U.S. patent application number 10/871747 was filed with the patent office on 2005-12-22 for integrated heat exchanger for use in a refrigeration system.
Invention is credited to Jia, Tao, Memory, Stephen B., Yin, Jianmin.
Application Number | 20050279127 10/871747 |
Document ID | / |
Family ID | 34979293 |
Filed Date | 2005-12-22 |
United States Patent
Application |
20050279127 |
Kind Code |
A1 |
Jia, Tao ; et al. |
December 22, 2005 |
Integrated heat exchanger for use in a refrigeration system
Abstract
A refrigeration system includes a multiple stage compressor 10
having at least two stages 12,14 for sequentially compressing the
refrigerant together with a gas cooler 21 connected to the
compressor 10 for receiving compressed refrigerant from the last
stage 14 of the compressor to cool the same. An evaporator 18 is
connected to the gas cooler 21 via an expansion device to receive
cool refrigerant therefrom and cool the fluid stream passing
through the evaporator 18. A return passage connects the evaporator
18 to the first stage 12 of the compressor and an intercooler 26 is
connected between the first stage 12 and the last stage 14 of the
compressor to cool refrigerant compressed by the first stage 12 and
direct the refrigerant cooled thereby to the last stage 14 for
further compression. The intercooler 26 and the gas cooler 21 are
integrated into a single unit 22 and receive a single cooling heat
exchange fluid and the gas cooler 21 has a larger heat transfer
surface area than the intercooler 26.
Inventors: |
Jia, Tao; (New Berlin,
WI) ; Memory, Stephen B.; (Kenosha, WI) ; Yin,
Jianmin; (Kenosha, WI) |
Correspondence
Address: |
WOOD, PHILLIPS, KATZ, CLARK & MORTIMER
500 W. MADISON STREET
SUITE 3800
CHICAGO
IL
60661
US
|
Family ID: |
34979293 |
Appl. No.: |
10/871747 |
Filed: |
June 18, 2004 |
Current U.S.
Class: |
62/510 ; 62/507;
62/513 |
Current CPC
Class: |
F25B 40/00 20130101;
F28D 1/0443 20130101; F25B 9/008 20130101; F25B 2309/061 20130101;
F28F 2009/0287 20130101; F25B 1/10 20130101; F28D 2021/0073
20130101; F25B 2500/18 20130101 |
Class at
Publication: |
062/510 ;
062/513; 062/507 |
International
Class: |
F25B 027/00; F25B
039/04; F25B 001/10; F25B 041/00 |
Claims
1. A refrigeration system comprising: a multistage compressor
having at least two stages for sequentially compressing a
refrigerant; a gas cooler connected to the compressor for receiving
compressed refrigerant from a last stage of the compressor to cool
the same; an evaporator connected to the gas cooler to receive
cooled refrigerant therefrom and cool a fluid stream passing
through the evaporator; a return passage connecting the evaporator
to a first stage of the compressor to return refrigerant thereto to
be compressed therein; and an intercooler connected between said
first stage and said last stage to cool refrigerant compressed by
said first stage and direct the refrigerant cooled thereby to said
last stage for further compression thereby; said intercooler and
said gas cooler being integrated into a single unit to receive a
single cooling heat exchange fluid, said gas cooler having a larger
heat transfer area than said intercooler, said heat transfer area
being the area of the respective coolers through which heat
transfer between said refrigerant and said single cooling heat
exchange fluid occurs.
2. The refrigeration system of claim 1 wherein said gas cooler is a
cross-counter flow heat exchanger having plural tube or passage
rows through which the refrigerant serially passes from back to
front in relation to the direction of flow of said single cooling
heat exchange fluid through said gas cooler.
3. The refrigeration system of claim 2 wherein said gas cooler and
said intercooler are in side-by-side abutting relation to define a
single, split face through which said single cooling heat exchange
fluid enters said unit, and include common header assemblies
extending between remote sides of said gas cooler and said
intercooler, and baffles in said header assemblies isolating
refrigerant flow paths in said intercooler from refrigerant flow
paths in said gas cooler.
4. The refrigeration system of claim 3 wherein said intercooler has
plural tube or passage rows through which the refrigerant serially
passes, the number of tube or passage rows in said intercooler
being less than the number of tube or passage rows in said gas
cooler.
5. The refrigeration system of claim 4 wherein the number of said
rows in said gas cooler is at least twice the number of said rows
in said gas cooler.
6. The refrigeration system of claim 5 wherein said rows in said
gas cooler are defined by aligned runs of serpentine tubes and said
rows in said intercooler are defined by U-shaped or serpentine
tubes.
7. The refrigeration system of claim 2 wherein said gas cooler and
said intercooler are interleaved with said tubes or passages of
said gas cooler being located between adjacent tubes or passages of
said intercooler.
8. The refrigeration system of claim 7 wherein there are plural
rows of tubes and passages in said intercooler and said rows in
said gas cooler are defined by aligned runs of serpentine tubes and
said rows in said intercooler are defined by aligned runs of
U-shaped or serpentine tubes.
9. The refrigeration system of claim 7 wherein said intercooler has
plural rows of tubes or passages and there are more tubes or
passages in each row of said gas cooler than said intercooler, and
the tubes or passages of said intercooler are substantially
uniformly distributed between tubers or passages of said gas
cooler.
10. The refrigeration system of claim 9 wherein said rows in said
gas cooler are defined by aligned runs of serpentine tubes and said
rows in said intercooler are defined by aligned runs U-shaped or
serpentine tubes.
11. An integrated, interleaved heat exchanger comprising: a first
plurality of tubes bent to define a plurality of aligned, parallel
runs; a second plurality of tubes bent to define a plurality of
aligned parallel runs; first header assemblies connected to ends of
the tubes of the first plurality and in fluid communication with
the interiors thereof; second header assemblies connected to the
ends of the tubes of the first plurality and in fluid communication
with the interiors thereof; the tubes of the first plurality being
located between the tubes of the second plurality in a
substantially uniform manner, and in spaced relation to one
another; the parallel runs of the tubes in each plurality defining
rows; and fins extending between adjacent tubes in said rows.
12. The integrated interleaved heat exchanger of claim 11 wherein
the tubes of both of said pluralities have the same number of
runs.
13. The integrated interleaved heat exchanger of claim 11 wherein
the number of runs defined by each tube in said first plurality is
greater than the number of runs defined by each tube of said second
plurality.
14. The integrated interleaved heat exchanger of claim 13 wherein
said first and second plurality of tubes and said fins define a
generally rectangular heat exchanger core and said header
assemblies are all on one side of said core.
15. The integrated interleaved heat exchanger of claim 11 wherein
the tubes of said first plurality are serpentine tubes and the
tubes of said second plurality are U-shaped or serpentine
tubes.
16. The integrated interleaved heat exchanger of claim 15 wherein
the number of runs defined by each tube in said first plurality is
greater than the number of runs defined by each tube in said second
plurality.
17. The integrated interleaved heat exchanger of claim 14 wherein
said first and second plurality of tubes and said fins define a
generally rectangular heat exchanger core and said header
assemblies are all on one side of said core.
18. The integrated interleaved heat exchanger of claim 13 wherein
the second plurality of tubes have corresponding ends located
inwardly of the ends of the tubes of said first plurality and said
second header assemblies are located between said first header
assemblies.
19. The integrated interleaved heat exchanger of claim 13 wherein
the second plurality of tubes have corresponding ends located
outwardly of the ends of said first plurality and said first header
assemblies are located between said second header assemblies.
Description
FIELD OF THE INVENTION
[0001] This invention relates to refrigeration systems and to an
integrated heat exchanger for use in such systems.
BACKGROUND OF THE INVENTION
[0002] Most refrigeration systems (which term, as used herein, is
intended to include air conditioning systems) operate on the vapor
compression cycle. In such a cycle, a refrigerant is compressed and
then the compressed refrigerant cooled before being expanded in an
evaporator to cool a heat exchange fluid. The heat exchange fluid
may be used to cool various objects, such as the contents of a
refrigerator or the occupants of a space. Until relatively
recently, common refrigerants were chloro-fluoro carbons (CFC's) or
hydro-chloro-fluoro carbons (HCFC's) because of their non
combustibility and relatively easy cycling through the system.
However, many such systems have been prone to refrigerant leakage,
particularly those in vehicular applications. The escaping
refrigerant, depending upon the type, is believed to damage the
ozone layer surrounding the earth in varying degrees. Consequently,
certain refrigerants such as CFC 12 are no longer manufactured and
resort has been made to more environmentally friendly refrigerants
such as HFC 134a. The search continues for even more
environmentally friendly refrigerants.
[0003] With the new refrigerants that are being utilized, changes
are required in many of the refrigeration systems in which they are
used to achieve optimum efficiency. And this is true whether one is
employing some of the newer refrigerants which still actually
physically condense from the gaseous phase to the liquid phase in
the system condenser or whether one is employing a so-called
transcritical refrigerant, such as CO.sub.2 which does not truly
condense during typical system operation but nonetheless requires
cooling after compression in a so-called gas cooler.
[0004] Some of these systems utilize a multiple-stage compressor
for increased efficiency, usually a two stage compressor, to
compress the expanded refrigerant after it is passed through the
evaporator to an elevated pressure at which it enters the system
condenser or gas cooler. For brevity, both condensers for true
condensing refrigerants and gas coolers used in transcritical
refrigerant systems will hereinafter be referred to as gas
coolers.
[0005] In any event, when multiple-stage compressors are utilized,
some means of cooling the refrigerant between stages is often
needed. This is typically accomplished using an air cooled
intercooler.
[0006] In common refrigeration systems, the gas cooler and
intercooler are typically separate components in the system loop.
Where there are few space constraints in the system, the use of
separate components is not a major concern. However, in
applications where space constraints are significant, it would be
desirable to have an integrated gas cooler/intercooler component
which functions with an efficiency that will match that of a system
utilizing separate components.
[0007] For example, in vehicular applications, available space for
air conditioning units is at a premium. Large components limit the
ability of the designer of the vehicle to achieve aerodynamic
slipperiness which, of course, affects fuel economy as well as the
ability to achieve a pleasing appearance. Further, a weight saving
may be achieved in an integrated unit over a system utilizing
separate components which similarly contributes to the fuel
economy. Thus, there is a real need for a refrigeration system
employing a multistage compressor that avoids the problems
associated with separate gas coolers and intercoolers.
[0008] The present invention is directed to fulfilling that
need.
SUMMARY OF THE INVENTION
[0009] It is the principal object of the invention to provide a new
and improved refrigeration system of the multistage compressor
type. It is also an object of the invention to provide a new and
improved integrated heat exchanger which may find use in such a
system as an integrated gas cooler and intercooler.
[0010] According to one aspect of the invention, a refrigeration
system having a multistage compressor with at least two stages for
sequentially compressing a refrigerant is provided. A gas cooler is
connected to the compressor for receiving compressed refrigerant
from the last stage of the compressor to cool the same. After an
expansion device, an evaporator is connected to the gas cooler to
receive compressed, cooled refrigerant therefrom and expand the
same to cool a fluid stream passing through the evaporator. A
return passage is provided and connects the evaporator to a first
stage of the compressor to return expanded refrigerant thereto to
be compressed therein and an intercooler is connected between the
first stage and the last stage of the compressor to cool
refrigerant compressed by the first stage and direct the
refrigerant cooled thereby to the last stage for further
compression in the compressor. The intercooler and the gas cooler
are integrated into a single unit to receive a single cooling heat
exchange fluid. The gas cooler has a larger heat transfer area than
that of the intercooler, the heat transfer area being the area of
the respective coolers through which heat transfer between the
refrigerant and the single cooling heat exchange fluid occurs.
[0011] In a preferred embodiment, the gas cooler is a cross-counter
flow heat exchanger having plural tube or passage rows through
which the refrigerant serially passes from back to front in
relation to the direction of flow of the single cooling heat
exchange fluid through the gas cooler.
[0012] According to one embodiment of the invention, the gas cooler
and the intercooler are in side-by-side abutting relation to define
a single, split face through which the single cooling heat exchange
fluid enters the unit and includes common header assemblies
extending between remote sides of the gas cooler and the
intercooler. Baffles are located in the header assemblies to
isolate the refrigerant flow paths in the intercooler from
refrigerant flow paths in the gas cooler.
[0013] In the embodiment described in the preceding paragraph, the
intercooler has plural tubes or passage rows through which the
refrigerant serially passes and the number of tubes or passage rows
in the intercooler is less than the number of tubes or passage rows
in the gas cooler.
[0014] Preferably, the number of rows in the gas cooler is at least
twice the number of rows in the intercooler.
[0015] In a highly preferred embodiment, the rows in the gas cooler
are defined by aligned runs of serpentine tubes and the rows in the
intercooler are defined by U-shaped or serpentine tubes.
[0016] In another embodiment of the invention, the gas cooler and
intercooler are interleaved with the tubes or passages of the gas
cooler being located between adjacent tubes or passages of the
intercooler.
[0017] In this embodiment as well, the gas cooler runs are defined
by serpentine tubes and the intercooler runs are defined by
U-shaped or serpentine tubes.
[0018] In a preferred embodiment, there are more tubes or passages
in each row of the gas cooler than in each row of the intercooler
and the tubes or passages of the intercooler are substantially
uniformly distributed between tubes or passages of the gas
cooler.
[0019] According to another facet of the invention, an integrated,
interleaved heat exchanger is provided which includes a first
plurality of tubes bent to define a plurality of parallel runs. A
second plurality of tubes bent to define a plurality of parallel
runs is also provided. First header assemblies are connected to the
ends of the tubes in the first plurality and are in fluid
communication with the interiors thereof while second header
assemblies are connected to the ends of the tubes of the second
plurality and are in fluid communication with the interiors of the
second plurality. The tubes of the first plurality are located
between the tubes of the second plurality in a substantially
uniformed manner and in spaced relation to one another. The
parallel runs of the tubes in each plurality defines rows, and fins
extend between adjacent tubes in the rows.
[0020] In one embodiment, the tubes of both of the pluralities have
the same number of runs while in another embodiment, the number of
runs defined by each tube in the first plurality is greater than
the number of runs defined by each tube of the second
plurality.
[0021] In preferred embodiment, the first and second plurality of
tubes and the fins define a generally rectangular heat exchanger
core and the header assemblies are all on one side of the core.
[0022] A preferred embodiment again contemplates that the tubes of
the first plurality be serpentine tubes and that the tubes of the
second plurality be U-shaped or serpentine tubes.
[0023] In one embodiment of the heat exchanger, the second
plurality of tubes have corresponding ends located inwardly of the
ends of the first plurality and the second header assemblies are
located between the first header assemblies. In another embodiment,
the second plurality of tubes have corresponding ends located
outwardly of the ends of the first plurality and the first header
assemblies are located between the second header assemblies.
[0024] Other objects and advantages will become apparent from the
following specification taken in connection with the accompanying
drawings.
DESCRIPTION OF THE DRAWINGS
[0025] FIG. 1 is a schematic illustrating a system made according
to the invention;
[0026] FIG. 2 is a front elevation of an integrated gas cooler and
intercooler made according to the invention;
[0027] FIG. 3 is a view similar to FIG. 2 but of another embodiment
of an integrated gas cooler and intercooler;
[0028] FIG. 4 is an exploded side elevation of the intercooler and
gas cooler components utilized in the integrated gas cooler and
intercooler of the embodiment of FIG. 2;
[0029] FIG. 5 is a somewhat schematic, enlarged, fragmentary view
of the arrangement of tubes employed in the embodiment of FIG.
3;
[0030] FIG. 6 is a side elevation of one embodiment of a header and
tube structure utilized in the embodiment of FIG. 3; and
[0031] FIG. 7 is a view similar to FIG. 6 but showing a modified
header and tube arrangement.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0032] Before proceeding to the detailed description of the various
embodiments, it is to be understood that the term "refrigeration
system" as used herein is used in a broad sense to include any
vapor compression based system utilized for cooling other objects.
It is intended to include not only refrigeration systems in the
narrow sense, such as refrigerators, refrigerated vehicles, etc.
but also to include systems utilized for cooling spaces and/or
occupants of such spaces, more narrowly understood to refer to air
conditioning systems.
[0033] It is also to be noted that the invention is applicable to
systems employed with refrigerants that in fact substantially fully
change from the vapor phase to the liquid phase in a heat exchanger
typically termed a condenser as well as in the systems utilizing so
called transcritical refrigerants, such as carbon dioxide, wherein
true condensation does not fully occur but nonetheless require a
gas cooler for cooling the refrigerant after it has been
compressed. Thus, the term gas cooler, as used herein, and as
alluded to previously, is intended to be generic to both gas
coolers in transcritical systems as well as to condensers in
subcritical systems.
[0034] It is also to be noted that the integrated gas cooler and
intercooler described herein is not restricted to use as an
integrated intercooler and gas cooler. It may be utilized in
systems wherein a single heat exchange fluid at two different
stages in its processing, may be heated or cooled by a single
stream of a heat transfer medium or where two different heat
exchange fluids can be advantageously heated or cooled by a single
stream of a heat transfer medium.
[0035] Consequently, no restriction to particular types of
refrigeration systems is intended except insofar as expressly
stated in the appended claims. Similarly, no restriction to a
specific use of the embodiments of heat exchanger described herein
in refrigeration systems is intended except insofar as specified in
the appended claims.
[0036] With the foregoing in mind, the system in FIG. 1 will now be
described.
[0037] The system is based on a multi-stage compressor, generally
designated 10 which typically will be a two stage compressor. Thus,
a first stage is shown at 12 and a second stage is shown at 14. An
inlet 16 to the compressor is connected to the outlet of an
evaporator 18 through which a heat exchange fluid is driven by a
fan 19 to be cooled, the heat exchange fluid typically being air
but in some instances could be another gas or even a liquid.
[0038] The compressor 10 includes an outlet 20 from the second
stage 14 which is connected to the gas cooler part 21 of an
integrated gas cooler, intercooler unit, generally designated 22.
The unit 22 is adapted to receive a heat exchange fluid, again
typically air, but which could be another gas or even a liquid,
driven by a fan 24 in a single stream through the gas cooler part
21 and through an intercooler part 26 of the unit 22.
[0039] The outlet 28 of the first compressor stage 12 is connected
to the intercooler part 26 to provide refrigerant compressed by the
first stage to the intercooler part 26. From the intercooler part
26, the refrigerant compressed by the first stage 12 is directed to
an inlet 30 to the second stage 14 of the compressor unit 10.
[0040] Compressed refrigerant cooled in the gas cooler part 21
exits the unit 22 and is directed through an expansion device (EXP
DEVICE) and then passed to the evaporator 18 where it cools the
heat exchange fluid directed through the evaporator 18 by the fan
19.
[0041] Other components may optionally be included in the system of
FIG. 1. Typically, such components would include an accumulator for
the refrigerant and, in large non-transcritical systems or in
transcritical systems, a so called suction line heat exchanger
(SLHX) as well.
[0042] Turning now to FIG. 2, one embodiment of an integrated heat
exchanger that may be employed as the unit 22 is illustrated. The
same includes the gas cooler part 21 located in side-by-side
relation with the intercooler part 26 and which abut at a common
boundary 31. A remote side of the intercooler is shown at 32 while
a remote side of the gas cooler is shown at 34. Refrigerant flow
passages 27, and only a few are shown, make up the gas cooler. The
flow passages 27 are conventionally tubes or tube runs in spaced
relation as shown in FIG. 2 and fins, typically serpentine fins 38,
are located between spaced ones of the flow passages 27.
[0043] The intercooler part 26 includes spaced flow passages 40
also typically tubes or tube runs separated by fins 38 in the usual
case. As it will be explained in greater detail hereinafter, in a
preferred embodiment, the flow passages 27 and 40 are made up of
flattened tubes. However, other types of flow passages could be
provided, including those of the so called "drawn-cup" type.
[0044] Common headers 42 (only one of which is shown) are connected
to and in fluid communication with the interior of the flow
passages 27 and 40 and extend basically from the remote side 32 of
the intercooler to the remote side 34 of the gas cooler. In the
ususal case, the headers 42 will be tubes but they could consist of
a header plate and attached tank if desired. A baffle 46 is located
along the interface 30 in each of the headers 42 to isolate
refrigerant flow within the gas cooler from refrigerant flow within
the intercooler 26. One of the headers 42 includes an inlet 48 for
the gas cooler part 21 and, on the opposite side of the baffle 46,
an inlet 50 for the intercooler part 26. Similarly, the other
header 42, specifically the header 42, illustrated in FIG. 2,
includes an outlet 52 for the gas cooler part 21 while, on the
opposite side of the baffle 46, the intercooler 26 includes an
outlet 54.
[0045] In FIG. 2, the front of the unit 22 is illustrated which is
to say that gas flow from the fan 24 (FIG. 1) enters through the
face side illustrated in FIG. 2 and passes through the fins 38
between the passages 27, 40 and exits through the opposite or back
side of the unit 22. Thus, it will be appreciated that in the
embodiment illustrated, the inlets 48 and 50 are at the back of the
unit 22 while the outlets 52 and 54 are on the front of the unit.
Consequently, as will become apparent from the explanation of the
passages 27,40 and their structure, the refrigerant enters the rear
of the heat exchanger and flows through the passages 27 across a
common face forwardly in the unit 22 to exit through the outlets
52, 54 to define a cross-counter flow heat exchanger for maximum
efficiency. However, if desired, flow regimes other than
cross-counter flow could be used.
[0046] It will also be appreciated that in the embodiment shown in
FIG. 2, the frontal area of the intercooler 26 is less than the
frontal area of the gas cooler 21. Also, different fin densities
could be used in the two sections to balance the air flow.
[0047] FIG. 3 shows an alternate embodiment of the invention
wherein the passages 27 and 40 are interleaved in a uniform matter
across the entire face of the unit 22. With reference to FIGS. 3
and 5, it will be seen that flow passages 40 for the intercooler
are interleaved or interlaced with the flow passages 27 for the gas
cooler 21. The flow passages are again spaced and provided with
fins 38 which extend between and are typically bonded as by brazing
to adjacent ones of the tubes.
[0048] The ends of the flow passages 27 and 40 end in first and
second sets of headers which may be in the form of tubes or in the
form of header plates and separate tanks. In the embodiment
illustrated in FIG. 3, a first set of headers 56 is connected to
the ends of the flow passages 40 while a second set of headers 58
is connected to the ends of the flow passages 27. Only one of each
of the headers 56 and 58 is illustrated in FIG. 3.
[0049] The illustration in FIG. 3 views the unit 22 from the front
thereof and thus, the forward most header 56 includes an outlet 60
which serves as the outlet for the intercooler passages 40. An
inlet 64 to the rearmost one of the headers 56 (not shown in FIG.
3) and the passages 40 are also disposed in such header.
[0050] The forward most header 58 includes an outlet 66 for the
flow paths 27 while an inlet 68 in the rearmost one of the headers
58 provides an inlet for the passages 27.
[0051] Scrutiny of FIGS. 3 and 5 will illustrate that the passages
27 are located in groups of twos separated by a passage 40 across
the entire face of the unit 22. Thus, there are more of the
passages 27 for the gas cooler than there are passages 40 for the
intercooler 26.
[0052] Turning now to FIG. 4, the arrangements of the components
for the embodiment illustrated in FIG. 2, specifically, the
components including the headers 42, the passages 27 and 40 the
fins 38 are illustrated in exploded form. In a preferred
embodiment, as mentioned previously, the passages 27 are formed of
flattened tubes and as seen in FIG. 4, each flattened tube 27 in
the gas cooler part 21 is a serpentine tube bent upon itself to
define four straight, parallel runs 70, 72, 74, and 76. The
corresponding runs 70, 72, 74, and 76 for each of the passages 27
are aligned with one another in the assembly to provide four rows
of the runs 70, 72, 74, and 76. The fins 38 extend from the face of
the unit 22, shown at 78 in FIG. 4 and, to the rear 80 thereof.
[0053] On the other hand, the passages 40 in a highly preferred
embodiment, are formed of a flattened tube having a single bend to
define a U-shaped tube having two straight, elongated, parallel
runs 82 and 84. The runs 82 and 84 are in two rows of runs with
individual fins 38 extending just slightly more than the major
dimension of the corresponding tube runs 82, 84.
[0054] Thus, in the embodiment of FIG. 2, the number of runs 70,
72, 74, 76 and the gas cooler part 21 is greater than the number of
runs 82, 84 in the intercooler part 26.
[0055] If desired, the passages 40, rather than being U-shaped as
shown in FIG. 4, may be of serpentine form and in the same form as
the passages 27.
[0056] FIGS. 6 and 7 show two alternate structures for use in
constructing the embodiment of FIG. 3.
[0057] In both of the embodiments shown in FIGS. 6 and 7, the same
configuration of the passages 27 and 40 as described in connection
with FIG. 4 may be employed. Of course, if desired, again, the
passages 40 could be other than U-shaped as shown in FIG. 4,
specifically, they could be serpentine and have the same number of
runs as the passages 27.
[0058] In the embodiments shown in both FIGS. 6 and 7, individual
fins 38 as shown in FIG. 4 for the passages 40 are dispensed with
in favor of fins 38 that extends through the entire front to back
dimension of the core defined by the passages 27 and 40 and the
fins 38.
[0059] Referring specifically to FIG. 6, it will be seen that ends
90 of the passages 40 are bent somewhat inwardly at the location
whereat they enter the headers 56 and thus, are disposed inwardly
of the tube ends 92 which receive the headers 58 for the passages
27.
[0060] In both embodiments, the headers 56 and 58 are on the same
side of the rectangular core defined by the passages 27, 40 and
fins 38 and in the embodiment illustrated in FIG. 6, the core width
at the headers is substantially the same as core width elsewhere on
the unit 22. In any event, the structure results in the headers 56
being nested between the headers 58.
[0061] In the embodiment illustrated in FIG. 7, the opposite is
true, namely, the headers 58 are nested between the headers 56
which are displaced slightly outwardly of respective front and back
side 78 and 80 by bends in the tubing ends 92 which flare
outwardly.
[0062] The principal difference between the embodiments of FIG. 6
and FIG. 7 is that the embodiment of FIG. 6, while having a narrow
core width, has a slightly greater core height than the embodiment
of FIG. 7.
[0063] Either header arrangement may be employed, depending upon
the spacial constraints of any particular system installation.
[0064] On some instances, the fins 38, where they extend between
passages 27 on the one hand and passages 40 on the other may be so
called split or slit fins wherein the slits minimize heat
conduction through the fins between the passages 27 and the
passages 40. Various constructions for achieving this are well
known and form no part of the present invention. Alternatively,
conventional fins, including louver fins could be used
throughout.
[0065] In the most preferred and optimal embodiment of the
invention, of which, is mentioned previously, is a cross-counter
flow construction, there can be any number of rows for the gas
cooler part 21 as desired. In general, the number of rows in the
intercooler part 26 will be less than the number of rows in the gas
cooler. This type of arrangement is preferred when the unit is used
as a integral gas cooler and intercooler unit. In such a case, the
ratio of the heat transfer area of the gas cooler to that of the
intercooler is typically somewhat greater than 2:1. By heat
transfer area, it is meant that area of each unit which transfers
heat from a refrigerant stream, typically the exposed area of the
passages 27, 40 and fins 38, to the fluid stream passing through
the unit as provided by, for example, the fan 24 shown in FIG. 1.
Stated another way, if the total heat transfer area of the
integrated unit 22 is one, the optimal ratio will be between
0.65:0.35 ranging to about 0.85: to 0.15.
[0066] In a refrigeration system, it will be recognized that the
mass flow rate through both the gas cooler part 21 and the
intercooler part 26 will be the same. If the same size of tubes are
used for the passages 27, 40, while maintaining the above mentioned
heat transfer surface ratio, the pressure drop of refrigerant could
reach excessively high levels in the intercooler part 26. The
reason for this is that the number of passages in the intercooler
part 26 is relatively small and pressure drop can become too high
because of increasing fluid velocity. For gas cooler parts 21 that
require four or more rows of runs than the passages 27, the
situation intensifies and the intercooler part 26 pressure drop
becomes too high.
[0067] Accordingly, It is desirable that the pressure drop in both
parts be at similar levels. To achieve this desire, one embodiment
of the invention contemplates the use of fewer of the rows of the
flow paths 40 in the intercooler part 26 than the number of rows of
the passages 27 and the gas cooler part 21. In the described
embodiments, because the length of the flow paths 40 for the
intercooler part 26 is approximately half of that of the flow paths
27 for the gas cooler part 21, the pressure drop in the intercooler
section 26 will be less in spite of the fact that fewer of the flow
paths 40 exists in the intercooler part 26 in comparison to the
number of flow paths 27 in the gas cooler 21. That is to say, the
reduced intercooler part pressure drop will be directly linked to
the reduction in length of the flow paths 40.
[0068] Another possibility is to increase the number of flow paths
40 in the intercooler part 26. The use of a lesser fin height in
the intercooler part 26 will allow the use of more tubes or flow
paths 40 in the intercooler part 26, although at the expense of
frontal free flow air for the coolant.
[0069] Alternatively, tubes with different internal cross sectional
areas may be employed in making up the flow paths 27 and 40. By
using a larger cross sectional area in the tubes making up the flow
paths 40, a reduction in pressure drop within the intercooler part
26 will result.
[0070] Most desirably, however, from the manufacturing standpoint,
one would use the same tubes and rely on changes in the number of
tubes or the number of runs or both to achieve the desired
similarity in pressure drop in both section in the unit 22.
[0071] From the foregoing, it will be appreciated that the
invention provides an improved refrigeration system by integrating
an intercooler between the stages of a multi-stage compressor with
the system gas cooler to achieve a significant spacial savings.
Similarly, a heat exchanger made according to the invention is
ideally suited for use in refrigeration systems but may be used
with efficacy in other systems where spacial requirements are of
concern.
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