Method for production of a heat exchanger with at least two fluid circulation circuits with a large number of channels and/or large dimensions

Abstract

A method for fabrication of heat exchangers with at least two fluid circuits each one comprising channels based on grooved plates includes assembling elementary exchanger modules, each of the elementary exchanger modules having been produced by diffusion bonding of grooved plates.

Claims

1. A method of production of a heat exchanger with at least two fluid circuits each one comprising channels, involving the following steps: a/ production of at least two elementary modules of the exchanger, the production of each elementary module involving the following steps: i/ production of one or more elements of one of the two fluid circuits, the so-called first circuit, each element of the first circuit comprising at least one metal plate comprising first grooves forming at least one portion of the channels of the first circuit; ii/ production of one or more elements of at least one other fluid circuit, the so-called second circuit, each element of the second circuit comprising at least one metal plate comprising second grooves forming at least one portion of the channels of the second circuit; iii/ stacking of the metal plates of the elements of the first and second circuits in order to form their channels; iv/ assembling by diffusion bonding of the element or elements of the first circuit and the element or elements of the second circuit, stacked one on the other; b/ modification of at least one of the elementary modules involving a reduction of the width of at least one of the borders and/or of the thickness of at least one of the anvils of at least one of the modules and optionally an opening of the channels of the first circuit and/or of the second circuit to the outside; c/ edge to edge positioning of the elementary modules, at least one of which is reduced, along one of their longitudinal edges or one of their lateral edges; d/ assembling of the interfaces between the edge to edge elementary modules in order to obtain the exchanger in one-piece form.

2. The method as claimed in claim 1, wherein before the stacking step iii/, one performs a step i1/ and ii1/ of cleaning of the plates of each element respectively of the first circuit and second circuit.

3. The method as claimed in claim 1, wherein one performs step iv/ by application of a hot isostatic compression (HIC) cycle at relatively low pressure to the tight and degassed stack of each elementary module.

4. The method as claimed in claim 3, wherein the cycle of HIC per step iv/ is performed at a pressure between 20 and 500 bar, preferably between 30 and 300 bar.

5. The method as claimed in claim 3, wherein the cycle of HIC per step iv/ is performed at a temperature between ambient temperature and 1100 C., preferably between 900 and 1100 C.

6. The method as claimed in claim 1, wherein during step b/ the reduction of the width of at least one of the borders and/or the thickness of at least one of the anvils of at least one of the modules is accomplished by removing the tools by demolding or machining, or by machining part of the nongrooved borders of the plates and/or the anvils.

7. The method as claimed in claim 1, wherein during step b/ the opening of the channels can be accomplished by machining of the ends of the module or a bore opposite to the channels.

8. The method as claimed in claim 1, wherein step c/ of edge to edge positioning consists of a stacking of the elementary modules by the principal faces of the end plates of the modules.

9. The method as claimed in claim 1, wherein step c/ of edge to edge positioning consists of an edge to edge alignment along the length of the elementary modules.

10. The method as claimed in claim 1, wherein step c/ of edge to edge positioning consists of a positioning of a lateral edge of one of the elementary modules against a lateral edge of the other of the elementary modules.

11. The method as claimed in claim 1, wherein step d/ is accomplished by electron beam welding, brazing, or diffusion bonding of the reduced modules between themselves.

12. The method as claimed in claim 11, step d/ consisting of a diffusion bonding with application of at least one hot isostatic compression (HIC) cycle.

13. The method as claimed in claim 12, the diffusion bonding of the reduced elementary modules per step d/ is done during the high-pressure cycle making it possible to finish the welding of the internal interfaces of the elementary modules, step b/ involving an opening of the channels of the first circuit and/or of the second circuit to the outside.

14. The method as claimed in claim 1, an elementary module comprising plates of different materials.

15. The method as claimed in claim 1, wherein the material or materials making up one elementary module are different from that or those of another elementary module.

16. The method as claimed in claim 1, involving a step e/ of final machining to finish the one-piece exchanger.

17. A heat exchanger with at least two fluid circuits obtained according to the method as claimed in claim 1.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0083] Other advantages and characteristics of the invention will be more evident from a perusal of the detailed description of sample embodiments of the invention, given as an illustration and not a limitation, with reference to the following figures, among which:

[0084] FIG. 1 is a cross-sectional view of an exchanger module according to the prior art, produced by HIC, showing the different zones of transmission of the welding force;

[0085] FIGS. 2A and 2B are schematic cross-sectional views of exchanger modules according to the prior art, produced by HIC during the same HIC cycle, respectively of greater and lesser stack height, showing the deformation of the channels of one of the fluid circuits as well as the slumping of the height of the modules;

[0086] FIGS. 3A, 3B and 3C are perspective views of a metal plate adapted to produce an elementary exchanger module according to the invention, respectively before the producing of grooves forming a portion of the fluid channels, with the grooves of one of the circuits at one of its principal faces and with the grooves of the other of the circuits at the other of its principal faces;

[0087] FIG. 4 is a perspective view of a sample elementary exchanger module according to the invention obtained by diffusion bonding assembly of grooved and stacked plates, before the step of opening of the channels;

[0088] FIG. 4A is a transverse and longitudinal section view of the stack of the elementary module per FIG. 4;

[0089] FIGS. 5, 6 and 7 are perspective views of three elementary exchanger modules produced according to the invention, prior to their mutual assembly in order to form a one-piece exchanger according to the invention;

[0090] FIG. 8 is a perspective view of a sample one-piece exchanger according to the invention produced by edge to edge positioning and then diffusion bonding assembly of the three elementary modules per FIGS. 5 to 7;

[0091] FIG. 8A is a cross-sectional view of the module per FIG. 8, showing the bores produced during the machining of the plates of the elementary modules, some of which enable the connecting of the different zones of the elementary modules positioned edge to edge and others enable the placing under vacuum of the interfaces to be welded between the elementary modules positioned edge to edge.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0092] The terms longitudinal and lateral are to be considered in relation to the geometrical shape of the metallic plates which determine the geometrical shape of the stacks of the heat exchanger module according to the invention. Thus, in the end the four longitudinal sides of the stack of an elementary exchanger module according to the invention are those extending parallel to the longitudinal axis X of the plates, that is, along their length. The two lateral sides of the stack are those extending along the lateral axis Y of the plates, orthogonally to the axis X, that is, along their width.

[0093] The terms on top and at bottom should be considered in relation to the direction of the stacking of the exchanger module. Thus, the plate on top, forming all or part of an anvil, is the last plate stacked on top of the others.

[0094] Step a/:

[0095] First of all, one produces in the same manner a number of several elementary exchanger modules which may be of different dimensions.

[0096] We shall describe the production by the first step a/ of an elementary module 1.1 from metal plates 10, such as plates of stainless steel of type 316L, with length l1 and width l2 (FIG. 3A). The borders and the anvils of the plates 10 are advantageously dimensioned such that the deformations are controlled during an assembly by HIC diffusion bonding.

[0097] Step i/: in order to produce an element of a first fluid circuit C1, one machines in one of the principal faces 101 of a metal plate 10 grooves 20 which are straight and parallel to the length l1 of the plate in the example illustrated (FIG. 3B).

[0098] Step ii/: in order to produce an element of a second fluid circuit C2, one machines in the other of the principal faces 102 of a metal plate 10 grooves 30 which are straight and parallel to the width of the plate in the example illustrated (FIG. 3C).

[0099] The grooves 20, 30 can be produced by any adapted means: machining, chemical etching, stamping, etc.

[0100] One then produces, as usual, the necessary attached pieces for the producing of the stack of grooved plates 10 and their assembly (tools). This may involve, in particular, alignment pins, holding tools (uniaxial diffusion bonding), optionally a container if the stack of plates is assembled by HIC diffusion bonding.

[0101] Steps i1/ and ii1/: cleaning is carried out with the aid of solvents and detergents of the plates 10.

[0102] Step iii/: after having cleaned them, one stacks the assemblage of plates 10 so as to form both the channel elements 2 of the first circuit C1 and the channel elements 3 of the second circuit C2.

[0103] During the stacking, all the plates 1 are aligned in relation to each other thanks to the alignment pins or centering pegs, not shown, which are inserted into blind holes.

[0104] FIGS. 4 and 4A show an example of the stacking to produce an elementary exchanger module 1.1 with a superpositioning of channels 2, 3 of the two fluid circuits C2.

[0105] Step iv/: The entire periphery of the stack (block) is rendered tight and each interface is degassed by an emerging orifice, which will be blocked up. To accomplish the sealing at the periphery of the stack, the entire stacking is done in a container.

[0106] The container, made of stainless steel sheet folded and welded by the TIG method, is itself cleaned, along with its cover. The cover is welded by TIG to the container and then the container is placed under vacuum by pumping through a tube welded to one of its sides. The tube is then pinched off, sliced, and itself welded to prevent the introduction of air inside the container.

[0107] One then subjects the container, and thus the complete stack, to a cycle of low-pressure HIC involving a heating of 900 to 1100 C. for a period of 1 to 4 h under a pressure of 30 to 300 bar, then a cooldown for several hours and a depressurization.

[0108] One carries out all of these steps i/ to iv/ for each of the elementary modules 1.1, 1.2, 1.3 which are going to make up the one-piece exchanger according to the invention.

[0109] Step b/: for each of the elementary modules 1.1, 1.2, 1.3, one then performs their reduction involving a decreasing of the borders by milling and the opening of the channels 2 and/or 3 by trimming the ends of the stack which are blocking them.

[0110] In the example illustrated:

[0111] the elementary module 1.1 is machined so as to have a length l4 and a width l3, with all the channels 2, 3 of both the first circuit and the second circuit which have been opened, that is, all of them emerging to the outside (FIG. 5);

[0112] the elementary module 1.2 is machined so as to have a length l4 and a width l5, with all the channels 2 of the first circuit, being parallel to the length of the exchanger, which have been opened at their two ends, while the channels 3 of the second circuit parallel to the width of the exchanger have been opened at only one of their ends (FIG. 6);

[0113] the elementary module 1.3 is machined so as to have a length l4 and a width l6, with all the channels 2 of the first circuit, being parallel to the length of the exchanger, which have been opened at their two ends, while the channels 3 of the second circuit parallel to the width of the exchanger have been opened at only one of their ends (FIG. 7).

[0114] Step c/: at the end of the machining of all the elementary modules, they are positioned edge to edge. In the example illustrated, one places side by side the three elementary modules 1.1, 1.2, 1.3 of the same length l4 but different width l3, l5, l6 by their longitudinal edge at the side, in order to form a block 1 of outer dimensions l4(l3+l5+l6) (FIG. 8).

[0115] Step d/: once the edge to edge positioning of the elementary modules 1.1, 1.2, 1.3 has been accomplished, one then performs the assembly of the interfaces of the exchanger so formed. This is advantageously done by means of HIC diffusion bonding. First of all, one cleans the reduced elementary modules with the aid of solvents and detergents.

[0116] Next, one performs the sealing of the interfaces by TIG welding, and then places under vacuum the sealed interfaces between the elementary modules and thus also those of the channels communicating with the latter, in order to ensure their continuity from one elementary module to another.

[0117] FIG. 8A thus shows the machining 31 (boring) performed in advance and making it possible to interconnect the different zones of channels 3 being welded, as well as the machining 32 making it possible to weld a pip and thus perform the evacuation.

[0118] One then performs the tight closing of the pips.

[0119] Finally, one applies to the block 1 of elementary modules 1.1, 1.2, 1.3 so obtained a cycle of low-pressure HIC, typically at a pressure between 20 and 500 bar, preferably between 30 and 300 bar. The choice of the pressure results from a compromise between the quality of the welding to be achieved and the acceptable deformation of the channels not opened.

[0120] One can subsequently perform one or more machining processes to finish the one-piece heat exchanger 1, in particular, to open the fluid circuit which was left closed.

[0121] One can then submit the exchanger to a high-pressure HIC cycle, typically under a pressure between 200 and 2000 bar, preferably between 500 and 1200 bar. During this cycle, one completes the assembly of the plates making up the elementary modules and that of the modules to each other.

[0122] One can also add on subsequently, by welding, fluid distribution manifolds, not shown, so as to feed and/or recuperate a fluid in each of the first C1 and second C2 circuits in the area of the ends of the grooves forming the channels 2, 3.

[0123] Thanks to the method according to steps a/ to d/, one obtains a one-piece heat exchanger assembled by HIC diffusion bonding which is compact, has large dimensions and/or a large number of channels whose geometrical shape has undergone very little deformation as regards the initial shape produced during the stacking.

[0124] Of course, the present invention is not limited to the variants and the embodiments described as an illustration and not a limitation.

[0125] In the example illustrated, the elementary exchanger modules are placed laterally side by side. One can also contemplate positioning them edge to edge in the height direction, that is, stacking them one on another. In this case, the two fluid circuits can be opened during the assembly process of the exchanger: the HIC cycle applied can then be a cycle of high pressure type as above. The positioning can also be done in the length direction, that is, placed end to end, following each other in succession, or in several directions at the same time.

[0126] In the example illustrated, all the plates making up all of the elementary modules are made of the same material, preferably a stainless steel of type 316L. One can also contemplate having plates of different material within the same elementary module or plates of different material from one elementary module to another.

[0127] In the example illustrated, the seals at the interfaces between elementary modules are made by welding. Any other means allowing the production of a seal and maintaining its integrity during the diffusion bonding of the block can be utilized.

[0128] The size of the channels for each of the fluid circuits can be different depending on the nature and the properties of the fluids being carried, the allowable head losses, and the desired flow rate. One may stack several elements of the same circuit in order to optimize a functionality of the exchanger, for example the heat transfer or the flow rate of one of the fluids.

[0129] While the example illustrated involves exchangers with precisely two fluid circuits, it is quite possible to fabricate an exchanger with three or more fluid circuits, starting from two, three or more elementary exchanger modules.

[0130] The two fluid manifolds can be arranged on either side of the exchanger, or alternating on the same side of the exchanger.

[0131] The heat exchangers obtained by the method of the invention can be assembled with each other, for example by using flanges or by welding on fluid supply pipelines. One may thus contemplate the production of a heat exchanger system with several exchangers connected to each other, in which the transfers occur in several steps with different mean temperatures or sufficiently reduced temperature differences per module to diminish the thermal stresses in the materials. For example, in the case of a heat exchanger in which one desires to transfer the heat from a first fluid to a second, one can conceive of an exchanger system in which each exchanger enables a decreasing of the temperature of the first fluid by a given value, thus limiting the stresses in regard to a design with a single exchanger having a more elevated temperature difference. For this, the inlet temperature of the second fluid may differ from one module to another. In another example, a reactor exchanger system allows a complex chemical reaction to be carried out in steps by precisely controlling the reaction temperature during each step, for an optimal control of the chemical reaction, a minimization of risks and a maximization of yields.

[0132] A system of heat exchangers with several exchangers also makes it possible to reduce the maintenance costs by allowing the individual replacement of a faulty exchanger, and the manufacturing costs by standardization of the exchangers.