FLAT PLATE HEAT EXCHANGER

Abstract

A flat plate heat exchanger module for use in aerospace applications, automotive applications, industrial applications or similar. The flat plate heat exchanger module comprises a stack of heat exchanger plates, where at least one of the heat exchanger plates further comprises at least one elongated aperture extending across the surface of the heat exchanger plate. This elongated aperture is in fluid isolation from the fluid flowing across the surface of the heat exchanger plate. The use of at least one elongated aperture throughout the stack of heat exchanger plates minimises the overall effect of the expansion and contraction of the metal due to exposure to high temperature gradients. A method of manufacturing such a heat exchanger module is also provided.

Claims

1. A flat plate heat exchanger module comprising; a stack of heat exchanger plates, wherein each heat exchanger plate comprises a metal foil sheet, wherein at least one fluid flow channel is provided in the surface of each heat exchanger plate; at least one inlet and at least one outlet for a first fluid; at least one inlet and at least one outlet for a second fluid; wherein a first fluid flow path for the first fluid and a second fluid flow path for the second fluid is formed from the channels in the stack of multiple heat exchanger plates, wherein each of the first and second fluid flow paths are in fluid isolation from one another; wherein at least one of the heat exchanger plates further comprises at least one elongated aperture extending across the surface of the heat exchanger plate, and wherein the elongated aperture is in fluid isolation from the first and second fluid flow paths.

2. A flat plate heat exchanger module according to claim 1, where the elongated aperture extends across the surface of each heat exchanger plate in a lateral direction.

3. A flat plate heat exchanger module according to any preceding claim, where at least one of the heat exchanger plates comprises at least two elongated apertures which extend in a lateral direction across the surface of the heat exchanger plate.

4. A flat plate heat exchanger module according to claim 3, where the at least two elongated apertures are arranged at regularly spaced intervals in the surface of the heat exchanger plate.

5. A flat plate heat exchanger module according to any preceding claim, where at least one of the elongated apertures extends across at least 50% of the plate in a lateral direction across the surface of the heat exchanger plate.

6. A flat plate heat exchanger module according to any one of claims 2 to 5, where the lateral direction is parallel to the primary direction of flow of the heatant fluid.

7. A flat plate heat exchanger module according to any preceding claim, further comprising at least one spacer plate, where the spacer plate comprises at least one elongated aperture.

8. A flat plate heat exchanger module according to claim 7, where the spacer plate comprises a metal foil sheet.

9. A flat plate heat exchanger module according to claim 7, where the spacer plate comprises a metal plate.

10. A flat plate heat exchanger module according to any one of claims 7 to 9, where at least one elongated aperture extends in a longitudinal direction across the surface of the spacer plate.

11. A flat plate heat exchanger module according to any one of claims 7 to 10, where at least one elongated aperture extends across at least 50% of the width of the spacer plate.

12. A flat plate heat exchanger module according to any one of claims 7 to 11, where at least one elongated aperture extends in a longitudinal direction across the entire width of the spacer plate.

13. A flat plate heat exchanger module according to any of claims 7 to 13, where the spacer plate comprises at least two elongated apertures which extend in a longitudinal direction across the surface of the plate.

14. A flat plate heat exchanger module according to any one of claims 10 to 13, where the longitudinal direction is perpendicular to the primary direction of flow of the heatant fluid.

15. A flat plate heat exchanger module according to any preceding claim, comprising an intermediate end plate, where the intermediate end plate comprises at least one elongated aperture which extends in a lateral direction across the surface of the plate.

16. A flat plate heat exchanger module according to claim 15, where the intermediate end plate comprises at least three elongated apertures which extend in a lateral direction across the surface of the plate.

17. A flat plate heat exchanger module according to any of claims 15 or 16, where at least one elongated aperture extends across at least 50% of the plate in a lateral direction.

18. A flat plate heat exchanger module according to any preceding claim, comprising at least two diffusion bonded heat exchanger plates positioned between two end plates.

19. A flat plate heat exchanger module according to any preceding claim, where at least one heat exchanger plate comprises a header portion with inlet and outlet ports for a first fluid and second fluid.

20. A flat plate heat exchanger module according to any of claims 7 to 19, where at least one spacer plate comprises a header portion with inlet and outlet ports for a first and second fluid.

21. A flat plate heat exchanger module according to any of claims 15 to 20, where at least one intermediate end plate comprises a header portion with inlet and outlet ports for a first and second fluid.

22. A flat plate heat exchanger module according to any of claims 19 to 21, where at least one edge of the header portion is corrugated.

23. A method of manufacturing a flat plate heat exchanger module comprising the following steps: providing at least one fluid flow channel on the surface of at least one metal foil sheet, where the metal foil sheet forms a heat exchanger plate; stacking at least two heat exchanger plates adjacent to one another, such that the at least two heat exchanger plates provide a first fluid flow path for a first fluid and a second fluid flow path for a second fluid, where each of the fluid flow paths are in fluid isolation from one another; providing at least one inlet and at least one outlet for the first fluid; providing at least one inlet and at least one outlet for the second fluid; arranging the plurality of diffusion bonded heat exchanger plates between two end plates, to form a module; diffusion bonding a plurality of heat exchanger plates together; providing at least one elongated aperture extending in a lateral direction across the surface of at least one heat exchanger plate, where the elongated aperture is in fluid isolation from the first and second fluid flow paths.

24. A method of manufacturing a flat plate heat exchanger module according to claim 23, where the at least one fluid flow channel is etched on the surface of at least one metal foil sheet.

25. A method of manufacturing a flat plate heat exchanger module according to claim 23 or claim 24, comprising a step of providing at least one spacer plate which is stacked adjacent to the heat exchanger plates, where at least one elongated aperture is etched into the spacer plate.

26. A method of manufacturing a flat plate heat exchanger module according to claim 25, where the spacer plate comprises a metal plate.

27. A method of manufacturing a flat plate heat exchanger module according to claim 25, where the spacer plate comprises a metal foil sheet.

28. A method of manufacturing a flat plate heat exchanger module according to any of claims 23 to 27, where at least one elongated aperture is etched into at least one heat exchanger plate in a lateral direction across the surface of the heat exchanger plate.

29. A method of manufacturing a flat plate heat exchanger module according to any one of claims 25 to 28, where at least one elongated aperture is etched into at least one spacer plate in a longitudinal direction across the surface of a spacer plate.

30. A method of manufacturing a flat plate heat exchanger module according to any one of claims 25 to 29, comprising the use of electrical discharge machining to create at least one elongated aperture in at least one spacer plate after the diffusion bonding step.

31. A method of manufacturing a flat plate heat exchanger module according to any one of claims 23 to 30, comprising aligning at least two elongated apertures in a stack of plates with each other before the plates are diffusion bonded to each other.

32. A method of manufacturing a flat plate heat exchanger module according to any one of claims 23 to 31, where the heat exchanger plates comprise a header portion, and where the header portion provides inlet and outlet ports for the first and second fluid.

33. A method of manufacturing a flat plate heat exchanger module according to any one of claims 23 to 32, where the spacer plate comprises a header portion, and where the header portion provides inlet and outlet ports for the first and second fluid.

34. A method of manufacturing a flat plate heat exchanger module according to any of claims 32 and 33, where excess material surrounding the inlet and outlet ports is removed from the header portion, such that the edge of the header portion is corrugated.

35. A flat plate heat exchanger module according to any one of claims 23 to 34, where at least two heat exchanger plates are diffusion bonded together.

36. A method of manufacturing a flat plate heat exchanger module according to any of claims 23 to 35, comprising: stacking at least two heat exchanger plates adjacent to each other, where each plate comprises at least one elongated aperture extending in a lateral direction across the surface of the heat exchanger plate; aligning the apertures of the heat exchanger plates; and diffusion bonding the heat exchanger plates together.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0056] The present disclosure may be carried out in various ways and embodiments of the disclosure will now be described by way of example with reference to the accompanying drawings, in which:

[0057] FIG. 1 is an expanded view of an example of a stack of heat exchanger plates, comprising a plurality of heat exchanger plates arranged between two end plates.

[0058] FIG. 2 is an isometric view of one example of a heat exchanger module comprising a stack of heat exchanger plates, with an inlet and outlet manifold for hot and cold fluids, respectively.

[0059] FIG. 3 is a schematic plan view of an exemplary individual heat exchanger plate, comprising three elongated apertures extending in a lateral direction across the plate, where the elongated apertures are adjacent to fluid flow channels.

[0060] FIG. 4 is a schematic plan view of an exemplary individual intermediate end plate, comprising three elongated apertures extending in a lateral direction across the surface of the plate.

[0061] FIG. 5 is a schematic plan view of an exemplary individual spacer plate, comprising at least two elongated apertures extending in a longitudinal direction across the surface of the plate.

[0062] FIG. 6 is a schematic plan view of an exemplary individual spacer plate, comprising at least two partially etched elongated apertures extending in a longitudinal direction across the surface of the plate.

[0063] FIG. 7 is a cross-section of an exemplary stack of plates, where a stack of intermediate end plates comprises at least two elongated apertures extending in a lateral direction, and at least two spacer plates comprise at least one elongated aperture extending in a longitudinal direction.

[0064] FIG. 8 is an isometric view of one end of the stack of plates of FIG. 7 before the aperture has been created in the longitudinal direction.

DETAILED DESCRIPTION

[0065] FIG. 1 illustrates an example of a stack of heat exchanger plates for a heat exchanger module 1, wherein each heat exchanger plate comprises a metal foil sheet. As illustrated in FIG. 1, from the bottom to the top, the stack comprises a first end plate 2, two heat exchanger plates 3, three intermediate end plates 4 two spacer plates 5, three intermediate end plates 4, two heat exchanger plates 3 and a second end plate 6. In FIG. 1, the plates are generally rectangular in shape, however, the plates could be of any shape. The number and types of plate may be chosen depending on the application and performance requirements of the module. Typically, between 1000 and 3000 heat exchanger plates can be utilised in a flat plate heat exchanger.

[0066] In the example illustrated in FIG. 1, intermediate end plates 4 are included in the stack of plates. The intermediate end plates 4 can comprise elongated apertures 15 which extend in a lateral direction across the surface of the plate.

[0067] In the illustrated example, two spacer plates 5 are provided, where each spacer plate comprises two elongated apertures 17 which extend in a second, longitudinal direction across the header portions of the plate. In addition, there is an elongated aperture 22 extending in both a lateral and longitudinal direction across the surface of central portion of the plate, as best illustrated in FIG. 7. The longitudinal direction extends parallel to the first edge 16 of the plate (the longest edge of the plate in this example). The longitudinal direction may extend in a direction which is perpendicular to the primary direction of flow of the heatant fluid.

[0068] The stack of plates of FIG. 1 are connected to four manifolds 18,19,20,21 to form a flat plate heat exchanger module 1 as illustrated in FIG. 2. The module comprises a stack of heat exchanger plates 3, wherein each heat exchanger plate 3 is aligned with the adjacent heat exchanger plates and optional spacer plates 5 and intermediate end plates 4, to form a stack of plates positioned within two end plates 2,6.

[0069] The four manifolds 18,19,20,21 may also be referred to as headers such as inlet / outlet headers. The manifolds provide a fluid connection to the inlet 11,13 and outlet 12,14 ports (which may themselves be referred to as headers) to and from the heat exchanger module 1. Two manifolds are used for a first fluid stream and the other two manifolds are used for a second fluid stream. The first fluid stream may be a cold fluid stream, also referred to as a coolant, and the second fluid stream may be a hot fluid stream, which may also be referred to as a heatant. The manifolds 18,19,20,21 facilitate the supply and collection of the coolant and heatant to and from the heat exchanger module 1.

[0070] In FIG. 2, the end plate 2 is depicted as having three elongated apertures 15 extending in a lateral direction. The spacer plates 5 of the example illustrated in FIG. 2 have been used to create three elongated apertures 22 extending in a longitudinal direction.

[0071] Fluid flow channels 7 are provided in the surface 8 of the metal foil sheet of the heat exchanger plates 3. This is illustrated in FIG. 3. The channels are formed with a typical size of 10 um to 5 mm. A first fluid flow path for the first fluid and a second fluid flow path for the second fluid is formed from the channels 7 in the stack of multiple heat exchanger plates 1, where each of the first and second fluid flow paths are in fluid isolation from one another. The fluid flow channels 7 extend in a generally lateral direction across the surface of the heat exchanger plate 3, directing a first or second fluid from the fluid inlet to the fluid outlet. The spacer plates 5, intermediate end plates 4, and end plates 2,6 of FIG. 1 do not have fluid flow channels 7 in their surfaces.

[0072] The heat exchanger plates 3 in the illustrated example comprise header portions 9,10. The header portions provide inlet 11 and outlet 12 ports for a first fluid and inlet 13 and outlet 14 ports for a second fluid. Each of the heat exchanger plates 3 further comprises multiple elongated apertures 15 extending therethrough, where the elongated apertures 15 are in fluid isolation from the first and second fluid flow path. The elongated apertures 15 are located in the channel-free portions of the heat exchanger plate 3, such that the elongated apertures 15 do not intercept the flow path of the fluid. The elongated apertures 15 are in fluid isolation from the first and second fluid flow path. The elongated apertures 15 extend in the lateral direction which is normal to a first edge of the heat exchanger plate (which in this illustration is the longest side of the plate). The lateral direction may extend in a direction which is parallel to the primary direction of flow of the heatant fluid through the heat exchanger.

[0073] The fluid flow channels 7 may be formed by etching the surface 8 of the metal foil of the heat exchanger plate. The fluid flow channels 7 do not penetrate through the heat exchanger plate itself.

[0074] In the example shown in FIG. 3, each of the heat exchanger plates 3 comprises three elongated apertures 15 although the number may depend on the configuration of the plate and its performance requirements. The elongated apertures extend entirely through the material of the heat exchanger plate 3 such that the elongated apertures are present on both sides of the heat exchanger plate 3.

[0075] In FIG. 2, three elongated apertures are provided in each of the two end plates 2,6, and these elongated apertures 15 extend in a lateral direction across the surface of the end plate. The end plates 2,6 can comprise a metal foil sheet or a metal plate. In the illustrated example of FIG. 1, the end plates do not have channels 7.

[0076] FIG. 3 is a plan view of an exemplary heat exchanger plate 3 from FIG. 1, comprising an individual foil sheet, which would lie in the plane of A-A as indicated in FIG. 2. The foil sheet comprises header portions 9,10 located on two sides of the plate at the lateral edges. Header portions 9,10 comprise inlet 11 and outlet 12 ports for the cold fluid, also referred to as the coolant. Inlet 13 and outlet 14 ports are provided for the hot fluid, also referred to as the heatant. A coolant may enter the inlet port 11 at a relatively low temperature, where it can be heated by the heatant as it travels through the heat exchanger module 20. The coolant can exit the outlet port 12 at a higher temperature than it was at the inlet port 11. Conversely, the heatant may enter the inlet port 13 at a relatively high temperature and lose heat to the coolant as it travels through the heat exchanger, leaving the outlet port 14 at a lower temperature. The heat exchanger plates are stacked, and one side of the heat exchanger plate will provide a fluid flow path for the coolant, whilst the next side of the plate will provide a fluid flow path for the heatant.

[0077] The channels 7 of the heat exchanger plate 1 may be linear across the majority of the plate and turn at each side to join the inlet and outlet ports. The channels 7, in the example shown, are provided as two sets of channels which extend either side of a central reservation 25 in which no channels are formed. Each central reservation 25 is centrally positioned within at least two channels 7. The exact design of the channels 7 on the surface of the plate 8 may vary. The elongated apertures 15 may be linear and are positioned adjacent to the channels 7. The elongated apertures 15 do not intersect the fluid channels 7 or the inlet 11,13 or outlet 12,14 ports of the first and second fluid. The elongated apertures 15 are positioned in fluid isolation from the first and second fluid flow paths.

[0078] The inlet 11,13 and outlet 12,14 ports may have a tear-drop shape, as illustrated in FIG. 3. The inlet 11,13 and outlet 12,14 ports may not necessarily have a tear-drop shape, but could alternatively have a round, oblong or oval shape, for example. The inlet and outlet ports are located at the periphery of the plate, along the edge of the header portions 9, 10.

[0079] As illustrated in FIG. 3, the elongated apertures 15 pass through the foil and extend in a lateral direction across the surface of heat exchanger plate. The elongated apertures 15 of FIG. 3 extend in a direction which is normal to a first edge 16 (shown in FIG. 1) of the heat exchanger plate. In the illustrated example, the first edge 16 of the foil sheet is the longest edge of the foil sheet.

[0080] In addition, FIG. 3 illustrates the optional removal of excess material from around the exterior of the inlet 11,13 and outlet 12,14 ports. The two longest sides of the header portions 9,10 do not have straight edges, in this example. The material of the header portions 9,10 provide the outer wall for the inlet 11,13 and outlet 12,14 ports of the two fluid flow paths. The wall thickness of the inlet and outlet ports needs to be sufficient to contain the first and second fluid flowing through the inlet and outlet ports at the pressures which are likely to be encountered during operation of the heat exchanger (with a safety factor). The required wall thickness for a set pressure (or pressure range) can be calculated. In the illustrated example, surplus material which is in excess of the required wall thickness has been trimmed or removed from the plate. As a result of this, the edge of the header portion 9,10 of the heat exchanger plate is corrugated in this example, but may also be ridged, ribbed, serrated or castellated, such that the shape of the edge of the foil corresponds with the shape and positions of the inlet 11,13 and outlet 12,14 ports.

[0081] The heat exchanger plate 3 of FIG. 3 also includes pin alignment slots 21,22 for the alignment of the plates prior to assembly of the module 20. The pin alignment slots 23,24 may be used to hold the heat exchanger plates 3, which comprise of metal foil sheets, in alignment before they are fixed in place (e.g. by diffusion bonding). The pin alignment slots 23,24 can assist with the alignment of the apertures 15,17 of adjacent heat exchanger plates 3, intermediate end plates 4, spacer plates 5, and end plates 2,6.

[0082] The intermediate end plate 4 of FIG. 1 is illustrated in FIG. 4. This plate would lie in the plane of A-A as indicated in FIG. 2. The intermediate end plate 4 of FIG. 4 may be a foil sheet or may be a metal plate. The intermediate end plate assists with providing a pressure tight seal with sufficient thickness to withstand high pressure fluid loads, particularly when diffusion bonded with adjacent plates. The intermediate end plate 4 comprises inlet ports 11 and outlet ports 12 for the coolant. Inlet ports 13 and outlet ports 14 are also provided for the heatant. In the example as illustrated in FIG. 4, the intermediate end plate 4 comprises three elongated apertures which extend in a lateral direction across the surface of the plate. Pin alignment slots 23 and 24 are provided for alignment and fixing of the intermediate end plate 4 to other plates, such as the heat exchanger plates 3 and spacer plates 5.

[0083] FIG. 5 is a plan view of the spacer plate 5 of FIG. 1, which would lie in the plane of A-A as indicated in FIG. 2. The spacer plate 5 may be a foil sheet or may be a metal plate. The spacer plate 5 comprises inlet ports 11 and outlet ports 12 for the coolant. Inlet ports 13 and outlet ports 14 are also provided for the heatant. Pin alignment slots 23 and 24 are provided for alignment and fixing of the spacer plate 5 to other plates, such as the heat exchanger plates 1. The spacer plate 5 of FIG. 5 does not have any channels for fluid flow.

[0084] An elongated aperture 17 extends across the spacer plate 5 in a longitudinal direction. The elongated aperture 17 may be linear as illustrated in FIG. 5. The longitudinal direction in this example is parallel to a first edge 16 of the spacer plate 5, where the first edge 16 is the longest edge of the plate. The longitudinal direction extends in a direction which is perpendicular to the primary direction of flow of the heatant fluid. The elongated apertures 17 provide a gap allowing for material from the central portion of the spacer plate 5 to be removed by machining operations to form elongated aperture 22. As the metal spacer plate 5 is heated, the metal will naturally expand. The elongated aperture 22 which is formed in the same plane as the fluid flow provides a space within which the metal of the spacer plate 5 can expand or distort in a second direction without placing pressure on the surrounding elements of the heat exchanger. The elongated aperture 22 is positioned in fluid isolation from the first and second fluid flow path, such that the fluid inlets and outlets are not intersected by the elongated aperture 22. Without the elongated aperture 22, thermal expansion of the metal plate can place stress on the connections between the inlet 11,13 and outlet 12,14 ports and other connection points, such as the connection with the inlet and outlet collectors.

[0085] The image shown in FIG. 5 illustrates a spacer plate 5 with elongated apertures 17 for removing material. FIG. 6 illustrates a spacer plate 5 with partially etched elongated apertures 27. The spacer plate 5 can be initially formed with partially etched elongated apertures 27 to maintain structural integrity during module assembly. After at least one spacer plate 5 has been diffusion bonded to adjacent plates, the length of the partially etched elongated aperture 27 can be extended by one of electrical discharge machining, drilling, laser or water jet cutting, using the pilot holes 26 to assist with achieving accurate positioning. The pilot holes 26 act as drilling datum after several plates have been diffusion bonded together. Preferably, the step of extending the length of the partially etched elongated aperture 27 to an elongated aperture is conducted after several plates have been diffusion bonded together.

[0086] FIG. 7 illustrates a cross-section of a stack of intermediate end plates 4 and two spacer plates 5 after a machining process has been used to remove the central portion of the spacer plates to create an elongated aperture 22 in the same plane as the foils. The spacer plates create an elongated aperture 22 extending in a longitudinal direction through the stack of plates. This figure illustrates the assembly after an additional machining step has been performed to remove the material from the spacer plates 5 between each of the two elongated apertures 17 illustrated in FIG. 5.

[0087] FIG. 8 provides an isometric view of one end of the stack of plates illustrated in FIG. 7. This illustrates an exemplary stack of heat exchanger plates 3, intermediate end plates 4 and spacer plates 5. In FIG. 8, an elongated aperture 17 is shown extending through two spacer plates 5 in a longitudinal direction. The coolant outlet port 12 is also illustrated.

[0088] A method of manufacturing a flat plate heat exchanger is also provided, which involves etching at least one fluid flow channel 7 on the surface of at least one metal foil sheet, where the metal foil sheet forms a heat exchanger plate 3. At least two heat exchanger plates 3 are stacked adjacent to one another, such that the at least two heat exchanger plates 3 provide a first fluid flow path for a first fluid and a second fluid flow path for a second fluid, where each of the fluid flow paths are in fluid isolation from one another. At least one inlet 11 and at least one outlet 12 is provided for the first fluid; and at least one inlet 13 and at least one outlet 14 is provided for the second fluid. Etching or laser cutting can be used to create at least one elongated aperture 15 extending in a lateral direction across the surface of at least one heat exchanger plate 3, where the elongated aperture 15 is created in a position which is in fluid isolation from the first and second fluid flow paths. The at least two heat exchanger plates 3 are diffusion bonded together and arranged between two end plates 2,6, to form a module 1.

[0089] Preferably chemical etching is used to create the fluid flow channels 7, however, the channels 7 could also be formed by water jet or laser cutting, stamping or moulding.

[0090] The elongated aperture 15 does not intersect the flow path of either the first or second fluid. This elongated aperture 15 provides strain relief to the foil when the foil distorts due to exposure to a temperature gradient. The elongated aperture may also be etched, drilled, or cut through other foil sheets or metal plates which are present in the heat exchanger module, which may include spacer plates 5 and end plates 2,6.

[0091] At least one inlet 11 and one outlet 12 is provided for the first fluid, and at least one inlet 13 and one outlet 14 is provided for the second fluid. These inlets 11,13 and outlets 12,14 can be etched, drilled, or otherwise machined into the metal foil of the heat exchanger plate 3.

[0092] Additional plates which are not heat exchanger plates can be stacked adjacent to the heat exchanger plates 3. These additional plates may not comprise fluid flow channels. The additional plates may be spacer plates 5, intermediate end plates 4 or end plates 2,6. The additional plates may comprise inlets 11,13 and outlets 12,14 for the first and second fluids. The additional plates may be etched to provide at least one elongated aperture extending in a lateral 15 and/or a longitudinal 17,22 direction. The additional plates may comprise a foil sheet or may comprise a metal plate.

[0093] The method of manufacturing a flat plate heat exchanger module may comprise a step of providing at least one intermediate end plate 4 which is stacked adjacent to the heat exchanger plates 3. The intermediate end plate 4 may comprise a metal plate or a metal foil sheet.

[0094] The method of manufacturing a flat plate heat exchanger module may comprise etching at least one elongated aperture into at least one heat exchanger plate 3 in a lateral direction 15 across the surface of the heat exchanger plate.

[0095] FIG. 6 is a plan view of one of the spacer plates 5 of FIG. 1 formed from a foil sheet. This figure illustrates a partly etched elongated aperture 27 extending in a longitudinal direction across the surface of the plate. Pilot holes 26 are etched in alignment with the elongated aperture 27. After at least one spacer plate 5 has been diffusion bonded to adjacent plates, the length of the partially etched elongated aperture 27 can be extended by one of electrical discharge machining, drilling, laser or water jet cutting, using the pilot holes 26 to assist with achieving accurate positioning. The pilot holes 26 act as drilling datum after several plates have been diffusion bonded together. Preferably, the step of extending the length of the partially etched elongated aperture 27 is conducted after several plates have been diffusion bonded together. Once this elongated aperture has been extended across the full width of the heat exchanger, another machining process can be used to remove the material of the spacer plate 5 between the elongated apertures located on opposite sides of the heat exchanger. This creates an aperture 22 within the heat exchanger in the same plane as the foils.

[0096] FIGS. 2-6 also illustrate the optional removal of excess material from the outer edge of the header portion 9 around the inlet 11,13 and outlet 12,14 ports. The longest edge 16 of the header is not straight, as excess material which is not required for containing the fluid flow through the inlet or outlet ports is removed or trimmed from the header of the spacer plate 5 during the manufacturing process. This results in a substantial improvement in the thermal stresses experienced by the heat exchanger module during use.

[0097] As discussed above, the heat exchanger plates 3, spacer plates 5, intermediate end plates 4, and/or end plates 2,6 may comprise header portions 9,10, and the header portions may be etched to provide inlet 11,13 and outlet 12,14 ports for the first and second fluid. Excess material surrounding the inlet 11,13 and outlet ports 12,14 may be removed from the header portions 9,10, such that the edge 16 of the header portions are corrugated, ridged, ribbed, serrated or castellated, such that the shape of the edge of the foil corresponds with the shape and positions of the inlet and outlet ports. The excess material may be removed by etching. Alternatively, the plates may be pre-formed with a corrugated edge, e.g. by moulding or stamping.

[0098] At least two heat exchanger plates 3 may be stacked adjacent to each other, where each plate comprises at least one elongated aperture 15 extending in a lateral direction across the surface of the heat exchanger plate; the apertures 15 of each heat exchanger plate 3 can be aligned; and the heat exchanger plates can be diffusion bonded together.

[0099] The method of manufacturing a flat plate heat exchanger module may include a step of aligning a stack of heat exchanger plates 3 with one or more spacer plates 5 and optionally with one or more intermediate end plates 4. The method may further include a step of aligning a stack of heat exchanger plates 3 with one or more spacer plates 5. The spacer plates 5, and/or the intermediate end plates 4 may comprise a metal foil or a thin metal plate. The method of manufacturing a flat plate heat exchanger module can include a step of aligning a stack of heat exchanger plates 3 with one or more spacer plates 5, intermediate end plates 4 within two end plates 2,6.

[0100] A stack of heat exchanger plates 3 may be diffusion bonded together with one or more spacer plates 5 and optionally one or more intermediate end plates 4. Alternatively, one or more spacer plates 5 may be diffusion bonded together with one or more intermediate end plates 4. Once the stack of plates is diffusion bonded together the plates form a heat exchanger module 1 which is effectively a block of material, comprising internal apertures and fluid flow channels.

[0101] Where the heat exchanger module contains spacer plates 5, the pilot holes 26 in those spacer plates may be drilled or machined to provide a continuous elongated aperture through the module. This then allows insertion of a tool (e.g. EDM wire) to remove the material between the partially etched elongated apertures 17 on opposite sides of the heat exchanger plate. The elongated aperture 17 provides a gap which allows the central portion of the spacer plate 5 to be removed by machining operations. This creates a planar aperture 22 within the heat exchanger in the same plane as the heat exchanger plate.

[0102] The method of manufacturing a flat plate heat exchanger may include a step of aligning the elongated apertures 15 of at least two heat exchanger plates 3 and at least one intermediate end plate 4 with each other before the plates 3,4 are diffusion bonded to each other. The method may include a step of forming a stack of spacer plates 5 and intermediate end plates 4, aligning the elongated apertures 15 in the stack of intermediate end plates 4 and diffusion bonding the spacer plates 5 to the intermediate end plates 4, for positioning alongside the heat exchanger plates 3.