US20180120034A1

US20180120034A1 - Bar and plate air-oil heat exchanger

Info

Publication number: US20180120034A1
Application number: US15/340,457
Authority: US
Inventors: Nayankumar Pandya
Original assignee: Ingersoll Rand Co
Current assignee: Ingersoll Rand Industrial US Inc
Priority date: 2016-11-01
Filing date: 2016-11-01
Publication date: 2018-05-03

Abstract

An air-oil heat exchanger used in a compression system that includes a compressor is disclosed. The heat exchanger can be used to cool oil in one embodiment which is used in a compression process. The heat exchanger can be a bar-and-plate type heat exchanger having a number of external fins, internal fins, parting sheets, and header bars. The external fins can include louvers formed therein. An arrangement of multiple unrelated components can be provided that improves pressure loss and reduces weight.

Description

TECHNICAL FIELD

The present invention generally relates to compression system heat exchangers, and more particularly, but not exclusively, to particular arrangement of bar and plate heat exchanger.

BACKGROUND

Providing improvements in bar and plate heat exchangers used in compression 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 for use with a compression system. Other embodiments include apparatuses, systems, devices, hardware, methods, and combinations for reduced pressure loss and low weight heat exchangers. 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 a schematic of a compression system having an air-oil heat exchanger.

FIG. 2 depicts a prior art example of a bar and plate heat exchanger.

FIG. 3 depicts an embodiment of an external fin.

FIG. 4 depicts an embodiment of an external fin.

FIG. 5 depicts an embodiment of an internal fin.

FIG. 6 depicts an alternative embodiment to that shown in FIG. 1.

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 and oil cooler 54. Although only the compressor 52 and oil cooler 54 is depicted, other components may also be included in any given embodiment of the compressor system 50, including, but not limited to, a compressor dryer, oil sump, etc. The compressor dryer can be a refrigerated dryer or a desiccant based dryer, among potential others. The compressor 52 is used to compress a compressible fluid 56, such as air, and deliver a compressed air 58 to an end user, customer, reservoir, or other suitable destination. The compressor 52 can take on a variety of forms. For example, in one non-limiting embodiment the compressor 52 is an oil filled screw compressor, but other forms are also contemplated herein.
The oil cooler 54 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. The oil cooler 52 can structured as an air-oil heat exchanger and in the illustrated embodiment includes a fan 60 or other suitable fluid moving devices which provides a stream of moving air useful in exchanging heat with oil routed through the oil cooler 54.
Yet another embodiment is shown in FIG. 6 of a compressor system 50 that includes additional components such as a motor 76, separator tank 78, combined air cooler 80 and oil cooler 54 (in which the coolers are connected and cooled by a common fan), combi block with thermal valve 82, and oil filter 84. 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.
A prior art embodiment of an oil cooler is shown in FIG. 2. Shown in the illustration is a cutaway view of a bar and plate type of heat exchanger 54. The heat exchanger 54 includes a number of external fins 62, internal fins 64, a side bracket 66, parting sheets 68, and header bar 70. In general, the bar and plate heat exchanger 54 shown in FIG. 2 includes a stack of alternating flat plates (e.g. the parting sheets 68) and fins (e.g. the internal fins 64 and external fins 62) 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 are 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 70 are shown on only one lateral side of the heat exchanger 54, the other side of the heat exchanger 54 can also include additional header bars 70.
The external fins 62 can be formed of any heat conductive material, and can be triangular shaped as illustrated in FIG. 2. Such materials that the external fins 62 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 62 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 62. 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 62, as can be seen by the groupings illustrated in FIG. 2.
FIG. 3 depicts one embodiment of the louvers 72. The louvers 72 can be set at a louver angle θ which is an acute angle formed between the louver 72 and surface of the external fin 62. The acute angle θ of the louvers 72 can all be oriented in the same direction along the length of the external fins 62 and on the same side of the fins 62, but in some embodiments other variations are possible. For example, in some embodiments the louvers 72 can be formed with an acute angle pointing in a direction against a flow of cooling air over a first half of the length of the external fins 62, while the second half of the length of the external fins 62 can have louvers pointing in an equivalent acute angle but oriented in a direction along the flow of cooling air. The louvers 72 can also have a louver pitch L_pwhich can be described as the distance between the tips of the louvers measured along the direction of the fin 62.
FIG. 4 depicts some geometric details of the external fins 62. The external fins 62 can have individual fins 74 which are distributed along the length of the external fins 62. The number of individual fins 74 can be counted over a given length and a quantification can be made of the frequency of fins. For example, the number of fins per inch can be counted and a “fin per inch” quantity can be used to describe the density of individual fins 74 over the length of the external fins 62. The F_hor fin height shown in FIG. 4 is the height of the fins 62 as they reach between adjacent walls (e.g. the parting sheets 68).
Turning now to FIG. 5, certain geometric details of the internal fins 64 are illustrated. The internal fins 64 can be of the offset strip fin type having a length λ, height h, and pitch s. The height of the internal fins 64 can be described as the open space between parting sheets 68 less the material thickness of the sheet that makes up the internal fins 64. The pitch can be the open space within the internal fins 64 between upright wall sections of the fins 64.
The external fins 62 and/or the internal fins 64 can be made using a variety of approaches, which include forming a unitary member, coupling separate components together to form the member, etc. To set forth just a few examples, the external fins 62 can be stamped into shape to form the triangular shape as depicted in the illustrated embodiment. The offset strip type of the internal fins 64 as illustrated can include a number of separate strips that are individually stamped, which are then brought together in an offset configuration before being consolidated into an internal fin construction.
It will be appreciated that in highly complex, multi-variate systems, it is not always clear which combination of parameters provide for improvements. The instant application has discovered heretofore unappreciated arrangement of multiple and unrelated components in the heat exchanger 54 which unexpectedly provided for an appreciable degree in reduced pressure loss and weight. Prior to their discovery as disclosed in the instant application, it was unknown which combination and degree of factors in the aggregate provided the best solution. As a result of the inventive concepts described herein, it was discovered that at least one potential candidate, internal strip length, was deemed to either not impact the overall study or minimally impact the study, while other parameters were changed quite significantly from the conventional baseline indicating that the state of the art was unaware of the combination and degree of changes required to provide a better solution.
The combination of parameters that have led to unexpected improvements are as follows (listing the known baseline prior system for comparison):


		Option 1
		Low air side	Option 2
Parameter	Baseline	pr. Drop	Low weight

External FIN HEIGHT	0.375	0.438	0.488
Internal FIN HEIGHT	0.125	0.098	0.100
Internal FIN PITCH	0.074	0.069	0.081
External FIN PER INCH	12	11	12
Internal strip length	0.14	0.14	0.14
External LOUVER ANGLE	23.0	25.2	23.5
External LOUVER PITCH	0.045	0.035	0.035
Output
Air side pr. Drop (Pa)	493.7	386.5	430.7
Heat transfer (W)	251317	253002	252603
Oil outlet temperature	76.0	75.8	75.9
(deg C.)
Coil weight (Kg)	105.0	89.6	85.9
Oil side pr. Drop (Pa)	38895	56993	50198

The dimensions quoted herein regarding various geometries of the heat exchanger need not always be precisely exact as is well understood. Manufacturing tolerances permit some degree of dimensional variation.
Of the parameters listed above, the first four listed in the chart (external fin height, internal fin height, internal fin pitch, and external fin per inch) where surprisingly found to be most important in achieving the desired objectives, while the remaining parameters (internal strip length, external louver angle, and external louver pitch) were deemed to be less important.
The arrangement of components as described above was determined assuming that a core face area of 15.39 square feet, core depth of 6 inches, blower air flow of 14,145 cubic feet per minute, air inlet temperature of 120 degrees F., oil inlet temperature of 212 degrees F., and an oil flow rate of 42,900 lb/hr.
It is possible to construct a heat exchanger using values that are between the numbers listed above in Option 1 and Option 2, which will provide for a tradeoff between low pressure loss and low weight.
The oil cooler 54 embodiments disclosed herein could be used for an air-to-air heat exchanger as well, such as might be used in interstage cooling of a multi-stage compressor system, or as an aftercooler in other embodiments, to set forth just a few non-limiting examples.
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 bar and plate heat exchanger having an arrangement of external fins disposed in a first flow path separated from an arrangement of internal fins disposed in a second flow path by a parting sheet, the first flow path distinct from the second flow path, wherein the arrangement of external fins and the arrangement of internal fins are structured according to the following:

external fin height of about 0.438″;

internal fin height of about 0.098″;

internal fin pitch of about 0.069″; and

external fin per inch of about 11.

2. The apparatus of claim 1, wherein the second flow path within which the internal fins are disposed is structured to contain oil.

3. The apparatus of claim 2, which further includes a compressor and an oil sump, the second flow path including a passage to convey oil between the oil sump and the internal fins.

4. The apparatus of claim 3, which further includes another arrangement of external fins, the arrangement of internal fins disposed between the arrangement of external fins and the another arrangement of external fins, which further includes another parting sheet between the internal fins and the another arrangement of external fins, and wherein internal strip length is about 0.14″.

5. The apparatus of claim 4, which further includes another arrangement of internal fins structured to flow oil and in fluid communication with the oil sump, and wherein the external fins includes a plurality of groupings of louvers defined by the external louver angle.

6. The apparatus of claim 5, which further includes a header bar disposed at an end of the arrangement of external fins, and wherein at least one of the plurality of groupings of louvers is oriented in a direction that opposes a direction of at least another one of the plurality of groupings of louvers.

7. The apparatus of claim 1, wherein the first flow path is constructed to convey a flow of air and is oriented transverse to the second flow path, and wherein the arrangement of internal fins further include an external louver angle of about 25.2 degrees, and an external louver pitch of about 0.035″, and wherein the arrangement of internal fins are offset strip fins.

8. An apparatus comprising:

a compressor system heat exchanger having a first external fin construction fluidly separated from a first internal fin construction by a parting sheet, wherein the arrangement of external fins and the arrangement of internal fins are structured according to the following:

external fin height of about 0.488″;

internal fin height of about 0.1″; and

internal fin pitch of about 0.081″.

9. The apparatus of claim 8, wherein the heat exchanger is an air/oil heat exchanger, with the first internal fin is structured to flow oil in a flow path that includes an oil sump.

10. The apparatus of claim 9, wherein the compressor system includes a rotatable compressor element structured to pressurize a flow of air, and wherein the first external fin is structured to flow air in a flow path for the air/oil heat exchanger.

11. The apparatus of claim 10, wherein the compressor system includes a second and third external fin construction, wherein the first, second, and third external fin construction are each a single unitary fin member constructed to be disposed within a fluid oil flow path, wherein external fin per inch is 12, and internal strip length is 0.14″.

12. The apparatus of claim 11, which further includes a header bar disposed at each end of the first, second, and third external fin construction, and which further includes a second and third internal fin construction.

13. The apparatus of claim 12, which further includes a plurality of parting sheets, each neighboring pair of external fin constructions and internal fin constructions having a parting sheet disposed therebetween.

14. The apparatus of claim 13, wherein each of the first, second, and third external fin constructions include a plurality of groupings of louvers.

15. The apparatus of claim 8, wherein the internal fin constructions are offset strip fins, and wherein the first flow path is transverse to the second flow path, and wherein the arrangement of external fins and the arrangement of internal fins are further structured according to: an external louver angle of about 23.5 degrees; and an external louver pitch of about 0.035″.

16. An apparatus comprising:

a heat exchanger of the bar and plate type for use with an air compressor system includes an plurality of external fins and a plurality of internal fins, and a parting plate disposed between the external fin device and the internal fin device, the parting plate separating a first flow path in which the external fin device is disposed and a second flow path in which the internal fin device is disposed, the external fin device and the internal fin device having an arrangement as follows:

external fin height between about 0.438″ and about 0.488″;

internal fin height between about 0.098″ and about 0.100″;

internal fin pitch between about 0.069″ and about 0.081″;

external fin per inch of between 11 and 12; and

internal strip length of about 0.14″.

17. The apparatus of claim 16, wherein the first flow path is transverse to the second flow path, the first flow path is an air flow path, and the second flow path is an oil flow path.

18. The apparatus of claim 17, which further includes an oil sump in fluid communication with the second flow path.

19. The apparatus of claim 18, wherein the plurality of internal fins includes a first set of internal fins offset and separate from a second set of internal fins, wherein the plurality of external fins includes a first set of external fins offset and separate from a second set of external fins, the heat exchanger having an alternating stacked pattern which includes the first set of internal fins, then the first set of external fins, then the second set of internal fins, then the second set of external fins.

20. The apparatus of claim 19, wherein the plurality of internal fins are offset strip fins, which further includes a header bar disposed at the end of each of the first and second set of external fins, and wherein the first set of external fins has separate groupings of louvers; and wherein the external fin device and the internal fin device having a further arrangement of: an external louver angle between about 23.5 degrees and about 25.2 degrees, and an external louver pitch of about 0.035″.