U.S. patent application number 12/088767 was filed with the patent office on 2008-10-23 for vapor compression system with condensate intercooling between compression stages.
This patent application is currently assigned to CARRIER CORPORATION. Invention is credited to Alexander Lifson, Michael F. Taras.
Application Number | 20080256975 12/088767 |
Document ID | / |
Family ID | 39107079 |
Filed Date | 2008-10-23 |
United States Patent
Application |
20080256975 |
Kind Code |
A1 |
Lifson; Alexander ; et
al. |
October 23, 2008 |
Vapor Compression System With Condensate Intercooling Between
Compression Stages
Abstract
A refrigerant vapor compression system includes a first
compression device and a second compression device disposed in a
refrigerant circuit in series relationship with respect to
refrigerant flow and an intercooler adapted to cool the refrigerant
passing from the first compression device to the second
compression. An evaporator is provided in the refrigerant circuit
wherein the refrigerant accepts heat from a moisture bearing gas
such as air. Condensate formed of moisture condensing out of the
gas is collected and supplied to the intercooler for cooling the
refrigerant flowing from the first compression device to the second
compression device.
Inventors: |
Lifson; Alexander; (Manlius,
NY) ; Taras; Michael F.; (Fayetteville, 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: |
39107079 |
Appl. No.: |
12/088767 |
Filed: |
August 21, 2006 |
PCT Filed: |
August 21, 2006 |
PCT NO: |
PCT/US06/32547 |
371 Date: |
March 31, 2008 |
Current U.S.
Class: |
62/510 ; 62/115;
62/509 |
Current CPC
Class: |
F25B 31/006 20130101;
F25B 2400/072 20130101; F25B 1/10 20130101; F25D 21/14
20130101 |
Class at
Publication: |
62/510 ; 62/509;
62/115 |
International
Class: |
F25B 1/10 20060101
F25B001/10; F25B 39/04 20060101 F25B039/04; F25B 1/00 20060101
F25B001/00 |
Claims
1. A refrigerant vapor compression system comprising: at least one
compression device having a first compression stage to compress a
refrigerant to a first pressure and a second compression stage to
further compress the refrigerant from the first pressure to a
second pressure; a heat accepting heat exchanger for passing the
refrigerant in heat exchange relationship with a moisture bearing
gas whereby the heat is transferred to the refrigerant to cool
moisture bearing gas and moisture in the moisture bearing gas is at
least partially condensed to form a condensate; and an intercooler
wherein the condensate exchanges heat with and accepts heat from
the refrigerant passing from the first compression stage to the
second compression stage.
2. A refrigerant vapor compression system as recited in claim 1
wherein the first compression stage comprises a first compressor
and the second compression stage comprises a second compressor, the
first compressor having a discharge outlet connected by a
refrigerant line in refrigerant flow communication to a suction
inlet of the second compressor.
3. A refrigerant vapor compression system as recited in claim 2
wherein the refrigerant line connecting the discharge outlet of the
first compressor to the suction inlet of the second compressor
traverses the intercooler.
4. A refrigerant vapor compression system as recited in claim 1
wherein the first compression stage comprises a first compression
stage of a compressor and the second compression stage comprises a
second compression stage of the same compressor, the refrigerant
being compressed in the compressor passes from the first
compression stage to the second compression stage.
5. A refrigerant vapor compression system as recited in claim 4
wherein the refrigerant passing from the first compression stage to
the second compression stage traverses the intercooler.
6. A refrigerant vapor compression system as recited in claim 1
further comprising a condensate collector operatively associated
with the heat accepting heat exchanger for collecting the
condensate condensed from the moisture bearing gas.
7. A refrigerant vapor compression system as recited in claim 6
further comprising a pump to supply the condensate from the
condensate collector to the intercooler.
8. A refrigerant vapor compression system as recited in claim 1
wherein said intercooler comprises: refrigerant conveying passages
having an exterior heat exchange surface; and at least one spray
nozzle to spray the condensate condensed from the moisture bearing
gas onto the exterior heat exchange surface of the refrigerant
conveying passages.
9. A refrigerant vapor compression system as recited in claim 8
wherein the at least one spray nozzle comprises an atomizing
nozzle.
10. A refrigerant vapor compression system as recited in claim 8
wherein the at least one spray nozzle comprises a rotary
atomizer.
11. A refrigerant vapor compression system as recited in claim 8
further comprising a condensate collector operatively associated
with the heat accepting heat exchanger for collecting the
condensate condensed from the moisture bearing gas.
12. A refrigerant vapor compression system as recited in claim 11
further comprising a pump to supply the condensate from the
condensate collector to the at least one spray nozzle.
13. A refrigerant vapor compression system as recited in claim 1
wherein the refrigerant is carbon dioxide.
14. A refrigerant vapor compression system as recited in claim 1
wherein said intercooler comprises a heat exchange device
incorporating refrigerant conveying passages having an exterior
heat exchange surface in contact with the condensate.
15. A refrigerant vapor compression system as recited in claim 14
wherein the intercooler heat exchange device is selected from the
group consisting of a plate heat exchanger, tubular heat exchanger
and immersed coil heat exchanger.
16. A refrigerant vapor compression system as recited in claim 14
further comprising a condensate collector operatively associated
with the heat accepting heat exchanger for collecting the
condensate condensed from the moisture bearing gas.
17. A refrigerant vapor compression system as recited in claim 16
further comprising a pump to supply the condensate from the
condensate collector to the intercooler.
18. A refrigerant vapor compression system as recited in claim 1
wherein the intercooler comprises a condensate collector
operatively associated with the heat accepting heat exchanger for
collecting the condensate condensed from the moisture bearing gas
and the intercooler heat exchange device is a refrigerant conveying
passage immersed in the condensate in said condensate
collector.
19. A refrigerant vapor compression system as recited in claim 1,
wherein at least one of said first and second compression stages
comprises at least a least a pair of compressors disposed in a
tandem compressor configuration.
20. A method of improving performance of a refrigerant vapor
compression system comprising the steps of: compressing the
refrigerant to a first pressure in a first compression stage and to
a second pressure in a second compression stage; passing the
refrigerant in heat exchange relationship with a moisture bearing
gas whereby the refrigerant accepts heat from the gas cooling the
gas and at least a portion of the moisture condenses from the gas
to form a condensate; and cooling the refrigerant between the first
compression stage and the second compression stage via heat
exchange with the condensate.
21. A method as recited in claim 20 wherein the step of compressing
the refrigerant to a first pressure in a first compression stage
and to a second pressure in a second compression stage comprises
compressing the refrigerant to a first pressure in a first
compressor and compressing the refrigerant to a second pressure in
a second compressor, the second compressor receiving refrigerant
from the first compressor substantially at the first pressure.
22. A method as recited in claim 20 wherein the step of compressing
the refrigerant to a first pressure in a first compression stage
and to a second pressure in a second compression stage comprises
compressing the refrigerant to a first pressure in a first stage of
a compressor and compressing the refrigerant to a second pressure
in a second stage of the same compressor.
23. A method as recited in claim 20 wherein the step of cooling the
refrigerant passing between the first compression stage and the
second compression stage via heat exchange with the condensate
includes evaporating at least a portion of the condensate.
24. A method as recited in claim 23 further comprising the steps
of: passing the refrigerant flowing between the first compression
stage and the second compression stage through at least one
refrigerant conveying passage; and spraying the condensate onto the
at least one refrigerant conveying passage.
25. A method as recited in claim 23 further comprising the step of:
passing the refrigerant flowing between the first compression stage
and the second compression stage through at least one refrigerant
conveying passage immersed in the condensate.
26. A method as recited in claim 20 wherein the refrigerant is
carbon dioxide.
27. A refrigerant vapor compression system comprising: a first
compressor to compress a refrigerant to a first pressure, said
first compressor having a suction inlet and a discharge outlet; a
second compressor to further compress the refrigerant to a second
pressure, the second compressor having a suction inlet and a
discharge outlet; a refrigerant circuit including a first
refrigerant line connecting the discharge outlet of said second
compressor in refrigerant flow communication with the suction inlet
of said first compressor and a second refrigerant line connecting
the discharge outlet of said first compressor with the suction
inlet of said second compressor; a heat rejecting heat exchanger
for passing refrigerant in heat exchange relationship with a
cooling fluid whereby the refrigerant rejects heat to the cooling
fluid, said heat rejecting heat exchanger disposed in the first
refrigerant line downstream with respect to refrigerant flow of the
discharge outlet of said second compressor; a heat accepting heat
exchanger for passing the refrigerant in heat exchange relationship
with a moisture bearing gas whereby the refrigerant accepts heat
from the gas to cool the gas and moisture in the gas is at least
partially condensed to form a condensate, said heat accepting heat
exchanger disposed in the first refrigerant line downstream with
respect to refrigerant flow of said heat rejecting heat exchanger;
an expansion device disposed in the refrigerant circuit downstream
with respect to refrigerant flow of said heat rejecting heat
exchanger and upstream with respect to refrigerant flow of said
heat accepting heat exchanger, said expansion device operative to
expand to lower pressure and temperature the refrigerant passing
through the first refrigerant line from said heat rejecting heat
exchanger to said heat accepting heat exchanger; and an intercooler
disposed in the second refrigerant line wherein the refrigerant
passing from said first compressor to second compressor exchanges
heat with the condensate whereby the refrigerant passing from said
first compressor to said second compressor is cooled by the
condensate.
28. A refrigerant vapor compression system as recited in claim 27
wherein the refrigerant is carbon dioxide.
29. A refrigerant vapor compression system as recited in claim 27
wherein said intercooler comprises a heat exchange device
incorporating refrigerant conveying passages having an exterior
heat exchange surface in contact with the condensate.
30. A refrigerant vapor compression system as recited in claim 29
wherein the intercooler heat exchange device is selected from the
group consisting of a plate heat exchanger, tubular heat exchanger
and immersed coil heat exchanger.
31. A refrigerant vapor compression system as recited in claim 27
further comprising a condensate collector operatively associated
with the heat accepting heat exchanger for collecting the
condensate condensed from the moisture bearing gas.
32. A refrigerant vapor compression system as recited in claim 27
further comprising a pump to supply the condensate from the
condensate collector to the intercooler.
33. A refrigerant vapor compression system as recited in claim 27
wherein the intercooler comprises a condensate collector
operatively associated with the heat accepting heat exchanger for
collecting the condensate condensed from the moisture bearing gas
and the intercooler heat exchange device is a refrigerant conveying
passage immersed in the condensate in said condensate collector.
Description
FIELD OF THE INVENTION
[0001] This invention relates generally to vapor compression
systems having multiple compression stages and, more particularly,
to the cooling of refrigerant vapor passing between an upstream
compression stage and a downstream compression stage in a
refrigerant vapor compression system.
BACKGROUND OF THE INVENTION
[0002] Refrigerant vapor compression systems are well known in the
art and commonly used for conditioning secondary fluid such as 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 transport and stationary refrigeration applications for
refrigerating air supplied to a temperature controlled space of a
truck, trailer, container, display case or the like for preserving
perishable items. Traditionally, most of these refrigerant vapor
compression systems operate at subcritical refrigerant pressures
and typically include a compressor, a condenser, an evaporator, and
an expansion device. Commonly, an expansion device is disposed
upstream, with respect to refrigerant flow, of the evaporator and
downstream of the condenser. These basic refrigerant system
components are interconnected by refrigerant lines in a closed
refrigerant circuit, arranged in accord with known refrigerant
vapor compression cycles, and operated in the subcritical pressure
range for the particular refrigerant in use. 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 and R407C.
[0003] Although HFC refrigerants are more environmentally friendly
than the chlorine containing HCFC refrigerants that they replaced,
"natural" refrigerants, such as carbon dioxide, are being turned to
for use in air conditioning and refrigeration systems instead of
HFC refrigerants. However, because carbon dioxide has a low
critical point, a vast majority of refrigerant vapor compression
systems charged with carbon dioxide as the refrigerant are designed
for operation in the transcritical cycle. In refrigerant vapor
compression systems operating in a transcritical cycle, the heat
rejection heat exchanger operates at refrigerant pressures above
the critical point, while the evaporator operates at refrigerant
pressures in the subcritical range. Additionally, refrigerant vapor
compression systems utilizing a low critical point refrigerant,
such as carbon dioxide, frequently employ a multi-stage compression
system, either multiple compressors disposed in series flow
arrangement with respect to refrigerant flow or a single compressor
having at least two compression stages. Typically, the pressure of
the refrigerant vapor discharging from the final stage of the
compression system, commonly referred to as the discharge pressure
or the high-side pressure, is high enough that the refrigerant
vapor does not condense as it traverses the heat rejection heat
exchanger. Consequently, with respect to systems operating in a
transcritical cycle, the heat rejection heat exchanger is commonly
referred to as, and functions as, a gas cooler, not a
condenser.
[0004] It is well appreciated by practitioners skilled in the art
of vapor compression that it is desirable to insert an intercooler
in the refrigerant circuit between compression stages in a
multi-stage compression system charged with a low critical point
refrigerant such as carbon dioxide. The vapor passing from the
discharge of an upstream compression stage to the suction of a
downstream compression stage flows in heat exchange relationship
with a cooling medium as the vapor traverses the intercooler
thereby cooling the vapor to improve the cycle performance and to
decrease the refrigerant discharge temperature. In conventional
transcritical vapor compression systems employing intercoolers, the
cooling medium is generally a secondary cooling fluid external to
the system, such as chilled water or ambient air, or a portion of
the cold system refrigerant diverted from elsewhere within the
refrigerant circuit.
[0005] U.S. Pat. No. 6,658,888 discloses a multi-stage compression
refrigerant vapor compression system charged with carbon dioxide
refrigerant and having an intercooler between stages of a
multi-stage compressor. The refrigerant vapor passing between
compression stages traverses the intercooler wherein it rejects
heat to the same cooling fluid medium having previously passed
through the gas cooler accepting heat from the refrigerant vapor
discharged from the compressor. After traversing the intercooler,
the heated cooling fluid medium exits the system. The cooling fluid
medium may be room air, tap water or recirculated water, depending
upon the application.
[0006] U.S. Pat. No. 6,698,234 also discloses a multi-stage
compression refrigerant vapor compression system charged with
carbon dioxide refrigerant and having an intercooler between stages
of a multi-stage compression system. In an embodiment disclosed
therein, a portion of the cold refrigerant downstream of the gas
cooler bypasses the system evaporator and is diverted to pass
through the intercooler in heat exchange relationship with the
refrigerant vapor flowing between compression stages. The diverted
refrigerant is expanded to a lower pressure and temperature prior
to passing through the intercooler. As the two refrigerant streams
pass in heat exchange relationship in the intercooler, the diverted
refrigerant stream is heated and the refrigerant vapor flowing
between compression stages is cooled. The heated diverted
refrigerant is returned to the suction side of the refrigerant
circuit downstream of the system evaporator.
[0007] It has to be noted that conventional subcritical multi-stage
vapor compression systems also benefit from intercoolers, although
these benefits are not as pronounced as for transcritical
systems.
SUMMARY OF THE INVENTION
[0008] It is an object of the invention to provide a multi-stage
vapor compression system including an intercooler for cooling vapor
passing between compression stages that use evaporator condensate
water as the cooling medium in the intercooler.
[0009] The refrigerant vapor compression system of the invention
includes a first compression device to compress a refrigerant to a
first pressure, a second compression device to further compress the
refrigerant from the first pressure to a second pressure, a heat
accepting heat exchanger (e.g. evaporator) for passing the
refrigerant in heat exchange relationship with a moisture bearing
gas (e.g. air) whereby the heat is transferred from the gas to the
refrigerant and at least some amount of moisture in the moisture
bearing gas is condensed to form a condensate (water), and an
intercooler wherein the condensate exchanges heat with and accepts
heat from the refrigerant passing from said first compression
device to the second compression device.
[0010] In an embodiment, the first compression device is a first
compressor and the second compression device is a second compressor
with the discharge outlet of the first compressor connected by a
refrigerant line in refrigerant flow communication to the suction
inlet of the second compressor. The refrigerant line connecting the
discharge outlet of the first compressor to the suction inlet of
the second compressor traverses the intercooler. In another
embodiment, the first compression device is a first compression
stage of a compressor and the second compression device is a second
compression stage of the same compressor. The refrigerant being
compressed in the compressor traverses the intercooler as it passes
from the first compression stage to the second compression
stage.
[0011] In an embodiment, the intercooler includes a refrigerant
conveying passage having an exterior heat exchange surface, which
can be enhanced for better heat transfer by one of the techniques
known in the art, and at least one spray nozzle to spray the
condensate condensed from the moisture bearing gas onto the
exterior heat exchange surface of the refrigerant conveying
passage. Alternatively, a heat exchanger construction may be
provided for the intercooler, preferably having moisture and
refrigerant flows arranged in a counterflow configuration. A
condensate collector may be provided in operative association with
the heat accepting heat exchanger for collecting the condensate
condensed from the moisture bearing gas. Condensate may be
gravity-fed from the condensate collector to the spray nozzle or
nozzles if the condensate collector is disposed at a higher
elevation than the intercooler. Alternatively, a pump may be
provided to supply the condensate from the condensate collector to
the intercooler.
[0012] In another aspect of the invention, a method is provided for
increasing the capacity of a refrigerant vapor compression system
by cooling the refrigerant between a first compression stage and a
second compression stage via heat exchange with the condensate. The
method of the invention includes the steps of: compressing the
refrigerant to a first pressure in a first compression stage and to
a second pressure in a second compression stage, passing the
refrigerant in heat exchange relationship with a moisture bearing
gas whereby the refrigerant accepts heat from the gas and at least
a portion of the moisture condenses from the gas to form a
condensate, and cooling the refrigerant between the first
compression stage and the second compression stage via heat
exchange with the condensate. The step of cooling the refrigerant
passing between the first compression stage and the second
compression stage via heat exchange with the condensate may
comprise cooling the refrigerant between the first compression
stage and the second compression stage via evaporating at least a
portion of the condensate. The method may include the steps of
passing the refrigerant flowing between the first compression stage
and the second compression stage through a refrigerant conveying
passage that may or may not have internal and external enhanced
heat transfer surfaces and spraying the condensate onto the
refrigerant conveying passage. Condensate delivery may be
accomplished with assistance of gravity or mechanical means such as
a condensate pump.
[0013] In a further aspect of the invention, a refrigerant vapor
compression system includes a first compressor to compress a
refrigerant to a first pressure, a second compressor to further
compress the refrigerant to a second pressure, a refrigerant
circuit including a first refrigerant line (or lines) passing
through other refrigerant system components and connecting the
discharge outlet of the second compressor in refrigerant flow
communication with the suction inlet of the first compressor and a
second refrigerant line connecting the discharge outlet of the
first compressor with the suction inlet of the second compressor, a
heat rejecting heat exchanger disposed in the first refrigerant
line downstream with respect to refrigerant flow of the discharge
outlet of said second compressor, a heat accepting heat exchanger
disposed in the first refrigerant line downstream with respect to
refrigerant flow of the heat rejecting heat exchanger for passing
the refrigerant in heat exchange relationship with a moisture
bearing gas whereby the refrigerant accepts heat from the gas and
moisture in the gas is at least partially condensed to form a
condensate, an expansion device operative to expand the refrigerant
passing through the first refrigerant line from the heat rejecting
heat exchanger to the heat accepting heat exchanger, and an
intercooler disposed in the second refrigerant line wherein the
refrigerant passing from the first compressor to the second
compressor exchanges heat with the condensate whereby the
refrigerant passing from the first compressor to the second
compressor is cooled.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] For a further understanding of these and other objects of
the invention, reference will be made to the following detailed
description of the invention which is to be read in connection with
the accompanying drawing, where:
[0015] FIG. 1 is a schematic diagram illustrating a first exemplary
embodiment of a refrigerant vapor compression system in accord with
the invention;
[0016] FIG. 2 is a schematic diagram illustrating a second
exemplary embodiment of a refrigerant vapor compression system in
accord with the invention;
[0017] FIG. 3 is a schematic diagram illustrating a third exemplary
embodiment of a refrigerant vapor compression system in accord with
the invention; and
[0018] FIG. 4 is a schematic diagram illustrating a fourth
exemplary embodiment of a refrigerant vapor compression system in
accord with the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0019] Referring now to FIGS. 1-4, as in conventional systems, the
refrigerant vapor compression system 10 includes a compression
device 30, a refrigerant heat rejecting heat exchanger 40, also
referred to herein as a gas cooler or a condenser (depending on an
application), a refrigerant heat absorbing heat exchanger 50, also
referred to herein as an evaporator, an expansion device 55,
illustrated as an expansion valve, operatively associated with the
evaporator 50, and various refrigerant lines 60A, 60B, 60C and 60D
connecting the aforementioned components in a conventional
refrigerant circuit. The compression device 30 functions to
compress and circulate refrigerant throughout the refrigerant
circuit as will be discussed in further detail hereinafter. The
compression device 30 may be a scroll compressor, a screw
compressor, a reciprocating compressor, a rotary compressor, a
centrifugal compressor or any other type of compressor or a
plurality of any such compressors. The compression device 30, as
depicted in FIGS. 1-4, has a first compression stage 30-1 and a
second compression stage 30-2. The compression device 30 may be a
pair of compressors 30-1 and 30-2, for example a pair of scroll
compressors, screw compressors, reciprocating compressors or rotary
compressors connected in series, having a refrigerant line 60D
connecting the discharge outlet port of the first compressor 30-1,
which constitutes the first compression stage, in refrigerant flow
communication with the suction inlet port of the second compressor
30-2, which constitutes the second compression stage.
Alternatively, the compression device 30 may be a single
refrigerant compressor having a first compression stage and a
second compression stage, for example a scroll compressor or a
screw compressor having at least a pair of staged compression
pockets 30-1, 30-2, or a reciprocating compressor having a first
bank 30-1 and a second bank 30-2 of cylinders. Also, it has to be
understood that although only two compression stages 30-1 and 30-2
are depicted in the FIGS. 1-4, any number of compression stages
connected in series is within the scope of this invention and can
benefit from the invention. Further, one or more compression stage
may consist of two or more compressors disposed in a so-called
tandem arrangement, that is compressors operating in parallel and
having at least one common manifold.
[0020] The refrigerant vapor compression system of the invention
may be operated in either a subcritical cycle or a transcritical
cycle. In a refrigerant vapor compression system operating in a
subcritical cycle, the refrigerant heat rejecting heat exchanger 40
constitutes a refrigerant condensing heat exchanger through which
hot, high pressure refrigerant vapor discharged from the
compression device 30-2 passes in heat exchange relationship with a
secondary cooling medium, most commonly ambient air in air
conditioning systems or refrigeration systems. In a refrigerant
vapor compression system operating in a transcritical cycle, the
refrigerant heat rejecting heat exchanger 40 constitutes a gas
cooler heat exchanger through which supercritical refrigerant vapor
discharged from the compression device 30-2 passes in heat exchange
relationship with a secondary cooling medium, again most commonly
ambient air in air conditioning systems or refrigeration systems.
In either case, the refrigerant passing through the heat exchanger
40 rejects heat as it passes in heat exchange relationship with a
secondary cooling fluid, typically ambient air passed over the
refrigerant conveying passages 44 by an air mover, such as one or
more fans 42 operatively associated with the heat exchanger 40.
[0021] Whether the system 10 is operating in a subcritical or a
transcritical cycle, the refrigerant leaving the heat rejecting
heat exchanger 40 passes through refrigerant line 60B to the
evaporator 50. In doing so, the refrigerant traverses the expansion
device 55 and expands to a lower pressure whereby the refrigerant
typically enters the evaporator 50 as a lower temperature, lower
pressure mixture of liquid and vapor. The evaporator 50 constitutes
a refrigerant evaporating heat exchanger through which the liquid
refrigerant passes in heat exchange relationship with a heating
fluid whereby the liquid refrigerant is evaporated and typically
superheated. The heating fluid (or the fluid to be cooled) passed
in heat exchange relationship with the refrigerant in the
evaporator 50 may be air passed over the evaporator external
surfaces by an air mover, such as one or more fans 52, and
thereafter supplied to a climate controlled environment such as a
comfort zone associated with an air conditioning system or a
perishable product storage zone associated with a refrigeration
unit. As the air passes over the refrigerant conveying passages 54
and other heat transfer enhancement elements (not shown) associated
with the passages 54 of the evaporator 50, at least a portion of
moisture contained in the air condenses out onto the exterior
surfaces of the evaporator and the condensed moisture, referred to
as condensate 16, then drains into a condensate collection device
20, for example a drain pan.
[0022] The lower pressure refrigerant vapor exiting the evaporator
50 returns through refrigerant line 60D to the suction port of the
compression device 30-1. The expansion device 55 may be a
conventional thermostatic expansion valve (TXV) or electronic
expansion valve (EXV) or a fixed restriction device such as an
orifice, an accurator, a capillary tube, or the like. As in
conventional refrigerant vapor compression systems, a sophisticated
expansion device receives a signal indicative of the refrigerant
temperature sensed by the temperature sensing element (not shown)
associated with the outlet of the evaporator 50, which may be a
conventional temperature sensing element, such as a bulb for a TXV
and a thermistor or a thermocouple, frequently coupled with a
pressure sensor, for an EXV, and meters the refrigerant flow
through the refrigerant line 60C to maintain a desired level of
superheat of the refrigerant vapor leaving the evaporator 50. As in
conventional practice, a suction accumulator (not shown) may be
disposed in refrigerant line 60C downstream with respect to
refrigerant flow of the evaporator 50 and upstream with respect to
refrigerant flow of the compression device 30-1 to remove and store
any liquid refrigerant passing through refrigerant line 60C,
thereby ensuring that liquid refrigerant does not pass to the
suction port of the compression device 30-1. As known, suction
accumulators are typically used in heat pump applications and
employed in conjunction with fixed restriction expansion
devices.
[0023] Additionally, the refrigerant vapor compression system 10
includes an intercooler 24 disposed in the refrigerant circuit
between the first compression device 30-1 and the second
compression device 30-2. Refrigerant vapor passing from the
evaporator 50 through refrigerant line 60C enters the suction inlet
of the first compression device 30-1, wherein the refrigerant vapor
is compressed to a higher intermediate pressure. The refrigerant
vapor then passes from the discharge outlet of the first
compression device 30-1 through refrigerant line 60D to enter the
suction inlet of the second compression device 30-2 wherein the
refrigerant vapor is compressed to a still higher discharge
pressure before passing from the discharge outlet of the second
compression device 30-2 into refrigerant line 60A. As the
refrigerant vapor passes through refrigerant line 60D, the
refrigerant vapor traverses the intercooler 24 wherein the
refrigerant vapor passing through the intercooler 24 is cooled via
rejecting heat to the evaporator condensate 16.
[0024] In the embodiment of the refrigerant vapor compression
system 10 of the invention depicted in FIG. 1, a pump 22 draws
condensate 16 collecting in the evaporator drain pan 20 therefrom
and passes the condensate 16 through condensate line 21 to a bank
of spray nozzles 26. The spray nozzles 26 are arrayed in operative
association with a refrigerant conveying tube coil or passage 25
forming the intercooler 24 to spray condensate 16 received through
condensate line 16 onto the exterior surfaces of the tubes of the
coil 25. As known in the art, the exterior surfaces of the tube
coil or passage 25 can be extended and enhanced for better heat
transfer. The refrigerant vapor traversing through the coil 25 as
it passes through refrigerant line 60D from the first compression
device 30-1 to the second compression device 30-2 is cooled as it
rejects heat to heat and evaporate at least a portion of the
condensate 16 sprayed onto the exterior of the coil 25. To improve
the evaporate cooling effect, the spray nozzles may comprise
atomizers, such as atomizing nozzles or rotary atomizers, which
produce a mist of relatively small size droplets of condensate onto
the exterior of the coil 25.
[0025] In the embodiment of the refrigerant vapor compression
system 10 of the invention depicted in FIG. 2, the pump 22
withdraws condensate 16 collecting in the evaporator drain pan 20
and passes the condensate 16 through condensate line 21 to and
through the intercooler 24 in heat exchange relationship with the
refrigerant passing through the intercooler 24. As the refrigerant
vapor traverses the intercooler 24, the refrigerant vapor is cooled
as it rejects heat to the condensate 16. The intercooler 24 may
comprise a plate-type heat exchanger, a tube-in-tube heat
exchanger, an immersed coil heat exchanger or any other type of
heat exchanger wherein the refrigerant vapor is passed in isolation
from but in heat exchange relationship with the evaporator
condensate. As the condensate passes in heat exchange relationship
with the refrigerant vapor, the condensate 16 is heated and/or
evaporated. As noted before, as known in the art, the exterior and
interior surfaces of the intercooler 24 can be enhanced to provide
better heat transfer characteristics. It has to be also noted that,
in this case, the intercooler coil 25 can be integrated into the
construction of the drain pan 20, if desired.
[0026] In the embodiment of the refrigerant vapor compression
system 10 of the invention depicted in FIG. 3, the system is
simplified by removing the pump 22 and disposing the evaporator 50
and its associated condensate drain pan 20 at a higher elevation
than the intercooler 24. Condensate 16 collecting in the evaporator
drain pan 20 drains therefrom under the force of gravity through
condensate line 21 to a plurality of spray nozzles 26. As in the
embodiment in FIG. 1, the spray nozzles 26 are again arrayed in
operative association with a refrigerant conveying tube coil or
passage 25 forming the intercooler 24 to spray condensate 16
received through condensate line 21 onto the exterior surface of
the tubes of the coil 25. The refrigerant vapor traversing through
the coil 25 as it passes through refrigerant line 60D from the
first compression device 30-1 to the second compression device 30-2
is cooled as it rejects heat to heat and at least partially
evaporate the condensate 16 sprayed onto the exterior of the coil
25. To improve the evaporate cooling effect, the spray nozzles may
comprise atomizers, such as atomizing nozzles or rotary atomizers,
which produce a mist of relatively small size droplets of
condensate onto the exterior of the coil 25.
[0027] In the embodiment of the refrigerant vapor compression
system 10 of the invention depicted in FIG. 4, the intercooler 24
is a refrigerant conveying tube coil or passage 25 immersed in the
condensate 16 collecting in the condensate pan 20. As noted before,
the exterior surfaces of tube coils or passages 25 forming the
intercooler 24 can be extended and enhanced for better heat
transfer. The refrigerant vapor flowing through the intercooler 24
as it passes through refrigerant line 60D from the first
compression device 30-1 to the second compression device 30-2 is
cooled as it rejects heat to heat and evaporate at least a portion
of the condensate 16 collected in the condensate pan 20. In this
embodiment, the evaporated condensate must be vented to the ambient
environment to ensure that the evaporated condensate does not
re-enter the conditioned air stream leaving the evaporator 50.
[0028] While the present invention has been particularly shown and
described with reference to the preferred mode as illustrated in
the drawings, it will be understood by one skilled in the art that
various changes in detail may be effected therein without departing
from the spirit and scope of the invention as defined by the
claims. For example, those skilled in the art will recognize that
many variations may be made to the exemplary embodiments described
herein while still using the cooling capacity of the evaporator
condensate to cool the refrigerant vapor passing between serially
arranged compressors or compressor stages thereby utilizing cooling
capacity that would otherwise be wasted.
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