WO2017072176A1

WO2017072176A1 - Method for producing a heat exchanger module having at least two fluid circulation circuits, with diffusion welding of frames and rods positioned in the frames

Info

Publication number: WO2017072176A1
Application number: PCT/EP2016/075805
Authority: WO
Inventors: Emmanuel Rigal; Jean-Marc Leibold; Fabien Vidotto
Original assignee: Commissariat A L'energie Atomique Et Aux Energies Alternatives
Priority date: 2015-10-26
Filing date: 2016-10-26
Publication date: 2017-05-04
Also published as: FR3042859B1; FR3042859A1

Abstract

The present invention relates to a novel method for manufacturing heat exchanger modules having at least two fluid circuits. The invention essentially consists in replacing the grooved plates conventionally used to form the fluid circuit elements with elements each made up of a frame, of leaves supported by and incorporated into the frame, and of a non-grooved plate the role of which is to physically separate two adjacent frames in the stack.

Description

METHOD OF MAKING A HEAT EXCHANGER MODULE HAVING AT LEAST TWO CIRCUITS OF FLUID CIRCUIT, WELDING-DIFFUSING FRAMES AND BAGUETTES POSITIONED IN

FRAMES

Technical area

The present invention relates to heat exchangers with at least two fluid circuits each having channels.

The invention relates more particularly to a new method of manufacturing such diffusion welding heat exchangers obtained either by the technique of hot isostatic compression (CIC), or by the technique of uni-axial compression hot.

The known heat exchangers comprise either one or at least two internal fluid circulation channel circuits. In the single-circuit heat exchangers, the heat exchange takes place between the circuit and a surrounding fluid in which it is immersed. In the exchangers with at least two fluid circuits, the heat exchange takes place between the two fluid circuits.

It is known chemical reactors which implement a continuous process in which a small amount of co-reactants is simultaneously injected at the inlet of a first fluid circuit, preferably equipped with a mixer, and is recovered. the chemical product obtained at the outlet of said first circuit. Among these known chemical reactors, some include a second fluid circuit, usually called utility, whose function is to thermally control the chemical reaction, either by providing the heat necessary for the reaction, or on the contrary by removing the heat released by that - this. Such chemical reactors with two fluid circuits with utility are usually called reactor-exchangers.

The present invention relates both to the production of heat exchangers with a function solely of heat exchange, and to the production of heat exchangers. Thus, by "heat exchanger with at least two fluid circuits", it is necessary to understand in the context of the invention, both a heat exchanger with a function of heat exchange only a reactor-exchanger.

State of the art

The heat exchangers, known as plate heat exchangers, have important advantages over heat exchangers, known as tube heat exchangers, in particular their thermal performance and their compactness thanks to a ratio of the surface to the volume of heat exchange favorably high.

The known tube exchangers are, for example, tube and shell exchangers, in which a bundle of upright or bent U-shaped or helical tubes is fixed on pierced plates and disposed inside a chamber called calender. In these tube and shell exchangers, one of the fluids circulates inside the tubes while the other fluid circulates inside the shell. These tube and shell exchangers have a large volume and are therefore of low compactness.

The known plate heat exchangers are more compact and are obtained by stacking plates comprising channels and assembled together.

The channels are made by stamping plates, if necessary by adding strips folded in the form of fins or by machining grooves. The machining is carried out by mechanical means, for example by milling or by chemical means. Chemical machining is usually called chemical or electrochemical etching.

The assembly of the plates together is intended to ensure the sealing and / or the mechanical strength of the exchangers, in particular the resistance to pressure of the fluids circulating inside. The assembly generally relates to a stack made by superimposing, in a regularly repeated sequence, plates of several types, each type corresponding to one of the fluid circuits, the stack may contain non-grooved separation plates.

Several assembly techniques are known and are implemented depending on the type of plate heat exchanger desired. The assembly can thus be obtained by mechanical means, such as tie rods holding the stack tight between two thick plates and rigid disposed at the ends. The sealing of the channels is then obtained by crushing reported joints. The assembly can also be obtained by welding, generally limited to the periphery of the plates, which sometimes requires to insert, after welding, the heat exchanger in a calender to allow it to withstand the pressure of the fluids. The assembly can still be obtained by brazing, in particular for exchangers for which fins are added. The assembly can finally be obtained by diffusion welding (welding-diffusion).

The last two techniques mentioned make it possible to produce exchangers that are particularly efficient in terms of mechanical strength. Indeed, thanks to these two techniques, the assembly is obtained not only at the periphery of the plates but also inside the exchanger.

Plate heat exchangers assembled by diffusion welding have joints that are even more mechanically efficient than the joints of the brazed exchangers due to the absence of the solder required for brazing.

Welding-diffusion consists of obtaining a solid state assembly by applying a hot force to the parts to be assembled during a given time.

The diffusion-welding assembly of the plates can be implemented by uni-axial hot pressing, a process which consists in simultaneously applying a high temperature and a loading that is essentially perpendicular to the plates to be assembled for a sufficient time to ensure the welding of the plates. between them. This operation is usually done under vacuum so as not to trap gas in the interfaces.

Welding-diffusion can also be implemented by Hot Isostatic Compaction (CIC). This technique consists in arranging the parts in a sealed envelope, called a container, evacuating and then subjecting this envelope to a high neutral gas pressure, generally from 500 bar to 1500 bar, at a high temperature, typically from 500 to 1200.degree. materials. The envelope transmitting the pressure to the parts while remaining sealed, we obtain the diffusion welding thereof. In the case of plate heat exchangers, the pressure must be reduced to maintain the deformation at an acceptable level, typically 30 to 300 bar.

In uni-axial or CIC welding-diffusion, a problem encountered during the welding of compact plate heat exchangers is to successfully weld the interfaces without excessively deforming the channels.

Indeed, the low level of pressure required to prevent the deformation of the channels does not generally allow to obtain resistant interfaces because it does not allow the complete removal of pores.

In addition, the transmission of the welding force in a stack of grooved plates is uneven, whether it is the uni-axial welding-diffusion process or the welding-diffusion process by CIC.

In non-grooved areas, usually around the plates, the welding force is well transmitted. In the grooved area or zones, generally in the center of the plates, the welding force is transmitted from one plate to the other by the ribs, also called isthmus, which separate the adjacent channels.

According to its lateral offset with respect to the isthmus of the other stages of the stack, a given isthmus can undergo a very important constraint, hence a strong deformation of the channels in its vicinity, or conversely a very low stress, of where a bad welding.

The quality of the interfaces and the deformation of the channels can therefore vary from one place to another of the stack, according to the shielding of the welding force by the channels.

The uni-axial diffusion-welding assembly of the plates is described in numerous documents. However, the mechanical strength and tightness of the assembly obtained are difficult to guarantee because, to prevent excessive deformation of the channels, it is necessary to choose a sufficiently low welding force.

To obtain joints of sufficient quality, that is to say with the absence of pores, despite this low force, it is possible to increase the welding temperature, but this results in an undesirable increase in the grain size of the material, which weakens it.

An alternative is to coat the surfaces to be welded with a ductile metal such as nickel, but here again the interfaces are weakened compared to a homogeneous diffusion welding such as would be obtained with a high welding force (without any metal). supply and without residual porosity), or with respect to the base material chosen for the application.

Finally, a proposed solution as described in patent US7900811B1 is to apply to a stack previously assembled by uni-axial diffusion welding a CIC high pressure cycle, open channels not to deform them, to complete the assembly, being understood that, it has been made under conditions to prevent the deformation of the channels, the resulting interfaces are imperfectly welded. However, while it is obvious to one skilled in the art that the application of a CIC treatment makes it possible to eliminate the isolated pores present at the interfaces, the porosity that opens into the channels is not necessarily eliminated. This solution is not universal, it is effective only if a certain quality of welding has been obtained during uni-axial diffusion welding. In welding-diffusion by CIC, as for uni-axial diffusion welding, a problem encountered during the welding of compact plate heat exchangers is that the low pressure used does not generally make it possible to obtain resistant interfaces.

The implementation in diffusion welding by CIC of the solutions relating to uni-axial diffusion welding mentioned above has the same drawbacks.

In addition, the industrial enclosures allowing the implementation of CIC are generally poorly suited to operating under low pressure. Thus, in practice there is a minimum operating pressure of these industrial enclosures which, to the inventors' knowledge, is a few tens of bar.

This minimum pressure is often too high and leads to an unacceptable distortion of the channels, especially in the case of exchangers with a high density of channels. One solution would be to reduce the density of channels but this amounts to reducing the compactness of the exchanger. Another solution would be to reduce the welding temperature to improve the strength of the material, but this results in a decrease in the quality of the welding.

However, several other solutions listed below exist for soldering by diffusion by CIC components with cooling channels avoiding excessive deformation.

A first solution, described in the patent FR2989158B1, is to use tubes to form the channels and sealingly seal at least one end of each tube to the envelope. In this way, the pressure gas for the CIC enters the channels but not the interfaces to be welded. The application of high welding pressures without significant deformation of the channels is possible. This solution can however be cumbersome to implement when the channels are very numerous. In addition, it is not possible when the channels are of complex geometry, because these shapes can not be shaped by tubes, even bent.

A second solution, described in the patent FR2879489B1, consists of reconstructing open channels at their end (s) only, by welding by TIG or laser blades at the top of grooves made in plates so, as previously to that the CIC gas enters the channels but not the interfaces to be soldered. The application of high welding pressures without significant deformation of the channels is again possible. This solution is also cumbersome to implement and expensive when the channels are very numerous. In addition, it is not possible when the channels are very small.

A third solution, described in the patent FR2949699B1 is to have, around grooves made in plates, a low support surface insert and apply a low pressure CIC cycle on a stack of such plates. The pressure being low, the deformation of the grooves is weak and the diffusion welding very imperfect. On the other hand, a strong plasticization of the insert is obtained because of its low bearing surface, which makes it possible to seal the grooves. In a second step, a machining operation is then performed to open the grooves (channels) and then a high-pressure CIC cycle is applied to complete the diffusion bonding of the stack, in particular the surfaces between the grooves. Here too, this solution is cumbersome to implement and expensive when the channels are very numerous, and it is not adapted to very small channels.

None of these three solutions is well suited to the case of a large number of plates and a large number of channels.

Another solution, described in the patent FR 3005499 B1, consists in assembling, by diffusion welding, firstly elements comprising the channels of the first type of fluid and then, in a second step, assembling them with elements comprising the channels of the second type. of fluid. This solution has advantages of several orders, including the possibility of simultaneously obtaining good interface quality and low deformation, but it remains quite heavy to implement and expensive because the assembly is performed in several times.

In summary, all these solutions are cumbersome to implement, expensive and not always well suited to the case of a large number of plates and a large number of channels.

There is therefore a need to further improve the processes for producing heat exchangers by diffusion welding to obtain compact heat exchangers, with channels of complex geometry and / or small dimensions and / or with a large number of plates and / or with a large number of channels, to improve the mechanical strength of their joints without causing excessive deformation of the channels, or unacceptable structure material grain magnification, to be able to control any point of the exchangers the quality of the joints, for example by non-destructive testing, and to have acceptable manufacturing costs and ease of implementation.

The object of the invention is to at least partially meet this (these) need (s).

Presentation of the invention

To do this, the subject of the invention is a method for producing a heat exchanger module with at least two fluid circuits each comprising channels, comprising the following steps:

a / realization of one or more elements of one of the two fluid circuits, said first circuit, each element of the first circuit comprising at least one metal frame closed on itself by being pierced with a central light and integrating or supporting blades projecting from at least one of the main faces of the frame and extending over at least the length or width of the central lumen;

b / production of one or more elements of at least one other fluid circuit, said second circuit, each element of the second circuit comprising at least one metal frame closed on itself with a central lumen and incorporating or supporting blades projecting from at least one of the main faces of the frame and extending over at least the length or width of the central lumen;

cl stack, with alternating metal frames incorporating or supporting the blades and solid separation plates, so as to form the channels or elements of the first and second circuit, the space between two adjacent channels being defined by the width of a blade;

d / assembly by welding-diffusion either by uni-axial compaction or hot isostatic pressing (CIC) between the element or elements of the first circuit and the element or elements of the second circuit, stacked on each other.

By "light" means here and in the context of the invention, a hole or opening opening on either side of the metal frame.

By "pierced with a light" is meant a frame comprising an opening opening on either side.

The invention therefore consists essentially of replacing the grooved plates used to form the fluid circuit elements by elements each consisting of a frame, blades supported and integrated into the frame, and a non-grooved plate whose role is to physically separate two adjacent frames in the stack. Thus, the spacing between the blades according to the invention defines all or part of the channels of fluid circuits that are formed by the grooves in a plate according to the state of the art. A solid partition plate according to the invention replaces the non-grooved portion of a plate according to the state of the art which is located under the grooves.

A frame has the same external dimensions, where appropriate to the thickness, a separating plate and one or more recessed areas in the center, separated by blades of the same thickness as its periphery or preferably slightly increased thickness. The periphery of the frame according to the invention therefore replaces the non-grooved periphery of a plate according to the state of the art and the blades separate different channels.

Compared to the state of the art, the manufacture of the elementary parts (frame, blades, solid separation plates) constituting the stack of a module according to the invention is simple and inexpensive, since it can be made only by cutting and not necessarily by machining as for grooved plates according to the state of the art. The implementation of diffusion welding is simplified and the welding is improved.

Thus, according to a first embodiment, a frame according to the invention can be obtained for example by laser cutting a sheet. Step a / and / or b / is then performed by placing the free ends of rods forming the blades in notches formed at the periphery of the central lumen of each frame.

Thus, according to this first variant, the rods are arranged inside the frame and replace the isthmus separating the grooves in the grooved plates according to the state of the art. The spaces between rods then constitute all or part of the fluid circulation channels.

Advantageously, the chopsticks can be of the welding rods type, which constitutes simple means to implement and cheap.

According to a second variant embodiment, the blades may be integral with the frame and form a single piece obtained for example by laser cutting and, where appropriate, light machining of the periphery on one or both sides, so as to leave the rods in relief relative to each other. to these. Thus, according to this second variant, step a / and / or b / is performed by machining a one-piece metal part producing the frame and the blades projecting from at least one of the main faces of the frame.

Preferably, the blades have a thickness greater than that of the frames of a value at most equal to 10%. typically up to 0.5mm. Advantageously, the section of the blades is such that, in the stack according to step c1, their contact with the solid separation plates is substantially linear or in plane-plane support limited to their main faces. Typically, the blades or rods have a cylindrical shape. But in general, their section can be any, especially rectangular. The blades or rods may be in the form of son, elements cut in sheets or other.

Preferably, the section of the rods is such that, in the stack before welding, their contact with the separator plates is substantially linear in nature, which can be obtained for example with rods of round section. Thus, the initial contact surface is very small, and the welding stress all the higher.

In other words, a stack of grooved plates according to the state of the art is therefore replaced according to the invention by alternately repeated stacking of a frame supporting or incorporating blades defining the first fluid circuit / a solid separation plate. a frame supporting or integrating blades defining the second fluid circuit / a solid separating plate, etc. As in the case of grooved plate stacks according to the state of the art, it is possible to have thick monolithic plates or series of several thin non-grooved plates at one and / or the other end of above or below the stack and / or within the stack. These end plates are anvils and are optionally made of a different material than frames / blades and separator plates.

Due to an extra thickness of the blades in the stack the lower faces of the solid separation plates are essentially in contact with the top of the blades and their upper faces are in contact with the base of the blades. The frame is in contact with at most one of the two faces of the separating plates. Therefore, the continuity of the material through the stack in the stacking direction is provided by the blades. During step d1 of welding-diffusion of this stack, the pressure will generate a preferential welding force at the blade interfaces / separator plates rather than at the interfaces only between the frames. Nevertheless, during welding, the progressive deformation of the blades and the slight possible ripple of the separating plates will allow the frames to come into contact with the separating plates to also lead to their welding. The constituent metallic material of each element of the first and second fluid circuits, as well as welded-on fluid collectors, is chosen according to the conditions of the use required for the exchanger module, namely the fluid pressure, the temperatures and nature of fluids flowing through the module. It may be for example aluminum, copper, nickel, titanium or alloys of these elements as well as a steel, especially an alloy steel or a stainless steel or a refractory metal selected from alloys of niobium, molybdenum, tantalum or tungsten.

For example, the frames and separating plates are advantageously made of stainless steel sheet type 1.4404, cold rolled and the rods are ER316L type stainless steel welding rods.

The fluid circulation channels have a width and a height that depend in particular on the nature and characteristics of the fluids conveyed and the desired heat exchange. The widths and heights may vary in particular along the path of the channels. In general, the compact heat exchanger modules according to the invention comprise channels whose dimensions vary from 0.1 mm to 10 mm, preferably from 1 to 5 mm. To do this, the thickness of a frame with its blades of an element of the first circuit implemented in steps a / d according to the invention may vary from 0.1 to 15 mm, preferably from 1 to 10mm. Finally, the pathways of the channels in their length may be straight or not, and may form elbows or patterns for example in chevrons.

For the step of stacking the frames and solid separation plates, it is possible to use centering pins or wedge the frames and plates on their edges and to secure them for example by welding.

Preferably, prior to stacking, that is to say before step c1, a step al / and b1 / cleaning the frames and solid separation plates of each element respectively of the first circuit and the second circuit is carried out. . The cleaning can be carried out for example using detergents or solvents.

According to an advantageous embodiment, step d is carried out by applying a relatively low pressure hot isostatic compression (CIC) cycle to the sealed and degassed stack. This CIC cycle is designated at relatively low pressure, because the pressures are lower than those of a CIC cycle designated high pressure, ie between 500 and 2000 bar, preferably between 800 and 1200 bar.

According to this mode, the d / CIC step is first carried out, an insertion of the stack into a metal envelope, called a container, and then a step of evacuating the inside of the container by a tube, known as a tube. welded on one side of the container, and finally a step of welding the tube on itself. Degassing of the channels and interfaces is thus achieved by evacuation, through the tube opening the container and it is closed. To carry out the degassing, this tube is connected to a vacuum pump, the pumping is performed at a given temperature, between room temperature and 400 ° C, then the tube is sealed by welding, without re-airing.

The typical DUC cycle typically involves simultaneous heating and pressurization, a temperature and pressure plateau followed by cooling and depressurization. This cycle is chosen in particular as a function of the material (s) of the frames, blades and solid separation plates constituting the elements of the first and second circuits. In particular, it is possible to choose the bearing temperature and the heating and pressurization (respectively cooling and depressurization) speeds, in particular taking into account the capacities of the CIC enclosure used.

Thus, preferably, the CIC cycle according to step d / is carried out according to the following characteristics taken alone or in combination:

at a pressure of between 20 and 500 bar, preferably between 30 and

300 bar; the choice of the pressure results from a compromise between quality of welding to obtain and acceptable deformation of the channels;

at a temperature of between 500 and 1200 ° C., preferably between 900 and 1100 ° C .; the temperature that is retained depends on the constituent material of the plates used and the maximum allowable grain size;

for a period of between 15 minutes and a few hours, preferably between 1 and 4 hours; the heating and pressurization times (respectively cooling and depressurization) depend on the characteristics and possibilities of the equipment (enclosure) used, they are usually several hours.

After step d /, a step e / opening the channels of the first circuit and the second circuit to the outside is advantageously carried out. The opening of the canals the first circuit, such as the subsequent channels of the second circuit, can be made by drilling or cutting the end of the plates that close them.

According to an advantageous embodiment, after this step e /, a step f / of applying a high-pressure hot isostatic compression (CIC) cycle to the already assembled stack is carried out, the channels of both the first circuit and the second circuit being open to the outside. The application of CIC high-pressure cycle with open channels allows a good transmission of the welding force to the interfaces and perfect assembly.

The CIC cycle according to step f / is preferably carried out at a pressure of between 500 and 2000 bar, preferably between 800 and 1200 bar. The CIC cycle according to step f / is advantageously carried out at a pressure of between 500 and 2000 bar, preferably between 800 and 1200 bar.

During a step g / later, the block obtained can then be advantageously machined to bring different elements, in particular fluid collectors, joints, screws, etc.

Advantageously, during this step g /, provision may be made for the welding of fluid collectors on the assembled module according to step e / or f /, a fluid collector being able to dispense or recover a fluid circulating in the first or the second circuit.

The invention also relates to a heat exchanger module with at least two fluid circuits obtained according to the method as described above.

The invention finally relates to a heat exchanger system comprising a plurality of modules as above, interconnected.

The invention finally relates to the use of an exchanger module as above or the above system:

as part of a heat exchanger of a nuclear reactor, such as a liquid metal cooled reactor (SFR) or

as part of the exchanger-reactor of a chemical reaction, such as methanation. detailed description

Other advantages and characteristics of the invention will emerge more clearly from a reading of the detailed description of exemplary embodiments of the invention, given for illustrative and nonlimiting purposes, with reference to the following figures among which:

FIG. 1 is a front view of a metal frame supporting rods of an element of a first fluid circuit C1 from which an example of the method for producing a two-circuit heat exchanger module fluid according to the invention is implemented;

- Figure 2 is a front view of a metal frame supporting rods of an element of a second fluid circuit C2 from which the first embodiment of the embodiment of the invention is implemented;

FIG. 3 is a schematic top view in transparency of a part of a stack showing the relative geometry and arrangement between the grooves of the first and second circuits according to the invention, made by alternately superposing at 90.degree. ° each other different frames with chopsticks.

The terms "longitudinal" and "lateral" are to be considered in relation to the geometrical shape of the metal frames 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 the exchanger module according to the invention are those which extend parallel to the longitudinal axis X of the plates, that is to say along their length L. two lateral sides of the stack are those which extend along the lateral axis Y of the plates, orthogonal to the axis X, that is to say according to their width 1.

The terms "above" and "below" are to be considered with respect to the direction of the stack of the exchanger module. Thus, the top plate, which forms all or part of an anvil, is the last plate that is stacked on others.

In the example illustrated according to the invention, a cross-current type heat exchanger is produced by diffusion welding in CIC.

Step a /: In order to produce an element of a first fluid circuit C1, separation plates, not shown, and parts 1 each consisting of a frame 10 of rectangular shape supporting rods 11 are provided. separation and frames 10 are obtained by laser beam cutting from a cold rolled steel sheet. Each rectangular frame 10 has a central recessed portion 100 and whose short sides each comprise a series of housings or notches 101 regularly spaced and intended to accommodate each a free end of a rod 11.

Once in place in the frame 10, that is to say, supported by the latter, the rods 11 form the ribs or isthms separated by the circulation channels of the first fluid Cl.

By way of example, each partition plate is made of 1.4404 stainless steel, the external dimensions of a plate are equal to 2x250x300mm.

Each frame 10 is also made of stainless steel 1.4404, the outer dimensions of a frame 10 are equal to 3x200x250mm. The recessed portion or central lumen 100 has outside dimensions equal to 151x200mm.

The number of housings or slots 101 regularly spaced on each small side of the central lumen 100 is 21. Each notch 101 has a width of 3.4mm and a depth of 3mm. Two adjacent notches are separated by 4mm.

The rods 11 are ER316L stainless steel welding rods. The number of rods is equal to 21. The rods 11 are of straight cylindrical section, of diameter 3,2mm and length equal to 205mm.

With the above data, the flow channels of the first fluid Cl formed by the spaces between rods 11, have a width of 4mm, a height of 3mm and a length of 200mm. The number of channels formed for the first fluid circuit is 22.

Step b /: In order to produce an element of a second fluid circuit C2, separation plates, not shown, and parts 2 each consisting of a rectangular frame 20 supporting rods 21 are provided. separation and frames 20 are obtained according to the same method as for those of the fluid circuit C2, ie by laser beam cutting from a cold-rolled steel sheet.

Thus, each rectangular frame 20 comprises a central recessed portion 200 and whose long sides each comprise a series of housings or notches 201 regularly spaced apart and intended to accommodate each a free end of a rod 21. Once in place in the frame 20, that is to say supported by the latter, the rods 21 form the ribs or isthms separated by the circulation channels of the first fluid C2.

For example, each frame 20 is also made of stainless steel 1.4404, the outer dimensions of a frame 10 are equal to 3x166x172mm. The recessed portion or central lumen 200 has outside dimensions equal to 151x200mm.

The number of slots or notches 201 regularly spaced on each side of the central light 200 is equal to 24. Each notch 201 has a width of 3.4mm and a depth of 3mm. Two adjacent notches are separated by 4mm.

The rods 21 are ER316L stainless steel welding rods. The number of rods here is equal to 24. The rods 21 are of straight cylindrical section, of diameter 3,2mm and length equal to 171mm.

With the above data, the flow channels of the first fluid C2 formed by the spaces between rods 21, have a width of 4mm, a height of 3mm and a length of 166mm. The number of channels formed for the second fluid circuit is 25.

Steps al / and bl /: cleaning is carried out using solvents and / or detergents separation plates and frames 10, 20. For this, all parts are degreased, rinsed, dried.

Step c1: After cleaning, alternately stacking a separating plate, a frame 10 supporting its rods 11, a separating plate, a frame 20 supporting rods 21 which are arranged perpendicular to the rods 11 of the frame 10, a plate of separation...

In this way, we reconstitute both the channel elements of the first circuit

C1, and the channel elements of the second circuit C2 cross currents with those of the circuit C1.

In the example with the figures above, a 0.2mm gap is present between the separator plates and the frames.

During stacking, all the separating plates and frames 10, 20 are aligned relative to one another by means of not shown centering pins, inserted into blind holes. In the example, the stack is ultimately constituted by a number of ten fluid circuit stages C1 and ten stages of the fluid circuit C2, supplemented by a number of four solid plates identical to the separation plates and which are set up at the beginning and end of the stack.

Step d /: The periphery of the complete stack (block) is sealed and each interface is degassed by an opening opening which is obstructed. To achieve sealing at the periphery of the stack, it is possible to complete the stack in a container.

The container, made of stainless steel sheet folded and welded by TIG process, is itself cleaned (for example degreased with acetone) as well as its cover in stainless steel sheet type 1.4307. The lid is welded TIG on the container and the container is evacuated by pumping, for example for a period of 12 hours through a welded tube on one of its sides, for example 8mm diameter. The tube is then pinched, cut and itself welded to prevent an introduction of air into the container.

The container is then subjected to a hot isostatic compression cycle

(CIC), at low pressure, comprising heating from 900 to 1100 ° C for a period of 1 to 4 hours under a pressure of 30 to 300 bar, then cooling in several hours and depressurization.

The container nip, measured at half width, is less than 3mm, or 3% of the thickness of the complete stack.

During this CIC cycle, the channels of the first fluid circuit and the channels of the second circuit are filled by the pressurized gas of the enclosure using the CIC cycle, which allows a good transmission of the welding force to the interfaces. between plates 1.

In the stack according to the invention, the linear contacts between rods 11,

21 and separation plates form a square mesh network and only the crossing points are the seat of a direct transmission of the welding force.

Step e /: At the end of the diffusion welding, the container is machined and the channels are uncorked by milling windows located opposite the ends of channels. These windows 3 are four in the example, as shown in Figure 3 in dashed lines. Step f /: a high pressure isostatic compression (CIC) cycle is then applied to the already assembled stack, the channels of both the first circuit and the second circuit being open to the outside.

Step g /: Unrepresented fluid distribution manifolds are then reported by welding, opposite the windows 3, so as to supply and / or recover a fluid in each of the first C1 and second C2 circuits at the ends of the grooves forming canals.

The size of the channels for each of the fluid circuits may be different depending on the nature and properties of the fluids to be conveyed, the allowable pressure drops and the desired flow rate. To vary the width of the channels, the spacing between adjacent rods is changed.

Several elements of the same circuit C1 or C2 can be stacked before alternating with an element of the other circuit, in order to optimize a functionality of the exchanger, for example heat exchange or flow rate. one of the fluids.

If the only illustrated example concerns exchangers with exactly two fluid circuits, it is quite possible to manufacture an exchanger with three or more fluid circuits.

The two fluid collectors can be arranged on either side of the stack constituting the module, or alternatively on the same side of the stack.

The heat exchanger modules obtained according to the method of the invention can be assembled to each other, for example by using flanges or by welding the fluid supply pipes. It is thus possible to envisage making a heat exchanger system with several interconnected modules in which the exchanges are made in several stages with different average temperatures or sufficiently small temperature variations per module in order to reduce the thermal stresses in the materials. For example, in the case of a heat exchanger in which it is desired to transfer heat from a first fluid to a second fluid, it is possible to design a modular heat exchanger system in which each module makes it possible to reduce the temperature of the first fluid. a given value, thus limiting the constraints with respect to the case of a single-module design with a higher temperature difference. For this, the inlet temperature of the second fluid may differ from one module to another. In another For example, a modular reactor-heat exchanger system enables a complex chemical reaction to be carried out in stages by precisely controlling the reaction temperature at each stage, for optimum control of the chemical reaction, minimization of risks and maximization of yields.

A multi-module heat exchanger system also reduces maintenance costs by allowing the individual replacement of a faulty module, or even the manufacturing costs by standardization of the modules.

Claims

A method of producing a heat exchanger module with at least two fluid circuits each comprising channels, comprising the following steps:

a / realization of one or more elements (1) of one of the two fluid circuits, said first circuit, each element of the first circuit comprising at least one metal frame (10) closed on itself and pierced with a central lumen (100) and incorporating or supporting blades (11) projecting from at least one of the main faces (12, 13) of the frame and extending over at least the length or width of the central lumen;

b / producing one or more elements (2) of at least one other fluid circuit, said second circuit, each element of the second circuit comprising at least one metal frame (20) closed on itself and pierced with a central lumen (200) incorporating or supporting blades (21) projecting from at least one of the main faces (22, 23) of the frame and extending over at least the length or width of the central lumen;

c / stacking, with alternating metal frames (10, 20) integrating or supporting the blades (11, 21) and solid separation plates, so as to form the channels or elements of the first and second circuits, the space between two adjacent channels being defined by the width of a blade (11, 21);

2. Method according to claim 1, wherein step a / and / or b / is carried out by placing the free ends of rods forming the blades into notches (101, 201) formed at the periphery of the light. each frame (10, 20).

3. Method according to claim 2, the rods being of welding rods type.

4. The method of claim 1, wherein step a / and / or b / is performed by machining a one-piece metal part making the frame and the blades protruding from at least one of the main faces of the frame.

5. Method according to any one of the preceding claims, wherein the blades have a thickness greater than that of the frames of a value at most equal to 10%.

6. Method according to any one of the preceding claims, wherein the section of the blades is such that, in the stack according to step c /, their contact with the solid separation plates is linear or in a plane-plane support limited to their main faces.

7. Method according to any one of the preceding claims, according to which, before step c / of stacking, a step al / and bl / cleaning of the frames and solid separation plates of each element respectively of the first circuit and second circuit.

8. A method according to any one of the preceding claims, wherein, wherein step d is performed by applying a relatively low pressure hot isostatic compression (CIC) cycle to the sealed and degassed stack.

9. The method of claim 8, wherein is carried out prior to step d / CIC, an insertion of the stack in a metal shell, said container, and a step of evacuating the interior of the container. by a tube, said queusot, welded to one side of the container, and finally a step of welding the tube on itself.

10. Process according to any one of claims 8 or 9, the CIC cycle according to step d / being carried out at a pressure between 20 and 500 bar, preferably between 30 and 300 bar.

11. A method according to any one of claims 8 to 10, the CIC cycle according to step d / being carried out at a temperature between 500 and 1200 ° C, preferably between 900 and 1100 ° C.

12. Method according to any one of the preceding claims, step d / being carried out for a period of between 15 min and a few hours, preferably between 1 and 4h.

13. Method according to any one of the preceding claims, according to which after step d /, a step e / is made to open the channels of the first circuit and the second circuit to the outside.

14. The method of claim 13, wherein after step e /, a f / application of a high pressure isostatic compression (CIC) cycle to the already assembled stack, the channels are carried out. both of the first circuit and the second circuit being open to the outside.

15. The method of claim 14, the CIC cycle according to step f / being carried out at a pressure between 500 and 2000 bar, preferably between 800 and 1200 bar.

16. Method according to any one of the preceding claims, comprising during a step g / later, the welding of fluid collectors on the module assembled according to step e / or f /, a fluid collector being able to distribute or recover a fluid flowing in the first or the second circuit.

17. Heat exchanger module with at least two fluid circuits obtained according to the method according to any one of the preceding claims.

18. Heat exchanger system comprising a plurality of modules according to claim 17 interconnected.

19. Use of an exchanger module according to claim 17 or the system according to claim 18 as part of heat exchanger of a nuclear reactor, such as a liquid-cooled reactor (SFR).

20. Use of an exchanger module according to claim 17 or the system according to claim 18 as part of exchanger-reactor of a chemical reaction, such as a methanation.