METHOD FOR MANUFACTURING A COLD DYNAMIC PROJECTION HEAT EXCHANGER AND ASSOCIATED HEAT EXCHANGER

Abstract

METHOD FOR MANUFACTURING A HEAT EXCHANGER BY COLD DYNAMIC SPRAYING AND ASSOCIATED HEAT EXCHANGER. The invention relates to a method for manufacturing a heat exchanger comprising at least one fluid circulation tube (12) configured to allow heat exchange between the fluid circulating in each tube (12) and a profile surrounding each tube, characterized in that it comprises a step of cold dynamic spraying of metal powder onto each tube (12) arranged in a first mold so as to form a first portion (14a) of the profile, and a step of cold dynamic spraying of metal powder onto each tube (12) arranged in a second mold (16b) so as to form a second portion (14b) of the profile. Figure for the abstract: Figure 6

Description

Title of the invention: METHOD FOR MANUFACTURING A HEAT EXCHANGER BY COLD DYNAMIC SPRAYING AND ASSOCIATED HEAT EXCHANGER Technical field of the invention

[0001] The invention relates to a method for manufacturing a heat exchanger, and the associated heat exchanger. In particular, the invention relates to a method for a heat exchanger which may be of the stainless steel-aluminum, aluminum-aluminum or other combinations of two materials for use in an aeronautical or space context. Technological background

[0002] Heat exchangers used in the aeronautical or space field may take the form of an envelope also called a profile, preferably made of aluminum, surrounding a tube, preferably made of stainless steel (commonly called stainless steel) in which a fluid circulates or taking the form of a profile, preferably made of aluminum, straight in one piece and in which a hollow volume allows the circulation of the fluid, in particular for a transfer of heat from the fluid to the outside of the profile via the tube and the profile. The profile may take for example the form of plates enclosing the tube or a part having a hollow cylinder in which the tube is inserted.

[0003] The assembly of the exchanger is then carried out by welding or brazing the plates forming the envelope between which the tube is arranged.

[0004] The use of welding or brazing for the assembly of the exchanger has several disadvantages.

[0005] In particular, when the final exchanger must comprise a tube forming a coil, the profile surrounding the tube must be bent at the same time as the tube to present the necessary shape. This bending of the tube and the profile can create risks of leaks and mechanical defects because the shape of the profile is not necessarily suitable for bending.

[0006] Furthermore, the difficulty of bending the profile often results in the need to divide the entire fluid circuit into several tube-profile assemblies which are joined (butt joints) by brazing or welding, for example orbital welding. The shape of the profile further complicates the production of these joints and their difficulty and number increases the risks of leaks and mechanical defects.

[0007] The inventors therefore sought a solution to facilitate manufacturing

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[0014] heat exchangers comprising a tube surrounded by a profile, in particular when the fluid circuit formed by the tube has a curved shape, for example a serpentine device which is conventional in the field of exchangers. Objectives of the invention The invention aims to provide a method for manufacturing a heat exchanger, and an associated heat exchanger. The invention aims in particular to provide, in at least one embodiment, a simple and industrializable manufacturing method. The invention also aims to provide, in at least one embodiment of the invention, a manufacturing method particularly suitable for exchangers comprising curved tubes. The invention also aims to provide, in at least one embodiment of the invention, a manufacturing method compatible with a very long tube, in particular a length greater than 3m. The invention also aims to provide, in at least one embodiment of the invention, a method of manufacturing the heat exchanger limiting the internal stresses to avoid deformations due to differential expansions during assembly. Presentation of the invention To do this, the invention relates to a method for manufacturing a heat exchanger comprising at least one tube for circulating a fluid and configured to allow heat exchange between the fluid circulating in each tube and a profile surrounding each tube, characterized in that it comprises: - a step of placing each tube in a first mold surrounding at least part of each tube, - a step of dynamic cold projection of metal powder onto each tube placed in the first mold so as to form a first portion of profile surrounding at least a first external surface of each tube, - a step of removing each tube and the first portion of profile from the first mold, - a step of placing each tube and the first portion of profile in a second mold surrounding at least part of each tube, - a step of cold dynamic projection of metal powder onto each tube arranged in the second mold so as to form a second portion of profile surrounding at least a second external surface of each tube. A manufacturing method according to the invention allows the creation of a profile directly on the fluid circulation tube(s) through the use of cold dynamic projection. The manufacturing method thus makes it possible to apply the profile on the tube regardless of its configuration, without requiring any profile shaping operation, for example by avoiding bending or splicing the profile, by carrying out these actions upstream on the tube.

[0015] Cold dynamic spraying, also called cold spraying, cold gas dynamic spraying, cold gas spraying, supersonic speed powder spraying, etc. is a method of spraying powder material to form a coating or for additive manufacturing which consists of accelerating the powdered filler material beyond a critical speed, at low temperatures compared to other powdered material spraying techniques, generally between approximately 300 and 1,100 °C. Cold dynamic spraying is frequently called cold spray in English.

[0016] The use of a tube as a base for the formation of the profile also makes it easier to form the fluid circulation circuit, unlike a manufacturing method based solely on an additive manufacturing process.

[0017] For the use of the manufactured exchanger, the manufacturing method advantageously comprises a final step of removing each tube and the two portions of the profile from the second mold. If necessary, one or more other molds can be used to form additional portions of the profile, in particular if the first two profile portions do not completely cover the tube. The molds are for example made of treated steel and can comprise extraction means once the cold dynamic projection is complete, such as for example screws.

[0018] The molds used have the desired shape both to correspond to a particular profile section shape, but also to correspond to a particular exchanger shape, for example a straight, serpentine, spiral exchanger, etc.

[0019] Advantageously and according to the invention, the method comprises a step of applying a metallic coating to each tube before the step of placing each tube in the first mold.

[0020] According to this aspect of the invention, the metal coating makes it possible to facilitate the adhesion of the metal powder sprayed onto the tube. This coating may in particular be formed from nickel or copper.

[0021] Advantageously and according to the invention, the heat exchanger comprises at least two fluid circulation tubes, a first tube and a second tube, and in that the step of placing in a first mold comprises a sub-step of matching an opening of the first tube with an opening of the second tube.

[0022] According to this aspect of the invention, the use of several tubes makes it possible to produce larger exchangers while facilitating the operations carried out on each tube. In particular, the use of several tubes can make it possible to facilitate the bending operations, the bending of a single long tube possibly being impossible depending on industrial constraints linked to the factory, the machine, the tube used and its manufacturing, handling, delivery constraints, etc. or to the nature of the tube itself (material, dimensions, etc.).

[0023] The matching between the openings of the tubes allows the formation of the fluid circulation circuit in the interior volume of the tubes.

[0024] Advantageously and according to the invention, the matching sub-step is followed by a step of brazing or welding the first tube with the second tube, at the matching openings.

[0025] According to this aspect of the invention, brazing or welding the tubes makes it possible to form the fluid circulation circuit before creating the profile.

[0026] According to another variant of the invention, the matched tubes are not brazed or welded, and the cold dynamic projection forming the profile makes it possible to assemble the tubes together, after the matching sub-step making it possible to ensure the formation of the circuit, without requiring brazing or welding of the tube beforehand. The profile makes it possible to seal the fluid circulation circuit formed by the tubes at the junctions of these tubes.

[0027] Advantageously and according to the invention, the metal powder sprayed during each cold dynamic spraying step is formed from aluminum powder.

[0028] According to this aspect of the invention, aluminum is frequently used in the space and aeronautical fields for its thermal conductivity properties, its mechanical properties and its lightness, which makes it a material frequently used in heat exchangers. Aluminum, in powder form, is also perfectly compatible with cold dynamic projection.

[0029] When the tube is made of stainless steel, the heat exchanger thus formed is of the type commonly called alu-stainless steel and when the tube is made of aluminum, the heat exchanger thus formed is of the type commonly called alu-alu.

[0030] According to other advantageous variants of the invention, other materials in powder form can be used, for example steel, Inconel® alloys, copper, etc.

[0031] Advantageously and according to the invention, the method comprises a preliminary step of bending at least one tube, each mold being shaped according to the shape of the bent tube.

[0032] According to this aspect of the invention, obtaining curvature in the exchanger is facilitated by the prior bending of the tube, compared to the methods of the prior art in which the tube and the profile were bent together. In particular, bending the tube before laying the profile is simpler than bending the assembled tube and profile, which reduces the risk of leakage or mechanical defect of the exchanger. In addition, bending the tube before laying the profile can be carried out on longer tube lengths than bending the assembled tube and profile, which makes it possible to reduce the number of splices required when the circuit formed by the tube(s) is large.

[0033] Advantageously and according to the invention, the first mold and the second mold are configured so that the profile has a rectangular section surrounding each fluid circulation tube.

[0034] According to this aspect of the invention, the rectangular shape of the profile is comparable to the shapes obtained in heat exchangers of the prior art, in particular formed from a tube surrounded by two plates enclosing the tube.

[0035] According to other alternative variants of the invention, the section of the profile may have other shapes surrounding the tube, for example circular, triangular, trapezoidal, etc.

[0036] The invention also relates to a heat exchanger comprising at least one tube for circulating a fluid and configured to allow heat exchange between the fluid circulating in each tube and a profile surrounding each tube, characterized in that it is obtained by a manufacturing method according to the invention.

[0037] An exchanger according to the invention presents lower risks of leakage and mechanical defects than exchangers of the prior art, in particular because their manufacture does not require bending of the profile which causes mechanical stresses which can lead to damage to the profile.

[0038] Advantageously and according to the invention, each tube is formed from stainless steel and the profile formed by the dynamically cold-projected metal powder is formed from aluminum.

[0039] The exchanger thus formed is an Alu-Inox type exchanger.

[0040] Advantageously and according to the invention, each tube is formed from aluminum and the profile formed by the dynamically cold-projected metal powder is formed from aluminum.

[0041] The exchanger thus formed is an Alu-Alu type exchanger.

[0042] The invention also relates to a manufacturing method and a heat exchanger characterized in combination by all or part of the characteristics mentioned above or below. List of figures

[0043] Other aims, characteristics and advantages of the invention will appear on reading the following description given solely for non-limiting purposes and which refers to the appended figures in which:

[0044] [Fig-1] is a schematic top view of a rectilinear heat exchanger obtained by a manufacturing method according to an embodiment of the invention;

[0045] [Fig.2] is a schematic front view of a rectilinear heat exchanger obtained by a manufacturing method according to an embodiment of the invention;

[0046] [Fig.3] is a schematic side view of a rectilinear heat exchanger obtained by a manufacturing method according to one embodiment of the invention;

[0047] [Fig.4] is a schematic side view of a first step of cold dynamic projection of a manufacturing method according to an embodiment of the invention;

[0048] [Fig.5] is a schematic side view of a heat exchanger being manufactured after the first cold dynamic spraying step of a manufacturing method according to one embodiment of the invention;

[0049] [Fig.6] is a schematic side view of a second cold dynamic projection step of a manufacturing method according to an embodiment of the invention;

[0050] [Fig.7] is a schematic side view of a heat exchanger being manufactured after the second cold dynamic spraying step of a manufacturing method according to one embodiment of the invention;

[0051] [Fig.8] is a schematic side view of the first and second molds used in a manufacturing method according to one embodiment of the invention;

[0052] [Fig.9] is a schematic top view of tubes of a serpentine heat exchanger used in a manufacturing method according to one embodiment of the invention;

[0053] [Fig. 10] is a schematic top view of a first cold dynamic spraying step of a method for manufacturing a serpentine heat exchanger according to one embodiment of the invention;

[0054] [Fig. 11] is a schematic top view of a second cold dynamic spraying step of a method for manufacturing a serpentine heat exchanger according to one embodiment of the invention.

[0055] Detailed description of an embodiment of the invention

[0056] In the figures, the scales and proportions are not strictly respected, for the purposes of illustration and clarity.

[0057] Furthermore, identical, similar or analogous elements are designated by the same references in all the figures.

[0058] [Fig.1], [Fig.2] and [Fig.3] schematically illustrate a heat exchanger 10 according to an embodiment of the invention, respectively from above, from the front and from the side. The heat exchanger 10 comprises a profile 14, preferably made of aluminum, crossed by a tube 12, preferably made of stainless steel or aluminum, forming a fluid circulation circuit allowing the circulation of a fluid, for a heat exchange between the fluid and the profile and more generally between the fluid and the external environment of the profile.

[0059] Depending on manufacturing constraints, the tube 12 may be formed from several tubes. combined together to form a longer tube.

[0060] In this embodiment, the tube 12 is rectilinear and thus forms a rectilinear exchanger 10.

[0061] [Fig.4] schematically represents from the side a first projection stage cold dynamics of a manufacturing method according to an embodiment of the invention.

[0062] [Fig.5] schematically represents from the side a heat exchanger 10 in progress manufacturing after the first step of cold dynamic projection of a manufacturing method according to an embodiment of the invention.

[0063] [Fig.6] schematically represents from the side a second projection stage cold dynamics of a manufacturing method according to an embodiment of the invention.

[0064] [Fig.7] schematically represents from the side a heat exchanger 10 in progress manufacturing after the second cold dynamic projection step of a manufacturing method according to an embodiment of the invention.

[0065] [Fig.8] schematically represents from the side the first mold 16a and the second mold 16b used in a manufacturing method according to an embodiment of the invention.

[0066] The heat exchanger is obtained by a manufacturing process comprising: - a step of placing each tube 12 in a first mold 16a at least partially surrounding each tube. Such a tube 12 placed in the first mold 16a is visible in [Fig.4] and the first mold 16a before the tube is placed is visible in [Fig.8]. - a first step of cold dynamic projection of metal powder onto each tube 12 arranged in the first mold 16a so as to form a first portion 14a of profile surrounding at least a first external surface of each tube 12. This step of cold dynamic projection is shown in [Fig.4], where a cold dynamic projector 18 propels a cold metal powder, here aluminum, at a supersonic speed at the level of an empty space of the first mold 16a in which the tube 12 is placed. The empty space is thus filled with a metal coating forming the first portion 14a of profile. - a step of removing each tube 12 and the first portion 14a of profile from the first mold 16a. The heat exchanger being manufactured following this removal is visible in [Fig.5], where it comprises the tube 12 and the first portion 14a of profile. - a step of placing each tube 12 and the first portion 14a of profile in a second mold 16b at least partially surrounding each tube 12. A such tube 12 and a first portion of profile placed in the second mold 16a is visible in [Fig.6] and the second mold 16b before the installation of the tube and the first portion of profile is visible in [Fig.8]. - a step of cold dynamic projection of metal powder onto each tube arranged in the second mold so as to form a second profile portion surrounding at least a second outer surface of each tube. This cold dynamic projection step is shown in [Fig.6], where the cold dynamic projector 18 propels a cold metal powder, here aluminum, at a supersonic speed at an empty space of the second mold 16b in which the tube 12 is placed. The empty space is thus filled with a metal coating forming the second profile portion 14b.

[0067] The heat exchanger 10 obtained following these steps is shown in [Fig.7]. The exchanger 10 thus comprises the tube 12 surrounded by the two portions 14a and 14b of the profile forming the profile. The profile thus obtained here is rectangular in shape. According to other embodiments, certain profile shapes may require other cold dynamic projection steps.

[0068] Following these steps, the manufacturing method may include additional steps not described, in particular known finishing steps such as the application of coating, machining, the addition of support parts, the addition of input / output housing, etc.

[0069] The manufacturing method also makes it possible to obtain exchangers of various shapes, for example so-called "serpentine" exchangers. To avoid bending of the profile, the method comprises a preliminary step of bending at least one tube and the molds are shaped to the bent tubes.

[0070] [Fig.9] schematically represents from above two tubes 12a, 12b of a serpentine heat exchanger used in a manufacturing method according to an embodiment of the invention.

[0071] [Fig. 10] schematically represents from above a first step of cold dynamic projection of a method of manufacturing a serpentine heat exchanger according to an embodiment of the invention;

[0072] [Fig. 11] schematically represents from above a second step of cold dynamic projection of a method of manufacturing a serpentine heat exchanger according to an embodiment of the invention.

[0073] In this embodiment, the two tubes have their openings matched at a junction 20. The junction 20 is shown in [Fig.9] with a spacing of the tubes deliberately exaggerated for reasons of clarity, the tubes being very close or in contact during the manufacture of the exchanger in order to avoid leaks, as seen in particular in Figures 10 and 11 where Injunction 20 is represented by a dotted line.

[0074] The tubes 12a and 12b can be assembled by brazing or welding, in particular orbital welding before forming the profile. Alternatively, as shown in FIGS. 10 and 11, the tubes can be arranged directly in the first mold 116b for a first step of cold dynamic projection by a projector 18, then in the second mold 116b for the second step of cold dynamic projection. The profile formed around the junction 20 following these steps thus forms the seal of the fluid circulation circuit formed by the tubes 12a, 12b. The two molds are shaped to the shape of the tubes after bending, in particular to the desired serpentine shape for the heat exchanger.

[0075] The invention is not limited to the embodiments described. In particular, the profile and the exchanger may have different shapes depending on the desired mechanical and thermal characteristics, or depending on the constraints of integrating the exchanger into a complex system, for example in an aircraft or a satellite.

Claims

Claims

1. Method for manufacturing a heat exchanger (10) comprising at least one tube (12; 12a, 12b) for circulating a fluid and configured to allow heat exchange between the fluid circulating in each tube (12; 12a, 12b) and a profile (14) surrounding each tube, characterized in that it comprises: - a step of placing each tube (12; 12a, 12b) in a first mold (16a, 116a) at least partially surrounding each tube (12; 12a, 12b), - a step of cold dynamic projection of metal powder onto each tube (12; 12a, 12b) arranged in the first mold (16a, 116a) so as to form a first portion (14a) of profile surrounding at least a first outer surface of each tube (12; 12a, 12b), - a step of removing each tube (12; 12a, 12b) and the first portion (14a) of profile from the first mold (16a, 116a), - a step of placing each tube (12;12a, 12b) and the first portion (14a) of profile in a second mold (16b, 116b) at least partially surrounding each tube (12; 12a, 12b), - a step of dynamic cold projection of metallic powder on each tube (12; 12a, 12b) arranged in the second mold (16b, 116b) so as to form a second portion (14b) of profile surrounding at least a second external surface of each tube.;

2. Manufacturing method according to claim 1, characterized in that the heat exchanger (10) comprises at least two fluid circulation tubes (12a, 12b), a first tube (12a) and a second tube (12b), and in that the step of placing in a first mold (16a, 116a) comprises a sub-step of matching an opening of the first tube (12a) with an opening of the second tube (12b).

3. Manufacturing method according to claim 2, characterized in that the matching sub-step is followed by a step of brazing or welding the first tube (12a) with the second tube (12b), at level of the matching openings.

4. Manufacturing method according to one of claims 1 to 3, characterized in that the metal powder sprayed during each cold dynamic spraying step is formed from aluminum powder.

5. Manufacturing method according to one of claims 1 to 4, characterized in that it comprises a preliminary step of bending at least one tube (12a, 12b), each mold (116a, 116b) being shaped according to the shape of the bent tube (12a, 12b).

6. Manufacturing method according to one of claims 1 to 5, characterized in that the first mold (16a, 116a) and the second mold (16b, 116b) are configured so that the profile has a final shape having a rectangular section surrounding each fluid circulation tube.

7. Manufacturing method according to one of claims 1 to 6, characterized in that it comprises a step of applying a metallic coating to each tube before the step of placing each tube in the first mold.

8. Heat exchanger comprising at least one tube (12, 12a, 12b) for circulating a fluid and configured to allow heat exchange between the fluid circulating in each tube (12, 12a, 12b) and a profile (14) surrounding each tube, characterized in that it is obtained by a manufacturing method according to one of claims 1 to 7.

9. Heat exchanger according to claim 8, characterized in that each tube (12, 12a, 12b) is formed from stainless steel and in that the profile (14) formed by the dynamically cold-sprayed metal powder is formed from aluminum.

10. Heat exchanger according to claim 8, characterized in that each tube (12, 12a, 12b) is formed from aluminum and in that the profile (14) formed by the dynamically cold-sprayed metal powder is formed from aluminum.

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