WO2012058105A1

WO2012058105A1 - Heat exchanger fin, roll forming die assembly for forming same, and method of forming

Info

Publication number: WO2012058105A1
Application number: PCT/US2011/057214
Authority: WO
Inventors: Michel Vouche
Original assignee: SPX Cooling Technologies Inc
Current assignee: SPX Cooling Technologies Inc
Priority date: 2010-10-28
Filing date: 2011-10-21
Publication date: 2012-05-03
Anticipated expiration: 2013-04-28
Also published as: CN103339455A

Abstract

A serpentine fin system includes a roll forming die and a sheet stock. The roll forming die includes a first and second die. The roll forming die is configured to form an undulating surface on to the sheet stock. The surface is folded in a serpentine pattern to form a plurality of passages to convey fluid through the fin unit.

Description

HEAT EXCHANGER FIN, ROLL FORMING DIE ASSEMBLY FOR FORMING SAME, AND METHOD OF FORMING

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Application Serial No. 61/407,676, filed on October 28, 2010, the disclosure of which is incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

[0002] The present invention generally relates to a heat exchanger fin and method of forming. More particularly, the present invention pertains to a honeycomb heat exchanger fin and method of rolling forming same.

BACKGROUND OF THE INVENTION

[0003] Heat exchangers are generally known and in widespread use throughout a variety of industries. Examples of well know heat exchangers include radiators for cars, condensers for refrigeration units, chillers for removing waste heat during energy production, and the like.

[0004] To improve efficiencies of these heat exchangers, radiating fin structures may be included to increase the surface area. Typically, these fins are individually cut and assembled for brazing and other manufacturing processes. Fins may play an important role in stiffening the tube against operating pressures. This is especially true of fiat tubes or oval tubes. The fins must be sufficiently robust to resist being deformed or otherwise damaged. Unfortunately, the thickness of the fins required to insure this robustness penalizes the cost of the heat exchanger. Moreover, the fins are generally parallel without contact point between adjacent fins. Therefore only the thickness of the fins prevent their buckling due to mechanical constraints.

[0005] Accordingly, it is desirable to provide a method and apparatus capable of overcoming the disadvantages described herein at least to some extent.

SUMMARY OF THE INVENTION

[0006] The foregoing needs are met, to a great extent, by the present invention, wherein in various respects a serpentine fin system, fin unit and method of fabricating the fin unit are provided.

[0007] An embodiment of the present invention pertains to a serpentine fin system. The system includes a roll forming die and a sheet stock. The roll forming die includes a first and second die. The roll forming die is configured to form an undulating surface on to the sheet stock. The surface is folded in a serpentine pattern to form a plurality of passages to convey fluid through the fin unit.

[0008] Another embodiment of the present invention relates to a fin unit for a heat exchanger. The fin unit includes a sheet stock having an undulating surface. The surface is folded in a serpentine pattern to form a plurality of passages to convey fluid through the fin unit.

[0009] Yet another embodiment of the present invention pertains to a heat exchanger, The heat exchanger includes a fin unit of sheet stock having an undulating surface. The surface is folded in a serpentine pattern to form a plurality of passages to convey fluid through the fin unit.

[0010] Yet another embodiment of the present invention relates to a method of fabricating a fin unit. The method including the steps of roll forming and folding a sheet stock. The sheet stock is roll formed to generate an undulating surface on to the sheet stock. The sheet stock is folded in a serpentine pattern to form a plurality of passages to convey fluid through the fin unit. [0011] There has thus been outlined, rather broadly, certain embodiments of the invention in order that the detailed description thereof herein maybe better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional embodiments of the invention that will be described below and which will form the subject matter of the claims appended hereto.

[0012] In this respect, before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of embodiments in addition to those described and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein, as well as the abstract, are for the purpose of description and should not be regarded as limiting.

[0013] As such, those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] FIG. 1 is a perspective view of a serpentine fin system according to an embodiment of the invention.

[0015] FIG. 2 is a side view of the serpentine fin system of FIG. 1.

[0016] FIG. 3 is a partially exploded view of a heat exchange device suitable for use with a fin unit of FIG. 1.

[0017] FIG. 4 is a top view of the heat exchange device according to FIG. 3 without the partially exploded portion. [0018] FIG. 5 is a detailed view of the heat exchange device according to

FIG. 4.

[0019] FIG. 6 is an exploded view of another heat exchange device similar to the heat exchange device shown in FIG. 3.

[0020] FIG. 7 is a detailed view of the heat exchange device according to

FIG. 6.

[0021] FIG. 8 is a side view of the serpentine fin system.

[0022] FIG. 9 is a side view of the serpentine fin system according to another embodiment.

DETAILED DESCRIPTION

[0023] The present invention provides a system and method for fabricating a serpentine fin unit suitable for use in a heat exchanger. For the purposes of this disclosure, the term, "serpentine" means wavy, undulating, accordion-like, fan folded, variations thereof, and the like. In one example of a preferred embodiment, the fin unit may be fabricated from a single piece of sheet stock as opposed to many ten or hundreds of individual plates stacked upon one another in conventional fin units. It is an unexpected benefit of embodiments of this invention that time and money may be saved and the fin unit is more efficient than conventional fin units. For example, because the fin unit may be fabricated from a single piece of material and in a unitary fashion, the sheet stock may be thinner than conventionally used. This thinner material saves material costs. In addition, the thinner material allows for greater fluid flow through the fin unit.

[0024] As shown in FIG. 1, a serpentine fin system 10 includes a roll forming die 12 with a first and second die 14 and 16 configured to form a sheet stock 18. A resulting formed sheet stock 20 includes a series of indentations 22. The sequence of indentions 22 is configured to facilitate compressing the formed sheet stock 20 into a fin unit 24 suitable for use as a heat exchange component. In this regard, a press 26 is configured to receive or draw in the formed sheet stock 20 and slow or stop the formed sheet stock 20 from advancing and compresses the serpentine into a tight alignment. In an embodiment, the formed sheet stock 20 includes fan folds or pleats that are formed as a result of passing through the forming die 12. As shown in FIG. 1, the fan fold are formed on alternating sides of the sheet stock 18. This series of fan folds predispose the formed sheet stock to fold into the fin unit 24. Press 26 finishes bending the formed sheet stock 20 at the peaks and valleys to produce the serpentine fin unit 24. As described herein, the fin unit 24 may be serpentine and include honeycomb channels configured to convey fluid therethrough.

[0025] The sheet stock 18 may include any suitable material. Examples of suitable materials generally include metals and polymers. More particularly, suitable materials include malleable metals with good thermo-conductive properties and resistance to corrosion. Specific examples of suitable materials may depend upon the particular heat exchange application, however, stainless steel, aluminum and aluminum alloys, copper and copper alloy, and the like are specific examples of suitable materials. A benefit of some embodiments is that the sheet stock 18 may be relatively thinner than sheet stock used in conventional heat exchange devices. This is due, at least partly, because the pleating or serpentining process allows the fin unit 24 to be formed as a single or unitary piece rather than as a stack of relatively delicate individual plates. The thinner sheet stock allows for faster and greater efficiency of thermal transfer. In addition, thinner sheet stock allows smaller honeycomb passages to be formed which also improves the efficiency of the thermal transfer by adding surface and thanks to a higher heat transfer coefficient.

[0026] FIG. 2 is a side view of the serpentine fin system 10 of FIG. 1. The serpentine fin system 10 of FIG. 1 is similar to the serpentine fin system 10 of FIG. 1 and thus, for the sake of brevity, those items described with reference to FIG. 1 will not be described again. As shown in FIG. 2. The formed sheet stock 20 includes a series of creases 30 and panels 32 that facilitate forming pleats. By modulating the distance between the creases 30, the thickness of the fin unit 24 may be modulated. For example, by increasing the distance between respective creases 30, the thickness of the fin unit 24 may be increased. Conversely, for example, by decreasing the distance between respective creases 30, the thickness of the fin unit 24 may be decreased. In this manner, the thickness of the fin unit 24 may be modulated to suit a particular heat exchange task.

[0027] FIG. 3 is a partially exploded view of a heat exchange device 40 suitable for use with a fin unit 24 of FIG. 1. As shown in FIG. 3, the heat exchange device 40 is a crossflow-type heat exchange. That is, a first fluid is conveyed in a first direction through the heat exchange device 40 while a second fluid is conveyed perpendicularly or at about 90° relative to the first fluid. However, it is to be noted that various embodiment of the invention are suitable for use with any type of heat exchange device. In the particular embodiment shown in FIG. 3. the heat exchange device 40 includes a plurality of the fin units 24 interposed with a plurality of conduits 42.

[0028] In other examples, the heat exchange device 40 may include a counter flow type heat exchange. In such a device, the first fluid is urged to flow in a first direction and the second fluid is urged to flow in a direction 180° from the flow of the first fluid.

[0029] Of note, while the heat exchange device 40 includes both fin units 24 and conduits 42, the heat exchange device 40 need not include both fin units 24 and conduits 42, but rather, may omit the conduits 42. If configured in such a way, the first fluid may be urged to flow in a first fin unit 24 and the second fluid may be urged to flow in a second fin unit 24. By varying the orientation of the first fin unit 24 relative to the second fin unit 24, a cross flow or counter flow heat exchange may be induced to occur.

[0030] FIG. 4 is a top view of the heat exchange device 40 according to FIG. 3. As shown in FIG. 4, each conduit 42 may be sandwiched between a pair of fin units 24. However, in other examples, the conduits 42 and fin units 24 may alternate. In FIG. 4, each conduit 42 is flanked or sandwiched between two respective fin units 24. However, in other examples, each conduit 42 need not be flanked or sandwiched between two respective fin units 24, but rather, a conduit 42 may be disposed adjacent to one or more fin units 24.

[0031] In still other examples, the conduit 42 may be omitted and the fin units 24 may be configured to convey both the first and second fluids. For example, a first fin unit 24 may be configured to convey the first fluid and a second fin unit 24 may be configured to convey the second fluid.

[0032] FIG. 5 is a detailed view of the heat exchange device 40 according to FIG. 4. As shown in FIG. 5, the fin unit 24 is configured to provide a plurality of passages 50 for the flow of fluid. In some embodiments the passages 50 may be sealed one from the other to improve the heat transfer, increase the rigidity of the fin unit 24, increase the strength of the fin unit 24, and the like. To seal the passages 50, adjacent walls of the passages 50 may be affixed along interfaces 52. These interfaces 52 may be affixed in any suitable manner such as, for example, brazing, soldering, welding, gluing, and the like.

[0033] Also shown in FIG. 5, the passages 50 are substantially round. This rounding of the passages 50 may be utilized to decrease the hydraulic diameter relative to faceted passages. As is generally known, the hydraulic diameter (D_H) is a commonly used term when calculating flow in noncircular tubes and channels. Using the equation

where A is the cross sectional area and P is the wetted perimeter, one can calculate flow, turbulent flow, shear stress and the like in a similar manner as one would for a round tube. By decreasing the hydraulic diameter, the heat transfer may be improved due to higher heat transfer coefficient and additional heat exchange surface, thereby, increasing the efficiency of the heat exchange device 40.

[0034] Of note, while the passages 50 shown in FIG. 5 are generally round or rounded, in other examples the passages 50 need not be round, but rather, may be polygonal, squared, triangular, or the like. Furthermore, the shape need not remain the same along the length of the passage 50, but rather, may twist, ungulate, or otherwise change along the length. In these or other ways, the passages may be optimized for particular applications. For example, in some applications, it may be beneficial to introduce turbulent flow. To introduce this turbulent flow, dimples or other such indentations may be disposed along the surface of the passages 50.

[0035] FIG. 6 is an exploded view of another heat exchange device 40 similar to the heat exchange device 40 shown in FIG. 3. As shown in FIG. 6, the fin units 24 are disposed between a plurality of panels 60. The panels 60 include mating surfaces 62. When assembled and the mating surfaces 62 are sealed to one another, the panels 60 form the conduits 42.

[0036] In various examples, the mating surfaces 62 maybe sealed in any suitable manner. Particular examples of suitable methods of sealing include soldering, brazing, welding, gluing, crimping, and the like. In addition, the mating surfaces 62 may be releasably sealed to one another by clips for example.

[0037] Optionally, a gasket may be disposed between the mating surfaces 62 to facilitate a fluid tight seal. Although not shown in FIG. 6, it is generally known that gaskets may be placed between sealing surfaces. In addition, if included, the gasket may be disposed in a channel configured to retain the gasket.

[0038] FIG. 7 is a detailed view of the heat exchange device 40 according to FIG. 6. As shown in FIG. 7, the plurality of passages 50 disposed in the fin unit 24 are substantially hexagonal in shape. This is in contrast to the substantially circularly shaped passages 50 shown in FIG. 5. However, the passages 50 need not be hexagonal or circular, but rather, may include any suitable shape or multiple shapes. Regardless, it is an advantage of embodiments that the reduced wall thickness reduces the cost of the heat exchanger.

[0039] As shown in FIG. 7, the fin unit 24 includes a plurality of attachment points 70 and one crease 30 per folded layer of the fin unit 24. It is an advantage of some embodiments of the invention that the crease 30 reduces the number of attachment points 70. That is, in conventional fin units, each layer is an individual piece and so does not include a crease such as the crease 30. In the particular example shown, the number of attachment points is reduced from 5 to 4 - a 20% decrease in the number of attachment points 70. This reduction in attachment points may lead to a corresponding reduction in the number of welds or other such operations and/or a corresponding increase in strength, durability, and the like.

[0040] FIG. 8 is a side view of the serpentine fin system 10. The serpentine fin system 10 of FIG. 8 is similar to the serpentine fin system 10 of FIG. 2 and thus, for the sake of brevity, those items described with reference to FIG. 2 will not be described again. As shown in FIG. 8, the first and second die 14 and 16 are configured to form the sheet stock 18 into the formed sheet stock 20 having relatively more rounded indentations 22 as compared to the relatively more squared off indentations 22 shown in FIG. 2.

[0041] FIG. 9 is a side view of the serpentine fin system 10 according to another embodiment. The serpentine fin system 10 of FIG. 9 is similar to the serpentine fin system 10 of FIGS. 1 -8 and thus, for the sake of brevity, those elements described herein above will not be described again. As shown in FIG. 9, the die 14 includes a set of inner forms 90 and outer forms 92. The inner forms 90 include surfaces configured to form a subset of the passages 50 disposed within an interior portion of the fin unit 24. The outer form 92 include surfaces configured to form a subset of the passages 50 disposed upon an exterior portion of the fin unit 24. In the example shown, the inner forms 90 are relatively smaller than the outer forms 92 because the 'exterior' passages 50 are formed by bending the formed sheet stock 20 back upon itself. Once formed, this subset of the passages 50 disposed upon an exterior portion of the fin unit 24 may be pressed to fold in an accordion-like manner to form the serpentine fin unit 24.

[0042] The many features and advantages of the invention are apparent from the detailed specification, and thus, it is intended by the appended claims to cover all such features and advantages of the invention which fall within the true spirit and scope of the invention. Further, since numerous modifications and variations will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation illustrated and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.

Claims

CLAIMS What is claimed is:

1. A serpentine fin forming system, the system comprising:

a roll forming die comprising:

a first die; and

a second die; and

a sheet stock, the roll forming die configured to form an undulating surface on to the sheet stock, the surface being folded in a serpentine pattern to form a plurality of passages to convey fluid through the fin unit.

2. The serpentine fin forming system according to claims 1 , wherein the roll forming die is configured to form a series of alternating fan fold

3. The serpentine fin forming system according to claims 1 , wherein the roll forming die is configured to form round passages.

4. The serpentine fin forming system according to claims 1 , wherein the roll forming die is configured to form hexagonal passages

5. The serpentine fin forming system according to claims 1, wherein the sheet stock is selected from the group consisting of steel, steel alloy, aluminum, aluminum alloys, copper, and copper alloys.

6. A fin unit for a heat exchanger, the fin unit comprising:

a sheet stock having an undulating surface, the surface being folded in a serpentine pattern to form a plurality of passages to convey fluid through the fin unit.

7. The fin unit according to claim 6, wherein the sheet stock includes a series of alternating fan folds.

8. The fin unit according to claim 6, wherein the passages are round.

9. The fin unit according to claim 6, wherein the passages are hexagonal.

10. The fin unit according to claim 6, wherein the sheet stock is selected from the group consisting of steel, steel alloy, aluminum, aluminum alloys, copper, and copper alloys.

11. A heat exchanger comprising:

a fin unit comprising:

a sheet stock having an undulating surface, the surface being folded in a serpentine pattern to form a plurality of passages to convey a first fluid through the fin unit in a first direction.

12. The heat exchanger according to claim 11 , further comprising:

a conduit in thermal contact with the fin unit, the conduit being configured to convey a second fluid in a second direction.

13. The heat exchanger according to claim 12, further comprising:

a second fin unit, wherein the fin unit is disposed on a first side of the conduit and the second fin unit is disposed on a second side of the conduit.

14. The heat exchanger according to claim 12, wherein the first flow direction is perpendicular to the second flow direction

15. The heat exchanger according to claim 12, wherein the first flow direction is opposite to the second flow direction

16. The heat exchanger according to claim 11, wherein the sheet stock includes a series of alternating fan folds.

17. The heat exchanger according to claim 1 1, wherein the passages are round.

18. The heat exchanger according to claim 11, wherein the passages are hexagonal.

19. The heat exchanger according to claim 11, wherein the sheet stock is selected from the group consisting of steel, steel alloy, aluminum, aluminum alloys, copper, and copper alloys.

20. A method of fabricating a fin unit comprising:

roll forming a sheet stock to generate an undulating surface on to the sheet stock; and

folding the sheet stock in a serpentine pattern to form a plurality of passages to convey fluid through the fin unit.