US20180252218A1

US20180252218A1 - Paired oil cooler and aftercooler fluid flow arrangement

Info

Publication number: US20180252218A1
Application number: US15/909,484
Authority: US
Inventors: Nayankumar Pandya
Original assignee: Ingersoll Rand Co
Current assignee: Ingersoll Rand Industrial US Inc
Priority date: 2017-03-01
Filing date: 2018-03-01
Publication date: 2018-09-06

Abstract

An air compressor system having a pair of heat exchangers which in one form can be an oil cooler and an aftercooler. The pair of heat exchangers can be a bar and plate heat exchanger type and which are aided in the heat transfer process by a fan the provides a source of cooling air. In one form the pair of heat exchangers can include internal passages that, when viewed relative to each other between each of the pair of heat exchangers, are arranged in a cross flow arrangement. A source of cooling fluid may traverse through respective faces of the heat exchangers while passages internal to the heat exchangers carry the respective fluid (e.g. oil or compressed air). Inlets and outlets of the heat exchangers can be arranged on opposite corners of each other.

Description

TECHNICAL FIELD

The present invention generally relates to cooling of compressor systems, and more particularly, but not exclusively, to fluid flow arrangements of heat exchangers used in the cooling of compressor systems.

BACKGROUND

Providing cooling for fluid sources within compressor systems remains an area of interest. Some existing systems have various shortcomings relative to certain applications. Accordingly, there remains a need for further contributions in this area of technology.

SUMMARY

One embodiment of the present invention is a unique heat exchanger pairing used in a compressor system. Other embodiments include apparatuses, systems, devices, hardware, methods, and combinations for cooling of compressor systems having a plurality of fluid flows. Further embodiments, forms, features, aspects, benefits, and advantages of the present application shall become apparent from the description and figures provided herewith.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 depicts an embodiment of a compressor system.

FIG. 2 depicts an embodiment of a bar and plate type heat exchanger.

FIG. 3A depicts a prior art arrangement of paired heat exchangers.

FIG. 3B depicts an embodiment of paired heat exchangers.

DETAILED DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS

For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended. Any alterations and further modifications in the described embodiments, and any further applications of the principles of the invention as described herein are contemplated as would normally occur to one skilled in the art to which the invention relates.
With reference to FIG. 1, a compressor system 50 is disclosed having a compressor 52 (also known as an “airend”) configured to compress an incoming flow of a working fluid 54 (e.g. air), and deliver the compressed working fluid 56 to an end user, customer, reservoir, or other suitable destination. The compressor, or airend, 52 operates in conjunction with a paired heat exchanger arrangement of an aftercooler 58 to provide some amount of cooling to the compressed air, as well as an oil cooler 60 used to cool oil or other fluid used during operation of the compressor 52. The compressor 52 can take on a variety of forms, including in one non-limiting embodiment an oil flooded screw compressor, but other forms are also contemplated herein. For example, the compressor 52 can be an oil free compressor, while the oil is used for bearing lubrication, for example. The oil cooler 60 is used to cool oil or other fluid used in conjunction with operation of the compressor 52. The oil, or other suitable fluid, can be used for lubrication and cooling purposes within the compressor 52, among other uses. Though only one compressor stage is suggested in the schematic of FIG. 1, other compressor stages can also be used such that aftercooler 58 can be used to cool an intermediate stage of compressor or a final stage of compression.
The aftercooler 58 and oil cooler 60 can be structured as air cooled heat exchangers using an external source of passing air (used as cooling air). In the illustrated embodiment a fan 62 or other suitable fluid moving device provides a moving stream of air useful in exchanging heat with compressed air routed through the aftercooler 58 and with oil routed through the oil cooler 60. The fan 62 can provide a push type of force convection as shown, but in other embodiments can be configured as a pull type of arrangement as well. In either case, it is contemplated that the aftercooler 58 receives fresh air prior to the oil cooler 60.
The compressor system 50 can also include additional components such as a motor 64 used to drive the compressor 52, a separator tank 66 to receive a mixed flow of oil and compressed working fluid and separate the oil from the compressed working fluid, a combined air cooler 80 and oil cooler 54 (in which the coolers are connected and cooled by a common fan), a combi block with thermal valve 68, and an oil filter 70. As will be appreciated, the separator 66 provides a flow of compressed air to the aftercooler 58, and the separated oil to the oil cooler 60. The route of mixed oil/air, separated oil and air, as well as the hot and cold sides of oil and air should be readily apparent from the figure.
One embodiment of a prior art oil cooler 60 is shown in FIG. 2. Shown in the illustration is a cutaway view of a bar and plate type of oil cooler 60. The oil cooler 60 includes a number of external fins 72 through which passes a flow of cooling fluid from the fan 62, internal fins 74 through which passes a flow of oil from the separator 66, a side bracket 76, parting sheets 78 used to separate the external fins 72 from the internal fins 74, and header bar 80. It will be appreciated that the “external” fins can be considered the external portion of the respective heat exchangers that is exposed to the externally sourced cooling fluid from the fan 62. For example, either or both of the heat exchangers can include an internal passage that conveys the externally sourced cooling fluid, such that the “external portion” of the passage can be considered that portion that is exposed to the externally sourced cooling fluid.
In general, the bar and plate style oil cooler 60 shown in FIG. 2 includes a stack of alternating flat plates (e.g. the parting sheets 78) and fins (e.g. the internal fins 74 and external fins 72) that are brazed together to form a single solid unit, though other manufacturing techniques may also be used. Though only a limited number of each of these components is illustrated in FIG. 2, it will be understood that other numbers of components can also be present. To set forth just one non-limiting example, although the header bars 80 are shown on only one lateral side of the oil cooler 60, the other side of the oil cooler 60 can also include additional header bars 80.
The external fins 72 can be formed of any heat conductive material, and can be triangular shaped as illustrated in FIG. 2. Such materials that the external fins 72 can be made out of include metal, which may be aluminum or aluminum alloy in many embodiments, but other metals and/or metal alloys are also contemplated herein. The external fins 72 can be described as fin members that are shaped in a triangular pattern that alternatingly extends between parting sheets located on either side of the external fins 72. Each of the fin members can include a plurality of louvers (described further below) formed as openings with an angled hood or vent which is useful to direct a passing fluid such as cooling air. The plurality of louvers can be assembled in small groupings that are distributed along the length of the external fins 72, as can be seen by the groupings illustrated in FIG. 2.
Similar to the external fins 72, the internal fins 74 can be formed of any suitable heat conductive material, and can be arranged in an offset strip type. Oil can flow through the internal fins 74 bounded by opposing parting sheets 78 and lateral stops.
The oil cooler 60 can have any number of rows of external fins 72 and internal fins 74. The fins 72 and 74 can take on an alternating patter as can be seen in the non-limiting illustrated embodiment. The row of passages provided through any given set of external fins 72 can extend from its lateral boundaries in a planar fashion, as is also true of the row of passages through any given set of internal fins 74. Thus, in one form the oil cooler 60 can have alternating planar arrangements of fins 72 and 74 which provide alternating planar passages of cooling fluid from the fan 62 and oil from the compressor. The direction of cooling fluid flow from the fan 62, however, is transverse to the direction of oil fluid flow through the internal fins 74. In one nonlimiting embodiment, the direction of cooling fluid flow is perpendicular to the direction of oil fluid flow through the internal fins 74. The flow paths of cooling fluid and oil are isolated from one another as will be appreciated. The term “perpendicular” in the context of any of the flow path orientations mentioned herein will be understood by those in the technical field to include those angles that are perfectly perpendicular as well as substantially perpendicular owing to slight variations that result from manufacturing tolerances, packaging constraints, etc. A perfect ninety degree angle is not required.
Though FIG. 2 illustrates an oil cooler, it will be appreciated that a similar bar and plate arrangement can be provided for the aftercooler 58. Thus, the aftercooler 58 can have alternating planar arrangements of internal fins (for passage of compressed air) and external fins (for passage of cooling fluid from the fan 62) which provide alternating planar passages of cooling fluid from the fan 62 and compressed air from the compressor 52. The direction of cooling fluid flow from the fan 62, however, is transverse to the direction of a flow of compressed air flow through internal fins of the aftercooler 58. In one nonlimiting embodiment, the direction of cooling fluid flow is at a right angle to the direction of compressed air flow through the internal fins.
Turning now to FIG. 3A, a prior art arrangement of the aftercooler 58 and oil cooler 60 is shown which illustrates a counter flow arrangement of oil and air (denoted by numerals 82 for oil flow and 84 for air flow) in which a bulk direction of oil in the oil cooler 60 moves counter to a bulk direction of compressed air flow in the aftercooler 58. It will be understood that the bulk direction of flow of either oil or air is considered just a predominant direction. For example, the plane of the internal passages shown in the illustrated embodiment is substantially aligned with the direction of the cooling fluid. It will be appreciated that the cooling fluid will generally have a bulk fluid flow direction in a global direction, though there may be local variations owing to the presence of structures, pressure gradients, turbulence, etc as will be well appreciated in the art.
The arrangement of oil cooler 60 and aftercooler 58 is such that they are paired together to receive a flow of cooling fluid from the fan 62, first being received by the aftercooler 58 and then by the oil cooler 60. The pairing of the oil cooler 60 and aftercooler 58 can be part of an integrated package where both heat exchangers are coupled together such that the package can be manipulated and transported as a unit. In other forms the heat exchangers can be separate devices that are transported and/or manipulated separately until installed in a compressor system. Furthermore, the pairing of the oil cooler 60 and aftercooler 58 is such that the respective heat exchangers can be substantially aligned when viewed along a direction of the cooling fluid flow from the fan 62 such that the frontal areas of both are substantially aligned with one another, but such alignment need not be precise.
The oil cooler 60 includes an oil inlet 86 and an oil outlet 88. An inlet header is provided near the inlet 86 and an outlet header is provided near the outlet 88. The inlet header can be used to distribute incoming oil along a length of the oil cooler, while the outlet header can be used to collect oil that has traversed the oil passages prior to being routed out of the outlet 88. In similar fashion, the aftercooler 58 includes an air inlet 90 and an air outlet 92, and can also include headers similar to that described above with respect to the oil cooler 60.
FIG. 3B depicts an arrangement of the instant application which provides a cross flow configuration of the aftercooler 58 and the oil cooler 60 as shown by the bulk flow arrows 82 (oil) and 84 (air). The cross flow configuration between the aftercooler 58 and oil cooler 60 can be accomplished in a number of different configurations so long as the bulk flow direction is cross, or perpendicular to each other. For example, the planes can cross or be perpendicular to each other on the edges of each plane, while in another form the face of one plane can be perpendicular to the edge of the other plane. Any rotation of one plane about its bulk flow direction relative to the other plane is sufficient to satisfy the condition that the bulk flow directions are perpendicular to each other, although the edge-on-edge configuration is most likely.
Oil enters the oil cooler 60 on one corner, and exits the oil cooler 60 at an opposite corner. The incoming oil is initially distributed internally to the oil cooler 60 via inlet header 94 on one end, and is collected via outlet header 96 on the other end prior to being routed to the outlet 88. The headers 94 and 96 can extend along one side of the oil cooler 60 and used to supply oil to the separate passages of oil as described above.
In similar fashion to the oil cooler 60 discussed immediately above, air enters the aftercooler 58 on one corner, and exits the aftercooler 58 at an opposite corner. The incoming air is initially distributed internally to the aftercooler 58 via inlet header 98 on one end, and is collected via outlet header 100 on the other end prior to being routed to the outlet 92. The headers 98 and 100 can extend along one side of the oil cooler 60 and used to supply air to the separate passages of air as described above.
Although the inlets 86/90 are described above as located on an opposite corner (e.g. catercorner) as the outlets 88/92, it will be understood that an exact geometric opposite location is not required to still be considered an opposite corner. As used herein the term opposite corner or catercorner will be understood to be generally opposite or catercorner, and not limited to a strict definition of being precisely on a diagonal line drawn between corners. Rather, the term diagonal or catercorner, or substantially diagonal or catercorner, as used herein generally means in the near vicinity of the diagonal across from one another, whether slightly disposed on one side or the other from the diagonal.
In other embodiments, either or both of the inlets 86 and 90 need not be located on an opposite corner as the respective outlets 88 and 92. So long as the cross flow arrangement of the oil in the oil cooler 60 relative to the air in the aftercooler 58 is maintained, the inlets 86/90 and outlets 88/92 can be placed in any suitable location. For example, the inlet 86 can be placed anywhere on the bottom (as seen in FIG. 3B) so long as the flow of oil across the height of the oil cooler 60 remains vertical (again, as seen from the illustrated embodiment in FIG. 3B). The outlet 88 for oil can also be located anywhere along the top (as seen in FIG. 3B). Thus, the placement of the inlets 86/90 and outlets 88/92 can be located in any variety of locations so long as the cross flow arrangement of the oil and air in the respective oil cooler 60 and aftercooler 58 is maintained.
Although the paired aftercooler 58 and oil cooler 60 are shown in a vertical orientation with cooling air passing horizontally therethrough, it is contemplated that the aftercooler 58 and oil cooler 60 can be positioned in other orientations such as horizontally, where cooling air passes vertically therethrough.
One aspect of the present application includes an apparatus comprising a pair of compressor system heat exchangers each having a header in fluid communication with internal passages structured for the bulk conveyance of a hot fluid between an inlet and outlet of the respective heat exchangers, each of the pair of compressor system heat exchangers also having an external exposed portion structured to receive an external flow of cooling fluid, the pair of compressor system heat exchangers placed in sequential manner and adjacent to one another such that a second heat exchanger of the pair of heat exchangers is arranged downstream of a first heat exchanger relative to a flow of the cooling fluid to receive an elevated temperature of cooling fluid as a result of a heat exchange process from the first heat exchanger, wherein the internal passages of the first heat exchanger are oriented in a first direction and the internal passages of the second heat exchanger are oriented in a second direction transverse to the first direction to provide a cross flow pattern.
A feature of the present application includes wherein the first heat exchanger includes a substantially rectilinear external form wherein the internal passages are arranged in a plane within the rectilinear external form of the first heat exchanger.
Another feature of the present application includes wherein the plane is substantially aligned with a bulk fluid direction of the cooling fluid.
Still another feature of the present application includes wherein the internal passages of the first heat exchanger and the internal passages of the second heat exchanger are fluidically isolated from one another.
Yet another feature of the present application includes wherein the pair of heat exchangers are part of a compressor system having a compressor, and wherein the first heat exchanger is structured as an aftercooler for the compressor.
Still yet another feature of the present application includes wherein the compressor of the compressor system is an oil flooded compressor, and wherein the second heat exchanger is structured as an oil cooler to cool the oil used in the oil flooded compressor.
Yet still another feature of the present application includes wherein the compressor system further includes a cooling fan structured to provide a flow of the cooling fluid used to exchange heat with the pair of heat exchangers.
A further feature of the present application includes wherein the heat exchanger is a bar and plate heat exchanger, and wherein the external exposed portion is part of an air passage to convey cooling air from a cooling fan, the air passage arranged transverse to the internal passages of the first heat exchanger.
A still further feature of the present application includes wherein the inlet of the first heat exchanger is located adjacent to the outlet of the second heat exchanger, and the outlet of the first heat exchanger is located adjacent to the inlet of the second heat exchanger.
Another aspect of the present application includes an apparatus comprising a first air compressor heat exchanger having a first internal header and a plurality of passages that communicate a first working fluid between an inlet and outlet of the first air compressor heat exchanger and the first internal header, the first air compressor heat exchanger also having an external surface structured to receive a cooling fluid and exchange heat between the cooling fluid and the first working fluid, and a second air compressor heat exchanger having a second internal header and a plurality of passages that communicate a second working fluid different in composition from the first working fluid between an inlet and outlet of the second air compressor heat exchanger and the second internal header, the second air compressor heat exchanger also having an external surface structured to receive the cooling fluid and exchange heat between the cooling fluid and the first working fluid after the first working fluid has exchanged heat with the first air compressor heat exchanger, wherein the internal passages of the first heat exchanger are arranged transverse to and fluidically isolated from the internal passages of the second heat exchanger such that fluid is not shared between the internal passages of the first and second heat exchangers.
A feature of the present application includes wherein the first air compressor heat exchanger and the second air compressor heat exchanger are aligned such that the projected frontal area of each of the first and second air compressor heat exchangers substantially overlap.
Another feature of the present application includes wherein the plurality of passages of the first heat exchanger are in a plane which is parallel to a plane which includes cooling fluid passages.
Still another feature of the present application includes wherein the plurality of passages of the first air compressor heat exchanger are oriented perpendicular to the plurality of passages of the second air compressor heat exchanger.
Yet another feature of the present application includes wherein the first air compressor heat exchanger includes the first internal header disposed on one end of the first air compressor heat exchanger, wherein the first air compressor heat exchanger includes a second internal header disposed on another end such that the plurality of passages of the first air compressor heat exchanger extend from the first internal header to the second internal header, the bulk conveyance of the cooling fluid oriented laterally between the first internal header and the second internal header.
Yet still another feature of the present application includes wherein the inlet of the first air compressor heat exchanger is located on a common side as the outlet of the second air compressor heat exchanger, and wherein the outlet of the first air compressor heat exchanger is located on a common side as the inlet of the second air compressor heat exchanger.
Still yet another feature of the present application includes wherein the first heat exchanger is rectilinear in shape, and wherein the inlet and outlet of the first heat exchanger are catercorner to each other.
Yet another aspect of the present application includes a method comprising operating an air compressor system which includes an oil flooded compressor and heat exchanger system, driving a fan to produce a stream of cooling fluid, routing the fluid to a stacked heat exchanger that includes an aftercooler for compressed air and an oil cooler placed side by side, the cooling fluid driven by the fan used to exchange heat with the aftercooler and the oil cooler, flowing compressed air through the aftercooler via a number of air passages that extend along a first direction, and conveying hot oil through the oil cooler via a number of oil passages that extend along a second direction transverse to the first direction.
A feature of the present application includes wherein the first direction is perpendicular to the second direction.
Another feature of the present application includes wherein the cooling fluid flows along a direction perpendicular to the first direction and the second direction.
Still another feature of the present application includes wherein the oil passages are arranged in stacked passage groupings, each group of passages aligned in a plane.
Yet another feature of the present application includes wherein an inlet of the aftercooler is arranged on a common corner heat exchanger as an outlet of the oil cooler, and wherein the outlet of the aftercooler and inlet of the oil cooler is arranged catercorner to the common corner.
While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiments have been shown and described and that all changes and modifications that come within the spirit of the inventions are desired to be protected. It should be understood that while the use of words such as preferable, preferably, preferred or more preferred utilized in the description above indicate that the feature so described may be more desirable, it nonetheless may not be necessary and embodiments lacking the same may be contemplated as within the scope of the invention, the scope being defined by the claims that follow. In reading the claims, it is intended that when words such as “a,” “an,” “at least one,” or “at least one portion” are used there is no intention to limit the claim to only one item unless specifically stated to the contrary in the claim. When the language “at least a portion” and/or “a portion” is used the item can include a portion and/or the entire item unless specifically stated to the contrary. Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” and “coupled” and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings.

Claims

What is claimed is:

1. An apparatus comprising:

a pair of compressor system heat exchangers each having a header in fluid communication with internal passages structured for the bulk conveyance of a hot fluid between an inlet and outlet of the respective heat exchangers, each of the pair of compressor system heat exchangers also having an external exposed portion structured to receive an external flow of cooling fluid, the pair of compressor system heat exchangers placed adjacent to one another such that a second heat exchanger of the pair of heat exchangers is arranged downstream of a first heat exchanger relative to a flow of the cooling fluid to receive an elevated temperature of cooling fluid as a result of a heat exchange process from the first heat exchanger, wherein the internal passages of the first heat exchanger are oriented in a first direction and the internal passages of the second heat exchanger are oriented in a second direction transverse to the first direction to provide a cross flow pattern.

2. The apparatus of claim 1, wherein the first heat exchanger includes a substantially rectilinear external form wherein the internal passages are arranged in a plane within the rectilinear external form of the first heat exchanger.

3. The apparatus of claim 2, wherein the plane is substantially aligned with a bulk fluid direction of the cooling fluid.

4. The apparatus of claim 3, wherein the internal passages of the first heat exchanger and the internal passages of the second heat exchanger are fluidically isolated from one another.

5. The apparatus of claim 1, wherein the pair of heat exchangers are part of a compressor system having a compressor, and wherein the first heat exchanger is structured as an aftercooler for the compressor.

6. The apparatus of claim 5, wherein the compressor of the compressor system is an oil flooded compressor, and wherein the second heat exchanger is structured as an oil cooler to cool the oil used in the oil flooded compressor.

7. The apparatus of claim 6, wherein the compressor system further includes a cooling fan structured to provide a flow of the cooling fluid used to exchange heat with the pair of heat exchangers.

8. The apparatus of claim 1, wherein the heat exchanger is a bar and plate heat exchanger, and wherein the external exposed portion is part of an air passage to convey cooling air from a cooling fan, the air passage arranged transverse to the internal passages of the first heat exchanger.

9. The apparatus of claim 8, wherein the inlet of the first heat exchanger is located adjacent to the outlet of the second heat exchanger, and the outlet of the first heat exchanger is located adjacent to the inlet of the second heat exchanger.

10. An apparatus comprising:

a first air compressor heat exchanger having a first internal header and a plurality of passages that communicate a first working fluid between an inlet and outlet of the first air compressor heat exchanger and the first internal header, the first air compressor heat exchanger also having an external surface structured to receive a cooling fluid and exchange heat between the cooling fluid and the first working fluid; and

a second air compressor heat exchanger having a second internal header and a plurality of passages that communicate a second working fluid different in composition from the first working fluid between an inlet and outlet of the second air compressor heat exchanger and the second internal header, the second air compressor heat exchanger also having an external surface structured to receive the cooling fluid and exchange heat between the cooling fluid and the first working fluid after the first working fluid has exchanged heat with the first air compressor heat exchanger;

wherein the internal passages of the first heat exchanger are arranged transverse to and fluidically isolated from the internal passages of the second heat exchanger such that fluid is not shared between the internal passages of the first and second heat exchangers.

11. The apparatus of claim 10, wherein the first air compressor heat exchanger and the second air compressor heat exchanger are aligned such that the projected frontal area of each of the first and second air compressor heat exchangers substantially overlap.

12. The apparatus of claim 11, wherein the plurality of passages of the first heat exchanger are in a plane which is parallel to a plane which includes cooling fluid passages.

13. The apparatus of claim 12, wherein the plurality of passages of the first air compressor heat exchanger are oriented perpendicular to the plurality of passages of the second air compressor heat exchanger.

14. The apparatus of claim 10, wherein the first air compressor heat exchanger includes the first internal header disposed on one end of the first air compressor heat exchanger, wherein the first air compressor heat exchanger includes a second internal header disposed on another end such that the plurality of passages of the first air compressor heat exchanger extend from the first internal header to the second internal header, the bulk conveyance of the cooling fluid oriented laterally between the first internal header and the second internal header.

15. The apparatus of claim 14, wherein the inlet of the first air compressor heat exchanger is located on a common side as the outlet of the second air compressor heat exchanger, and wherein the outlet of the first air compressor heat exchanger is located on a common side as the inlet of the second air compressor heat exchanger.

16. The apparatus of claim 15, wherein the first heat exchanger is rectilinear in shape, and wherein the inlet and outlet of the first heat exchanger are catercorner to each other.

17. A method comprising:

operating an air compressor system which includes an oil flooded compressor and heat exchanger system;

driving a fan to produce a stream of cooling fluid;

routing the fluid to a stacked heat exchanger that includes an aftercooler for compressed air and an oil cooler placed side by side, the cooling fluid driven by the fan used to exchange heat with the aftercooler and the oil cooler;

flowing compressed air through the aftercooler via a number of air passages that extend along a first direction; and

conveying hot oil through the oil cooler via a number of oil passages that extend along a second direction transverse to the first direction.

18. The method of claim 17, wherein the first direction is perpendicular to the second direction.

19. The method of claim 18, wherein the cooling fluid flows along a direction perpendicular to the first direction and the second direction.

20. The method of claim 17, wherein the oil passages are arranged in stacked passage groupings, each group of passages aligned in a plane.

21. The method of claim 17, wherein an inlet of the aftercooler is arranged on a common corner heat exchanger as an outlet of the oil cooler, and wherein the outlet of the aftercooler and inlet of the oil cooler is arranged catercorner to the common corner.