6 is a schematic illustration of an alternate
embodiment of the refrigerant vapor compression system illustrated
in FIG. 5;
[0017] FIG. 7 is a schematic illustration of an alternate
embodiment of the refrigerant vapor compression system illustrated
in FIG. 5;
[0018] FIG. 8 is a sectioned elevation view of an exemplary
embodiment of an intercooler in accordance with an aspect of the
invention;
[0019] FIG. 9 is a sectioned plan view taken along line 9-9 of FIG.
8; and
[0020] FIG. 10 is a schematic illustration of an exemplary
embodiment of the refrigerant vapor compression system
incorporating an intercooler bypass circuit.
DETAILED DESCRIPTION OF THE INVENTION
[0021] There is depicted in FIG. 1 an exemplary embodiment of a
refrigerated container 10 having a temperature controlled cargo
space 12 the atmosphere of which is refrigerated by operation of a
refrigeration unit 14 associated with the cargo space 12. In the
depicted embodiment of the refrigerated container 10, the
refrigeration unit 14 is mounted in a wall of the refrigerated
container 10, typically in the front wall 18 in conventional
practice. However, the refrigeration unit 14 may be mounted in the
roof, floor or other walls of the refrigerated container 10.
Additionally, the refrigerated container 10 has at least one access
door 16 through which perishable goods, such as, for example, fresh
or frozen food products, may be loaded into and removed from the
cargo space 12 of the refrigerated container 10.
[0022] Referring now to FIGS. 2-7, there are depicted schematically
various exemplary embodiments of a refrigerant vapor compression
system 20 suitable for use in the refrigeration unit 14 for
refrigerating air drawn from and supplied back to the temperature
controlled cargo space 12. Although the refrigerant vapor
compression system 20 will be described herein in connection with a
refrigerated container 10 of the type commonly used for
transporting perishable goods by ship, by rail, by land or
intermodally, it is to be understood that he refrigerant vapor
compression system 20 may also be used in refrigeration units for
refrigerating the cargo space of a truck, a trailer or the like for
transporting perishable goods. The refrigerant vapor compression
system 20 is also suitable for use in conditioning air to be
supplied to a climate controlled comfort zone within a residence,
office building, hospital, school, restaurant or other facility.
The refrigerant vapor compression system 20 could also be employed
in refrigerating air supplied to display cases, merchandisers,
freezer cabinets, cold rooms or other perishable and frozen product
storage areas in commercial establishments.
[0023] The refrigerant vapor compression system 20 includes a
multi-stage compression device 30, a refrigerant heat rejection
heat exchanger 40, also referred to herein as a gas cooler, a
refrigerant heat absorption heat exchanger 50, also referred to
herein as an evaporator, and a primary expansion device 55, such as
for example an electronic expansion valve or a thermostatic
expansion valve, operatively associated with the evaporator 50,
with various refrigerant lines 22, 24 26 and 28 connecting the
aforementioned components in a primary refrigerant circuit.
[0024] The compression device 30 functions to compress the
refrigerant and to circulate refrigerant through the primary
refrigerant circuit as will be discussed in further detail
hereinafter. The compression device 30 may comprise a single,
multiple-stage refrigerant compressor, for example a reciprocating
compressor, having a first compression stage 30a and a second stage
30b, or may comprise a pair of compressors 30a and 30b, connected
in series refrigerant flow relationship in the primary refrigerant
circuit via a refrigerant line 28 connecting the discharge outlet
port of the first compression stage compressor 30a in refrigerant
flow communication with the suction inlet port of the second
compression stage compressor 30b. The first and second compression
stages 30a and 30b are disposed in series refrigerant flow
relationship with the refrigerant leaving the first compression
stage 30a passing to the second compression stage 30b for further
compression. In the first compression stage the refrigerant vapor
is compressed from a lower pressure to an intermediate pressure. In
the second compression stage, the refrigerant vapor is compressed
from an intermediate pressure to higher pressure. In a two
compressor embodiment, the compressors may be scroll compressors,
screw compressors, reciprocating compressors, rotary compressors or
any other type of compressor or a combination of any such
compressors.
[0025] The refrigerant heat rejection heat exchanger 40 may
comprise a finned tube heat exchanger 42 through which hot, high
pressure refrigerant discharged from the second compression stage
30b (i.e. the final compression charge) passes in heat exchange
relationship with a secondary fluid, most commonly ambient air
drawn through the heat exchanger 42 by the fan(s) 44. The finned
tube heat exchanger 42 may comprise, for example, a fin and round
tube heat exchange coil or a fin and flat mini-channel tube heat
exchanger. If the pressure of the refrigerant discharging from the
second compression stage 30b, commonly referred to as the
compressor discharge pressure exceeds the critical point of the
refrigerant, the refrigerant vapor compression system 20 operates
in a transcritical cycle and the refrigerant heat rejection heat
exchanger 40 functions as a gas cooler. If the compressor discharge
pressure is below the critical point of the refrigerant, the
refrigerant vapor compression system 20 operates in a subcritical
cycle and the refrigerant heat rejection heat exchanger 40
functions as a condenser.
[0026] The refrigerant heat absorption heat exchanger 50 may also
comprise a finned tube coil heat exchanger 52, such as a fin and
round tube heat exchanger or a fin and flat, mini-channel tube heat
exchanger. The refrigerant heat absorption heat exchanger 50
functions as a refrigerant evaporator whether the refrigerant vapor
compression system is operating in a transcritical cycle or a
subcritical cycle. Before entering the refrigerant heat absorption
heat exchanger 50, the refrigerant passing through refrigerant line
24 traverses the expansion device 55, such as, for example, an
electronic expansion valve or a thermostatic expansion valve, and
expands to a lower pressure and a lower temperature to enter heat
exchanger 52. As the liquid refrigerant traverses the heat
exchanger 52, the liquid refrigerant passes in heat exchange
relationship with a heating fluid whereby the liquid refrigerant is
evaporated and typically superheated to a desired degree. The low
pressure vapor refrigerant leaving heat exchanger 52 passes through
refrigerant line 26 to the suction inlet of the first compression
stage 30a. The heating fluid may be air drawn by an associated
fan(s) 54 from a climate controlled environment, such as a
perishable/frozen cargo storage zone associated with a transport
refrigeration unit, or a food display or storage area of a
commercial establishment, or a building comfort zone associated
with an air conditioning system, to be cooled, and generally also
dehumidified, and thence returned to a climate controlled
environment.
[0027] In the embodiments depicted in FIGS. 3, 4 and 6, 7, the
refrigerant vapor compression system 20 further includes and
economizer circuit associated with the primary refrigerant circuit.
The economizer circuit includes an economizer device 60, 70, an
economizer circuit expansion device 65 and a vapor injection line
in refrigerant flow communication with an intermediate pressure
stage of the compression process. In the embodiments depicted in
FIGS. 3 and 6, the economizer device comprises a flash tank
economizer 60. In the embodiments depicted in FIGS. 4 and 7, the
economizer device comprises a refrigerant-to-refrigerant heat
exchanger 70. The economizer expansion device 65 may, for example,
be an electronic expansion valve, a thermostatic expansion valve or
a fixed orifice expansion device.
[0028] Referring now to FIGS. 3 and 6, in particular, the flash
tank economizer 60 is interdisposed in refrigerant line 24 between
the refrigerant heat rejection heat exchanger 40 and the primary
expansion device 55. The economizer circuit expansion device 65 is
disposed in refrigerant line 24 upstream of the flash tank
economizer 60. The flash tank economizer 60 defines a chamber 62
into which expanded refrigerant having traversed the economizer
circuit expansion device 65 enters and separates into a liquid
refrigerant portion and a vapor refrigerant portion. The liquid
refrigerant collects in the chamber 62 and is metered therefrom
through the downstream leg of refrigerant line 24 by the primary
expansion device 55 to flow to the refrigerant heat absorption heat
exchanger 50. The vapor refrigerant collects in the chamber 62
above the liquid refrigerant and passes therefrom through vapor
injection line 64 for injection of refrigerant vapor into an
intermediate stage of the compression process. In the depicted
embodiments, the vapor injection line 64 communicates with
refrigerant line 28 interconnecting the outlet of the first
compression stage 30a to the inlet of the second compression stage
30b. It is to be understood, however, that refrigerant vapor
injection line 64 can open directly into an intermediate stage of
the compression process rather than opening into refrigerant line
28.
[0029] Referring now to FIGS. 4 and 7, in particular, the
refrigerant-to-refrigerant heat exchanger economizer 70 includes a
first refrigerant pass 72 and a second refrigerant pass 74 arranged
in heat transfer relationship. The first refrigerant pass 72 is
interdisposed in refrigerant line 24 and forms part of the primary
refrigerant circuit. The second refrigerant pass 74 is
interdisposed in refrigerant line 78 that forms part of an
economizer circuit. The economizer circuit refrigerant line 78 taps
into refrigerant line 24 and connects in refrigerant flow
communication with an intermediate pressure stage of the
compression process. In the exemplary embodiment depicted in FIGS.
4 and 7, the economizer circuit refrigerant line 78 taps into
refrigerant line 24 of the primary refrigerant circuit upstream
with respect to refrigerant flow of the first pass 72 of the
refrigerant-to-refrigerant heat exchanger economizer 70 and opens
into refrigerant line 28 interconnecting the outlet of the first
compression stage 30a to the inlet of the second compression stage
30b. The first refrigerant pass 72 and the second refrigerant pass
74 of the refrigerant-to-refrigerant heat exchanger economizer 70
may be arranged in a parallel flow heat exchange relationship or in
a counter flow heat exchange relationship, as desired. The
refrigerant-to-refrigerant heat exchanger 70 may be a brazed plate
heat exchanger, a tube-in-tube heat exchanger, a tube-on-tube heat
exchanger or a shell-and-tube heat exchanger. The economizer
circuit expansion device 65 is disposed in refrigerant line 78
upstream with respect to refrigerant flow of the second pass 74 of
the refrigerant-to-refrigerant heat exchanger economizer 70 and
meters the refrigerant flowing through refrigerant line 78 and the
second pass 74 of the refrigerant-to-refrigerant heat exchanger
economizer 70. As the expanded refrigerant flow having traversed
the economizer circuit expansion device 65 passes through the
second pass 74 in heat exchange relationship with the hot, high
pressure refrigerant passing through the first pass 72, that
refrigerant is evaporated and the resultant refrigerant vapor
passes into refrigerant line 28 to be admitted to the second
compression stage 30b.
[0030] To improve the energy efficiency and cooling capacity of the
refrigerant vapor compression system 20, particularly when
operating in a transcritical cycle and charged with carbon dioxide
or a mixture including carbon dioxide as the refrigerant, the
refrigerant vapor compression system 20 includes an intercooler 80
interdisposed in refrigerant line 28 of the primary refrigerant
circuit between the first compression stage 30a and the second
compression stage 30b, as depicted in FIGS. 2-7. The intercooler 80
comprises a refrigerant-to-secondary fluid heat exchanger, such as
for example a finned tube heat exchanger 82, through which
intermediate temperature, intermediate pressure refrigerant passing
from the first compression stage 30a to the second compression
stage 30b passes in heat exchange relationship with ambient air
drawn through the heat exchanger 82 by the fan(s) 44. The finned
tube heat exchanger 82 may comprise, for example, a fin and round
tube heat exchange coil or a fin and flat mini-channel tube heat
exchanger.
[0031] In the depicted embodiments, the intercooler 80 is located
in the air stream at the air outlet of the refrigerant heat
rejection heat exchanger 40. In this arrangement, the ambient air
drawn by the fan(s) 44 passes first through the refrigerant heat
rejection heat exchanger 40 in heat exchange relationship with the
hot, high pressure refrigerant vapor passing through the heat
exchanger coil 42 and thereafter passes through the intercooler 80
in heat exchange relationship with the intermediate temperature and
intermediate pressure refrigerant passing through the intercooler
hear exchanger 82. In this arrangement, the refrigerant passing
through the refrigerant heat rejection heat exchanger 40 will be
cooled by the incoming ambient air stream, thereby more effectively
reducing the temperature of the refrigerant leaving the refrigerant
heat rejection heat exchanger 40, which is critical for the system
cooling capacity and energy efficiency, particularly when the
refrigerant vapor compression system 20 is operating in a
transcritical cycle with carbon dioxide refrigerant.
[0032] The refrigerant vapor compression system 20 may also include
a second refrigerant heat rejection heat exchanger 90 and a second
intercooler 100, such as depicted in FIGS. 5-7, that are not cooled
by air, but instead are cooled by a secondary liquid, such as for
example water. However, it is to be understood that other liquids,
such as for example glycol or glycol/water mixtures, could be used
as the secondary fluid. The second refrigeration heat rejection
heat exchanger 90 comprises a refrigerant-to-liquid heat exchanger
having a secondary liquid pass 92 and a refrigerant pass 94
arranged in heat transfer relationship. The refrigerant pass 94 is
interdisposed in refrigerant line 24 and forms part of the primary
refrigerant circuit. In operation, refrigerant having traversed the
heat exchanger coil 42 of the refrigerant heat rejection heat
exchanger 40 passes through the refrigerant pass 94 of the second
refrigerant heat rejection heat exchanger 90 in heat exchange
relationship with the secondary fluid, for example water, passing
through the secondary liquid pass 92 whereby the refrigerant is
further cooled. The secondary fluid pass 92 and the refrigerant
pass 94 of the second refrigerant heat rejection heat exchanger 90
may be arranged in a parallel flow heat exchange relationship or in
a counter flow heat exchange relationship, as desired. The second
refrigerant heat rejection heat exchanger 90 may be a brazed plate
heat exchanger, a tube-in-tube heat exchanger, a tube-on-tube heat
exchanger or a shell-and-tube heat exchanger.
[0033] The second intercooler 100 comprises a refrigerant-to-liquid
heat exchanger having a secondary liquid pass 102 and a refrigerant
pass 104 arranged in heat transfer relationship. The refrigerant
pass 104 is interdisposed in refrigerant line 28 that interconnects
the first compression stage 30a in refrigerant flow communication
with the second compression stage 30b and forms part of the primary
refrigerant circuit. In operation, refrigerant having traversed the
heat exchanger 82 of the intercooler 80 passes through the
refrigerant pass 104 of the second intercooler 100 in heat exchange
relationship with the secondary fluid, for example water, passing
through the secondary liquid pass 102 whereby the refrigerant is
cooled interstage of the first compression stage 30a and the second
compression stage 104. The secondary fluid pass 102 and the
refrigerant pass 104 of the second intercooler 100 may be arranged
in a parallel flow heat exchange relationship or in a counter flow
heat exchange relationship, as desired. The second intercooler 100
may be a brazed plate heat exchanger, a tube-in-tube heat
exchanger, a tube-on-tube heat exchanger or a shell-and-tube heat
exchanger.
[0034] As depicted in FIGS. 5-7, the second intercooler 100 is
disposed downstream with respect to water flow of the second
condenser 90. That is, the cooling water, or other secondary
cooling liquid, is pumped through the secondary cooling liquid line
106 by an associated pump 108 to first flow through the secondary
fluid pass 92 in heat exchange relationship with the refrigerant
flowing through the refrigerant pass 94 of the second refrigerant
heat absorption heat exchanger and thence through the secondary
liquid pass 102 in heat exchange relationship with the refrigerant
flowing through the refrigerant pass 104 of the second intercooler
100. In this arrangement, the refrigerant passing through the
second refrigerant heat rejection heat exchanger 90 will be cooled
by the incoming flow of cooling water, thereby more effectively
reducing the temperature of the refrigerant passing through the
refrigerant pass 94, which is critical for the system cooling
capacity and energy efficiency, particularly when the refrigerant
vapor compression system 20 is operating in a transcritical cycle
with carbon dioxide refrigerant. However, it is to be understood
that the second intercooler 100 may instead be disposed with
refrigerant pass 104 upstream of refrigerant pass 94 of the second
refrigerant heat rejection heat exchanger 90 with respect to the
flow of cooling water through the secondary cooling liquid line
106, if desired.
[0035] The second refrigerant heat rejection heat exchanger 90 and
the second intercooler 100 may also be disposed in parallel flow
relationship with respect to the flow of cooling water. For
example, the second refrigerant heat rejection heat exchanger 90
and the second intercooler 100 may comprise a double tube-on-tube
heat exchanger 110 having two refrigerant tubes disposed in close
contact with a single cooling water tube. For example, referring
now to FIGS. 8 and 9, the double tube-on-tube heat exchanger 110
includes a first refrigerant tube 112 defining the refrigerant pass
94 of the second refrigerant heat rejection heat exchanger 90, a
second refrigerant tube 114 defining the refrigerant pass 104 of
the second intercooler 90, and a cooling water tube 116 defining in
combination both the cooling water pass 92 of the second
refrigerant heat rejection heat exchanger 90 and the cooling water
pass 102 of the intercooler 100. The first and second refrigerant
tubes 112, 114, respectively, may be disposed on opposite sides of
the cooling water tube 116 so as to flank the cooling water tube
116 and lie in close contact with the cooling water tube 116
thereby facilitating heat exchange between the respective
refrigerant flows passing through refrigerant passes 94, 104
defined by the first and second refrigerant tubes 114, 116,
respectively, with the cooling water flowing through the combined
secondary cooling liquid passages 92, 102 defined by the centrally
disposed cooling water tube 116. The direction of flow of the
refrigerant flows passing through the refrigerant passes 94, 104
relative to the cooling water flow passing through the cooling
water tube 116 may be arranged with both refrigerant flows in a
counterflow arrangement with the cooling water flow, with both
refrigerant flows in a parallel flow arrangement with the cooling
water flow, or with one of the refrigerant flows in a counterflow
arrangement with the cooling water flow and the other of the
refrigerant flows in a parallel flow arrangement with the cooling
water flow.
[0036] Refrigerant vapor compression systems used in transport
refrigeration applications are subject to a wide range of outdoor
ambient conditions over which the refrigerant vapor compression
system must operate. Under some conditions, it may not be desirable
to operate the refrigerant vapor compression system 20 with the
refrigerant vapor passing from the first compression stage to the
second compression stage passing through an intercooler For
example, under low ambient air temperature conditions, refrigerant
vapor passing from the first compression stage to the second
compression stage could actually condense, partially or even fully,
to liquid refrigerant in traversing the intercooler. Such a
situation is to be avoid as liquid refrigerant entering the
compression device 30 would be detrimental to performance and could
result in damage to the compression device 20.
[0037] Accordingly, referring now to FIG. 10, the refrigerant vapor
compression systems 20 disclosed may further include an intercooler
bypass circuit 32 including a bypass line 34, and a selectively
operable bypass valve 36 disposed in the bypass line 34. The bypass
valve 36 may be a selectively positionable valve having a fully
open position and a fully closed position, such as for example a
two position, open/closed solenoid valve. With the bypass valve 36
in an open position, refrigerant flow communication is established
through bypass line 34 directly between the outlet of the first
compression stage 30a and the inlet of the second compression stage
30b, whereby substantially all of the refrigerant vapor discharging
from the first compression will flow through bypass line 34 to the
second compression stage without traversing the intercooler 80. A
check valve 38 may be interdisposed in refrigerant line 28 so as to
preclude backflow of refrigerant vapor through refrigerant line 28.
Although the bypass circuit 32 is illustrated in FIG. 10
incorporated in the embodiment of the refrigerant vapor compression
system 20 depicted in FIG. 3, it is to be understood that the
intercooler bypass circuit 32 may be similarly incorporated in the
various embodiments of the refrigerant vapor compression system 20
as depicted in any of FIGS. 2-7.
[0038] The terminology used herein is for the purpose of
description, not limitation. Specific structural and functional
details disclosed herein are not to be interpreted as limiting, but
merely as basis for teaching one skilled in the art to employ the
present invention. Those skilled in the art will also recognize the
equivalents that may be substituted for elements described with
reference to the exemplary embodiments disclosed herein without
departing from the scope of the present invention.
[0039] While the present invention has been particularly shown and
described with reference to the exemplary embodiments as
illustrated in the drawing, it will be recognized by those skilled
in the art that various modifications may be made without departing
from the spirit and scope of the invention. Therefore, it is
intended that the present disclosure not be limited to the
particular embodiment(s) disclosed as, but that the disclosure will
include all embodiments falling within the scope of the appended
claims.
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