Method for manufacturing heat exchanger by brazing

Abstract

A method of manufacturing a heat exchanger includes providing a plurality of tubes. Each tube of the plurality of tubes has an outer cladding on an outer surface, an inner cladding on an inner surface, and a weld extending along a length of the plurality of tubes. The method further includes arranging the plurality of tubes such that each tube of the plurality of tubes is inserted into a corresponding header slot, where a weld of each tube of the plurality of tubes is oriented downward with respect to gravity; and brazing each tube of the plurality of tubes and the header after each tube has been inserted into the corresponding header slot. The braze melts the inner cladding and gathers inside the plurality of tubes and along an inner side of the weld seam to form a cladding cover portion that wraps debris generated when the weld seam is formed.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. patent application No. 17 / 963,721, filed on October 11, 2022. Technical Field

[0003] The present invention relates to a heat exchanger and a method of manufacturing a heat exchanger. Background Art

[0004] Heat exchangers include components such as tubes, headers, and fins that are joined together in a welding process. For example, flat sheet stock is typically rolled or formed into a cylindrical shape and welded to form tubes. The welding process can be messy, and it may not be desirable to retain a large amount of weld overburden and debris in areas of the heat exchanger. Typically, the heat exchanger components are cleaned at or near the end of the heat exchanger production process to at least partially remove the weld overburden and debris. Summary of the invention

[0005] In one aspect, the present invention provides a method for manufacturing a heat exchanger. The method includes providing a plurality of tubes. Each of the plurality of tubes has an outer cladding on an outer surface of the plurality of tubes, an inner cladding on an inner surface of the plurality of tubes, and a weld extending along the length of the plurality of tubes. The method also includes arranging the plurality of tubes into a slot of a header so that each of the plurality of tubes is inserted into a corresponding header slot, and brazing each of the plurality of tubes and the header after each tube has been inserted into a corresponding header slot. The plurality of tubes are arranged into the header slot, wherein the weld of each of the plurality of tubes is oriented downward relative to gravity. The brazing causes the inner cladding to melt and to converge inside the plurality of tubes and along the inner side of the weld to form a cladding cover portion inside each of the plurality of tubes, the cladding cover portion encapsulating debris generated when forming the weld.

[0006] Other features and aspects of the invention will become apparent by consideration of the following detailed description and accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 is a front view of the heat exchanger.

[0008] Figure 2 It is shown Figure 1 Flowchart of the assembly process of a heat exchanger.

[0009] Figure 3 is used for Figure 1 A partial perspective view of the tubes of a heat exchanger.

[0010] Figure 4is a perspective view of the tubes arranged on the header of the heat exchanger.

[0011] Figure 5 Is welded to Figure 1 A perspective view of the tubes of a heat exchanger header.

[0012] Figure 6 yes Figure 1 A top-down assembly view of a heat exchanger.

[0013] Figure 7 yes Figure 1 Bottom-up assembly view of a heat exchanger.

[0014] Figure 8 yes Figure 1 Perspective view of the tubes of a heat exchanger after brazing.

[0015] Fig. 9 yes Figure 8 A magnified view of a tube within a tube.

[0016] Before explaining any embodiment of the present invention in detail, it should be understood that the application of the present invention is not limited to the details of construction and arrangement of parts set forth in the following description or shown in the accompanying drawings. The present invention can have other embodiments and can be practiced or implemented in various ways. In addition, it should be understood that the words and terms used herein are for descriptive purposes and should not be considered as limiting. DETAILED DESCRIPTION

[0017] Figure 1 A heat exchanger 10 is shown that includes a first collection tank assembly 14 and a second collection tank assembly 18. The first collection tank assembly 14 includes a header 22 and a collection tank 26 having an inlet 30. The second collection tank assembly 18 includes a header 34 and a collection tank 38 having an outlet 42. Each header 22, 34 includes a face that defines a header plane A1, A2. In some embodiments, each of the headers 22, 34 is aluminum with a braze clad on one or both sides thereof. In some embodiments, the collection tanks 26, 38 are formed of plastic, and in such embodiments, gaskets are disposed between the collection tanks 26, 38 and their respective headers 22, 34, respectively. In some embodiments, the collection tanks 26, 38 are made of aluminum and brazed to the headers 22, 34. A plurality of tubes 46 fluidly couple the first collection tank assembly 14 and the second collection tank assembly 18, and are coupled to the headers 22, 34 of the first collection tank assembly 14 and the second collection tank assembly 18. In some embodiments, the tubes 46 are formed of aluminum and have a braze clad on one or both sides. In the diagram showing an exemplary tube 46 among the plurality of tubes 46 Figure 3, the tubes 46 have an inner cladding on the inner surface 50 of the tubes 46 and an outer cladding on the outer surface 54 of the tubes 46. Each tube 46 has a first circular edge 58 and a second circular edge 62. Each tube 46 extends linearly between the circular edges 58, 62. At the first circular edge 58, each tube 46 has a weld 64 extending along the length of the tube 46. Figure 6 As shown, the side plates 66 are located at the ends of the heat exchanger 10. The side plates 66 are formed of aluminum and have cladding on one or both sides of the side plates 66.

[0018] Figure 2 A method 70 of manufacturing a heat exchanger 10 or at least a first collection tank assembly 14 and / or a second collection tank assembly 18 of a heat exchanger 10 is shown. To simplify the description, the following explanation will only cover the manufacture of the first collection tank assembly 14. First, as shown at step 74, the heat exchanger 10 is provided with a plurality of tubes 46. Each tube includes an outer cladding on an outer surface 54, an inner cladding on an inner surface 50, and a weld 64 extending along the length of the tube 46.

[0019] At step 84, each tube 46 is arranged in an array, stack or formation on the header 22. In the illustrated embodiment, each tube 46 or all tubes 46 of the heat exchanger 10 are arranged in a formation. During step 84, as shown in FIG. Figure 4 As shown, the tubes 46 are inserted through the slots 78 formed in the face of the header 22 such that the tubes 46 extend through the plane A1 of the header 22. In the formation of tubes 46, the first circular edge 58 of each tube 46 is aligned with the first end 82 of the corresponding slot 78 in the header 22. During step 84, the side plate 66 is on a first side of the stack and the opposing side plate 66 is on a second side of the stack.

[0020] Continue to refer Figure 4 , the tubes 46 and the header 22 are oriented so that the first circular edge 58 of each tube 46 is positioned closer to the ground A3 than the rest of the tube 46 along the gravity direction A4. The gravity direction A4 is defined as the downward direction. In other words, the first circular edge 58 of each tube 46 is positioned between the ground A3 and the second circular edge 62 of the tube 46. When the formation of the tubes 46 and the header 22 are oriented so that the first circular edge 58 of each tube 46 is positioned closer to the ground A3 than the rest of the tube 46, Figure 1 The header plane A1 extends perpendicular to the ground surface A3, so that the weld 64 is oriented downward relative to the rest of the tube 46. In other words, the header plane A1 extends parallel to the gravity direction A4.

[0021] At step 86 and as Figure 4 and Figure 5As shown, each of the tubes 46 is coupled to a corresponding slot 78 in the header 22. Coupling the tubes 46 to the header slots 78 includes sealing and brazing each tube 46 to the corresponding header slot 78. Each first circular edge 58 of the tubes 46 is sealed to a corresponding first end 82 of the header slot 78, and each second circular edge 62 of the tubes 46 is sealed to a corresponding second end 90 of the header slot 78. In the illustrated embodiment, the first circular edge 58 of each tube 46 or all of the tubes 46 of the heat exchanger 10 is sealed to a corresponding first end 82 of the header slot 78. The circular edges 58, 62 of the tubes 46 are welded to the header 22 on a liquid side surface 94, thereby preventing flux from penetrating the header 22 to contact the liquid side surface 94 or the circular edges 58, 62 of the tubes 46. The liquid side surface of the header 22 is the side of the header that contacts the liquid when the assembled header 22 is in use.

[0022] Figure 5 An exemplary process of welding the tubes 46 to the headers 22 using a multi-torch welder 92 is shown. No brazing filler or back solder is applied between the tubes 46 and the respective headers 22, 34 because the joining surfaces are clad with a brazing material that eventually melts to bond the tubes 46 to the respective headers 22, 34. That is, the cladding on the exterior surface 54 of the tubes 46 melts to bond the tubes 46 to the respective headers 22, 34. The slots 78 have collars that extend to the inside of the headers 22. These collars have walls that are thinner than the nominal thickness of the headers 22. In some embodiments, the thickness of these collars is thinner than the nominal thickness of the material forming the headers 22. Ideally, the thickness of the collar material is equal to the thickness of the tube material.

[0023] refer to Figure 4 and Figure 5 During step 86, the production line includes a welding machine on one side of the production line, which may be, for example, Figure 4 , or may be other types of conventional welders. The production line may include welders on both sides of the production line. When the header 22 and tube 46 stop at the welder position, the welder welds the tube 46 to the header 22. For a production line with a welder on only one side, the header 22 must be rotated to weld the tube 46 to the header 22 on the opposite side. For a production line with welders on both sides, the tube 46 can be welded to the header 22, 34 on both sides of the header 22 at the same time. The geometry of the slot 78 in the header 22 helps to create a weld between the tube 46 and the header 22. The insertion distance of the tube 46 into the header 22 is such that the tube 46 extends through the header 22 and beyond the edge of the collar. The welding process melts the end of the tube 46 and a portion of the collar to create a weld bead that completely surrounds the header slot 78, thereby sealing the tube 46 to the header slot 78.

[0024] In some embodiments, the welder includes a torch head that can move in a predetermined pattern and includes multiple torches. The pattern is programmed so that during welding of the tube 46 to the collar, at least one torch moves around the perimeter of each tube 46 or collar. The torch may also follow a pattern of passing through the nose region of the tube 46 at least once and ideally multiple times in each nose region (narrow end of the tube) of the tube 46. The weld pattern at the nose region may look like an "X". The purpose of the weld at step 86 is to completely seal the tube 46 to the header 22 around the header slot 78. The weld bead will be located within a range between flush with the inside of the header 22 and 2-3 millimeters (mm) from the inside wall of the header 22.

[0025] In some embodiments, method 70 includes step 98. At step 98, reference Figure 6 and Figure 7 , a temporary cover 102 is coupled to the header 22, thereby covering the liquid side surface 94 and the portion 106 of the tubes 46 extending through the header 22 on the liquid side surface 94 side of the header 22. During step 98, the temporary cover 102 extends completely over the header 22 around the periphery of the header 22 and overlaps the side wall of the header 22 on the outside of the side wall. In some embodiments, the temporary cover 102 fits on the inside of the header 22, completely covers the inside of the header 22 and the portion 106 of the tubes 46, and overlaps the side wall of the header 22 on the inside of the side wall. In another embodiment, instead of the temporary cover 102, the collection tank 26 is brazed to the header 22 during the brazing operation. The temporary cover 102 can be made of plastic or metal. The temporary cover 102 can be fastened to the header 22 by an interference fit, a snap fit, a clamp, a band, or a mechanical fixing device having a geometry that engages both the header 22 and the temporary cover 102.

[0026] At step 110, flux is applied to the tubes 46, the side plates 66, and the surfaces of the header 22 that face the tubes 46. The flux removes oxidation on these surfaces during the subsequent brazing process, thereby preventing corrosion and promoting free flow of braze material from the braze cladding. Because the temporary cover 102 covers the liquid side surface 94 and the portion 106 of the tubes 46 that is welded to the header 22 prior to applying the flux at step 110, contamination of the tubes 46 that may sometimes occur during the application of the flux is inhibited. Thus, subsequent contamination of the liquid (such as a fuel cell coolant) as it passes through the tubes 46 is inhibited. In some embodiments, the temporary cover 102 is removed from the header 22 after the flux is applied and prior to brazing, particularly when the temporary cover 102 is formed of a plastic material.

[0027] At step 114, the header 22 undergoes a brazing process while the temporary cover 102 remains on the header 22. During step 114, as shown in FIG. Figure 7As shown in , the brazing material of the braze clad melts to bond the tubes 46 to the header 22 at the air side surface 118 (i.e., the surface that is not contacted by the liquid passing through the header and / or the tubes 46 in normal use of the header 22 and the tubes 46), thereby forming a braze fillet 122 at the air side surface 118, which further strengthens the connection between the tubes 46 and the header 22. In some embodiments, the heat exchanger 10 is moved into a brazing furnace for a controlled atmosphere brazing (CAB) process. In the brazing process, the clad material melts due to the heat of the furnace, and the base material of the components does not melt. The outer clad on the outer surface 54 of each tube 46 flows to the connection area between the components. The connection area is where the tube 46 intersects the header 22 at the air side surface 118 of the header 22. When the heat exchanger 10 is removed from the furnace, the clad material on the outer surface 54 of each tube 46 cools and forms a connection portion in these areas. In some embodiments, the collection tank 26 is brazed directly to the header 22 to form a heat exchanger tank.

[0028] During the brazing process, the unwanted debris will be brazed within the inner cladding of the tube 46 during the brazing process to provide a cleaner tube interior volume. Figure 8 and Fig. 9 , the internal cladding on the inner surface 50 of each tube 46 also melts during the brazing process. The cladding melts and travels along the gravity direction to reach the first circular edge 58 of the tube 46. The cladding gathers inside the plurality of tubes 46 at the first circular edge 58 along the inner side of the weld 64 to form a cladding cover portion 126, thereby covering the debris generated when the weld 64 is formed at the first circular edge 58 of the tube 46. The cladding cover portion 126 extends along the length of the tube 46 at the first circular edge 58. The length of the tube 46 is defined along the extension direction of the tube 46. When the formation of the tubes 46 is oriented so that the first circular edge 58 of the tube 46 is positioned closer to the ground A3 than the second circular edge 62 of the tube 46, the weld 64 extends perpendicular to the gravity direction A4. This allows the cladding cover portion 126 to be formed with a substantially uniform depth D1 along the length of the tube 46.

[0029] Fig. 9The cladding cover portion 126 and the depth D1 are shown. The depth D1 is the shortest distance between the inner side of the weld 64 and the side 128 of the cladding cover portion 126 opposite the inner side of the weld 64. In some embodiments, the depth D1 of the cladding cover portion 126 is at least 0.1 mm and at most 1 mm. In other embodiments, the depth D1 of the cladding cover portion 126 is at least 0.25 mm and at most 0.5 mm. In further embodiments, the depth D1 of the cladding cover portion 126 is at least 0.35 mm and at most 0.4 mm. The inner cladding on the inner surface 50 and the outer cladding on the outer surface 54 can be formed of an aluminum alloy, so that the cladding cover portion 126 is also formed of an aluminum alloy. The aluminum alloy forms the cladding cover portion 126 and captures dust and debris at the weld 64 to inhibit the coolant flowing through the plurality of tubes 46 from absorbing the dust and debris.

[0030] At step 130, the temporary cover 102 is removed from the header 22. At step 134, the collection tank 26 is coupled to the header 22 via, for example, crimping. In some embodiments, the collection tank 26 is stainless steel and snaps onto the header 22. When the collection tank 26 is coupled to the header 22, a gasket is disposed between the collection tank 26 and the header 22.

[0031] In an alternative embodiment, the collection tank 26 is coupled to the header 22 at step 98, rather than the temporary cover 102. In this alternative embodiment, the collection tank 26 remains open during step 110, thereby inhibiting contamination of the tube 46. Also in this alternative embodiment, the collection tank 26 is removed prior to step 114 so that the collection tank 26 (which may be formed of plastic) does not melt during the brazing process. After the brazing process at step 114, the collection tank 26 will then be recoupled to the header 22. In further alternative embodiments, the method 70 includes only steps 74, 84, and 114. In still other alternative embodiments, the method 70 includes only steps 74, 84, 114, and 134.

[0032] In some embodiments, the heat exchanger 10 is part of a fuel cell and the liquid is a fuel cell coolant. In some embodiments, instead of welding the portion 106 of the tube 46 to the liquid side surface 94 of the header 22, the slots 78 in the header 22 are filled with a sealant, which prevents the flux from entering the header 22 and contacting the liquid side surface 94. The sealant is then dissolved during the brazing process. In some embodiments, the collection tanks 26, 38 are aluminum with cladding on one or both sides, and the collection tanks 26, 38 are brazed to the headers 22, 34 during the brazing step 114 of the method 70.

[0033] In operation of the heat exchanger 10, a liquid (e.g., water and / or coolant) flows into the inlet 30 of the collection tank 26 at a relatively high temperature, and then flows through the tube 46 to the collection tank 38, and finally flows out of the outlet 42. When flowing through the tube 46, the liquid is cooled because heat escapes the liquid via the tube 46, which is generally cooled by the air flow. In some embodiments, the heat exchanger 10 is used for coolant cooling of fuel cells. For many applications, the coolant is required to have very few impurities, such as flux residues, dust and debris. In this way, the cladding cover portion 126 covers the weld 64 at the first circular edge 58 of the tube 46, thereby covering and enveloping the dust and debris associated with the weld 64 and reducing impurities circulated by the coolant in the tube 46.

[0034] By inserting each tube 46 of the heat exchanger 10 into a corresponding header slot 78, with the weld 64 of each tube in the plurality of tubes 78 oriented downward relative to gravity, the method 70 advantageously improves ease of manufacturing. Without forming the cladding cover portion 126, dust and debris at the weld will not be trapped. The coolant flowing through the tube 46 will then pick up the dust and debris and circulate the dust and debris to other systems connected to the heat exchanger 10 along the cooling circuit. This may damage other systems connected along the cooling circuit. In order to remove dust and debris from the tube 46, the manufacturer may use a manufacturing method that includes additional steps, such as chemically washing the interior surface 50 of the tube 46 with environmentally harmful chemicals. The disposal of environmentally harmful chemicals can be particularly troublesome. Therefore, the method 70 described in the present disclosure reduces the number of steps to manufacture the heat exchanger 10, reduces the negative environmental impact from manufacturing the heat exchanger 10, and reduces the use of environmentally harmful chemicals within the heat exchanger production facility.

[0035] Although the invention has been described in detail with reference to certain preferred embodiments, variations and modifications exist within the scope and spirit of one or more independent aspects of the invention described.

Claims

1. A method for manufacturing a heat exchanger, comprising: providing a plurality of tubes having an outer cladding on an outer surface of each tube in the plurality of tubes, an inner cladding on an inner surface of each tube in the plurality of tubes, and a weld extending along a length of each tube in the plurality of tubes; arranging the plurality of tubes into slots of a header such that each tube of the plurality of tubes is inserted into a corresponding header slot, wherein the weld of each tube of the plurality of tubes is oriented downward relative to gravity; After the plurality of tubes have been inserted into the header slots, the plurality of tubes and the header are brazed, the brazing causing the internal cladding to melt and gather inside the plurality of tubes and along the inner side of the weld to form a cladding cover portion inside each tube of the plurality of tubes, the cladding cover portion encapsulating debris generated when forming the weld.

2. The method according to claim 1, wherein: The weld of each tube of the plurality of tubes extends along the entire length of each tube of the plurality of tubes.

3. The method according to claim 1, wherein: A face of the header defines a plane, wherein the header slots are formed in the face of the header such that the plurality of tubes extend through the plane, and wherein the plane extends generally parallel to a direction of gravity.

4. The method according to claim 1, wherein: The outer cladding and the inner cladding are formed of an aluminum alloy.

5. The method according to claim 1, wherein: The cladding jacket portion has a depth extending from the weld seam along a gravity direction through the cladding jacket portion and to an interior volume of the tube, wherein the depth is at least 0.35 millimeters (mm).

6. The method according to claim 5, wherein: The cladding cover portion has a depth of at most 0.4 mm.

7. The method according to claim 1, wherein: The plurality of tubes are formed of a material having a melting point lower than a melting point of the inner cladding.

8. The method according to claim 1, wherein: The cladding shroud portion is configured to inhibit coolant flowing through the plurality of tubes from absorbing dust and / or debris left behind by the formation of the weld.

9. The method according to claim 1, wherein: Arranging the plurality of tubes into the slots of the header includes arranging each tube of the heat exchanger into the slots of the header such that a weld of each tube of the heat exchanger is oriented downward relative to gravity.

10. The method of claim 1, further comprising coupling the plurality of tubes to the corresponding header slots by sealing and brazing the plurality of tubes to the corresponding header slots.

11. The method according to claim 10, wherein: Sealing the plurality of tubes to the corresponding header slots includes sealing a perimeter of each tube of the plurality of tubes to the corresponding header slot.

12. The method according to claim 11, wherein: Coupling the plurality of tubes to the corresponding header slots includes sealing the plurality of tubes to the corresponding header slots such that each tube of the heat exchanger is sealed in a corresponding header slot, wherein a weld of each tube of the heat exchanger is oriented downward relative to gravity.

13. The method according to claim 1, wherein: Brazing the header and the plurality of tubes includes melting an outer cladding on the outer surfaces of the plurality of tubes and bonding the plurality of tubes to the header once the melted outer cladding has cooled and hardened.

14. The method of claim 10, further comprising coupling a shroud to the header to cover a liquid side surface of the header and to cover ends of the tubes.

15. The method according to claim 14, wherein: Coupling the cover to the header is performed after sealing the plurality of tubes to the corresponding header slots.

16. The method of claim 14, further comprising applying flux to the air side surface of the header and to the plurality of tubes.

17. The method according to claim 16, wherein: Sealing the plurality of tubes to the corresponding manifold slots includes sealing the plurality of tubes on the liquid side surface of the manifold such that flux is inhibited from penetrating the manifold to contact the liquid side surface.

18. The method according to claim 16, wherein: Coupling the shroud to the header is performed prior to applying flux to the airside surface of the header and to the plurality of tubes.

19. The method according to claim 16, wherein: Applying flux is performed prior to brazing the plurality of tubes to the corresponding header slots.

20. The method of claim 1, further comprising coupling the header to a collection tank after brazing the plurality of tubes and the header.

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