stack of plates
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- ALFA LAVAL CORP AB
- Filing Date
- 2024-12-06
- Publication Date
- 2026-07-10
AI Technical Summary
Existing technologies struggle to permanently and flawlessly connect substantially flat plates, especially in fuel cells and electrolyzers, leading to a high likelihood of leaks and failures.
The design employs a bend in each board, allowing the boards to be stacked up and down along the stacking direction. The bends form clearly defined contact lines, and capillary action guides the brazing material to solidify at these contact lines, forming a leak-free joint.
It achieves tight and well-defined contact between essentially flat boards, ensuring leak-free joints and improving the reliability of board stacking.
Smart Images
Figure CN122374877A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to board stacks, systems including the board stacks, and methods for manufacturing board stacks. Background Technology
[0002] Board stacks can be permanently joined using various techniques. Joints can be formed using a joining method in which the boards are subjected to heat below their melting point. Such joining methods can involve brazing using added brazing materials (in the form of foil, paste, or powder, such as copper or nickel).
[0003] The aforementioned technique is typically used for permanently connecting corrugated metal plates in permanently sealed heat exchangers. The corrugations of the opposing plates come into contact with each other at clearly defined contact points. Molten brazing material accumulates at the contact points between the corrugated plates due to capillary forces, wetting the contact points and ensuring a proper, leak-free joint between the plates.
[0004] However, permanently connecting substantially flat plates is much more difficult than connecting corrugated plates because there are no clearly defined contact points between them. Substantially flat plates are particularly suitable for manufacturing fuel cells, electrolyzers, or similar devices, but are also used in some heat exchanger applications. A substantially flat plate is understood to be a plate defining a planar surface intended for connection to a corresponding planar surface of an opposing plate. However, these plates typically have through channels and port holes for accommodating fluids.
[0005] Flat plates are typically permanently joined by applying brazing material along the edges of the substantially flat plates or along port holes. However, this typically does not result in a leak-free joint. Because opposing plates cannot actually be positioned perfectly flat relative to each other, random contact points are typically present between the plates during stacking. During plate stacking, there will always be an area between opposing plates where there will be more or less clearance.
[0006] Because capillary forces are stronger in areas with a smaller gap between opposing plates and weaker in areas with a larger gap, molten brazing material or plate material will flow from areas with a larger gap (i.e., a larger distance) to areas with a smaller gap (i.e., a smaller distance). Therefore, areas with a larger gap may not receive a sufficient amount of molten material, and thus may not bond properly, potentially leading to leaks at those locations. This is considered a defect.
[0007] Using flat plates also makes it difficult to ensure they are joined in the correct location (i.e., near the edges or port holes). If the minimum distance between plates is closer to the center, there is a risk that all or most of the molten material will accumulate at that location. This can also lead to failure. Below is a brief description of some applications of substantially flat plates: Fuel cells use substantially flat plates and generate electricity through an electrochemical reaction between hydrogen-based fuel and an oxidant. A fuel cell typically comprises a set of fuel cell substrates assembled in series. Each fuel cell substrate includes a group of four (or more) substantially flat metal plates. The fuel cell substrate includes fuel plates, separator plates, oxidant plates, and an electrolyte plate located between the fuel and oxidant plates. The fuel and oxidant plates each include channels for distributing fuel and oxidant. The electrolyte plate contains an electrolyte material. The separator plates separate the fuel and oxidant plates. Current is generated by the electrochemical reaction between the fuel and oxidant that occurs at the electrolyte plate.
[0008] Electrolyzers also use largely flat plates to produce hydrogen and oxygen from water using electrical energy. Similar to fuel cells, electrolyzers consist of a set of largely flat metal plates and may face similar challenges.
[0009] The fuel cell substrate or electrolyzer consists of essentially flat plates arranged continuously face-to-face and joined along their outer edges to prevent leakage. They are also joined along port openings. However, as mentioned above, joining flat surfaces is very challenging due to the lack of clearly defined contact areas between the plates. Therefore, molten material may accumulate at random locations where there is little or no contact between the plates due to capillary forces, leaving other areas open. Consequently, the likelihood of defects in the joints is very high. Defective joints can lead to leaks between the plates.
[0010] EP3301747 describes an internally manifold-type solid oxide fuel cell stack.
[0011] Therefore, there is a need in the field to find a technology for permanently connecting flat plates that does not have the disadvantages mentioned above. Summary of the Invention
[0012] One object of the present invention is to overcome, at least in part, one or more limitations of the prior art. In particular, the object is to provide a stack of substantially flat plates that are permanently bonded without defects (such as leaks or failures, for example, when brazing material accumulates in one or more undesirable locations).
[0013] Another object of the present invention is to ensure close contact between large, substantially flat surfaces, as well as well-defined contact between surfaces.
[0014] As a first aspect of the invention, a plate stack is provided, wherein each plate is substantially flat, and wherein at least one plate includes a bend, the plates being stacked vertically on top of each other along a stacking direction, wherein each plate extends in a horizontal direction perpendicular to the stacking direction and defined by a longitudinal and a transverse direction, the plates defining at least a first plate gap between a first plate and an opposing second plate, and at least a second plate gap between a second plate and an opposing third plate, wherein the first and second gaps are arranged along the stacking direction, wherein the second plate has at least a first bend defining a first angled portion of the plate, the first angled portion having an extension deviating from the horizontal direction, wherein the second plate has at least a second bend defining a second angled portion of the plate, the second angled portion having an extension deviating from the horizontal direction in a direction different from the first angled portion, and wherein the distance between any first gap and second gap is less than the thickness of any plate.
[0015] The plates are generally flat, with one or more having bends. The first and second angled portions extend along a combination of the longitudinal and stacking directions. This can also be a combination of the transverse and stacking directions. The first and second bends are intentional bends, and each bend represents a significant and abrupt deviation from the horizontal direction.
[0016] An intentional, noticeable bend in the board is a slight deviation from the board's longitudinal or transverse direction. This causes the board to deviate from its horizontal orientation, resulting in an upward or downward deviation towards the stacking direction. An intentional bend allows for precise deviation of the board from its horizontal orientation.
[0017] Multiple consecutive plates are arranged in a stack. Opposing plates are defined as those arranged near adjacent plates in two consecutive plates. The stack comprises at least three plates, with a plate gap defining each of them. The plate gaps are typically very small. They essentially define the contact plane between the plates. The distance between two consecutive plates is less than the thickness of the plate. Because the plates are typically very thin, this means the plate thickness is usually less than 1 mm.
[0018] The first angled portion of the second plate has an extension across the gap between the second plates and contacts the third plate along a first contact line, which is a permanent joint between the second and third plates, and wherein the second angled portion of the second plate has an extension across the gap between the first and second plates and contacts the first plate along a second contact line, which is a permanent joint between the first and second plates.
[0019] The board stack can also be a mirror version, such that a first angled portion of the second board has an extension across the gap between the first boards and contacts the first board along a first contact line, which is a permanent joint between the first and second boards, and a second angled portion of the second board has an extension across the gap between the first and second boards and contacts the third board along a second contact line, which is a permanent joint between the second and third boards.
[0020] A bent plate with an angled portion meets an adjacent plate at the contact line, which is the intersection of the bent plate and the adjacent plate, thus connecting the surfaces of the two opposing plates. The contact line is a clearly defined path along the extension direction; that is, it extends as a straight line with a specific length.
[0021] The plates are made of metal, such as stainless steel. They are generally flat, meaning they are not corrugated. Plates with at least one intentionally curved portion are also defined as generally flat, as this is true along most of their extension, with at least one intentionally curved portion located at their outer edge. Some plates used in fuel cell applications define port holes and / or channels for fuel or oxidant in the inner region; however, the plate itself is generally flat.
[0022] The bending of the plate causes it to eventually contact the adjacent plate in the longitudinal direction, that is, across the clearance (gap) between the two continuous plates, creating a well-defined contact area between the two plates. Therefore, the contact point between the two continuous plates will attract molten brazing material or plate material from the area with the larger clearance, because capillary forces are stronger in areas with smaller distances between adjacent plates and weaker in areas with larger distances. Thus, the intentional bending causes the plate to meet the adjacent plate, resulting in well-defined contact lines that can attract brazing material.
[0023] According to a further embodiment of the first aspect, the first angled portion of the second plate has an extension defined by a first angle between the first angled portion and the horizontal direction, wherein the second angled portion of the second plate has an extension defined by a second angle between the second angled portion and the horizontal direction, and wherein the first angle is less than, greater than or equal to the second angle.
[0024] Each of the first and second angled portions has a relatively short extension. Because the intentionally curved portion is located near the edge of the plate, the angled portion defines a deviation from the horizontal direction near the end of the plate. This curved plate has its outer edge at approximately the same position as the adjacent plate. Thus, a large area between the substantially flat plates is surrounded and sealed by the contact line, making these areas leak-proof.
[0025] According to a further embodiment of the first aspect, the plate stack defines at least a third plate gap between the third plate and the opposing fourth plate along the stacking direction, wherein the third plate has a third bend defining a third angled portion of the plate, the third angled portion having an extension deviating from the horizontal direction, wherein the third angled portion of the third plate has an extension across the third plate gap and contacts the fourth plate along a third contact line, the third contact line being a permanent joint between the third plate and the fourth plate, and wherein the third angled portion of the third plate has an extension defined by a third angle between the third angled portion and the horizontal direction.
[0026] This is an embodiment of two consecutive plates with curved portions; one plate has two angled portions, and adjacent plates have one angled portion. Each curved plate contacts the more distant opposing plate. The plate stack can also be a mirror version, such that the second plate has a curved portion, and the third plate has first and second curved portions, such that the second plate contacts the first plate along a contact line, and the third plate contacts the second and fourth plates along contact lines, respectively. This achieves a more complex structure of curved plates, which can seal areas at different levels in the plate stack.
[0027] According to a further embodiment of the first aspect, the first angle, the second angle, and the third angle are constant angles along their respective angled portions. Therefore, each angled portion extends in a straight line; the first angle has a constant value such that the first angled portion has the same direction of extension over its entire length, the second angle has a constant value such that the second angled portion has the same direction of extension over its entire length, and the third angle has a constant value such that the third angled portion has the same direction of extension over its entire length.
[0028] According to a further embodiment of the first aspect, the first contact line contacts the third plate at an offset relative to the third curved portion of the third plate in a horizontal direction. The first contact line may contact the third plate at a horizontal portion of the third plate or at a third angled portion of the third plate.
[0029] According to a further embodiment of the first aspect, the first contact line contacts the third plate at a third angled portion, wherein the first angle is greater than the third angle. For the first contact line to adhere to the third angled portion of the third plate, the second plate needs to be offset more from the horizontal plane than the third plate.
[0030] According to a further embodiment of the first aspect, at least one of the contact lines surrounds the plate near its edge. The contact line may surround the plate, allowing the plate gap to form a fluid-tight internal region. Port orifices may be used to introduce fuel and oxidant into the fuel cell and may be surrounded at unused plate gaps.
[0031] According to a further embodiment of the first aspect, each of the first angle, the second angle, and the third angle is in the range of 0 to 20°, specifically 4°-6°, and / or 6°-8°, and / or 8°-9°, and / or 9°-10°, and / or 10°-11°, and / or 11°-13°, and / or 13°-15°, and / or 15°-17°, and / or 17°-19°.
[0032] According to a further embodiment of the first aspect, the first contact line, the second contact line, and the third contact line extend in a longitudinal or transverse direction. The contact lines follow the contour of a stack around the plates. The plates are typically rectangular with vertical corners.
[0033] According to a further embodiment of the first aspect, the first contact line, the second contact line, and the third contact line extend along a combination of longitudinal and transverse directions. Therefore, the contact lines can also be arranged where the profile has no vertical edges, such as rounded corners, or where edges are chamfered or beveled.
[0034] According to a second aspect of the invention, the objective is achieved by a system comprising a stack of plates according to any of the embodiments mentioned above, the system being a fuel cell or an electrolyzer.
[0035] Fuel cells and electrolyzers are examples of applications that use essentially flat plates.
[0036] According to a third aspect of the invention, the objective is achieved by a method of manufacturing a stack of plates, wherein each plate is substantially flat, and wherein at least one plate includes a bent portion, comprising the following steps: The plate is pressed into at least a first curved portion and a second curved portion, which define a first angled portion and a second angled portion of the plate. A curved plate is arranged between two opposing plates along the stacking direction, thereby defining a first plate gap and a second plate gap between the plates. Furthermore, the distance between any first gap and any second gap is limited to be less than the thickness of any plate. The first contact line is located between the bent plate and the first opposing plate, and the second contact line is located between the bent plate and the second opposing plate. A permanent connection plate is formed at the first contact line and the second contact line.
[0037] Methods to achieve a curved section include cutting, bending, stretching, and pressing.
[0038] According to a further embodiment of the third aspect, the method further includes an initial step of applying brazing material to at least one of the contact lines.
[0039] While various techniques can be used to permanently bond boards, brazing material is preferred. Brazing material is preferably applied directly to the board via printing (such as screen printing). To reduce the risk of brazing material runoff, it can be deposited directly onto the board at the location where contact lines will form. Printing techniques can be used to precisely deposit brazing material onto the board at the locations where contact lines will form.
[0040] The brazing material has a lower melting temperature than the metal in the plate, and therefore, when the plate is heated above the melting point of the brazing material, the brazing material becomes liquid and fills the gaps between the plates through capillary action. Upon cooling, the brazing material solidifies to form a joint.
[0041] According to a further embodiment of the third aspect, at least one of the contact lines surrounds the plate near its edge.
[0042] The method described above according to the third aspect is preferably used in conjunction with plate stacking according to the first aspect. Attached Figure Description
[0043] Figure 1 It is a side sectional view of a stack of multiple plates.
[0044] Figure 2 It is a side sectional view of a stack of three plates.
[0045] Figure 3 It is a side sectional view of a stack of four plates.
[0046] Figure 4 It is based on Figure 3 Perspective and close-up views of the stacked boards after they are permanently linked together. Detailed Implementation
[0047] Figure 1 A perspective view of a stack of substantially flat plates 100 stacked one on top of the other is disclosed. The plates are stacked along a stacking direction (defined by the Z-axis). Each plate extends horizontally, perpendicular to the stacking direction and defined by longitudinal and transverse directions. The longitudinal direction is defined by the X-axis, and the transverse direction is defined by the Y-axis. These three axes are defined according to a Cartesian coordinate system.
[0048] The boards have substantially the same area and are stacked one on top of the other, in substantially the same position, leaving substantially the same footprint, i.e., with roughly the same outer edge extension when viewed along the XY direction. The boards are arranged sequentially; the first board is followed by the next second board, and so on. An exemplary set of boards is shown. A board stack typically includes at least three boards.
[0049] Figure 2An embodiment with a stack of three plates is shown. A first plate 11, a second plate 12, and a third plate 13 are shown at one of its outer ends. In this embodiment, the first plate 11 is the top plate, and the second plate 12 is disposed between the first plate 11 and the third plate 13. The plates are arranged parallel to each other, one above the other, and there is a gap between two consecutive plates. There is a first gap 21 between the first plate 11 and the second plate 12, and a second gap 22 between the second plate 12 and the third plate 13. Each plate has a thickness defined as a distance t along the stacking direction Z. Each gap has a distance d between two adjacent plates (i.e., the distance between their opposite surfaces), defined along the stacking direction Z.
[0050] All three plates are substantially flat. However, the second plate 12 deviates from the horizontal near its outer edge due to a first bend 121 and a second bend 122. The first bend 121 causes the plate to extend away from the horizontal direction, which is defined by a first angle α relative to the horizontal direction. This defines a first angled portion 12a of the second plate 12. The first angled portion 12a meets the third plate 13 at a first contact line 41. And at this location of the second plate 12, the second bend 122 causes the plate to have another deviation relative to the horizontal direction defined by a second angle β. The second plate eventually meets the first plate 11 along a second contact line 42, which is the outer edge of the second plate 12. The portion of the second plate between the first contact line 41 and the second contact line 42 is the second angled portion 12b. The contact lines 41, 42 follow the profile of the plate stack at the intersection between the two plates. Therefore, the contact lines 41, 42 surround the plate stack near the edge.
[0051] Figure 3 An embodiment of a board stack having four plates is disclosed. A first plate 11, a second plate 12, a third plate 13, and a fourth plate 14 are arranged and shown at the outer ends of the board stack. In this embodiment, the first plate 11 is the top plate, and the second plate 12 and the third plate 13 are arranged between the first plate 11 and the fourth plate 14. The plates are arranged parallel to each other, one above the other, and opposite to each other. There are gaps between two consecutive plates. There is a first gap 21 between the first plate 11 and the second plate 12, a second gap 22 between the second plate 12 and the third plate 13, and a third gap 23 between the third plate 13 and the fourth plate 14.
[0052] All four plates are substantially flat. However, the second plate 12 deviates from the horizontal near its outer edge due to a first bend 121 and a second bend 122. The first bend 121 causes the plate to extend away from the horizontal direction, which is defined by a first angle α relative to the horizontal direction. Thus, a first angled portion 12a is defined for the second plate 12. The first angled portion 12a meets the third plate 13 at a first contact line 41. And at this position of the second plate 12, the second bend 122 causes the plate to have another deviation from the horizontal direction (different from the first angled portion 12a) defined by a second angle β. The second plate eventually meets the first plate 11 along a second contact line 42 located at the outer edge of the second plate 12. The portion of the second plate between the first contact line 41 and the second contact line 42 is defined as a second angled portion 12b. The third plate 13 deviates from the horizontal at its outer edge due to a third bend 131. The third bend 131 causes the plate to extend away from the horizontal direction, which is defined by a third angle γ relative to the horizontal direction. This defines the third angled portion 13a of the third plate 13. The third angled portion 13a meets the fourth plate 14 at the third contact line 43, which is located at the outer edge of the third plate 13 and close to the outer edge of the fourth plate 14.
[0053] The contact line 41 of the second plate 12 is slightly offset from the third bend 131 and meets the third plate 13. Therefore, the contact line 41 and the third bend 131 are not located in the same position when viewed in the horizontal direction (i.e., longitudinal direction X and transverse direction Y).
[0054] The angled portions extend along a combination of the longitudinal and stacking directions (XZ) or a combination of the transverse and stacking directions (YZ). The first and second bends are intentional bends, and each bend represents a significant and abrupt deviation from the horizontal direction.
[0055] The joining technique used can be brazing, as previously described. The brazing material has a lower melting temperature than the metal of the plate. Therefore, when the plate is heated to a temperature above the melting point of the brazing material, the brazing material applied to the plate becomes liquid and fills the gaps between the plates through capillary action. Capillary forces are stronger where the gap between two consecutive plates is smaller, and thus the liquefied brazing material will accumulate at locations where the distance between the plates is narrower. The brazing material solidifies upon cooling and forms a joint. Therefore, the joint is defined by the bonding contact line (i.e., around the contact line).
[0056] Similarly, in Figure 3 In this configuration, each plate has a thickness defined as a distance t, and each gap has a distance d defined along the stacking direction Z between adjacent plates, as shown below. Figure 2 As shown. This is not included in the figure.
[0057] All angles are constant along their respective angled portions. This means that each angled portion has a straight line extension. The first angle α has a constant value such that the first angled portion has the same direction of extension along its entire length, the second angle β has a constant value such that the second angled portion has the same direction of extension along its entire length, and the third angle γ has a constant value such that the third angled portion has the same direction of extension along its entire length.
[0058] The angles are typically in the range of 0° to 20°, with each of the first, second, and third angles falling within the ranges of 4°–6°, and / or 6°–8°, and / or 8°–9°, and / or 9°–10°, and / or 10°–11°, and / or 11°–13°, and / or 13°–15°, and / or 15°–17°, and / or 17°–19°. Figure 3 In this context, it may mean that the first angle α can have a value of 8°-15°, the second angle β can have a value of 17°-20°, and the third angle γ can have a value of 4°-8°.
[0059] Contact lines 41, 42, and 43 are stacked around the plate near the edge, so the contact lines are arranged at the periphery of the plate, which means they are arranged near the outer edge of the plate.
[0060] Only exemplary embodiments of a plate stack have been disclosed. Further embodiments with more than four plates arranged one above the other are also conceivable. Thus, other combinations of plates in a plate stack can be formed. However, the two outermost plates (i.e., the first and last plates along the stacking direction) are substantially flat plates without any intentional bends.
[0061] Figure 4 A perspective view of an embodiment of a board stack 100' is shown, the board stack consisting of... Figure 3 The plates in the middle are formed after the plates are permanently connected. Figure 3 The board is used as an example; the board stack can also be made by Figure 2 It consists of three or more boards. The stack of boards includes port holes.
[0062] When manufacturing a board stack, the intentional bending of the boards can be achieved by cutting, bending, stretching, pressing, etc. Different techniques can be applied to permanently connect the boards into a stack, with brazing materials being preferred. Although this disclosure describes boards permanently sealed together by brazing, those skilled in the art will understand that fusion welding or similar methods can also be used.
[0063] The plates, angles, and gaps described in this article have been exaggerated for greater visibility.
[0064] Reference List 11: First board 12: Second board 12a: The first angled portion of the second plate 12b: The second angled portion of the second plate 13: Third Board 13a: The third angled portion of the third plate 14: Fourth Board 21: Gap between the first plates 22: Gap between the second plates 23: Gap between the third plates 41: First contact line 42: Second contact line 43: Third contact line 100: Board stacking 100': Board stacking 121: The first bend of the second plate 122: The second bend of the second plate 131: The third bend of the third plate X: Vertical direction Y: Horizontal direction Z: Stacking direction α: First angle (of the second board) β: Second angle (of the second plate) γ: Third angle (of the third plate) t: Plate thickness d: Distance of the gap
Claims
1. A stack of plates (100, 100') wherein each plate is substantially flat, and wherein at least one plate includes a bend, the plates being stacked vertically on top of each other along a stacking (Z) direction. Each plate extends in a horizontal direction perpendicular to the stacking direction and defined by longitudinal (X) and transverse (Y) directions. The plates define at least a first plate gap (21) between the first plate (11) and the opposite second plate (12), and at least a second plate gap (22) between the second plate (12) and the opposite third plate (13). The first gap and the second gap (21, 22) are arranged along the stack (Z) direction. The second plate (12) has at least a first curved portion (121) defining a first angled portion (12a) of the plate, the first angled portion having an extension deviating from the horizontal direction. The second plate (12) has at least a second curved portion (122) defining a second angled portion (12b) of the plate, the second angled portion having an extension deviating from the horizontal direction in a direction different from the first angled portion (12a). Wherein the distance (d) between any of the first gaps and the second gaps (21, 22) is less than the thickness (t) of any of the plates (11, 12, 13), The first angled portion (12a) of the second plate (12) extends across the gap (22) between the second plates and contacts the third plate (13) along a first contact line (41), the first contact line being a permanent joint between the second plate and the third plate (12, 13), and the second angled portion (12b) of the second plate (12) extends across the gap between the first plate and the gap between the second plates (21, 22) and contacts the first plate (11) along a second contact line (42), the second contact line being a permanent joint between the first plate and the second plate (11, 12).
2. The stacking of plates according to claim 1, wherein, The first angled portion (12a) of the second plate (12) has an extension defined by a first angle (α) between the first angled portion (12a) and the horizontal direction. The second angled portion (12b) of the second plate (12) has an extension defined by a second angle (β) between the second angled portion (12b) and the horizontal direction. And the first angle (α) is less than, greater than or equal to the second angle (β).
3. A stack of plates according to any of the preceding claims, wherein, The stacking of the plates defines at least a third plate gap (23) between the third plate (13) and the opposing fourth plate (14) along the stack (Z) direction. The third plate (13) has a third curved portion (131) defining a third angled portion (13a) of the plate, the third angled portion having an extension deviating from the horizontal direction. The third angled portion (13a) of the third plate (13) extends across the gap (23) between the third plates and contacts the fourth plate (14) along a third contact line (43), the third contact line being a permanent joint between the third plate and the fourth plate (13, 14). Furthermore, the third angled portion (13a) of the third plate (13) has an extension defined by a third angle (γ) between the third angled portion (13a) and the horizontal direction.
4. A stack of plates according to any of the preceding claims, wherein, The first angle, the second angle, and the third angle (α, β, γ) are constant angles along their respective angled portions.
5. The stacking of plates according to claim 3 or 4, wherein, The first contact line (41) contacts the third plate (13) offset relative to the third bend (131) of the third plate (13) along the horizontal direction.
6. A stack of plates according to any of the preceding claims 3-5, wherein, The first contact line (41) contacts the third plate (13) on the third angled portion (13a). And the first angle (α) is greater than the third angle (γ).
7. A stack of plates according to any of the preceding claims 1-6, wherein, At least one of the contact lines (41, 42, 43) surrounds the plate near the edge of the plate.
8. A stack of plates according to any of the preceding claims 2-7, wherein, Each of the first angle, the second angle, and the third angle (α, β, γ) is in the range of 0 to 20°.
9. A stack of plates according to any of the preceding claims 1-8, wherein, The first contact line, the second contact line, and the third contact line (41, 42, 43) extend along the longitudinal (X) direction or along the transverse (Y) direction.
10. A stack of plates according to any of the preceding claims 1-8, wherein, The first contact line, the second contact line, and the third contact line (41, 42, 43) extend along a combination of the longitudinal (X) and the transverse (Y) directions.
11. A stack of plates according to any of the preceding claims, wherein, The permanent joint is a brazed joint.
12. A system comprising a stack of plates according to any of the preceding claims, wherein the system is a fuel cell or an electrolyzer.
13. A method for manufacturing a stack of boards, wherein, Each plate is substantially flat, and at least one of the plates includes a bent portion, comprising the following steps: The plate is pressed into a shape that includes at least a first curved portion defining a first angled portion of the plate and a second curved portion defining a second angled portion of the plate. A bent plate is arranged between two opposing plates along the stacking direction, such that a first plate gap and a second plate gap are defined between the plates, wherein the distance (d) between any of the first gap and the second gap is defined to be less than the thickness (t) of any of the plates, wherein a first contact line is defined between the bent plate and the first opposing plate, and wherein a second contact line is defined between the bent plate and the second opposing plate. The plate is permanently connected at the first contact line and the second contact line.
14. The method of claim 13, further comprising the initial step of applying brazing material to at least one of the contact lines.
15. The method according to any of the preceding claims 13-14, wherein, At least one of the contact lines surrounds the plate near its edge.