METHOD FOR MANUFACTURING A TITANIUM HEAT EXCHANGER

Description

TECHNICAL FIELD

[0001] The present invention relates to a method for manufacturing a heat exchanger. STATE OF PRIOR ART

[0002] A heat exchanger allows the exchange of heat between a hot fluid and a cold fluid, such as a heat transfer fluid. To this end, the heat exchanger takes the form of a plate containing a network of channels through which one fluid flows while the other fluid flows over the surface of the plate. Documents JP S57193248 and US 3839975A disclose manufacturing processes for such heat exchangers.

[0003] Such a plate is usually made of stainless steel or graphite.

[0004] While such a heat exchanger is easy to manufacture and efficient, it is relatively heavy. Such conditions can be met when the heat exchanger is implemented in a fuel cell using dihydrogen and dioxygen. DESCRIPTION OF THE INVENTION

[0005] One object of the present invention is to provide a method for manufacturing a heat exchanger from titanium strips that yields a lighter heat exchanger with performance at least equivalent to that of prior art heat exchangers. Furthermore, the proposed methods allow for the simple and rapid production of a heat exchanger.

[0006] To this end, a manufacturing process for a plate comprising channels is proposed, the manufacturing process comprising, in accordance with claim 1: a layering step in which two titanium or titanium alloy strips are layered one on top of the other, a welding step in which the two strips are welded together along the weld lines, a sealing step in which the areas between the first and second strips where the areas between the weld lines meet at one of the edges of the first and second strips are sealed, a pressurization step during which a compressed fluid is injected at another edge of the first and second strips, where the areas between the weld lines open between the first and second strips so as to achieve the expansion of the strips, and an unclogging step during which the areas sealed during the sealing step are unclogged, where the layering step consists successively of a first placement step during which the first strip is placed on a mold, a second placement step during which the second strip is placed on the first strip, and a covering step during which a counter-mold is placed on the second strip, where the mold and the counter-mold have a plurality of holes, and the welding step consists of introducing needles into the holes of the mold and counter-needles into the holes of the counter-mold and supplying the needles and counter-needles with a voltage generator to weld the two strips together along the weld lines, and where the mold and the counter-mold have, between the holes, female forms corresponding to channel impressions to be obtained.

[0007] This manufacturing process allows titanium strips to be welded together and shaped by applying pressure. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The features of the invention mentioned above, as well as others, will become clearer upon reading the following description of an exemplary embodiment, said description being made in relation to the accompanying drawings, among which: [ Fig. 1 ] is a cross-sectional view of a plate of a heat exchanger obtained by a manufacturing process according to the invention, [ Fig. 2 ] is a perspective view of a tool implemented in a manufacturing process according to a first embodiment which is not the subject of claim 1, [ Fig. 3 ] is a perspective view of a tool implemented in a manufacturing process according to an embodiment of the invention, and [ Fig. 4 ] is a cross-sectional view of a tool implemented in a manufacturing process according to a third embodiment which is not the subject of claim 1. DETAILED DESCRIPTION OF IMPLEMENTATION METHODS

[0009] There Fig. 1 shows a plate 100 which can be used in a heat exchanger and which comprises a first strip 102 and a second strip 104. Both strips 102 and 104 are made of titanium or titanium alloy.

[0010] The two strips 102 and 104 are placed side by side.

[0011] Each strip 102, 104 has deformations 106, 108, here in the form of an elliptical arc. Each deformation 106 of the first strip 102 is opposite a deformation 108 of the second strip 104 so as to delimit between them a channel 150 which allows a fluid to be channeled, in particular a heat transfer fluid when the plate 100 is used in a heat exchanger.

[0012] The shape of deformations 106, 108 can vary and take, for example, a trapezoidal, omega, circular, triangular shape, ...

[0013] Plate 100 is then positioned between a supply system which feeds plate 100 with the heat transfer fluid, and a recovery system which recovers the heat transfer fluid at the outlet of plate 100. Fluid continuity between the supply system and plate 100 is achieved at the level of a first edge of plate 100 and fluid continuity between plate 100 and the recovery system is achieved at the level of a second edge of plate 100, that is to say that the channels 150 are open at the level of this first edge and this second edge in order to allow the passage of the heat transfer fluid.

[0014] The two strips 102 and 104 are fixed to each other by weld points 110 made between two neighboring deformations 106, 108.

[0015] The production of such a 100 titanium plate makes it possible to create a lighter and equally efficient heat exchanger, particularly when used in a fuel cell cooling system.

[0016] There Fig. 2 shows a tool 200 which allows two titanium or titanium alloy strips 102 and 104 to be shaped into the plate 100 in a process which is not the subject of claim 1. For ease of viewing, the second strip 104 is partially cut.

[0017] The tool 200 includes a base 202 and a welding tool 204. The welding tool 204 here includes support pieces 206a-b between which is delimited a welding channel 208 and a welding unit 210 which moves along the welding channel 208, for example by means of a mobile carriage.

[0018] The 210 welding unit is, for example, a laser emitter that allows for laser welding, but any other technique can be used, such as electron beam welding, resistance welding, friction stir welding, or diffusion welding.

[0019] When a weld line has been completed, the support pieces 206a-b and the welding unit 210 are moved to complete a new weld line.

[0020] The two strips 102 and 104 are arranged one on top of the other and between the base 202 and the welding tool 204 and more particularly here between the base 202 and the support pieces 206a-b.

[0021] After the welding unit 210 has completed all the weld lines, the areas between the weld lines, i.e. the areas where the two strips 102 and 104 are not welded together, will be deformed and will eventually form the channels 150 of the plate 100.

[0022] As mentioned above, some channels 150 allow the flow of the heat transfer fluid which enters the plate 100 or which exits from the plate 100 and these channels 150 open respectively at the level of a first edge 50 of the plate 100 and at the level of a second edge 52 of the plate 100 which correspond respectively to first edges of the first strip 102 and the second strip 104, and to second edges of the first strip 102 and the second strip 104.

[0023] The areas between the weld lines will lead to the creation of these channels 150 opening onto the edges 50 and 52 and they therefore extend respectively to the first edge 50 of the plate 100 and to the second edge 52 of the plate 100.

[0024] To shape the channels 150, a pressurized fluid is injected between the strips 102 and 104 and at the points between the weld lines. The two strips 102 and 104 will then move apart at these points to form the channels 150. To inject the pressurized fluid, it is necessary to seal the points between the first strip 102 and the second strip 104, located at one of the edges 50, 52 of the first strip 102 and the second strip 104, along which the points between the weld lines open at one end. The pressurized fluid is then injected at the other edge 52, 50 of the first strip 102 and the second strip 104, along which the points between the weld lines open at their other ends.

[0025] To ensure the channels 150 conform as expected, before the injection of the pressurized fluid, the first strip 102 and the second strip 104 are placed between two dies, each die having female shapes corresponding to the impressions of the channels 150 to be formed. Thus, during the injection of the compressed fluid, the strips 102 and 104 will separate and conform to the female shapes, thereby forming the channels 150. The female shapes are formed on the faces of the dies that are against the strips 102 and 104.

[0026] The previously sealed areas are then unblocked to allow the fluid to flow into the channels 150 of the plate 100.

[0027] A method for manufacturing a plate 100 of a heat exchanger which is not the subject of claim 1 comprises; a first positioning step during which a first strip 102 is placed on the base 202, a second positioning step during which a second strip 104 is placed on the first strip 102, a covering step during which the support pieces 206a-b are arranged on the second strip 104, a welding step during which the welding unit 210 is moved along the welding channel 208 to weld the two strips 102 and 104 together along the weld lines, a sealing step during which the areas between the first strip 102 and the second strip 104 at which the areas between the weld lines open at one of the edges 50, 52 of the first strip 102 and the second strip 104 are sealed,a third positioning step during which the first strip 102 and the second strip 104 welded together are placed between two dies, each having female shapes; a pressurization step during which the compressed fluid is injected at another edge 52, 50 of the first strip 102 and the second strip 104, where the areas between the weld lines open between the first strip 102 and the second strip 104 so as to achieve the expansion of the strips 102 and 104 at the female shapes; and an unclogging step during which the areas sealed during the sealing step are unsealed.

[0028] The welding step is repeated for each weld line after moving the support pieces 204a-b in order to obtain the desired pattern for the channels 150. Such a process is relatively simple and quick to implement.

[0029] The sealing step can be performed during the welding step.

[0030] To improve weld accuracy, i.e., to prevent the two strips 102 and 104 from fusing together over too large an area, beads 212 of thermal and electrical insulation are deposited between the two strips 102 and 104 at points where no weld should be made between them, i.e., in the areas between the weld lines. The beads 212 are made, for example, of ceramic powder.

[0031] Eventually, the areas where the 212 cords were deposited will constitute the 150 channels of the 100 plate.

[0032] The 212 beads extend to the first edge 50 of the plate 100 and to the second edge 52 of the plate 100 as for the areas between the weld lines.

[0033] The manufacturing process then includes, between the first placement step and the second placement step, a deposition step during which cords 212 of an insulator are deposited on the first strip 102 and where the cords 212 extend between two edges of the first strip 102, and the second placement step then consists of placing the second strip 104 on the cords 212 and where the cords 212 extend between two edges of the second strip 104.

[0034] If necessary, the insulating cords 212 can be removed by injecting a suitable fluid into the channels 150.

[0035] There Fig. 3 shows a tool 300 which allows two strips 102 and 104 of titanium or titanium alloy to be shaped into the plate 100 during a process according to an embodiment of the invention.

[0036] The tool 300 includes a mold 302 forming here a base, a counter-mold 303 which is positioned above the mold 302 and a welding tool 304.

[0037] The two strips 102 and 104 are arranged between the mold 302 and the counter-mold 303.

[0038] The mold 302 and the counter-mold 303 have a plurality of holes 306a-b where the holes 306a-b have axes perpendicular to the planes of the strips 102 and 104.

[0039] The welding tool 304 comprises a plurality of needles 307a where each needle 307a fits into a hole 306a in the mold 302 and a plurality of counter-needles 307b where each counter-needle 307b fits into a hole 306b in the counter-mold 303.

[0040] The needles 307a can be arranged opposite the counter-needles 307b. However, it is possible for the needles 307a to be arranged in a staggered pattern with respect to the counter-needles 307b.

[0041] The welding tool 304 also includes a voltage generator which powers the needles 307a and counter-needles 307b in order to generate a welding arc between the strips 102 and 104 and each needle 307a or each counter-counter-needle 307b.

[0042] In the embodiment of the invention presented to the Fig. 3 , the welding tool 304 has a row of needles 307a and a row of counter-needles 307b, but it is possible to provide several rows of needles 307a and counter-needles 307b and to supply the desired needles 307a and counter-needles 307b.

[0043] In the embodiment presented to the Fig. 3 The holes 306a of the mold 302 are linearly offset from each other by a pitch P, and the holes 306b of the counter-mold 303 are also linearly offset from each other by the same pitch P. The holes 306a of the mold 302 and the holes 306b of the counter-mold 303 are linearly offset from each other by half a pitch P such that a hole 306b of the counter-mold 303 is equidistant from two consecutive holes 306a of the mold 302, and vice versa. The pitch P extends parallel to the direction of the weld lines to be produced.

[0044] At each needle 307a and each counter-needle 307b, a weld point is made. By successively moving the needles 307a and counter-needles 307b, it is possible to create a series of weld points that will ultimately form weld lines. The offset of the needles 307a and counter-needles 307b allows for a weld to be made first on the side of the first strip 102, then on the side of the second strip 104.

[0045] The weld line is formed by a succession of weld points alternately made by the needles 307a and the counter-needles 307b.

[0046] After the welding tool 304 has completed all the weld lines, the areas between the weld lines, i.e. the areas where the two strips 102 and 104 are not welded together, will be deformed and will eventually form the channels 150 of the plate 100.

[0047] As previously explained, the areas between the weld lines will lead to the creation of these channels 150 opening onto the edges of the strips 102 and 104 and they therefore extend respectively to the first edge of the plate 100 and to the second edge of the plate 100.

[0048] To shape the channels 150, a pressurized fluid is injected between the strips 102 and 104 and at the points between the weld lines. The two strips 102 and 104 will then move apart at these points to form the channels 150. To perform the pressurized fluid injection, it is necessary to seal the points between the first strip 102 and the second strip 104, located at one edge of the first strip 102 and the second strip 104, along which the points between the weld lines open at one end. The pressurized fluid injection then takes place at the other edge of the first strip 102 and the second strip 104, along which the points between the weld lines open at their other ends.

[0049] To achieve the desired channel 150 shape, the mold 302 and the counter-mold 303 have female profiles 308a-b between the holes 306a-b, corresponding to the impressions of the channels 150 to be formed. Thus, during the injection of the compressed fluid, the strips 102 and 104 will move apart and conform to the female profiles 308a-b, thereby forming the channels 150. The female profiles 308a-b are formed on the faces of the mold 302 and the counter-mold 303 that are against the strips 102 and 104.

[0050] The previously sealed areas are then unblocked to allow the fluid to flow into the channels 150 of the plate 100.

[0051] A method for manufacturing a plate 100 of a heat exchanger, according to an embodiment of the invention, comprises: a first setup step during which a first strip 102 is placed on the mold 302, a second setup step during which a second strip 104 is placed on the first strip 102, a covering step during which the counter-mold 303 is placed on the second strip 104, a welding step during which the needles 307a are introduced into the holes 306a of the mold 302 and the counter-needles 307b are introduced into the holes 306b of the counter-mold 303, and the needles 307a and the counter-needles 307b are powered by the voltage generator to weld the two strips 102 and 104 together along the weld lines,a sealing step during which the areas between the first strip 102 and the second strip 104, where the areas between the weld lines open at one of the edges of the first strip 102 and the second strip 104, are sealed; a pressurization step during which a compressed fluid is injected at another edge of the first strip 102 and the second strip 104, where the areas between the weld lines open between the first strip 102 and the second strip 104, so as to achieve the expansion of the strips 102 and 104 at the female forms; and an unsealing step during which the areas sealed during the sealing step are unsealed.

[0052] The welding step is repeated for each weld line after movement of the needles 307a and counter-needles 307b or by successive activations of several rows of needles 307a and counter-needles 307b.

[0053] The manufacturing process common to the method of production of the Fig. 2 and the method of implementation of the Fig. 3 consists of successively: a layering step in which the two strips 102 and 104 are layered one on top of the other, a welding step in which the two strips 102 and 104 are welded together along the weld lines, a sealing step in which the areas between the first strip 102 and the second strip 104, where the areas between the weld lines open at one of the edges 50, 52 of the first strip 102 and the second strip 104, are sealed, a pressurization step in which a compressed fluid is injected at another edge 52, 50 of the first strip 102 and the second strip 104, where the areas between the weld lines open between the first strip 102 and the second strip 104 so as to achieve the expansion of the strips 102 and 104, and an unblocking step during which the areas sealed during the sealing step are unblocked.

[0054] In the first case, the superposition step consists successively of the first placement step during which a first strip 102 is placed on the base 202, the second placement step during which a second strip 104 is placed on the first strip 102, and the covering step during which the support pieces 206a-b are arranged on the second strip 104. The welding step then consists of moving the welding unit 210 along the welding channel 208 to weld the two strips 102 and 104 together along the weld lines.

[0055] In the embodiment according to the invention, the superposition step consists successively of the first placement step during which a first strip 102 is placed on the mold 302, the second placement step during which a second strip 104 is placed on the first strip 102, and the covering step during which the counter-mold 303 is placed on the second strip 104.

[0056] There Fig. 4 shows a tool 400 which allows two titanium or titanium alloy strips 102 and 104 to be shaped into the plate 100 in a process according to an embodiment which is not the subject of claim 1.

[0057] The tool 400 includes a mold 402 forming here a base, a counter-mold 403 which is positioned above the mold 402 and a welding tool 404.

[0058] The two strips 102 and 104 are arranged between the mold 402 and the counter-mold 403.

[0059] The mold 402 and the counter-mold 403 have a plurality of welding elements 406, such as resistive heating elements which are aligned in several rows, and where the welding elements 406 of the mold 402 and the counter-mold 403 are aligned, here vertically.

[0060] The welding tool 404 includes the plurality of welding elements 406 distributed in rows on the mold 402 and the counter-mold 403 and a current generator which supplies the welding elements 406 in order to create an electric arc which generates a temperature increase which will cause the strips 102 and 104 to weld together.

[0061] A weld line is made at each row of 406 welding elements.

[0062] The mold 402 and the counter-mold 403 also include female forms 408a-b corresponding to the impressions of the channels 150 to be obtained.

[0063] The welding elements 406 and the female forms 408a-b are made on the faces of the mold 402 and the counter-mold 403 which are against the strips 102 and 104.

[0064] The principle of manufacturing plate 100 consists of welding all the edges of the two strips 102 and 104 together in order to delimit a closed volume between them. A pressurized fluid is then introduced into this closed volume, for example through a tube 409 opening into the closed volume. Then the mold 402 and the counter-mold 403 are brought together to force contact between the two strips 102 and 104 between the welding elements 406. During this step, the tube 409 is sealed to prevent leakage of the pressurized fluid, and at the same time, by conserving the volume of the pressurized fluid in the closed volume, the strips 102 and 104 are deformed at the female forms 408a-b in order to form the channels 150. The welding elements 406 are then activated to perform the welding of the two strips 102 and 104 along the weld lines.The ends of the channels 150 through which the heat transfer fluid flows are then opened, for example by cutting the edges of the strips 102 and 104.

[0065] After the welding tool 404 has completed all the weld lines, the areas between the weld lines, i.e. the areas where the two strips 102 and 104 are not welded together and have therefore been deformed, constitute the channels 150 of the plate 100.

[0066] After opening the ends of the channels 150, the areas between the weld lines open onto the edges of the strips 102 and 104 and therefore extend respectively to the first edge of the plate 100 and to the second edge of the plate 100.

[0067] A method for manufacturing a plate 100 of a heat exchanger according to an embodiment not covered by claim 1 comprises successively: a first positioning step during which the second strip 104 is placed on the first strip 102, a first welding step during which the edges of the two strips 102 and 104 are welded together to delimit a closed volume, a pressurization step during which a compressed fluid is injected into the closed volume so as to inflate the closed volume, a second positioning step during which the inflated strips 102 and 104 are arranged between a mold 402 and a counter-mold 403, where the mold 402 has welding elements 406 and female forms 408a, and where the counter-mold 403 has welding elements 406 aligned with the welding elements 406 of the mold 402 and female forms 408b aligned with the female forms 408a of the mold 402,a tightening step during which the mold 402 and the counter-mold 403 are brought together so that the two strips 102 and 104 are in contact along the welding elements 406 and deformed into the female shapes 408a-b, and a second welding step during which the welding elements 406 are activated to weld the two strips 102 and 104 together along the weld lines.

[0068] The pressurized fluid can be, for example, air, oil, or any other suitable fluid.

[0069] Such heat exchangers 100 can be stacked so as to bring into contact and fix the deformations 106, 108 of one heat exchanger 100 with the deformations 108, 106 of another heat exchanger 100 arranged above, in order to create open channels which are delimited by the deformations 106 and 108 of the two heat exchangers 100 and the welded areas, i.e. between the channels 150. Thus, in the context of a fuel cell, a coolant can circulate in the channels 150 in order to perform the heat exchanger function while in the open channels thus formed air and hydrogen can circulate.

Claims

1. Method for manufacturing a plate (100) including channels (150), the manufacturing method including: - a superimposing step during which two strips (102, 104) of titanium or titanium alloy are superimposed on one another, - a welding step during which the two strips (102, 104) are welded together along the weld lines, - a closing step during which the zones between the first strip (102) and the second strip (104) where the zones between the weld lines open out at one of the edges (50, 52) of the first strip (102) and of the second strip (104) are closed, - a pressurization step during which a compressed fluid is injected at another edge (52, 50) of the first strip (102) and of the second strip (104), where the zones between the weld lines open out between the first strip (102) and the second strip (104) so as to expand the strips (102, 104), and - an opening stage during which the zones closed during the closing stage are opened, where the superimposing step consists successively of a first placeing step during which the first strip (102) is placed on a mould (302), a second placing step during which the second strip (104) is placed on the first strip (102), and a covering step during which a countermould (303) is placed on the second strip (104), where the mould (302) and the countermould (303) include a plurality of holes (306a-b), and in that the welding step consists of inserting needles (307a) into the holes (306a) in the mould (302) and counter needles (307b) into the holes (306b) in the countermould (303) and powering the needles (307a) and the counter needles (307b) with a voltage generator to weld the two strips (102, 104) together along the weld lines, and where the mould (302) and the countermould (303) include, between the holes (306a-b), female shapes (308a-b) corresponding to impressions of the channels (150) to be obtained.