Heat exchanger module

Abstract

A heat exchanger module (100) comprising at least one first layer (10) for a first fluid and at least one second layer (20) for a second fluid wherein the first layer (10) and the second layer (20) are separated by a partition (30), the first layer (10) comprising a first wall (12) serpentine between opposite sides (31, 32) of the first layer (10) so as to define a first channel (14), the second layer (20) comprising a second wall (22) serpentine between opposite sides (31, 32) of the first layer (10) so as to define a second channel (14), and a second layer (20) serpentine between opposite sides (31, 32) of the second layer (20) so as to define a second channel (24), in which the pitch (p1) of the first wall is less than the pitch (p2) of the second wall, the thickness (e1) of the first wall is less than the thickness (e2) of the second wall, and the ratio of the pitch (p1) to the height (h1) of the first wall is less than the ratio of the pitch (p2) to the height (h2) of the second wall.

Description

Technical Field

[0001] The present disclosure relates to the technical field of heat exchangers, and more particularly to a heat exchanger module and a method for manufacturing the heat exchanger module. Background Art

[0002] The good efficiency of a heat exchanger is furthermore defined by the effective transfer area. The fluid flowing through the heat exchanger should be exposed to as much material as possible to effectively transfer its heat to the structure of the heat exchanger and ultimately to the other fluids.

[0003] However, this principle can be difficult to apply in practice because the properties of the fluids should be considered as well as other constraints imposed on the heat exchanger, such as its mechanical characteristics.

[0004] Therefore, a new type of heat exchanger module and manufacturing method is needed. Summary of the invention

[0005] In this regard, the present disclosure relates to a heat exchanger module comprising at least one first layer for a first fluid to flow therein between a first inlet and a first outlet, and at least one second layer for a second fluid to flow therein between a second inlet and a second outlet, wherein the at least one first layer and the at least one second layer are separated by a partition, the first layer comprises a first wall which meanders between opposite sides of the first layer so as to define a first channel extending between the first inlet and the first outlet, the second layer comprises a second wall which meanders between opposite sides of the second layer so as to define a second channel extending between the second inlet and the second outlet, wherein the pitch of the first wall is smaller than the pitch of the second wall, the thickness of the first wall is smaller than the thickness of the second wall, and the ratio of the pitch to the height of the first wall is smaller than the ratio of the pitch to the height of the second wall.

[0006] The heat exchanger module includes one or more first layers and one or more second layers. As used herein, for the sake of brevity and unless the context otherwise indicates, "a", "an", and "the" are intended to mean "at least one" or "each" and also include plural forms. In addition, an element (e.g., a layer, a wall, a channel, etc.) mentioned without "first" or "second" may refer to one or both of the first element and the second element.

[0007] Similarly, although one partition has been defined, the heat exchanger module may include multiple partitions each separating two consecutive layers of the heat exchanger module. Instead, each of the first and second layers may be defined between two partitions, possibly with the exception of the end layers. The facing surfaces of the two partitions may define opposite sides of the layer, with the first wall and the second wall respectively meandering therebetween.

[0008] In meandering, the wall may create multiple junctions between opposite sides of the layer that separate the layer into channels. That is, the wall may continuously and repeatedly travel from one opposite side of the layer to the other while advancing in another direction. The wall may meander in a plane transverse to the channel. The wall may meander in a periodic manner.

[0009] The pitch of the wall is defined as the distance between the point where the wall reaches one of the opposite sides of the layer and the corresponding point where the wall next reaches the same side of the layer. The pitch may be constant. If the wall meanders periodically, the pitch of the wall corresponds to the period of the wall.

[0010] The thickness of a wall is defined as the smallest dimension of the wall. The thickness is measured generally transversely to the wall. The thickness may be constant, or an average thickness may be considered.

[0011] The height of the wall is defined as the height of the meandering wall along its extension, ie the distance between two opposite sides of the layer. The height may be constant, or else an average height may be considered.

[0012] When discussing parameters, the terms "large", "small", etc. should be understood as relative to each other, even if they are used alone. For example, a small pitch of a first wall means that the pitch of the first wall is relatively small compared to the pitch of the second wall.

[0013] Due to the small thickness of the first wall, the small pitch and the small ratio of the pitch to the height, the first layer comprises a high density of channels, which facilitates heat exchange, especially when the fluid flowing in the first channels is gaseous (e.g. air). In addition, the small ratio of the pitch to the height of the first wall compensates for its small thickness in terms of the mechanical resistance of the heat exchanger module.

[0014] Optionally, the first wall, the second wall and the partition are assembled by diffusion bonding. As known in the art per se, diffusion bonding is an assembly technique based on the principle of solid-state diffusion. Diffusion bonding is typically performed under high temperature and high pressure conditions. Due to the structure defined above, the heat exchanger module can withstand the pressure applied during diffusion bonding. In addition, compared with other welding techniques such as brazing, diffusion bonding is a technique that does not require additional welding materials. Therefore, diffusion bonding the first wall, the second wall and the partition ensures that the heat exchanger module does not contain any brazing welds in the layer, which can be corroded by potentially corrosive fluids (such as molten salts) flowing therein.

[0015] Optionally, the partition, the first wall and the second wall are metallic. This includes metals as well as alloys and metal composites.

[0016] Optionally, the thickness of the partition is greater than or equal to the thickness of the second wall. The thickness or height of the partition is the smallest dimension of the partition and corresponds to the distance between the first layer and the second layer adjacent to and on either side of the partition. Thus, the partition contributes to the mechanical strength of the heat exchanger module while homogenizing the heat transfer between the first layer and the second layer. In other embodiments, the thickness of the partition may be less than the thickness of the second wall.

[0017] Optionally, the height of the first wall is greater than the height of the second wall. In other embodiments, the height of the first wall may be less than or equal to the height of the second wall.

[0018] Optionally, the ratio of the height of the first wall to the thickness of the first wall is greater than or equal to 8, preferably 10, preferably 12. The meandering of the first wall may be obtained by folding the first wall.

[0019] Optionally, the ratio of the height of the second wall to the thickness of the second wall is less than or equal to 8, preferably 6, preferably 5, preferably 4. The meandering of the second wall may be obtained by extruding the second wall.

[0020] Optionally, a ratio of the pitch of the first wall to the height of the first wall is less than or equal to 2, preferably 1, preferably 0.6.

[0021] Optionally, a ratio of the pitch of the second wall to the height of the second wall is greater than or equal to 2, preferably 2.2, preferably 2.4.

[0022] Optionally, the ratio of the pitch of the second wall to the pitch of the first wall is greater than 2, preferably 3, preferably 4, preferably 6.

[0023] Optionally, the pitch of the first wall is in the range of 0.5 to 3 millimeters (mm), preferably 1 to 2 mm.

[0024] Optionally, the pitch of the second wall is in the range of 3 to 10 mm, preferably 4 to 8 mm.

[0025] Optionally, the height of the first wall is in the range of 2 to 15 mm, preferably 2 to 5 mm.

[0026] Optionally, the height of the second wall is in the range of 1 to 10 mm, preferably 1.5 to 4 mm, preferably 2 to 3 mm.

[0027] Optionally, the thickness of the first wall is in the range of 0.05 to 0.5 mm, preferably 0.10 to 0.30 mm.

[0028] Optionally, the thickness of the second wall is in the range of 0.2 to 1.2 mm, preferably 0.30 to 0.50 mm.

[0029] Optionally, the thickness of the separator is in the range of 0.4 to 1 mm, preferably 0.50 to 0.70 mm.

[0030] Optionally, between the opposite sides of the first layer, the first wall has a maximum angle with the opposite side greater than or equal to 70°. That is, the portion of the first wall connecting one opposite side to the other opposite side forms an angle with each of the opposite sides. The angle reaches a maximum value of at least 70°. The maximum angle may be greater than 80° and may even reach 90°, in which case the first wall has a portion perpendicular to the opposite sides of the first layer.

[0031] Optionally, between opposite sides of the second layer, the second wall has a maximum angle with the opposite side that is less than 70°. More generally, the maximum angle of the second wall is less than the maximum angle of the first wall.

[0032] Optionally, the heat exchanger module includes a plurality of second layers, wherein the meandering second wall of one of the second layers is in opposite phase to the meandering second wall of an adjacent one of the second layers. In other words, the meandering second wall of one of the second layers is offset by half a pitch relative to the meandering second wall of an adjacent one of the second layers. Therefore, the valley of the second wall of one of the second layers is aligned with the peak of the second wall of the adjacent second layer, and vice versa. This ensures that the pressure applied to the heat exchanger module is well transferred from one second layer to another second layer, and the deformation of the limiting layer and the partition is limited.

[0033] Optionally, the first channel and the second channel define a counter-flow.Alternatively, the first channel and the second channel may define a parallel flow, or also a cross flow.

[0034] Optionally, the heat exchanger module includes at least one side support that separates two adjacent baffles at the ends of the first layer and / or the second layer, and the at least one side support supports the two adjacent baffles relative to each other. The side support can close the corresponding layer in one direction. For example, the side support can extend between two opposite sides of the corresponding layer and extend from the inlet to the outlet of the layer. In addition to providing fluid tightness in the layer, the side support also contributes to the mechanical strength of the heat exchanger module.

[0035] The present disclosure also relates to a method for manufacturing a heat exchanger module as described above, the method comprising:

[0036] - providing a first wall and folding the first wall so that it meanders and defines a first passage extending between a first inlet and a first outlet;

[0037] - providing a second wall and extruding the second wall so that it meanders and defines a second passage extending between a second inlet and a second outlet, wherein the pitch of the first wall is less than the pitch of the second wall, the thickness of the first wall is less than the thickness of the second wall, and the ratio of the pitch to the height of the first wall is less than the ratio of the pitch to the height of the second wall;

[0038] - providing a partition between the first wall and the second wall;

[0039] - Assembling the first wall, the second wall and the partition, whereby the first wall defines a first layer for a first fluid to flow therein between the first inlet and the first outlet, and the second wall defines a second layer for a second fluid to flow therein between the second inlet and the second outlet.

[0040] The resulting heat exchanger module may have any of the above-mentioned features and the manufacturing method may be modified accordingly.

[0041] In particular, in the manufacturing method, the assembling optionally includes diffusion bonding the first wall, the second wall and the partition. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The invention and its advantages will be better understood by reading the following detailed description of embodiments given as non-limiting examples. This description refers to the accompanying drawings, in which: Figure 1 is a cross-sectional view of a heat exchanger module according to an embodiment. DETAILED DESCRIPTION

[0043] refer to Figure 1 To describe a heat exchanger module 100 according to an embodiment, Figure 1 A cross section thereof is shown. Although the main aspects of the present disclosure are shown, Figure 1 Not to scale.

[0044] The stacking direction or height direction is Figure 1 The width direction is perpendicular to the stacking direction and corresponds to Figure 1 The length direction is the main direction in which at least one fluid will flow in the heat exchanger module 100 and corresponds to a direction perpendicular to the stacking direction and the width direction in this example. Here, the length direction is orthogonal to Figure 1 plane.

[0045] The heat exchanger module 100 includes a plurality of layers stacked on top of each other, including at least one first layer 10 and at least one second layer 20. The first layer 10 has Figure 1 The first inlet and the first outlet are located in front of and behind the plane of the heat exchanger and are configured to receive a first fluid flow, such as a gas such as air. Similarly, the second layer 20 has a second inlet and a second outlet, which are located respectively in the case of a parallel flow heat exchanger. Figure 1in front of and behind the plane of the heat exchanger, or in the case of a counterflow heat exchanger, respectively Figure 1 The second layer is configured to receive a second fluid flow, such as a liquid such as molten salt.

[0046] The first layer 10 and the second layer 20 are separated by a separator 30. The separator 30 extends over the entire first layer 10 and the second layer 20 so as to prevent the fluids of the first layer 10 and the second layer 20 from mixing.

[0047] The first layers 10 and the second layers 20 are stacked alternately with partitions 30 in between. A desired number of first layers 10, partitions 30, and second layers 20 may be stacked on top of each other to obtain a heat exchanger module 100 with a desired flow capacity. At the end of the stack, an end plate 33 may be provided. The end plate 33 may be similar in structure to the partitions 30, but may be thicker to provide a sturdy housing for the heat exchanger module 100.

[0048] Thus, in the stacking direction, each layer 10, 20 is closed by the partition 30. In the width direction, each layer 10, 20 may be closed by a corresponding side support 34. That is, the side support separates two adjacent partitions 30 at the ends of the first layer 10 and the second layer 20, respectively. The side support 34 supports the two adjacent partitions 30 relative to each other.

[0049] The side struts 34 may be in the form of solid rods extending primarily in the length direction. The side struts 34 may be at least as thick as the partitions 30 .

[0050] In the length direction, the layers 10, 20 are not closed but open to corresponding inlets and outlets, as described in detail above.

[0051] In this embodiment, the first layer 10 is provided with a channel structure to facilitate circulation of the first fluid and enhance heat transfer. Specifically, the first layer 10 comprises a first wall 12 which meanders between opposite sides 31, 32 of the first layer 10 to define a first channel 14 extending between a first inlet and a first outlet.

[0052] Here, the opposite sides 31 , 32 of the first layer 10 are formed by facing surfaces of respective separators 30 adjacent to the first layer 10 .

[0053] The first wall 12 may be a metal wall. In this example, the serpentine shape of the first wall 12 forms a plurality of fins 16, which may be generally straight and / or inclined, such as in Figure 1 As shown in the cross section of FIG. In this example, the fin 16 forms an angle with the opposite sides 31, 32. Here, the angle is generally constant (e.g., constant except for edge effects), but in general, and the angle can vary. The angle reaches a maximum angle A1. The maximum angle A1 can be greater than or equal to 70°.

[0054] The fins 16 are joined to each other in contact with each of the opposite sides 31, 32 of the first layer 10 alternately at the plateau portions 18. A space between two consecutive fins among the fins 16 and the opposite sides 31, 32 forms one of the first channels 14 mentioned above.

[0055] The first wall 12 has a height hi, a thickness e1 and a pitch p1. The height hi corresponds to the distance between the opposite sides 31, 32 of the first layer 10. In this embodiment, the first wall 12 meanders periodically, so that the pitch p1 corresponds to the period of the first wall 12.

[0056] Starting from a substantially planar sheet, the first wall 12 may be formed by folding so that it is meandering. That is, the first wall 12 may be folded multiple times, for example one fold at a time on a continuous production line, to form the fins 16 and the plateau portions 18. In order to perform the folding process, the height h1 should be relatively large relative to the thickness e1. In other words, the ratio of the height h1 of the first wall 12 to the thickness e1 of the first wall 12, i.e., h1 / e1, may be greater than or equal to 8, preferably 10, preferably 12. In addition, the ratio of the pitch p1 of the first wall 12 to the height h1 of the first wall 12, i.e., p1 / h1, may be less than or equal to 2, preferably 1, preferably 0.6. Folding enables a high density of fins 16 to be achieved within the first layer 10.

[0057] In this embodiment, the second layer 20 is provided with a channel structure to facilitate the circulation of the second fluid and enhance heat transfer. Specifically, the second layer 20 includes a second wall 22 that meanders between opposite sides 31, 32 of the second layer 20 to define a second channel 24 extending between a second inlet and a second outlet.

[0058] Similar to the first layer 10 , the opposite sides 31 , 32 of the second layer 20 are formed by facing surfaces of the respective separators 30 adjacent to the second layer 20 .

[0059] The second wall 22 may be a metal wall. In this example, the meandering of the second wall 22 forms a plurality of corrugations 26. Each corrugation 26 is in contact with one of the opposite sides 31, 32 and is closed by the other of the opposite sides 31, 32. The space between the corrugation 26 and the closed side of the opposite sides 31, 32 forms one of the second channels 24 mentioned above.

[0060] In this example, the portion of the second wall 22 that runs from one of the opposing sides 31, 32 to the other forms an angle with the opposing sides 31, 32. Here, the angle is substantially constant (e.g., constant except for edge effects), but typically, and the angle may vary. The angle reaches a maximum angle A2. The maximum angle A2 may be less than 70°.

[0061] The second wall 22 has a height h2, a thickness e2, and a pitch p2. The height h2 corresponds to the distance between the opposite sides 31, 32 of the second layer 20. In this embodiment, the second wall 22 is periodically meandering such that the pitch p2 corresponds to the period of the second wall 22.

[0062] Starting from a sheet in a basic plane, the second wall 22 can be formed by extrusion so as to be meandering. That is, the second wall 22 can be inserted into a press and extruded through a stamping die to force the sheet to assume the shape of the die. The appropriate shape of the die enables the corrugations 26 to be obtained. For performing the extrusion process, the height h2 should be relatively small with respect to the thickness e1 to prevent the sheet from tearing. In other words, the ratio of the height h2 of the second wall 22 to the thickness e2 of the second wall 22, i.e., h2 / e2, can be less than or equal to 8, preferably 6, preferably 5, preferably 4. Further, the ratio of the pitch p2 of the second wall 22 to the height h2 of the second wall 22, i.e., p2 / h2, can be greater than or equal to 2, preferably 2.2, preferably 2.4. The extrusion enables the corrugations 26 with a small density to be achieved in the second layer 10 with a relatively large thickness e2.

[0063] The parameters of the first wall 12 and the second wall 22 are such that the pitch p1 of the first wall 12 is less than the pitch p2 of the second wall 22 (p1 < p2). Further, the thickness e1 of the first wall 12 is less than the thickness e2 of the second wall 22 (e1 < e2). Additionally, the ratio of the pitch p1 of the first wall 12 to the height h1 is less than the ratio of the pitch p2 of the second wall 22 to the height h2 (p1 / h1 < p2 / h2).

[0064] Thus, the first wall 12 and the second wall 22 are accordingly adapted to be manufactured by folding and extrusion. The first wall 12 provides a surface suitable for efficient heat exchange with a first fluid (such as air), while the second wall 22 provides a surface suitable for efficient heat exchange with a second fluid (such as molten salt). Further, the relatively dense structure of the first wall 12 (determined by the height h1 and the pitch p1) compensates for the smaller thickness e1, while the large thickness e2 of the second wall allows for a less dense structure and thus different values of the height h2 and the pitch p2.

[0065] The separator 30 can have a thickness h3 greater than the thickness e2 of the second wall 22 (h3 > e2). In other embodiments, the thickness h3 of the separator 30 can be equal to or less than the thickness e2 of the second wall 22.

[0066] For example, the ratio of the pitch p2 of the second wall 22 to the pitch p1 of the first wall 12, i.e., p2 / p1, is greater than 2, preferably 3, preferably 4, preferably 6.

[0067] In this embodiment, the height, pitch, and thickness parameters can have the following values.

[0068] The pitch p1 of the first wall 12 is in the range of 0.5 to 3 mm, preferably 1 to 2 mm.

[0069] The pitch p2 of the second wall 22 is in the range of 3 to 10 mm, preferably 4 to 8 mm.

[0070] The height h1 of the first wall 12 is in the range of 2 to 15 mm, preferably 2 to 5 mm.

[0071] The height h2 of the second wall 22 is in the range of 1 to 10 mm, preferably 1.5 to 4 mm, preferably 2 to 3 mm.

[0072] The thickness e1 of the first wall 12 is in the range of 0.05 to 0.5 mm, preferably 0.10 to 0.30 mm.

[0073] The thickness of the second wall 22 is in the range of 0.2 to 1.2 mm, preferably 0.30 to 0.50 mm.

[0074] Horizontal to Figure 1 In the plane of the first wall 12, ie in the length direction, the first wall 12 and / or the second wall 22 may be straight, inclined, wavy, etc. as desired.

[0075] Once arranged, the first wall 10, the second wall 20 and the partitions 30, and if applicable the end plates 33 and the side struts 34, can be assembled to form the heat exchanger module 100. In one embodiment, the assembly includes diffusion bonding these components together. That is, after stacking, heat and pressure are applied to trigger solid state diffusion between the components in contact with each other.

[0076] To further enhance the mechanical strength of the heat exchanger module 100, particularly during diffusion bonding, the second wall 22A of one of the second layers 20 and the second wall 22B of an adjacent one of the second layers 20 may be in opposite phases. Figure 1 As shown in FIG, at a given position in the width direction, the corrugations 26 of the second wall 22A are turned upside down relative to the facing corrugations 26 of the second wall 22B. This ensures that the force applied by the second wall 22A to the adjacent partition 30 is properly supported by the second wall 22B of the adjacent second layer 20 after being transmitted to the first wall 10 and the subsequent partition 30.

[0077] Although the present disclosure relates to specific exemplary embodiments, modifications may be made to these examples without departing from the general scope of the invention as defined by the claims. In particular, individual features of the different shown / mentioned embodiments may be combined in additional embodiments. Accordingly, the description and drawings should be regarded as illustrative rather than in a restrictive sense.

Claims

1. A heat exchanger module (100) comprising at least one first layer (10) for a first fluid to flow between a first inlet and a first outlet, and at least one second layer (20) for a second fluid to flow between a second inlet and a second outlet, wherein: The at least one first layer (10) and the at least one second layer (20) are separated by a partition (30), the first layer (10) comprising a first wall (12) which meanders between opposite sides (31, 32) of the first layer (10) so as to define a first channel (14) extending between the first inlet and the first outlet, the second layer (20) comprising a second wall (22) which meanders between opposite sides (31, 32) of the second layer (20) so as to define a second channel (24) extending between the second inlet and the second outlet, wherein a pitch (p1) of the first wall is smaller than a pitch (p2) of the second wall, a thickness (e1) of the first wall is smaller than a thickness (e2) of the second wall, and a ratio of a pitch (p1) to a height (h1) of the first wall is smaller than a ratio of a pitch (p2) to a height (h2) of the second wall.

2. The heat exchanger module according to claim 1, wherein: The first wall (12), the second wall (22) and the partition (30) are assembled by diffusion bonding.

3. The heat exchanger module according to claim 1 or 2, wherein: The height (h1) of the first wall is greater than the height (h2) of the second wall.

4. The heat exchanger module according to any one of claims 1 to 3, wherein: The ratio of the height (h1) of the first wall to the thickness (e1) of the first wall is greater than or equal to 8; and / or wherein, A ratio of a height (h2) of the second wall to a thickness (e2) of the second wall is less than or equal to 8.

5. The heat exchanger module according to any one of claims 1 to 4, wherein: The ratio of the pitch (p1) of the first wall to the height (h1) of the first wall is less than or equal to 2; and / or wherein, A ratio of a pitch (p2) of the second wall to a height (h2) of the second wall is greater than or equal to 2.

6. The heat exchanger module according to any one of claims 1 to 5, wherein: A ratio of a pitch (p2) of the second wall to a pitch (p1) of the first wall is greater than 2.

7. The heat exchanger module according to any one of claims 1 to 6, wherein: - the pitch (p1) of the first wall is in the range of 0.5 to 3 mm; and / or - the pitch (p2) of the second wall is in the range of 3 to 10 mm; and / or - the height (h1) of the first wall is in the range of 2 to 15 mm; and / or - the height (h2) of the second wall is in the range of 1 to 10 mm; and / or - the thickness (e1) of the first wall is in the range of 0.05 to 0.5 mm, preferably 0.10 to 0.30 mm; and / or The thickness (e2) of the second wall is in the range of 0.2 to 1.2 mm, preferably 0.30 to 0.50 mm.

8. The heat exchanger module according to any one of claims 1 to 7, wherein: Between opposite sides (31, 32) of the first layer (10), the first wall (12) has a maximum angle (A1) with the opposite sides (31, 32) greater than or equal to 70°; and / or wherein, Between the opposite sides (31, 32) of the second layer (20), the second wall (22) has a maximum angle (A2) with the opposite sides (31, 32) that is less than 70°.

9. The heat exchanger module according to any one of claims 1 to 8, comprising a plurality of said second layers (20), wherein: The meandering second wall (22A) of one of the second layers is in opposite phase to the meandering second wall (22B) of an adjacent one of the second layers.

10. The heat exchanger module according to any one of claims 1 to 9, wherein: The first passage (14) and the second passage (24) define a counter-flow.

11. A heat exchanger module according to any one of claims 1 to 10, comprising at least one side support (34) separating two adjacent partitions (30) at the end of the first layer (10) and / or the second layer (20), wherein the at least one side support (34) supports the two adjacent partitions (30) relative to each other.

12. A method for manufacturing a heat exchanger module (100) according to any one of claims 1 to 11, the method comprising: - providing a first wall (12) and folding said first wall (12) so as to meander and define a first passage (14) extending between a first inlet and a first outlet; - providing a second wall (22) and extruding the second wall (22) so as to meander and define a second channel (24) extending between a second inlet and a second outlet, wherein the pitch (p1) of the first wall is smaller than the pitch (p2) of the second wall, the thickness (e1) of the first wall is smaller than the thickness (e2) of the second wall, and the ratio of the pitch (p1) to the height (h1) of the first wall is smaller than the ratio of the pitch (p2) to the height (h2) of the second wall; - providing a partition (30) between said first wall (12) and said second wall (22); - Assembling the first wall (12), the second wall (22) and the partition (30), whereby the first wall (12) defines a first layer (10) for a first fluid to flow therein between the first inlet and the first outlet, and the second wall (22) defines a second layer (20) for a second fluid to flow therein between the second inlet and the second outlet.

13. The method according to claim 12, wherein: The assembling includes diffusion bonding the first wall (12), the second wall (22), and the spacer (30).

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