U.S. patent application number 12/867846 was filed with the patent office on 2010-12-30 for refrigerant vapor compression system.
This patent application is currently assigned to Carrier Corporation. Invention is credited to Alexander Lifson, Michael F. Taras.
Application Number | 20100326100 12/867846 |
Document ID | / |
Family ID | 40985810 |
Filed Date | 2010-12-30 |
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United States Patent
Application |
20100326100 |
Kind Code |
A1 |
Taras; Michael F. ; et
al. |
December 30, 2010 |
REFRIGERANT VAPOR COMPRESSION SYSTEM
Abstract
A refrigerant vapor compression system includes a first
compression device, a refrigerant heat rejection heat exchanger, an
expansion device, a refrigerant heat absorption heat exchanger, a
second compression device, and a refrigerant-to-refrigerant heat
exchanger having first refrigerant flow pass, a second refrigerant
flow pass and a third refrigerant flow pass, with the second
refrigerant flow pass disposed in heat exchange relationship with
each of the first refrigerant flow pass and the third refrigerant
flow pass. The second refrigerant flow pass is interdisposed in an
economizer circuit. The heat transfer interaction between the first
and second refrigerant flow passes functions as a subcooler of
refrigerant flowing to the refrigerant heat absorption heat
exchanger and the heat transfer interaction between the second and
third refrigerant flow passes functions as an intercooler of
refrigerant passing from the discharge outlet of the second
compression device to the suction inlet of the first compression
device.
Inventors: |
Taras; Michael F.;
(Fayetteville, NY) ; Lifson; Alexander; (Manlius,
NY) |
Correspondence
Address: |
MARJAMA MULDOON BLASIAK & SULLIVAN LLP
250 SOUTH CLINTON STREET, SUITE 300
SYRACUSE
NY
13202
US
|
Assignee: |
Carrier Corporation
Farmington
CT
|
Family ID: |
40985810 |
Appl. No.: |
12/867846 |
Filed: |
February 19, 2008 |
PCT Filed: |
February 19, 2008 |
PCT NO: |
PCT/US08/54268 |
371 Date: |
August 16, 2010 |
Current U.S.
Class: |
62/115 ; 62/510;
62/513 |
Current CPC
Class: |
F25B 2400/072 20130101;
F25B 1/10 20130101; F25B 2400/13 20130101; F25B 2400/075
20130101 |
Class at
Publication: |
62/115 ; 62/510;
62/513 |
International
Class: |
F25B 1/00 20060101
F25B001/00; F25B 1/10 20060101 F25B001/10; F25B 41/00 20060101
F25B041/00 |
Claims
1. A refrigerant vapor compression system comprising: a first
compression device, a refrigerant heat rejection heat exchanger, a
primary expansion device, a refrigerant heat absorption heat
exchanger, and a second compression device connected in serial
refrigerant flow communication in a primary refrigerant circuit
with a refrigerant discharge outlet of said second compression
device in refrigerant flow communication with a suction inlet of
said first compression device; and a common heat exchanger
providing an economizer function for cooling refrigerant passing
through the primary refrigerant circuit from said refrigerant heat
rejection heat exchanger to said primary expansion device and an
intercooler function for cooling refrigerant passing through said
primary refrigerant circuit from the refrigerant discharge outlet
of said second compression device to the refrigerant suction inlet
of said first compression device.
2. A refrigerant vapor compression system comprising: a first
compression device, a refrigerant heat rejection heat exchanger, a
primary expansion device, a refrigerant heat absorption heat
exchanger, and a second compression device connected in serial
refrigerant flow communication in a primary refrigerant circuit,
each of said first and second compression devices having a
refrigerant discharge outlet and a refrigerant suction inlet; a
refrigerant-to-refrigerant heat exchanger having a first
refrigerant flow pass, a second refrigerant flow pass and a third
refrigerant flow pass, said first refrigerant flow pass
interdisposed in the primary refrigerant circuit between a
refrigerant outlet of said refrigerant heat rejection heat
exchanger and a refrigerant inlet to said refrigerant heat
absorption heat exchanger, said third refrigerant flow pass
interdisposed in the primary refrigerant circuit between the
refrigerant discharge outlet of said second compression device and
the refrigerant suction inlet of said first compression device,
said second refrigerant flow pass disposed in heat exchange
relationship with at least said first refrigerant flow pass and
said third refrigerant flow pass; an economizer refrigerant circuit
including an economizer refrigerant line having an inlet in
refrigerant flow communication with the primary refrigerant circuit
at a location downstream of the refrigerant outlet of said
refrigerant heat rejection heat exchanger and upstream of the
refrigerant inlet to said refrigerant heat absorption heat
exchanger, said second refrigerant flow pass interdisposed in said
economizer refrigerant circuit.
3. A refrigerant vapor compression system as recited in claim 2
wherein the economizer refrigerant line of said economizer circuit
is in refrigerant flow communication with an intermediate pressure
stage of said second compression device.
4. A refrigerant vapor compression system as recited in claim 3
wherein said second compression device comprises a single,
multi-stage compressor and the economizer refrigerant line of said
economizer refrigerant circuit is in refrigerant flow communication
with an intermediate pressure stage of the multi-stage
compressor.
5. A refrigerant vapor compression system as recited in claim 2
wherein the economizer refrigerant line of said economizer circuit
is in refrigerant flow communication with an intermediate pressure
stage of said first compression device.
6. A refrigerant vapor compression system as recited in claim 5
wherein said first compression device comprises a single,
multi-stage compressor and the economizer refrigerant line of said
economizer refrigerant circuit is in refrigerant flow communication
with an intermediate pressure stage of the multi-stage
compressor.
7. A refrigerant vapor compression system as recited in claim 2
wherein said second compression device comprises a multi-stage
compressor having a first compression stage and a second
compression stage disposed in series refrigerant flow relationship,
with a refrigerant discharge of said first compression stage in
refrigerant flow communication with a refrigerant inlet of said
second compression stage, said second pass of said
refrigerant-to-refrigerant heat exchanger in refrigerant flow
communication with the refrigerant inlet of said second compression
stage, and said third pass of said refrigerant-to-refrigerant heat
exchanger in refrigerant flow communication with the refrigerant
inlet of said first compression device.
8. A refrigerant vapor compression system as recited in claim 2
wherein said first compression device comprises a multi-stage
compressor having a first compression stage and a second
compression stage disposed in series refrigerant flow relationship,
with a refrigerant discharge of said first compression stage in
refrigerant flow communication with a refrigerant inlet of said
second compression stage, said second pass of said
refrigerant-to-refrigerant heat exchanger in refrigerant flow
communication with the refrigerant inlet of said second compression
stage, and said third pass of said refrigerant-to-refrigerant heat
exchanger in refrigerant flow communication with the refrigerant
inlet of said first compression stage.
9. A refrigerant vapor compression system as recited in claim 2
further comprising a third compression device having a refrigerant
outlet in refrigerant flow communication with a refrigerant inlet
to said refrigerant heat rejection heat exchanger and a refrigerant
inlet, the second pass of said refrigerant-to-refrigerant heat
exchanger in refrigerant flow communication with the refrigerant
inlet of said third compression device.
10. A refrigerant vapor compression system as recited in claim 2
further comprising a pre-cooler heat exchanger interdisposed in the
primary refrigerant circuit downstream, with respect to refrigerant
flow, of the refrigerant outlet of said second compression device
and upstream, with respect to refrigerant flow, of said third pass
of said refrigerant-to-refrigerant heat exchanger.
11. A refrigerant vapor compression system as recited in claim 10
wherein said pre-cooler heat exchanger is disposed in heat transfer
relationship with a secondary fluid being passed in heat transfer
relationship with the refrigerant passing through said refrigerant
heat rejection heat exchanger.
12. A refrigerant vapor compression system as recited in claim 11
wherein the secondary fluid is ambient air.
13. A refrigerant vapor compression system as recited in claim 10
wherein said pre-cooler heat exchanger shares the same housing
structure with the heat rejection heat exchanger.
14. A refrigerant vapor compression system as recited in claim 10
wherein said pre-cooler heat exchanger shares the same heat
exchanger core with the heat rejection heat exchanger.
15. A method of operating a refrigerant vapor compression system
having a first compression device, a refrigerant heat rejection
heat exchanger, a primary expansion device, a refrigerant heat
absorption heat exchanger, and a second compression device
connected in serial refrigerant flow communication in a primary
refrigerant circuit with a refrigerant discharge outlet of said
second compression device in refrigerant flow communication with a
suction inlet of said first compression device; said method
comprising the steps of: passing a first portion of the refrigerant
leaving the refrigerant heat rejection heat exchanger through the
primary refrigerant circuit to the refrigerant heat absorption heat
exchanger; expanding a second portion of the refrigerant downstream
of the refrigerant heat rejection heat exchanger to an intermediate
pressure; passing said second portion of the refrigerant in heat
exchange relationship with said first portion of the refrigerant at
a location in the primary refrigerant circuit upstream, with
respect to refrigerant flow, of the primary expansion device; and
passing said second portion of the refrigerant in heat exchange
relationship with the refrigerant flowing through the primary
refrigerant circuit from the refrigerant discharge outlet of the
second compression device to the refrigerant suction inlet of the
first compression device.
16. A method as recited in claim 15 further comprising passing said
second portion of the refrigerant in counterflow heat exchange
relationship both with said first portion of the refrigerant and
with the refrigerant flowing through the primary refrigerant
circuit from the second compression device to the first compression
device.
17. A method as recited in claim 15 further comprising the step of
pre-cooling the refrigerant flowing through the primary refrigerant
circuit from the second compression device to the first compression
device prior to passing said second portion of the refrigerant in
heat exchange relationship with the refrigerant flowing through the
primary refrigerant circuit from the second compression device to
the first compression device.
Description
FIELD OF THE INVENTION
[0001] This invention relates generally to refrigerant vapor
compression systems and, more particularly, to enhancing the
performance of a refrigerant vapor compression system.
BACKGROUND OF THE INVENTION
[0002] Refrigerant vapor compression systems are commonly used in
transport refrigeration applications for refrigerating the
atmosphere within a temperature-controlled cargo space of a truck,
trailer, container or the like for transporting perishable or
frozen items. 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
and for conditioning air to be supplied to a climate-controlled
comfort zone within a residence, office building, hospital, school,
restaurant or other facility.
[0003] Typically, these refrigerant vapor compression systems
include a compression device, a refrigerant heat rejection heat
exchanger, an expansion device and a refrigerant heat absorption
heat exchanger, serially interconnected by various refrigerant
lines in refrigerant flow communication in a closed-loop
refrigerant circuit, arranged in accord with known refrigerant
vapor compression cycles. Commonly, the expansion device, which is
disposed in the refrigerant circuit upstream, with respect to
refrigerant flow, of the refrigerant heat absorption heat exchanger
and downstream, with respect to refrigerant flow, of the
refrigerant heat rejection heat exchanger, is a fixed orifice, a
capillary tube, a thermostatic expansion valve (TXV) or an
electronic expansion valve (EXV).
[0004] In refrigerant vapor compression systems operating in a
subcritical cycle, the refrigerant heat rejection heat exchanger
functions as a refrigerant vapor condenser. 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 air conditioning and
refrigeration systems, including transport refrigeration systems,
instead of HFC refrigerants. However, 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 cycle, at least for portion of
the time.
[0005] In refrigerant vapor compression systems operating in a
transcritical cycle, the pressure and temperature of the
refrigerant vapor discharged from the compression device and
passing through the refrigerant heat rejection heat exchanger are
at supercritical pressure and temperature, that is a pressure and
temperature of the refrigerant are above the critical point of the
specific refrigerant with which the system is charged. Therefore,
the refrigerant heat rejection heat exchanger functions as a
refrigerant gas cooler, rather than as a condenser. Having
traversed the refrigerant heat rejection heat exchanger, the
supercritical pressure refrigerant vapor is expanded to a lower
subcritical pressure and lower temperature as the refrigerant vapor
traverses the expansion device. Therefore, the refrigerant enters
the refrigerant heat absorption heat exchanger as a liquid
refrigerant, or more typically, as a mixture of liquid and vapor
refrigerant, and the refrigerant heat absorption heat exchanger
functions as an evaporator operating at a subcritical refrigerant
pressure.
[0006] To improve performance of the refrigerant vapor compression
system and to control the temperature of the refrigerant vapor
discharged from the final stage of the compressor over a wide range
of operating conditions, it is known to equip such systems with an
economizer cycle incorporating a refrigerant-to-refrigerant
economizer heat exchanger. The economizer heat exchanger is
generally disposed in the refrigerant circuit intermediate the heat
rejection heat exchanger and the heat absorption heat exchanger,
with respect to refrigerant flow. In the economized mode of
operation, at least a portion of the refrigerant leaving the heat
rejection heat exchanger is diverted from the primary refrigerant
circuit, expanded to an intermediate pressure and then passed
through the economizer heat exchanger in heat exchange relationship
with the main portion of the refrigerant leaving the heat rejection
heat exchanger. In this manner, any liquid in the economized
expanded refrigerant flow is typically evaporated, and then the
economized refrigerant flow is typically superheated, while the
refrigerant passing through the primary refrigerant circuit from
the heat rejection heat exchanger to the heat absorption heat
exchanger is further cooled. Typically, the expanded refrigerant
vapor is injected into an intermediate stage in the compression
process, either through an injection port or ports opening into an
intermediate pressure stage of the compression chamber (or
chambers) of a single compressor or, in the case of a multi-stage
compressor system, into a refrigerant line extending between the
discharge outlet of the upstream compressor and the suction inlet
of the downstream compressor.
[0007] U.S. Pat. No. 7,114,349 discloses a refrigerant vapor
compression system with a refrigerant-to-refrigerant heat exchanger
having a first refrigerant pass, a second refrigerant pass and a
third refrigerant pass. The first pass is interdisposed in the
primary refrigerant circuit downstream of the condenser, with
respect to refrigerant flow, and upstream of the evaporator, with
respect to refrigerant flow. The second pass is interdisposed in an
economizer circuit refrigerant line downstream, with respect to
refrigerant flow, of an economizer expansion device. The third
refrigerant pass is interdisposed in the primary refrigerant
circuit downstream, with respect to refrigerant flow, of the
evaporator and upstream, with respect to refrigerant flow, of the
suction inlet to the compressor. The first refrigerant pass is
disposed in heat transfer relationship with each of the second
refrigerant pass and the third refrigerant pass. The heat transfer
interaction between the first refrigerant pass and the third
refrigerant pass functions as a high side-to-low side heat
exchanger wherein the high pressure, high temperature refrigerant
passing through the first refrigerant pass is cooled and the low
pressure, lower temperature refrigerant vapor passing through the
third refrigerant pass is heated. Additionally, when the
refrigerant system is operating in an economized mode, the heat
transfer interaction between the first refrigerant pass and the
second refrigerant pass functions as an economizer heat exchanger
wherein the high pressure, high temperature refrigerant passing
through the first refrigerant pass is again cooled and the lower
pressure, lower temperature expanded refrigerant vapor or
vapor/liquid mixture passing through the second refrigerant pass is
heated. After traversing the second refrigerant pass of the
refrigerant-to-refrigerant heat exchanger, the expanded refrigerant
is injected into an intermediate pressure stage of the compressor
or returned to the primary refrigerant circuit at a point
downstream, with respect to refrigerant flow, of the evaporator and
upstream, with respect to refrigerant flow, of the suction inlet of
the compressor.
SUMMARY OF THE INVENTION
[0008] A refrigerant vapor compression system includes a primary
refrigerant circuit having a first compression device, a
refrigerant heat rejection heat exchanger, an expansion device, a
refrigerant heat absorption heat exchanger, and a second
compression device connected in serial refrigerant flow
communication, with the refrigerant discharge outlet of the second
compression device being connected in refrigerant flow
communication with the refrigerant inlet of the first compression
device, and a common heat exchanger providing an economizer
function and an intercooler function. The economizer function
serves to cool refrigerant passing through the primary refrigerant
circuit from the refrigerant heat rejection heat exchanger to the
primary expansion device. The intercooler function serves to cool
refrigerant passing through the primary refrigerant circuit from
the refrigerant discharge outlet of the second compression device
to the refrigerant suction inlet of the first compression
device
[0009] In an embodiment, the refrigerant vapor compression system
includes a primary refrigerant circuit having a first compression
device, a refrigerant heat rejection heat exchanger, an expansion
device, a refrigerant heat absorption heat exchanger, and a second
compression device connected in serial refrigerant flow
communication, with the refrigerant discharge outlet of the second
compression device being connected in refrigerant flow
communication with the refrigerant inlet of the first compression
device, and further includes a refrigerant-to-refrigerant heat
exchanger and an economizer circuit. The refrigerant-to-refrigerant
heat exchanger has a first refrigerant flow pass, a second
refrigerant flow pass and a third refrigerant flow pass, with the
second refrigerant flow pass disposed in heat exchange relationship
with each of the first refrigerant flow pass and the third
refrigerant flow pass. The first refrigerant flow pass is
interdisposed in the primary refrigerant circuit downstream, with
respect to refrigerant flow, of the refrigerant heat rejection heat
exchanger and upstream, with respect to refrigerant flow, of the
expansion device. The third refrigerant flow pass is interdisposed
in the primary refrigerant circuit between the refrigerant
discharge of the second compression device and the refrigerant
inlet of the first compression device, both with respect to
refrigerant flow. The economizer circuit includes an economizer
refrigerant line having an inlet in refrigerant flow communication
with the primary refrigerant circuit at a location downstream of
the refrigerant outlet of the refrigerant heat rejection heat
exchanger, with respect to refrigerant flow, and upstream of the
refrigerant inlet to the refrigerant heat absorption heat
exchanger, also with respect to refrigerant flow. The second
refrigerant flow pass is interdisposed in the economizer
refrigerant line. An economizer expansion device is disposed in the
refrigerant line upstream, with respect to refrigerant flow of the
second refrigerant flow pass.
[0010] In an embodiment, the second compression device comprises a
single, multi-stage compressor and the outlet of the economizer
refrigerant line is in refrigerant flow communication with an
intermediate pressure stage of this second multi-stage compression
device. In an embodiment, the second compression device comprises a
first compressor and a second compressor disposed in serial
refrigerant flow relationship, with the refrigerant discharge of
the second compressor being in refrigerant flow communication with
the refrigerant suction of the first compressor, and the economizer
refrigerant line is in refrigerant flow communication with the
refrigerant inlet of the second compressor of the second
compression device. In another embodiment, the refrigerant vapor
compression system further includes a third compression device
disposed in parallel refrigerant flow relationship with the first
compression device, with the discharge outlet of the third
compression device being in refrigerant flow communication with the
refrigerant inlet of the refrigerant heat rejection heat exchanger
and the economizer refrigerant line in refrigerant flow
communication with the refrigerant inlet of the third compression
device.
[0011] In a further embodiment, the refrigerant vapor compression
system includes a pre-cooler heat exchanger interdisposed in the
primary refrigerant circuit downstream, with respect to refrigerant
flow, of the refrigerant outlet of the second compression device
and upstream, with respect to refrigerant flow, of the third
refrigerant flow pass of the refrigerant-to-refrigerant heat
exchanger. The pre-cooler heat exchanger may be disposed in heat
transfer relationship with a secondary fluid, such as, for example,
ambient air, being passed in heat transfer relationship with the
refrigerant passing through the refrigerant heat rejection heat
exchanger.
[0012] In an aspect of the invention, a method of operating a
refrigerant vapor compression system having a first compression
device, a refrigerant heat rejection heat exchanger, a primary
expansion device, a refrigerant heat absorption heat exchanger, and
a second compression device connected in serial refrigerant flow
communication in a primary refrigerant circuit with a refrigerant
discharge outlet of said second compression device in refrigerant
flow communication with a suction inlet of said first compression
device is provided. The method includes the steps of: passing a
first portion of the refrigerant leaving the refrigerant heat
rejection heat exchanger through the primary expansion device of
the primary refrigerant circuit to the refrigerant heat absorption
heat exchanger; expanding a second portion of the refrigerant in an
economizer expansion device downstream of the refrigerant heat
rejection heat exchanger to an intermediate pressure and
temperature; passing the second portion of the refrigerant in heat
exchange relationship with said first portion of the refrigerant at
a location upstream, with respect to refrigerant flow, of the
primary expansion device; and passing the second portion of the
refrigerant in heat exchange relationship with the refrigerant
flowing through the primary refrigerant circuit from the
refrigerant discharge outlet of the second compression device to
the refrigerant suction inlet of the first compression device.
[0013] In an embodiment, the method includes passing the second
portion of the refrigerant in counterflow heat exchange
relationship both with the first portion of the refrigerant and
with the refrigerant flowing through the primary refrigerant
circuit from the second compression device to the first compression
device. In an embodiment, the method further includes the step of
pre-cooling the refrigerant flowing through the primary refrigerant
circuit from the second compression device to the first compression
device prior to passing the second portion of the refrigerant in
heat exchange relationship with the refrigerant flowing through the
primary refrigerant circuit from the second compression device to
the first compression device.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] For a further understanding of the invention, reference will
be made to the flowing detailed description of the invention which
is to be read in connection with the accompanying drawing,
wherein:
[0015] FIG. 1 is a schematic diagram illustrating a first exemplary
embodiment of a vapor compression system in accord with the
invention;
[0016] FIG. 2 is a schematic diagram illustrating a second
exemplary embodiment of a vapor compression system in accord with
the invention;
[0017] FIG. 3 is a schematic diagram illustrating a third exemplary
embodiment of a vapor compression system in accord with the
invention; and
[0018] FIG. 4 is a schematic diagram illustrating a fourth
exemplary embodiment of a vapor compression system in accord with
the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0019] Referring now to FIGS. 1-4, there are depicted therein
several exemplary embodiments of a refrigerant vapor compression
system 100 suitable for use in a transport refrigeration
applications for refrigerating air supplied to a
temperature-controlled cargo space of a truck, trailer, container
or the like for transporting perishable and frozen goods; in
commercial refrigeration applications for refrigerating air
supplied to display cases, merchandisers, freezer cabinets, cold
rooms or other perishable and frozen product storage areas in
commercial establishments; and in air conditioning applications for
residences, office buildings, hospitals, schools, restaurants and
other facilities.
[0020] The refrigerant vapor compression system 100 includes a
first compression device 20, a refrigerant heat rejection heat
exchanger 40, a refrigerant heat absorption heat exchanger 50, and
a second compression device 30 connected in serial refrigerant flow
communication in a primary refrigerant circuit via refrigerant
lines 2, 4, 6 and 8. Each of the first and second compression
devices 20, 30 has a refrigerant discharge outlet and a refrigerant
suction inlet. The refrigerant line 2 connects the discharge outlet
23 of the first compression device 20 in fluid communication with
the inlet to the tube bank 42 of the heat rejection heat exchanger
40. The refrigerant line 4 connects the outlet of the tube bank 42
of the heat rejection heat exchanger 40 in fluid communication with
the inlet to the tube bank 52 of the refrigerant heat absorption
heat exchanger 50. The refrigerant line 6 connects the outlet of
the tank tube 52 of the heat absorption heat exchanger 50 in fluid
communication with the refrigerant suction inlet 31 of the second
compression device 30. The refrigerant line 8 connects the
discharge outlet 33 of the second compression device 30 in fluid
communication with the suction inlet 21 of the first compression
device 20 to complete the primary refrigerant circuit.
[0021] When the refrigerant vapor compression system 100 is
operated in a transcritical vapor compression cycle, the
refrigerant vapor discharging from the first compression device 20
through the discharge outlet 23 thereof into the refrigerant line 2
is at a supercritical pressure and temperature. Therefore, the
refrigerant heat rejection heat exchanger 40 functions as a gas
cooler. The tube bank 42 of the heat rejection heat exchanger 40
may comprise, for example, a finned round tube heat exchanger tube
bank, such as for example in a plate fin and round tube heat
exchanger, or a corrugated fin and multi-channel flattened tube
heat exchanger tube bank, such as for example in a minichannel or
microchannel heat exchanger. In traversing the heat rejection heat
exchanger 40, the refrigerant passes through the heat exchange
tubes of the tube bank 42 in heat exchange relationship with a
secondary fluid, typically ambient air, generally outdoor air,
being drawn through the tube bank 42 by an air mover 44, such as
one or more fans, operatively associated with the tube bank 42 of
the heat rejection heat exchanger 40. An expansion valve 55,
operatively associated with the heat absorption heat exchanger 50,
which functions as an evaporator, is interdisposed in the
refrigerant line 4 upstream, with respect to refrigerant flow, of
the heat absorption heat exchanger 50 and downstream, with respect
to refrigerant flow, of the heat rejection heat exchanger 40.
[0022] The refrigerant leaves the heat rejection heat exchange 40
at a supercritical pressure and lower temperature and passes
through the refrigerant line 4 that connects in fluid communication
with the inlet to the heat absorption heat exchanger 50. In doing
so, the refrigerant traverses through the expansion device 55
interdisposed in the refrigerant line 4 intermediate the heat
rejection heat exchanger 40 and the heat absorption heat exchanger
50. The expansion device 55 may be a restriction type expansion
device, such as a capillary tube or a fixed plate orifice, a
thermostatic expansion valve or an electronic expansion valve. In
traversing the expansion device 55, the high pressure refrigerant
is expanded to a lower temperature and lower pressure to form a
subcritical refrigerant liquid or, more commonly, a subcritical
liquid/vapor refrigerant mixture.
[0023] In traversing the heat absorption heat exchanger 50, the
refrigerant passes through the heat exchange tubes of the tube bank
52 in heat exchange relationship with air to be conditioned,
typically air, at least partially, drawn from and to be returned to
a climate-controlled environment, being drawn through the tube bank
52 by an air mover 54, such as one or more fans, operatively
associated with the tube bank 52 of the heat absorption heat
exchanger 50, whereby the air is cooled, and typically
dehumidified, while the refrigerant is evaporated and typically
superheated. The tube bank 52 of the heat absorption heat exchanger
50 may comprise, for example, a finned round tube heat exchanger
tube bank, such as for example in a plate fin and round tube heat
exchanger, or a corrugated fin and multi-channel flattened tube
heat exchanger tube bank, such as for example in a minichannel or
microchannel heat exchanger. The subcritical pressure refrigerant
vapor leaving the heat absorption heat exchanger 50 passes through
the refrigerant line 6 to the refrigerant inlet 31 of the second
compression device 30.
[0024] The refrigerant vapor compression system 100 further
includes a refrigerant-to-refrigerant heat exchanger 60 that
functions as both an economizer heat exchanger and a refrigerant
intercooler. The refrigerant-to-refrigerant heat exchanger 60
includes a first refrigerant flow pass 62, a second refrigerant
flow pass 64 and a third refrigerant flow pass 66. The first
refrigerant flow pass 62 is interdisposed in the refrigerant line 4
of the primary refrigerant circuit downstream, with respect to
refrigerant flow, of the refrigerant outlet of the refrigerant heat
rejection heat exchanger 40 and upstream, with respect to
refrigerant flow, of the expansion device 55 disposed upstream,
with respect to refrigerant flow, of the refrigerant inlet to the
refrigerant heat absorption heat exchanger 50. The third
refrigerant flow pass 66 is interdisposed in the refrigerant line 8
of the primary refrigerant circuit between the refrigerant
discharge outlet 33 of the second compression device 30 and the
refrigerant suction inlet 21 of the first compression device
20.
[0025] The second refrigerant flow pass 64 is interdisposed in an
economizer refrigerant line 10 of the economizer refrigerant
circuit of the refrigerant vapor compression system 100. The
economizer refrigerant line 10 establishes refrigerant flow
communication between the refrigerant line 4 of the primary
refrigerant circuit and an intermediate pressure stage of the
compression process. An economizer circuit expansion device 65 is
disposed in the refrigerant line 10 upstream, with respect to
refrigerant flow therethrough, of the second pass 64 of the
refrigerant-to-refrigerant heat exchanger 60. The economizer
refrigerant line 10 may tap a portion of refrigerant from the
refrigerant line 4 at a location upstream, with respect to
refrigerant flow, of the first refrigerant flow pass 62 of the
refrigerant-to-refrigerant heat exchanger 60, as depicted in FIG.
1, or at a location downstream, with respect to refrigerant flow,
of the first refrigerant flow pass 62 of the
refrigerant-to-refrigerant heat exchanger 60 and upstream, also
with respect to refrigerant flow, of the primary expansion valve
55, as depicted in FIG. 2. The economizer refrigerant line 10
delivers refrigerant passing therethrough to an intermediate
pressure stage of the compression process, that is, to a location
in the compression process having a pressure above the suction
inlet pressure at the second compressor 30 and below the discharge
pressure at the discharge outlet of the first compressor 20. In the
embodiments depicted in FIGS. 1 and 2, the outlet of the economizer
refrigerant line 10 opens in fluid flow communication with an
intermediate pressure port 35 of the second compressor 30, whereby
the economizer refrigerant flow will be injected back into the
compression process upstream, with respect to refrigerant flow, of
the intercooler circuit 8. However, it is to be understood that the
economizer refrigerant line 10 could, if desired, instead be
arranged to open in fluid flow communication with an intermediate
pressure port of the first compressor 20, whereby the economizer
refrigerant flow would be injected back into the compression
process downstream of the intercooler circuit 8.
[0026] The high pressure, high temperature refrigerant tapped from
the refrigerant line 4 of the primary refrigerant circuit traverses
the economizer expansion device 65 as it passes through the
economizer refrigerant line 10 prior to traversing the second pass
64 of the refrigerant-to-refrigerant heat exchanger 60. In
traversing the economizer expansion device 65, the high pressure,
high temperature refrigerant is expanded to an intermediate
pressure and temperature, that is a pressure and temperature lower
than the refrigerant discharge temperature and pressure,
respectively, but higher than the refrigerant suction pressure and
temperature, respectively. The second refrigerant flow pass 64 is
disposed in heat exchange relationship with each of the first
refrigerant flow pass 62 and the third refrigerant flow pass 66.
When the refrigerant vapor compression system 100 is operated in a
transcritical vapor compression cycle, the refrigerant tapped from
the refrigerant line 4 is a single-phase refrigerant at a
supercritical pressure and the expanded refrigerant flowing through
the economizer refrigerant line 10 downstream of the economizer
expansion device 65 is typically a refrigerant liquid/vapor mixture
at a subcritical pressure. The economizer expansion device 65 may
be a restriction type expansion device, such as a capillary tube or
a fixed plate orifice, a thermostatic expansion valve operatively
associated with a temperature sensing bulb, or an electronic
expansion valve.
[0027] As mentioned above, the second refrigerant flow pass 64 is
disposed in heat exchange relationship with each of the first
refrigerant flow pass 62 and the third refrigerant flow pass 66.
When the refrigerant vapor compression system 100 is operated in a
subcritical vapor compression cycle, the refrigerant tapped from
the refrigerant line 4 is a liquid at a subcritical pressure and
the expanded refrigerant flowing through the economizer refrigerant
line 10 downstream of the economizer expansion device 65 is
typically a refrigerant liquid/vapor mixture at a lower subcritical
pressure. Thus, refrigerant flowing through the second refrigerant
flow pass 64 will always be a cooling medium with respect to the
refrigerant passing through the first refrigerant flow pass 62 and
also with respect to the refrigerant passing through the third
refrigerant flow pass 66. It should be noted that the second
refrigerant pass 64 may be arranged so as to pass refrigerant
through the refrigerant-to-refrigerant heat exchanger in a
direction opposite to, i.e. in counterflow to, the flow of
refrigerant through the first and third refrigerant passes 62 and
66, as depicted in FIGS. 1 and 2, or in the same direction as, i.e.
in parallel flow to, the flow of refrigerant through the first and
third refrigerant passes 62 and 66, as depicted in FIGS. 3 and 4.
However, it is to be understood that it is more desirable, from a
heat transfer effectiveness perspective, to have the second
refrigerant flow pass 64 arranged in a counterflow configuration
with respect to the first and third refrigerant flow passes 62 and
66.
[0028] Therefore, when the system 100 is operating in an economized
mode, the refrigerant-to-refrigerant heat exchanger 60 functions as
both a refrigerant intercooler and an economizer heat exchanger.
The intercooler function is provided by the heat transfer
interaction between the second refrigerant flow pass 64 and the
third refrigerant flow pass 66 as the expanded refrigerant passing
through the second refrigerant flow pass 64 cools the refrigerant
passing through the third refrigerant flow pass 66 from the
discharge outlet of the second compression device 30 to the suction
inlet of the first compression device 20 via the refrigerant line
8. The economizer function is provided by the heat transfer
interaction between the second refrigerant flow pass 64 and the
first refrigerant flow pass 62 as the expanded refrigerant passing
through the second refrigerant flow pass 64 cools the refrigerant
passing through the first refrigerant flow pass 62 from the
refrigerant heat rejection heat exchanger 40 to the refrigerant
heat absorption line heat exchanger 50 via the refrigerant line
4.
[0029] In the exemplary embodiments of the refrigerant vapor
compression system 100 depicted in FIGS. 1 and 2, the first
compression device 20 and the second compression device 30 comprise
separate compressors connected in series refrigerant flow
relationship with the refrigerant discharge outlet 33 of the second
compressor 30 connected in refrigerant flow communication with the
refrigerant suction inlet 21 of the first compressor 20, with the
first compressor 20 operating at a higher pressure than the
pressure at which the second compressor 30 operates. As depicted in
FIGS. 1 and 2, in these embodiments, the economizer refrigerant
line 10 opens in refrigerant flow communication to an intermediate
pressure stage of the second, i.e. lower pressure, compressor 30,
although, as mentioned above, the economizer refrigerant line 10
can be configured to open in refrigerant flow communication to an
intermediate pressure stage of the first, i.e. higher pressure,
compressor 20, if desired and feasible. In these embodiments each
of the compressors 20 and 30 generally comprises a single stage
refrigerant compressor, such as, for example, a scroll compressor,
a rotary compressor, a screw compressor, a reciprocating
compressor, a centrifugal compressor or the like.
[0030] In the exemplary embodiment of the refrigerant vapor
compression system 100 depicted in FIG. 2, refrigerant leaving the
discharge outlet 33 of the second compressor 30 transverses a heat
exchange tube bank 46 in heat exchange relationship with ambient
air, prior to entering the third refrigerant flow pass 66 of the
refrigerant-to-refrigerant heat exchanger 60, and then returning to
the suction inlet 21 of the first compressor 20. Such arrangement
provides pre-cooling of the refrigerant exiting the discharge
outlet 33 of the compressor 30 by ambient air, prior to entering
the third refrigerant flow pass 66 of the
refrigerant-to-refrigerant heat exchanger 60, where it is further
cooled by the economized refrigerant flow transverse the second
refrigerant flow pass 64. It has to be understood that the
pre-cooling heat exchange tube bank 46 can be arranged in
sequential configuration or in parallel configuration, with respect
to ambient airflow, in relation to the heat rejection heat
exchanger tube bank 42. Further, the pre-cooler tube bank 46 can
share the same heat exchanger core and/or housing structure with
the heat rejection heat exchanger tube bank 42 or can be configured
as a separate stand-alone heat exchanger, as well as can utilize
the same air moving device 44, as shown in the FIGS. 2-4, or can be
associated with a separate dedicated air moving device. As the heat
rejection heat exchanger tube bank 42, the heat exchange tube bank
46 may be, for instance, of a round tube and plate fin type or a
corrugated fin and flattened tube type.
[0031] In the exemplary embodiment of the refrigerant vapor
compression system 100 depicted in FIG. 3, the second compression
device 30 comprises a multi-stage compression device having at
least a lower pressure compression stage 30a and a higher pressure
compression stage 30b with refrigerant flow passing directly from
the lower pressure compression stage 30a to the higher pressure
compression stage 30b. In this embodiment, the economizer
refrigerant line 10 opens in refrigerant flow communication to an
intermediate pressure point of the compression process, such as,
for example, into the refrigerant passing from the lower pressure
stage 30a to the higher pressure stage 30b of the second
compression device 30. In this embodiment, the second compression
device 30 may comprise a single, multi-stage compressor having at
least a first compression stage 30a and a second compression stage
30b, such as, for example, a scroll compressor, or a screw
compressor having staged compression pockets, or a reciprocating
compressor having at least a first bank of cylinders and a second
bank of cylinders, or a pair of single-stage compressors 30a and
30b connected in series refrigerant flow relationship such as, for
example, a pair of scroll compressors, screw compressors,
centrifugal compressors, reciprocating compressors (or separate
cylinders of a single reciprocating compressor) or rotary
compressors, with the discharge outlet of the upstream compressor
connected in serial refrigerant flow communication with the suction
inlet of the downstream compressor. In this embodiment, the first
compression device 20 generally comprises a single stage
refrigerant compressor, such as, for example, a scroll compressor,
a rotary compressor, a screw compressor, a reciprocating
compressor, a centrifugal compressor or the like.
[0032] In the exemplary embodiment of the refrigerant vapor
compression system 100 depicted in FIG. 4, the economizer
refrigerant line 10 opens in refrigerant flow communication to a
third compression device 70, rather than into an intermediate
pressure stage of the second compression device 30. The third
compression device 70 comprises a separate compressor disposed in
parallel refrigerant flow relationship with the first compression
device 20, that is both the first compression device 20 and the
third compression device 70 discharge refrigerant at the same
pressure into the refrigerant line 2 of the primary refrigerant
circuit. However, the third compression device 70 and the first
compression device 20 can share the same compressor housing, as for
example, in the case of separate cylinder banks of a reciprocating
compressor. Further, the third compression device 70 and the second
compression device 30 can be separate parts of the same compressor
as well. In this embodiment, the third compression device 70 is in
effect part of the economizer circuit. The refrigerant expanded in
the economizer expansion device 65 having passed through the second
refrigerant flow pass 64 of the economizer heat exchanger 60 as the
cooling medium passes through the economizer refrigerant line 10
which connects to the suction inlet 71 of the third compressor 70.
In this embodiment, each of the first compression device 20, the
second compression device 30 and the third compression device 70
generally comprise a single stage refrigerant compressor, such as,
for example, a scroll compressor, a rotary compressor, a screw
compressor, a reciprocating compressor, a centrifugal compressor or
the like. However, each of the compression devices 20, 30 and 70
may comprise a multi-stage compressor, if desired.
[0033] As mentioned above, as depicted in FIGS. 2-4, the
refrigerant vapor compression system 100 may include a pre-cooler
heat exchanger tube bank 46 interdisposed in the refrigerant line 8
of the primary refrigerant circuit upstream, with respect to
refrigerant flow, of the intercooler, i.e. the third refrigerant
flow pass 66 of the refrigerant-to-refrigerant heat exchanger 60.
In operation, the refrigerant vapor passing from the refrigerant
discharge outlet 33 of the second compression device 30 through the
refrigerant line 8 of the primary refrigerant circuit traverses the
pre-cooler heat exchanger tube bank 46 to be initially cooled by
the air, typically ambient air, also flowing through the
refrigerant heat rejection heat exchanger 40, before passing
through the third refrigerant flow pass 66 of the
refrigerant-to-refrigerant heat exchanger 60 to be further cooled
prior to passing to the refrigerant suction inlet 21 of the first
compression device 20.
[0034] The present invention is described above with reference to
the several embodiments depicted schematically in FIGS. 1-4. These
embodiments are exemplary, and not limiting, of refrigerant vapor
compression systems embodying the teachings of the invention.
Persons skilled in the art will recognize that variations and
modifications of these embodiments, including but not limited to
rearrangement of the various of the components of refrigerant vapor
compression systems, and additional equivalent embodiments of the
refrigerant vapor compression system, some of which have been
mentioned herein, may be made that embody the teachings of the
invention without departing from the spirit and scope of the
invention as defined by the following claims.
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