Separator plate for an electrochemical system

Abstract

The invention relates to a separator plate for an electrochemical system. The electrochemical system can in particular be a fuel cell system, an electrochemical compressor, an electrolyzer or a redox flow battery. The invention also discloses an electrochemical system comprising multiple separator plates of this type.

Description

[0001] REINZ Sealing GmbH, Robert Bosch GmbH

[0002] 1

[0003] Separator plate for an electrochemical system

[0004] The invention relates to a separator plate for an electrochemical system. The electrochemical system can, in particular, be a fuel cell system, an electrochemical compressor, an electrolyzer, or a redox flow battery. An electrochemical system comprising a plurality of such separator plates is also disclosed.

[0005] Known electrochemical systems of this type typically comprise a stack of electrochemical cells, each separated from one another by separator plates. In the context of such stacks, the separator plates are also referred to as bipolar plates. The separator plates can serve, for example, to electrically contact the electrodes of the individual electrochemical cells (e.g., fuel cells) and / or to electrically connect neighboring cells (series connection of the cells). Typically, the separator plates are formed from two individual plates, in particular joined together. The individual plates can be joined together in a materially bonded manner, e.g., by one or more welded joints, in particular by one or more laser-welded joints.

[0006] The separator plates or the individual plates can each have or form structures that are designed, for example, to supply the electrochemical cells arranged between adjacent separator plates with one or more media and / or to transport reaction products away. In particular, these structures can be used to guide a cooling fluid through a space between the individual plates of a separator plate. The structures can, for example, comprise sequences of webs and channels. The media can therefore be fuels (e.g., hydrogen or methanol), reaction gases (e.g., air or oxygen), or coolants. In the context of this disclosure, the terms medium and fluid can be used synonymously.

[0007] Furthermore, the separator plates usually each have at least one through-opening through which the media can be guided to or away from the electrochemical cells or membrane electrode assemblies (MEAs) arranged between adjacent separator plates of the stack. From such a through-opening, a respective fluid is guided by means of the structures described above into a respective first distribution region and from there into a flow field opposite the active region of the cell or MEA. After flowing through the active region, the fluid is fed back to an outlet through-opening via a second distribution region, also called a collection region. An example of this can be found in DE 20 2016 107 302 U1.

[0008] It is known to conduct a first fluid, e.g., a fuel, on a first outer side of the separator plate, i.e., an outer side of a first individual plate, and to conduct a second fluid, e.g., a reaction gas, on a second outer side of the separator plate facing away from the first outer side, i.e., an outer side of a second individual plate. In contrast, a cooling fluid is usually conducted in an interior space defined by the inner sides of the individual plates. The fluid-conducting structures on the respective outer sides of the individual plates form complementarily shaped structures on their inner sides, which conduct the cooling fluid.

[0009] However, it has been shown that the performance of such electrochemical systems can still be optimized. For example, the fluid channels between the through-holes and a flow field still occupy a significant portion of the surface area on the respective sides of a separator plate. This surface area is not available as the active area of ​​the cell and therefore does not directly contribute to its performance.

[0010] An object of the present invention is therefore to improve the performance of an electrochemical system having a plurality of such separator plates.

[0011] This problem is solved by the subject matter of the independent claims. Advantageous further developments are specified in the dependent claims as well as in this description and the figures.

[0012] Accordingly, a separator plate for an electrochemical system is proposed, the system comprising:

[0013] - a first single plate and a second single plate, the inner sides of which face each other,

[0014] - at least one first through-opening for passing air or oxygen through the separator plate, - at least one second through-opening for passing hydrogen through the separator plate, wherein the first individual plate has a first flow field on its outer side and at least one first distribution region which fluidically connects the first flow field and the first through-opening, wherein the second individual plate has a second flow field on its outer side and at least one second distribution region which fluidically connects the second flow field and the second through-opening, wherein the first and second distribution regions each have a plurality of fluid-conducting channels, wherein the first and second flow fields each have a flow field main flow axis along which they can be flowed through by the respective fluid,and a length dimension of the first and second distribution region extends parallel to the respective flow field main flow axis, ie to the respective flow field main flow axis of the flow field to which a distribution region under consideration is fluidically connected, wherein the first and second distribution region each have a width dimension orthogonal to the respective flow field main flow axis, wherein:

[0015] - a maximum length of the first distribution area is less than 28% of a maximum width of the first distribution area; and

[0016] - a channel length of the first distribution area averaged over the number of channels is less than 30%, in particular less than 28% of the maximum width of the first distribution area.

[0017] It was discovered that by appropriately specifying the length and width, and compared to existing solutions, the surface area of ​​the first distribution area on the outside of the first individual plate can be significantly reduced without significantly impairing the function of the separator plate. Conversely, the surface area of ​​the first flow field can be increased, improving the performance of an electrochemical system comprising the separator plate. The second distribution area can also be reduced accordingly, while the surface area of ​​the second flow field can be increased.

[0018] Such length and width specifications are not provided for in the prior art. This is usually avoided because reducing the size of a distribution area along one dimension would require compensating increases in another dimension to provide sufficient flow cross-sections for the fluid to be conveyed. Instead, the invention recognizes that the various parameters of the distribution area can be jointly varied and combined in such a way that the surface area of ​​the distribution area can be reduced without significantly impairing the fluid distribution.

[0019] The aim was to reduce the length of the distribution field for a fixed flow field without significantly changing its width. Instead, an average channel length was reduced. As a result, the required proportions were maintained.

[0020] Any distribution region disclosed here can be configured to allow a guided fluid to flow through it, in particular continuously and / or simultaneously in all channels encompassed by the distribution region. Preferably, none of the distribution regions has channels or regions in which fluid can accumulate. The channels of each distribution region can be embossed into the respective plate. Each channel can be elongated and / or delimited by webs. Any two adjacent channels can be separated from each other by a web between them.

[0021] Furthermore, any distribution region disclosed herein can be spatially positioned between the through-opening, in particular a center of gravity thereof, and the flow field that the distribution region fluidically connects to one another. This intermediate positioning can, in particular, be along the flow field's main flow axis of the flow field fluidically connected to the distribution region.

[0022] Usually, in addition to the passages for oxygen and hydrogen, the separator plate also has a passage for coolant. The passage for coolant is preferably arranged between the passage for oxygen and the passage for hydrogen in a direction perpendicular to the flow field main flow axis. The end of the distribution area facing away from the flow field can be defined by the furthest point of a distribution area from which the medium guided on the outer surface of the individual plate is guided between the coolant passage and the distribution area in the direction of the flow field past the coolant passage. The width of a distribution area can be defined such that it corresponds to the width of the associated flow field. The latter can be defined as the distance between the points deflected most strongly from the plane of the flat surface, i.e.of the channel base, the outermost channel of the flow field. If one or both of these outermost channels exhibit not only a line of maximum deflection from the plane of the plane, but also a bottom surface of maximum deflection from the plane of the plane, the center line of this bottom surface, i.e., the center orthogonal to the flow field's main flow axis, is considered. If the flow field is formed by periodically deflected, for example, wave-shaped channels and webs, the width of the flow field, and thus also the width of the distribution area, can be determined from the width of the center lines of the lowest points of the outermost channels or the corresponding bottom surfaces.

[0023] If the flow field does not only have straight, parallel channels and webs or periodically deflected channels, the average width of the last 10% of the length of the flow field adjacent to the distribution area in question can be considered as the width of the flow field.

[0024] The end of the flow field toward the distribution area can be defined at the point where, on an outer side of the flow field, which, for example, forms an outer side or an outer edge of the flow field when viewed transversely to the flow field's main flow axis, the centerline of the outermost channel experiences a first change in direction relative to the flow field's main flow axis, which change amounts to at least 0.5% of the width of the flow field. This can mean that the centerline changes its direction relative to the flow field's main flow axis, so that the distance of the centerline from this flow field's main flow axis changes by at least 0.5% of the width of the flow field. The location at which this change in distance first occurs can define the end of the flow field toward the distribution area.

[0025] If the changes occur at different locations on both outer sides, the location that is closer to the outer edge of the individual plate that is at least substantially orthogonal to the flow field main flow axis and that lies beyond the nearest through openings can be considered.

[0026] In the case of wave-shaped flow fields, only those changes that do not follow the wave pattern should be considered. The separator plate can have regions with different heights, e.g. an area that is lowered relative to another region. For example, mean, minimum or maximum heights of the respective regions can be considered. Alternatively, one can speak of differences in the thickness of the separator plate. The regions with different heights can each extend over a large part of the width of the separator plate, in particular over the region in which fluid-carrying channels are formed, wherein this width can run transversely to any of the main axes of the flow field. The differences in thickness are preferably not formed in the regions in which the sealing elements are formed.

[0027] Additionally or alternatively, these regions can be distributed along any of the flow field's main axes and / or follow one another. As explained below, the distribution region and the flow field can be arranged in regions that differ from one another, wherein a height, in particular a mean or maximum height, of these regions differs from one another. Locations of maximum height can, for example, comprise web crests, wherein a respective web can run between adjacent channels and separate them from one another. At the transition between a distribution region and the flow field, a further region of different height can be arranged, which has a lower height than both the rest of the flow field and the rest of the distribution region.This transition area can be allocated proportionally to both with regard to the aforementioned demarcation between flow field and distribution area or belong to only one of the two; in this case, only the aforementioned width definition should be decisive.

[0028] The height and thickness can be measured orthogonally to a flat surface plane of the separator plate and in particular to a flat surface plane of any of its individual plates. In a manner known per se, the flat surface plane of a respective individual plate can be defined, for example, by an edge of the individual plate or by those flat areas of the individual plate that are not deformed as a result of a stamping or deep-drawing process to form the web-channel structures or beads described herein. On the one hand, the flat surface planes can run in the neutral fibers of the corresponding sections of the plates; on the other hand, it is also possible to consider the surfaces of the relevant sections of the plates as flat surface planes. With the latter approach, however, it must be ensured that when considering distances or the like, the material thickness of only one of two plates considered is taken into account.By providing regions of different heights, for example, a first region may be lowered relative to the plane of the planar surface, whereas another region may be lowered more or less significantly relative to the plane of the planar surface. Alternatively, the further region may be located in the plane of the planar surface or raised relative to it. Raising the region relative to the plane of the planar surface may be equivalent to removing opposing regions of the individual panels, whereas lowering the region may reduce the distance between these opposing regions.

[0029] According to one variant, the separator plate comprises a height-reduced and / or lowered first region, which is preferably configured for coverage by a gas diffusion layer (GDL). The first region can be height-reduced or lowered, for example, relative to a planar surface and / or relative to a second region explained below. The first region can comprise the flow fields of the separator plate. A GDL can be arranged, as is known, on one or both surfaces of an MEA, which is supported by the separator plate and is arranged, in particular, between two adjacent separator plates of a stack. The first region can be used as an active region by overlapping the GDL and the MEA.

[0030] Additionally or alternatively, the separator plate comprises at least one second region that is raised and / or not of reduced height. This can apply, for example, compared to a flat surface and / or the first region explained above. When comparing the heights of the first and second regions, locations of maximum height of these regions can be compared with each other, in particular, the web crests of these regions. Any distribution region disclosed here can be encompassed by a raised second region.

[0031] In summary, a further development provides that the separator plate has a first region which in particular comprises the flow fields and which has a lower, in particular maximum, height compared to at least one second region, wherein the second region comprises at least one first and at least one second distribution region of the type explained above. These first and second regions can therefore be defined such that they comprise portions of the outer sides of both individual plates, i.e. complete sections and in particular complete cross-sections of the joined separator plate. In this sense, the aforementioned transition region can represent a third region in terms of height, but in terms of width can belong either entirely to the first region, entirely to the second region, or partly to the first and partly to the second region, depending on the width of the outermost channels on both sides.

[0032] Any flow field disclosed here may, for example, be characterized in that all webs and channels encompassed thereby are rectilinear over at least a large part of their length and run parallel to one another and parallel to a flow field main flow direction of this flow field.

[0033] Alternatively, the webs and channels of a respective flow field can also be wave-shaped and run next to each other and along the main flow axis with a similar wave shape.

[0034] The flow field main flow axis can correspond to a longitudinal axis and / or an axis of symmetry, in particular a mirror symmetry axis, of a respective flow field or run parallel thereto. The separator plate can have two outer edges or longitudinal sides that are opposite one another and, at least in sections, each run along at least one of the flow field main flow axes. The flow field main flow axes of the first and second flow fields can run parallel to one another or coincide with one another, in particular in an orthogonal projection into a common plane.

[0035] To achieve low flow resistance, it is advantageous if the channel lengths, as well as the total and average channel lengths in a distribution area, are short. The average channel length can be determined by summing all individual channel lengths of a distribution area on the outer side of a single plate and then dividing by the number of these channels.

[0036] According to a further development, a maximum length of the second distribution region is less than 65%, preferably less than 55%, in particular less than 50%, of the maximum length of the first distribution region. A corresponding reduction in the size of the second distribution region creates additional degrees of freedom in order to provide flow spaces for the cooling fluid, in particular by means of the second individual plates. In particular, this can reduce the flow resistance of the cooling fluid in the first distribution region. A reduced length of the second distribution region compared to the first distribution region is also acceptable because the second distribution region carries hydrogen, for which flow resistances that are only partially relevant result from this reduction. However, it can also be provided that the maximum length of the second distribution region is greater than 35%, in particular greater than 40%, of the maximum length of the first distribution region.

[0037] A further development provides that the first and second flow fields are lowered relative to the respective first and second distribution regions connected thereto. The connection relates to the fluid-conducting connection of the distribution region and the flow field. In particular, the lowering can apply with respect to locations of maximum height encompassed by the distribution regions and flow fields. These can be, for example, web crests and preferably not channel bottoms. This further development can be realized in particular by and / or can in particular comprise the flow fields being encompassed by a first region of the type discussed above and the distribution regions being encompassed by a second region of the type discussed above, wherein the first region is lowered relative to the second region.

[0038] In a further embodiment, the maximum length of the first and second distribution areas lies between a transition from the respective distribution area and (or to) an associated flow field and a point of the respective distribution area that is maximally remote from this transition.

[0039] Additionally or alternatively, a maximum dimension of the first and second distribution regions can be orthogonal to one of the flow field main flow axes, respectively, in an edge region of the first and second distribution regions, in which fluid from the correspondingly connected one of the first and second flow fields is fed into the distribution regions or in which fluid from the distribution regions is fed into the correspondingly connected one of the first and second flow fields. In particular, the maximum dimension can be orthogonal to the flow field main flow axis of the flow field that is fluidly connected to the distribution region in question.

[0040] The invention also relates to an electrochemical system comprising a plurality of separator plates according to any aspect disclosed herein.

[0041] The invention is explained below with reference to the accompanying schematic figures. The same reference numerals may be used for similar or equivalent features throughout the figures. Figure 1 shows a perspective view of an electrochemical system with a plurality of stacked separator plates with membrane electrode assemblies arranged between them.

[0042] Figure 2 shows a perspective view of two separator plates of a system similar to Figure 1 with a membrane electrode assembly (MEA) arranged between the separator plates.

[0043] Figure 3 is an illustration of a portion of a separator plate according to an example of the prior art.

[0044] Figure 4 is a simplified schematic representation of the fluid flow in the separator plate from Figure 3.

[0045] Figure 5 is an illustration of a portion of a separator plate according to a first embodiment of the invention.

[0046] Figure 6 is a simplified schematic representation of the fluid flow in the separator plate from Fig. 5.

[0047] Figure 7 is a schematically simplified representation of the fluid guide in a separator plate according to a further embodiment of the invention

[0048] Figure 1 shows an electrochemical system 1 of the type proposed here with a plurality of identical metallic separator plates 2 (or bipolar plates). These are arranged in a stack 6 and stacked along a z-direction 7. The separator plates 2 of the stack 6 are clamped between two end plates 3, 4. The z-direction 7 is also called the stacking direction. In the present example, the system 1 is a fuel cell stack. Two adjacent separator plates 2 of the stack 6 enclose an electrochemical cell between them, which serves, for example, to convert chemical energy into electrical energy. To form the electrochemical cells of the system 1, a membrane electrode assembly (MEA) 10 is arranged between each adjacent separator plates 2 of the stack 6 (see Figure 2 below). The MEAs typically each contain at least one membrane, e.g., an electrolyte membrane.Furthermore, a gas diffusion layer (GDL) can be arranged on one or both surfaces of the MEA. In alternative embodiments, the system 1 can also be designed as an electrolyzer, compressor, or redox flow battery. Separator plates can also be used in these electrochemical systems. The structure of these separator plates can correspond to the structure of the separator plates 2 explained in more detail here, even if the media conveyed on or through the separator plates in an electrolyzer, an electrochemical compressor, or a redox flow battery can differ from the media used in a fuel cell system.

[0049] The z-axis 7, together with an x-axis 8 and a y-axis 9, spans a right-handed Cartesian coordinate system. The separator plates 2 each define a plate plane, wherein the plate planes of the separator plates 2 are each aligned parallel to the xy-plane and thus perpendicular to the stacking direction (z-axis 7). The end plate 4 has a plurality of media connections 5 through which media can be supplied to the system 1 and through which media can be removed from the system 1. These media that can be supplied to the system 1 and removed from the system 1 can include, for example, fuels such as molecular hydrogen or methanol, reaction gases such as air or oxygen, reaction products such as water vapor or depleted fuels, or a cooling fluid such as water and / or glycol.

[0050] Figure 2 shows a perspective view of two adjacent separator plates 2 or bipolar plates that may be comprised of an electrochemical system of the type of system 1 shown in Figure 1. The separator plates 2 correspond to an example from the prior art. However, the properties and features explained below with reference to them may also apply to the separator plates 2 according to the invention disclosed here or be provided in them, unless otherwise stated or apparent.

[0051] Fig. 2 also shows a known membrane electrode assembly (MEA) 10 arranged between these adjacent separator plates 2, wherein the MEA 10 in Fig. 2 is largely concealed by the separator plate 2 facing the viewer. The separator plate 2 is formed from two materially joined individual plates 2a, 2b, of which in Fig. 2 only the individual plate 2a facing the viewer is visible, which conceals the other individual plate 2b. The individual plates 2a, 2b can each be made of a metal sheet, e.g., a stainless steel sheet. The individual plates 2a, 2b can, for example, be welded to one another, e.g., by laser welding, or can be connected only when the stack is stacked. In particular, the design of fluid-conducting structures on the outer side of the individual plate 2a facing the viewer can differ in Fig. 2 from the structures according to the invention in the further figures below.

[0052] The individual plates 2a, 2b have aligned through-openings, which form through-openings 11a-c of the separator plate 2. When a plurality of separator plates 2 are stacked, the through-openings 11a-c form lines that extend through the stack 6 in the stacking direction 7 (see Figure 1). Typically, each of the lines formed by the through-openings 11a-c is in fluid communication with one of the ports 5 in the end plate 4 of the system 1. For example, a cooling fluid can be introduced into the stack 6 or discharged from the stack 6 via the lines formed by the through-openings 11a. The lines formed by the through-openings 11b, 11c, on the other hand, can be designed to supply the electrochemical cells of the fuel cell stack of the system 1 with fuel and reaction gas, and to discharge the reaction products from the stack 6.

[0053] To seal the through-openings 11a-c from the interior of the stack 6 and from the environment, the individual plate 2a facing the viewer has sealing arrangements in the form of sealing beads 12a-c. These are arranged around the through-openings 11a-c and completely enclose the through-openings 11a-c. The second individual plate 2b also has corresponding sealing beads 12a-c on the rear side of the separator plate 2 facing away from the viewer in Figure 2 for sealing the through-openings 11a-c (not shown). Alternative sealing systems, such as elastomer seals, can also be used.

[0054] Adjacent to the electrochemically active region 18 of the MEA, the individual plate 2a facing the viewer has, on its outer side facing the viewer, a flow field 17a with structures for guiding a reaction medium along the outer side of the individual plate 2a. These structures are designed in Figure 2 in the form of a plurality of webs and channels running between the webs and delimited by the webs. On the outer side of the separator plate 2 facing the viewer, the individual plate 2a facing the viewer also has two distribution regions 20a. The distribution regions 20a each comprise structures which are designed to distribute a medium introduced from a first of the two through-openings 11b into one of the distribution regions 20a over the active region 18 by means of the flow field 17a or to guide a medium introduced from the active region 18 orto collect or concentrate the medium flowing from the flow field 17a to the second of the through-openings 11b. In the latter case, the collecting distribution region 20a can also be referred to as a collection region. The fluid-conducting structures of the distribution regions 20a are also represented in Figure 2 by webs and channels extending between the webs and delimited by the webs.

[0055] Without this being specifically shown in Figure 2, a cooling fluid distribution structure 19 formed and / or enclosed between the individual plates 2a, 2b also has distribution regions 20c that overlap with the distribution regions 20a, b of the individual plates 2a, 2b. This cooling fluid distribution structure 19 is fluidically connected to a flow field 17c that overlaps with the flow fields 17a, b of the outer sides of the individual plates 2a, 2b or is enclosed between them, or encompasses this flow field 17c. The web-channel structures on the outer sides of the individual plates 2a, 2b form complementarily shaped web-channel structures on the corresponding inner sides and thus complementarily shaped web-channel structures of the cooling fluid distribution structure 19.

[0056] The two through-openings 11b, or the lines formed by the through-openings 11b through the plate stack of system 1, are each fluidically connected to one another via passages 13b in sealing beads 12b, via the distribution structures of the distribution regions 20, and via the flow field 17a of the individual plate 2a facing the viewer of Figure 2. This individual plate 2a is a second individual plate 2a within the meaning of this disclosure. A fluid guided along the outer side of this individual plate 2a is preferably hydrogen, so that the through-openings 11b are preferably hydrogen through-openings 11b. This results in particular from the smallest cross-section of the hydrogen through-openings 11b compared to the other through-openings 11a, 11c.

[0057] In an analogous manner, the two through-openings 11c or the lines formed by the through-openings 11c through the plate stack of the system 1 are each in fluid communication with one another via corresponding bead feedthroughs 13c, via corresponding distribution structures, and via a corresponding flow field on an outer side of the individual plate 2b facing away from the viewer of Figure 2. This individual plate 2b is a first individual plate 2b within the meaning of this disclosure. A fluid guided along the outer side of this individual plate 2b is preferably air or oxygen, so that the through-openings 11c are preferably air or oxygen through-openings 11c. This results in particular from the largest cross-section of the air or oxygen through-openings 11c compared to the other through-openings 11a, 11b.

[0058] The through-openings 11a, however, or the lines formed by the through-openings 11a through the plate stack of the system 1, are each fluidly connected to one another via a cavity enclosed or surrounded by the individual plates 2a, 2b, which forms the cooling fluid distribution structure 19. This is achieved, for example, again via feedthroughs 13a. This cavity or this cooling fluid distribution structure 19 serves to guide a cooling fluid through the separator plate 2, in particular for cooling the electrochemically active region 18 of the MEA. The through-openings 11a are therefore cooling fluid through-openings, which is particularly evident from their average cross-sectional size compared to the other through-openings 11b, 11c.

[0059] Figure 3 shows a partial area of ​​a separator plate 2 according to the prior art, analogous to the separator plate 2 in Figure 2. This partial area corresponds to an end area comprising three of the through-openings 11a-c. The positioning of these through-openings 11a-c clearly shows that the view is rotated by 90° compared to Figure 2.

[0060] Figure 3 shows the outside of the second individual plate 2a (anode plate), as can be seen from the depicted distribution area 20a and its indicated extension of channels 36a. These channels 36a are spaced from each other by material webs (not separately marked) and extend from the through-opening 11b toward the flow field 17a.

[0061] An extension of the distribution region 20b is also indicated by hatching. In this region of the outer side of the second individual plate 2a, there are preferably only those web-channel structures that provide a flow space inside the assembled separator plate for cooling fluid, but no web-channel structures that are accessible on the outer side for gas escaping from the through-opening 11b, for example hydrogen. The cooling fluid can reach this region via a left-hand and angled part of the passages 13a at the through-opening 11a in Figure 3. Cooling fluid can flow along a part of the inner side of the distribution region 20a via the right-hand and oppositely angled part of the passages 13a at the through-opening 11a in Figure 3. This is further illustrated in Figure 4, in which fluid flows in the separator plate 2 from Figure 3 are shown in a simplified schematic.Figure 4 again shows the through-openings 11a-c as well as an extension of the distribution areas 20a, b. These are shown in a superimposed form, for example, resulting from an orthogonal projection into a common plane. The representation in Figure 4 therefore corresponds to a view through the separator plate 2 from Figure 3, with the hatching only representing hatching and not channels or webs as such.

[0062] The fluids exiting the passage openings 11a-c are marked by different arrow types. The flow fields 17a-c are also shown superimposed, as evident from the fact that all arrow types are depicted in their area. A flow field main flow axis S is shown, the orientation of which is the same for each of the flow fields 17a-c in Figure 4.

[0063] First, in the case of the through-opening 11a, one can again see the exit of cooling fluid via the passages 13a (not shown separately). This exit occurs essentially in the two different directions described above, which are angled relative to one another. The cooling fluid thus initially flows backwards along parts of both distribution regions 20a, b before entering an overlap region in which sections of both distribution regions 20a, b lie opposite one another and overlap. This overlap region corresponds to the area shown in Figure 3 with cross-hatching. From this overlap region, the cooling fluid finally flows into the flow field 17c of the cooling fluid distribution structure.

[0064] For the distribution areas 20a, b, the generally parallel flow directions present therein are marked by corresponding arrows. Channels 36a, b within the distribution areas 20a, b, not shown in detail, run along these arrows.

[0065] As further quantities or parameters of the distribution areas 20a, b, an average channel length klvquer is entered, but as an example only for one of the distribution areas 20a, b.

[0066] Also shown is a length hk, ha of the distribution regions 20a, b. This is measured along and / or parallel to the flow field main flow axis S. It extends between a first location of the distribution region 20a, b, which is closest to the flow field 17a, b fluidically connected to the distribution region 20a, b under consideration, and a second location of the distribution region 20a, b, which is furthest away from the corresponding flow field 17a, b. This second location corresponds to an end of the distribution region 20a, b facing away from the associated flow field 17a, b. The second location or the remote end is defined by the furthest point of the distribution area 20a, b, from which on the outer surface of the corresponding individual plate 2a, 2b the medium guided on this outer surface is guided between the coolant passage opening 11a and the distribution area 20a, b in the direction of the flow field 17a, b past the coolant passage opening 11a.In other words, it is the point of the distribution area 20a, b which is furthest away from the flow field 17a, b along the flow field main flow axis S, from which point on the outer surface of the corresponding individual plate 2a, 2b the medium guided on this outer surface is guided from the associated through-opening 11b, 11c through the distribution area 20a, b in the direction of the flow field 17a, b.

[0067] Finally, a width bactive of the flow fields 17a-c is also entered, which in the example shown is aligned and dimensioned similarly for all flow fields 17a-c. In particular, a maximum width bactive of the flow fields 17a-c can be considered, which, as shown, exists at the transition between the distribution regions 20a, b and flow fields 17a-c. A dimension of the distribution regions 20a, b orthogonal to the flow field main flow axis S at this transition has the same value as the flow field width bactive. At this transition, the respective fluidically connected distribution regions 20a, b and flow fields 17a, b exchange fluid with one another. However, immediately after entering or immediately before exiting one of the distribution regions 20a, 20b, the width of the distribution region changes because the outermost channels run at an angle to the flow field main flow axis S.

[0068] Figure 4 also shows a first and second region 40, 42 of the separator plate, which have different heights relative to one another or, in other words, define different height levels of the separator plate. The first region 40 comprises the flow fields 17a-c. The second region 42 comprises the distribution regions 20a, b. The first region 40 is lower than the second region 42, i.e. lowered into the image plane of Fig. 4. This applies in particular to web crests that are present between channels of the flow fields 17a and 17b and the distribution regions 20a, b. A maximum or middle position of these web crests, for example, is lower in the first region 40 than in the second region 42. A height axis, along which these positions are viewed, is perpendicular to the image plane of Fig. 4. A transition region 41 is indicated in Fig. 4 by means of a rectangle enclosed in dashed lines.In this transition region, the height of the webs on the outer side of the second individual plate 2a can be even lower than in the aforementioned first and second regions 40, 42. Whether this transition region is counted entirely or partially as part of the distribution region 20a and / or the flow field 17a is preferably determined not by its height, but by its width. This means that preferably, at most such a portion of the transition region 41 can be assigned to the flow field 17a that lies in a region in which the outermost channels of the flow field 17a do not yet exhibit a change in direction of more than 0.5% of the width of the flow field 17a. Remaining portions of the transition region 41, in particular those that extend toward an adjacent distribution region 20a following the aforementioned changes in direction, are preferably assigned to this distribution region 20a.

[0069] Fig. 5 is a view analogous to Fig. 3, but for a separator plate 2 according to an embodiment of the invention, wherein, however, sections of the through-openings 11a-c as well as the upper outer edge of the separator plate 2 have been omitted. One difference from Fig. 3 can be seen in that the passages 13a in the region of the through-opening 11a are aligned such that they allow the cooling fluid to flow in essentially in only one direction, namely along an inner side of a part of the first distribution region 20b of the first individual plate 2b. Thus, with the illustrated and inventive design of the distribution regions 20a, b, which is explained in more detail below with reference to Fig. 6, it is neither possible nor desired to allow cooling fluid to flow along part of the inner side of the second distribution region 20a of the second individual plate 2a.

[0070] This is illustrated by the schematic representation of Figure 6, the type of representation being fundamentally comparable to Figure 4. Since there is no projection 46 (see Figure 4) of the second distribution region 20a relative to the first distribution region 20b comparable to Figure 4, no cooling fluid can be guided along the inside of the second distribution region 20a starting from the through-opening 11a. Such a relative projection 46 is formed in the variant of Figure 4 in that the second distribution region 20a, in contrast to Figure 6, does not completely overlap with the first distribution region 20b, see the simply hatched portion of the second distribution region 20a. A further essential difference between the embodiment according to the invention and the previously known variant of Figures 3 & 4, explained below, concerns the size ratios of the distribution region parameters.These are selected such that the respective area of ​​the distribution areas 20a, b is smaller than in Figures 3 & 4. This area-reducing definition of the distribution area parameters is favored by the cooling fluid routing described above along the rear side of only one of the distribution areas 20b, since, for example, no overhang 46 comparable to Figure 4 needs to be maintained. However, this cooling fluid routing, including the elimination of the overhang 46, is not a mandatory requirement for being able to define the distribution area parameters in the manner described below, as will also be clarified in the context of Figure 7.

[0071] Compared to the variant of Figures 3 and 4, in Fig. 6, in particular, the area of ​​the first distribution region 20b on the outer side of the first individual plates 2b has been reduced. The former area 48 of the first distribution region 20b or its former outline according to the variant of Figures 3 and 4 is marked with dashed lines. It can be seen that, in particular, the maximum length hk of the first distribution region 20b has been reduced compared to this former area 48, since the corresponding point of maximum length has been moved in the direction of the flow field 17b fluidically connected to the first distribution region 20b. At the same time, the maximum width bactive of the first distribution region 20b or of the flow field 17b has been left essentially unchanged.The position of the axis along which hk is maximum shifts to the right in comparison from Figures 3 and 4 to Figures 5 and 6, which on the one hand allows sufficient flow cross-sections for the fluid guided by the distribution area 20b and at the same time results in a reduction of the mean channel length klvquer relative to the variant of Figures 3 and 4.

[0072] For the second distribution area 20a, the height ha was also reduced relative to the width bactive. In this example, the height reduction is smaller than in the case of the first distribution area 20b. Here, too, the position of the maximum height ha is shifted compared to Figures 3 and 4. In the case of the second distribution area 20a, this is acceptable, since only very large reductions in the flow cross-section would lead to significant flow resistance for the hydrogen carried by it.

[0073] Specifically, the parameters are defined as follows:

[0074] - The maximum length hk of the first distribution area 20b is less than 28% of a maximum width bactive of the first distribution area 20b; - The channel length klvquer of the first distribution area 20b averaged over the number of channels 36b is less than 30%, in particular less than 28% of the maximum width bactive of the first distribution area 20b; and preferably:

[0075] - The maximum length ha of the second distribution area 20a is less than at least 55% of the maximum length hk of the first distribution area 20b and / or greater than at least 35% of the maximum length hk of the first distribution area 20b.

[0076] In this way, the indicated reductions in the area of ​​the distribution areas 20a, b could be achieved without an undue increase in the flow resistances for the fluids carried by the distribution areas 20a, b.

[0077] Figure 7 is a view, analogous to Figure 6, of a separator plate 2 according to a further embodiment of the invention. As in Figure 4 and in contrast to Figure 6, it can be seen that the passages 13a in the region of the through-opening 11a are aligned such that they allow the cooling fluid to flow in diagonally, in order to allow cooling fluid to flow both along a portion of the inside of the first distribution region 20b of the first individual plate 2b and along a portion of the inside of the second distribution region 20a of the second individual plate 2a. As in Figure 4, a projection 46 of the second distribution region 20a is present relative to the first distribution region 20b.

[0078] On the other hand, the inventive embodiment of Figure 7 has similar differences to the inventive embodiment of Figures 5 and 6 compared to the previously known variant of Figures 3 and 4 with regard to the size ratios of the distribution area parameters. These are again selected such that the respective area of ​​the distribution areas 20a, b is smaller than in Figures 3 and 4, even though an overhang 46 is now present.

[0079] Again, the former outline 48 of the first distribution region 20b is marked with dashed lines according to the variant of Figure 4. The reduction in size of the distribution region 20b is not quite as pronounced as in the inventive example shown in Figures 5 and 6. Nevertheless, here too, the maximum length hk of the first distribution region 20b is reduced compared to this former area 48. The position of the axis along which hk is maximum is also shifted to the right in the latter when comparing Figure 4 with Figure 7, which, as in Figure 6, on the one hand enables sufficient flow cross-sections for the fluid guided by the distribution region 20b and, at the same time, results in a reduction in the average channel length klvquer relative to the variant of Figure 4.

[0080] In addition, the former outline 48' of the second distribution area 20a is shown in dashed lines according to the variant of Figure 4. This distribution area 20a is also reduced in size in Figure 7 compared to the original size in Figure 4. Furthermore, the position of the maximum height ha is shifted slightly towards the center, ie to the left, compared to Figure 4.

[0081] Again, the parameters are set as follows:

[0082] - The maximum length hk of the first distribution area 20b is less than 28% of a maximum width baktiv of the first distribution area 20b;

[0083] - The channel length klvquer of the first distribution area 20b averaged over the number of channels 36b is less than 30%, in particular less than 28% of the maximum width baktiv of the first distribution area 20b; and preferably:

[0084] - The maximum length ha of the second distribution area 20a is greater than at least 35% of the maximum length hk of the first distribution area 20b.

[0085] Here too, the indicated reductions in the area of ​​the distribution areas 20a, b could be achieved without an inadmissible increase in the flow resistances for the fluids carried by the distribution areas 20a, b.

Claims

Patent claims 1. Separator plate (2) for an electrochemical system (1), comprising: - a first single plate (2b) and a second single plate (2a), the inner sides of which face each other, - at least one first through-opening (11c) for passing air or oxygen through the separator plate (2), - at least one second through-opening (11b) for conducting hydrogen through the separator plate (2), wherein the first individual plate (2b) has on its outer side a first flow field (17b) and at least one first distribution region (20b) which connects the first flow field (17b) and the first through-opening in a fluid-conducting manner, wherein the second individual plate (2a) has on its outer side a second flow field (17a) and at least one second distribution region (20a) which connects the second flow field (17a) and the second through-opening (11b) in a fluid-conducting manner, wherein the first and second distribution regions (20a, 20b) each have a plurality of fluid-conducting channels (36a, 36b), wherein the first and second flow fields (17a, 17b) each have a flow field main flow axis (S) along which they can be flowed through by the respective fluid, and a length dimension (hk, ha) of the first and second distribution area (20a,20b) extends parallel to the respective flow field main flow axis (S), wherein the first and second distribution region (20a, 20b) each have a width dimension (bactive) orthogonal to the respective flow field main flow axis, wherein:, - a maximum length (hk) of the first distribution area (20b) is less than 28% of a maximum width (baktiv) of the first distribution area (20b); and - a channel length (klvquer) of the first distribution area (20b) averaged over the number of channels (36b) is less than 30%, in particular less than 28% of the maximum width (baktiv) of the first distribution area (20b).

2. Separator plate (2) according to one of the preceding claims, a maximum length (ha) of the second distribution region (20a) is less than 65%, in particular less than 55%, in particular less than 50% of the maximum length (hk) of the first distribution region (20b).

3. Separator plate (2) according to one of the preceding claims, wherein the maximum length (ha) of the second distribution region (20a) is greater than 35%, in particular greater than 40%, of the maximum length (hk) of the first distribution region (20b).

4. Separator plate (2) according to one of the preceding claims, wherein the first and second flow fields (17a, b) are lowered relative to the respective first and second distribution areas (20a, b) connected thereto.

5. Separator plate (2) according to one of the preceding claims, wherein the maximum length (ha, hk) of the first and second distribution region (20a, b) is between a transition of the respective distribution region (20a, b) and associated flow field (17a, b) and a point of the respective distribution region (20a, b) that is maximally removed from this transition.

6. Separator plate (2) according to one of the preceding claims, wherein a maximum dimension of the first and second distribution region (20a, b) orthogonal to one of the flow field main flow axes (S) is present in an edge region of the first and second distribution region (20a, b) in each case, in which fluid is fed from the correspondingly connected one of the first and second flow fields (17a, b) or in which fluid is fed into the correspondingly connected one of the first and second flow fields (17a, b).

7. Electrochemical system (1) comprising a plurality of separator plates (2) according to one of the preceding claims.

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