Method for producing a heat exchanger module having at least two fluid flow circuits

Abstract

A method for producing heat exchangers having at least two fluid circuits each having channels, including the following steps: producing one or a plurality of elements of a first fluid circuit, each element having at least two metal plates, at least one of which has first grooves; stacking the at least two metal plates of each element in such a way that the first grooves form the channels of the first circuit; assembling each element of the first circuit by diffusion welding between the two stacked metal plates; producing one or a plurality of elements of at least one second fluid circuit, each element of the second circuit having at least a portion of the channels of the second circuit; assembling, either by diffusion welding, or by brazing, or by diffusion brazing between the element or elements of the first circuit and the element or elements of the second circuit.

Claims

1. A method for producing a heat exchanger module having at least two fluid circuits which each comprise channels, comprising the following steps: a/ producing one or more elements of one of the two fluid circuits, referred to as the first circuit, each element of the first circuit comprising at least two metal plates, at least one comprises first grooves and at least one being a flat plate or the at least two metal plates comprise first grooves; b/ stacking the at least two metal plates of each element so that the first grooves of one of the plates and the at least one flat plate or the grooves of the at least two metal plates define outer peripheral surfaces of the channels of the first circuit; c/ assembling by means of diffusion welding between the at least two stacked metal plates of each element of the first circuit; d/ producing one or more elements of at least one other fluid circuit, referred to as the second circuit, each element of the second circuit comprising at least a portion of the channels of the second circuit; e/ assembling by means of diffusion welding or by means of soldering, or by means of diffusion soldering, between the element(s) of the first circuit and the element(s) of the second circuit.

2. The method as claimed in claim 1, according to which, after step c/, a step c2/ of opening the channels of the first circuit toward the outer side is carried out.

3. The method as claimed in claim 2, according to which, after step c2/, a step c3/ of application of a hot isostatic pressing cycle (HIP) at a pressure of between 500 and 2000 bar to each stack which has already been assembled is carried out.

4. The method as claimed in claim 3, according to which, before and/or after step c3/, a step c4/ of non-destructive control of the channels of the first circuit is carried out.

5. The method as claimed in claim 1, according to which after step b/, a step b1/ of sealing the periphery of the at least two metal plates of each element is carried out, then a step b2/ of degasification of the inner side of each sealed stack is carried out through an opening hole at each interface between plates, a step b3/ of closing the opening hole is carried out, and finally step c/ is carried out by application of a hot isostatic pressing cycle (HIP) at relatively low pressure to each stack which is sealed and degasified.

6. The method as claimed in claim 5, according to which step b1/ is carried out by welding the periphery of each stack.

7. The method as claimed in claim 5, according to which step b1/ is carried out by means of insertion of each stack into a metal casing, referred to as a container, then a step of welding the container, the opening hole also opening in a tube, referred to as a pumping port, which is welded to a face of the container, step b2/ being carried out via the pumping port and step b3/ being carried out by welding the pumping port.

8. The method as claimed in claim 5, the HIP cycle according to step c/ being carried out at a pressure of between 20 and 500 bar.

9. The method as claimed in claim 5, the HIP cycle according to step c/ being carried out at a temperature of between 500 and 1200 C.

10. The method as claimed in claim 1, according to which, after step c/, a step c1/ is carried out of reduction of thickness, of at least one assembled metal plate.

11. The method as claimed in claim 10, according to which, after step c1/, a step c2/ of opening the channels of the first circuit toward the outer side is carried out.

12. The method as claimed in claim 10, according to which, after step c1/, a step c4/ of non-destructive control of the channels of the first circuit is carried out.

13. The method as claimed in claim 1, according to which step d/ is carried out, for each element of the second circuit, via a step d1/ of stacking at least two metal plates, at least one of which comprises second grooves which form a portion of the channels of the second circuit, then a step d2/ of assembly by means of diffusion welding between the at least two stacked metal plates of each element of the second circuit.

14. The method as claimed in claim 13, according to which the second grooves are produced by grooving at least one main face or the two main faces of each element of the first circuit opposite those which form the channels of the first circuit.

15. The method as claimed in claim 13, according to which the second grooves are produced by grooving main faces of metal plates which are separate from the elements of the first circuit.

16. The method as claimed in claim 1, step c/ being carried out by means of uniaxial compression.

17. The method as claimed in claim 16, step c/ being carried out with a compression force of between 1 and 500 kg/cm.sup.2.

18. The method as claimed in claim 1, according to which before step b/, a step a1/ of cleaning the plates of each element of the first circuit is carried out.

19. The method as claimed in claim 1, step c/ being carried out for a duration of between 15 minutes and 2 hours.

20. The method as claimed in claim 1, according to which, after step c/, a step c4/ of non-destructive control of the channels of the first circuit is carried out.

21. The method as claimed in claim 1, according to which step d/ is carried out, for each element of the second circuit, via a step d1/ of inserting tubes which are arranged parallel with each other and which form a portion of the channels of the second circuit.

22. The method as claimed in claim 1, according to which step e/ is carried out by means of application of a hot isostatic pressing (HIP) cycle at a pressure of between 500 and 2000 bar, between the element(s) of the first circuit and the element(s) of the second circuit, the channels of both the first circuit and the second circuit being open toward the outer side.

23. The method as claimed in claim 1, according to which, between step d/ and e/, the channels of the first circuit being open toward the outer side and those of the second circuit formed, step d2/ is carried out by application of a hot isostatic pressing cycle (HIP) at a pressure of between 20 and 500 bar, between the element(s) of the first circuit and the element(s) of the second circuit.

24. The method as claimed in claim 1, comprising a step f/of welding fluid collectors to the assembled module according to step e/, a fluid collector being capable of distributing or recovering a fluid which flows in the first or the second circuit.

25. A heat exchange module having at least two fluid circuits obtained in accordance with the method as claimed in claim 1, wherein one of the fluid circuits, referred to as the first circuit comprises outer peripheral surfaces of channels defined by first grooves of at least one plate and at least one flat plate stacked or by first grooves of at least two metal plates stacked.

26. A heat exchanger system comprising a plurality of modules as claimed in claim 25, which are connected to each other.

27. An exchanger module as claimed in claim 25 as part of a heat exchanger of a nuclear reactor.

Description

DETAILED DESCRIPTION

(1) Other advantages and features of the invention will be better appreciated from a reading of the detailed description of embodiments of the invention given by way of non-limiting illustration with reference to the following Figures, in which:

(2) FIG. 1 is a front view of a metal plate of an element of a first fluid circuit C1 from which a first example of the production method of a heat exchanger module having two fluid circuits according to the invention is implemented;

(3) FIG. 1A is a sectioned view along A-A of the plate according to FIG. 1;

(4) FIG. 1B is a detailed view along B of the plate according to FIG. 1;

(5) FIG. 2 is a perspective cross-section of an element of the first fluid circuit produced from two metal plates according to FIG. 1;

(6) FIG. 2A is a cross-section of the element of the first fluid circuit according to FIG. 2;

(7) FIG. 3 is a perspective view of an element of the first fluid circuit according to FIG. 2 which has been grooved on the main faces thereof in order to form the channels of the second fluid circuit C2 of the heat exchange module according to the invention;

(8) FIG. 3A is a perspective cross-section of an element of FIG. 3 showing both the channels of the first fluid circuit C1 and the grooves in order to form the channels of the second fluid circuit C2;

(9) FIG. 4 is a perspective view of a stack of eleven elements according to FIG. 3 and two additional plates at one side and the other of these eleven elements in order to form the exchanger module according to the invention;

(10) FIG. 4A is a perspective cross-section of the stack according to FIG. 4 before it is subjected to an HIP cycle according to the invention;

(11) FIG. 5 is a perspective view of the stack of FIG. 4 after it has been subjected to a low-pressure HIP cycle and a high-pressure HIP cycle in accordance with the invention and after cutting the lateral edges thereof in order to open the channels of the second fluid circuit C2;

(12) FIG. 6 is a cross-sectional view of another embodiment of an element of the second fluid circuit, different from the production in accordance with the preceding Figures.

(13) The terms longitudinal and lateral are intended to be considered in relation to the geometric shape of the metal plates which determine the geometric shape of the stacks of the heat exchanger module according to the invention. In this manner, in the end the four longitudinal sides of the stack of the exchanger module according to the invention are those which extend parallel with the longitudinal axis X of the plates, that is to say, along their length L. The two lateral sides of the stack are those which extend along the lateral Y axis of the plates, orthogonally with respect to the X axis, that is to say, along their width 1 or 1.

(14) It is set out that, in FIGS. 3, 3A, 4, 4A and 5A, no interface has been illustrated between the plates which constitute the elements of the circuit 1 since at this stage they are welded. In the same manner, in FIG. 5, the interfaces of the circuit 2 have not been illustrated.

EXAMPLE 1

(15) Step a/: In order to produce an element 2 of a first fluid circuit C1, two mutually identical metal plates 1 are produced having rectangular shapes L*1 and a thickness H, grooves 10 having a depth H1, a width 11 and specific spacing e (FIGS. 1, 1A, 1B). The processing operations of the grooves of the two plates 1 are carried out in accordance with two patterns in a mirror image of each other: as illustrated in FIG. 1, these may advantageously be zig-zag patterns with bends of 90 and inclinations of 45 relative to the longitudinal axis X of the plates 1.

(16) By way of example, the plates 1 are of stainless steel 1.4404, the dimensions L*1*H of a plate 1 are equal to 602*150*4 mm, the dimensions H1*11 of the grooves are equal to 1*2 mm with tolerances which are equal to 0.02 mm and 0.05 mm, respectively, the radii of curvature of the grooves R0, R1, R2 are equal to 0.3 mm, 0.1 mm and 2.1 mm, respectively, the distance e between two consecutive grooves, that is, the width of an isthmus, is equal to 1 mm with a tolerance which is equal to 0.05 mm. The distance d1 between the end of the grooves 10 and a longitudinal edge of a plate 10 is equal to 11 mm.

(17) Step a1/: a cleaning of the plates 1 is carried out using solvents and detergents.

(18) Step b/: after having cleaned them, the two plates 1 are stacked in order to reconstitute an element 2 of the first circuit C1 comprising a series of channels 11 in a zig-zag arrangement having a height equal to 2*H1, that is, 2 mm in the example (FIGS. 2 and 2A). The two plates 1 are aligned relative to each other using centering pins which are not illustrated.

(19) Step b1/: the periphery of each element 2 which is constituted by the two metal plates 1 which are stacked one on the other forming channels is sealed by means of welding.

(20) Step b2/: the interface between the two plates of each sealed stack through an opening hole is degasified.

(21) Step b3/: the opening hole is closed.

(22) Step c/: a batch of eleven identical stacks 2 is subjected to a so-called low-pressure HIP cycle, comprising heating for 2 hours at 1020 C. at 100 bar, a maintenance level of one hour at 1020 C. at 100 bar then cooling for several hours and finally depressurization.

(23) Step c2/: The longitudinal sides of the eleven elements 2 of the first circuit are then processed so as to open toward the outer side the ends of the channels 11 which are formed by the grooves 10. The opening of the channels 11 is produced by means of cutting the ends of the element 2 which close them, that is to say, by cutting a longitudinal strip having a width which is substantially equal to the distance d1, over the entire length L of each element 2. The width 1 of each element 2 is thus equal to 12*d1, that is to say, 128 mm in the example above.

(24) There are thus obtained eleven elements 2 of the first fluid circuit which it is possible to readily control individually by means of ultrasound or radiography.

(25) Step c3/: after the opening step c2/, a so-called high-pressure hot isostatic pressing (HIP) cycle is applied to each of the stacks 2 which have already been assembled. This high-pressure HIP cycle involves heating for 3 hours at 1080 C. at 1000 bar for 3 hours.

(26) Eleven elements 2 of the first fluid circuit C1 are thus obtained which it is possible to readily control individually by means of ultrasound or radiography.

(27) A new control of each of the eleven elements 2 is preferably carried out by means of ultrasound.

(28) Step d/:

(29) Step d1/: The two main faces of each of these eleven elements 2 of the first circuit obtained and only one main face of two additional plates 4 are then grooved in order to reconstitute the channels of a second fluid circuit C2 therein. The second grooves 30 do not open at the outer side (FIG. 3). By way of example, each groove 30 has a width I2 equal to 5.75 mm, a depth (height) H2 equal to 1.75 mm, and is separated from a consecutive groove 30 by an isthmus (rib) having a width e2 equal to 1.75 mm. The distance d2 between the end of the grooves 30 and a lateral edge of an element 2 is equal to 11 mm.

(30) After having cleaned all the elements, they are stacked in order to obtain a superimposition of eleven elements 2 of the first fluid circuit C1 and twelve elements 3 of the second fluid circuit C2 whose channels 31 are formed by the second grooves 30 (FIG. 4). The elements are aligned using centering pins which are inserted into blind holes.

(31) Then, the periphery of the complete stack 5 is sealed and each interface is degasified via an opening hole which is blocked. In order to produce the sealing at the periphery of the stack, it is possible either to arrange the complete stack 5 in a container leaving openings opposite the channels 11 of the first circuit C1, or to weld the periphery of all the plates 1 which constitute the stack 5.

(32) Step d2/: The complete stack is subjected to a low-pressure HIP cycle involving heating for 2 hours at 1020 C. at 100 bar, a maintenance level of three hours at 1020 C. at 100 bar, then cooling for several hours and depressurization.

(33) During this second HIP cycle, the channels 11 of the first fluid circuit are filled by the pressurized gas of the chamber which implements the HIP cycle, which enables good transmission of the welding force to the interfaces of the plates 1 which form the channels 31 of the second fluid circuit C2.

(34) The channels 31 of the second fluid circuit C2 are then opened by processing the lateral sides of the module constituted by the complete stack 5. The opening of the channels 31 is carried out by cutting the ends of the stack 5 which block them, that is to say, by cutting a lateral strip at one side and the other of the stack over the entire width 1, the strip having a width which is substantially equal to the distance d2. The length L of the stack 5 is thus equal to L2*d2, that is, 580 mm in the example mentioned above.

(35) The channels 31 of the second circuit C2 are thus open over each of the lateral edges of the stack 5 whilst the channels 11 of the first circuit C1 are open over each of the longitudinal edges of the stack 5 (FIG. 5).

(36) Step e/: Following the processing, that is to say, once the channels 31 of the second fluid circuit are open toward the outer side of the stack, an HIP cycle at 1080 C. is applied to the module obtained in this manner at 1000 bar for 3 hours in order to eliminate the residual defects in the welded joints.

(37) Step f: Finally, fluid distribution collectors which are not illustrated are connected by means of welding in order to supply and/or recover a fluid in each of the first C1 and second C2 circuits in the region of the ends of the grooves which form the channels 11, 31.

(38) As a result of the method according to steps a/ to f/, a heat exchange module which is compact and assembled by means of diffusion welding using HIP is produced.

(39) Such a heat exchange module according to example 1/ may be considered to have fluid circulation channels of small dimensions and with complex geometries (in zig-zag form).

(40) By way of example, an exchanger module according to example 1/ may be a rectangular parallelepiped having two square faces. The dimensions of such a module may be equal to 580128104 mm.

EXAMPLE 2

(41) The same steps are carried out as for the example 1, with the difference that, in addition, the main faces of the eleven elements 2 of the first circuit C1 are processed until the wall thickness between the base of the grooves 10 and the exterior is equal to half the desired thickness between each of the two circuits C1, C2.

(42) A stack 5 is produced by interposing between the eleven elements 2 of the first fluid circuit C1 the twelve elements 30, 4 of the second fluid circuit which have been produced and processed in accordance with the same principle.

(43) Then, the periphery of the planar faces obtained in this manner is welded, they are degasified and a high-pressure HIP cycle is applied at 1080 C. at 1000 bar for 3 hours.

EXAMPLE 3

(44) The same steps are carried out as for example 1, with the difference that, in addition, the main faces of the eleven elements 2 of the first circuit C1 are processed until the wall thickness between the base of the grooves 10 and the outer side is equal to half of the desired thickness between each of the two circuits.

(45) There are ten elements of the second fluid circuit C2 in this instance which are each constituted by a sheet 6 which is itself constituted by square rectified tubes 60 which are arranged parallel with each other and two bars 7 of the same thickness as the tubes, which are added parallel with the tubes at each side of the sheet 6 (FIG. 6). The outer dimensions of a sheet 6, that is, the width and the length, are equal to those of a grooved plate 1 which constitutes an element 2 of the first circuit C1.

(46) A stack is then produced by interposing between two consecutive elements 2 of the first circuit C1 a sheet 6 of rectified square tubes 60 which are butt-jointed to each other.

(47) The periphery of the interfaces obtained in this manner is welded, they are degasified, then an HIP cycle is applied at 1080 C., 1000 bar for 3 hours.

(48) Of course, the present invention is not limited to the described variants and embodiments provided by way of illustration and non-limiting example.

(49) The channels may also have a geometry other than a zig-zag pattern as illustrated in FIG. 1 whilst being elongate.

(50) The size of the channels for each of the fluid circuits may be different depending on the nature and the properties of the fluids to be conveyed, the permissible pressure drops and the output desired. It is possible to stack a plurality of elements of the same circuit in order to optimize a functionality of the exchanger, for example, the thermal exchange or the flow of one of the fluids.

(51) Though the examples illustrated 1/ to 3/ relate to exchangers having precisely two fluid circuits, it is quite possible to produce an exchanger having three fluid circuits or more.

(52) The two fluid collectors may be arranged at one side and the other of the stack which constitutes the module, or alternatively at the same side of the stack.

(53) The heat exchanger modules obtained in accordance with the method of the invention may be assembled one on the other, for example, by using flanges or by welding the fluid supply pipes. It is thus possible to envisage producing a heat exchange system which has a plurality of modules which are connected to each other and in which the exchanges are carried out in a plurality of steps with different mean temperatures or temperature deviations per module which are sufficiently small to reduce the thermal stresses in the materials. For example, in the case of a heat exchanger in which it is desirable to transfer the heat of a first fluid to a second, it is possible to configure a modular exchanger system in which each module enables the temperature of the first fluid to be reduced by a specific value, thus limiting the stresses relative to the case of a configuration with a single module which has a higher temperature deviation. To this end, the inlet temperature of the second fluid may differ from one module to another. In another example, a modular reactor/exchanger system enables a complex chemical reaction to be carried out in stages by controlling precisely the reaction temperature at each stage, for an optimum control of the chemical reaction, a minimization of the risks and a maximization of the output.

(54) A heat exchanger system having a plurality of modules also enables the maintenance costs to be reduced, by allowing the individual replacement of a defective module or the production costs by means of standardization of the modules.

REFERENCES MENTIONED

(55) [1] <<Fusion reactor first wall fabrication techniques by G. Le Marois, E. Rigal, P. Bucci, (Fusion Engineering and Design pp 61-62 (2002) 103-110 Elsevier Science B.V); [2] <<Assemblage par diffusion>>Techniques de l'ingnieur [BM 7747].