WO2024256510A1 - Separator plate for an electrochemical system - Google Patents

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

für ein elektrochemisches

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for an electrochemical

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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 with a plurality of such separator plates is also disclosed.

Known electrochemical systems of the type mentioned normally comprise a stack of electrochemical cells, each of which is 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 adjacent cells (series connection of the cells). The separator plates are typically 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.

The separator plates or the individual plates can each have or form structures which are designed, for example, to supply the electrochemical cells arranged between adjacent separator plates with one or more media and/or to transport away reaction products. In particular, these structures can be used to guide a cooling fluid through a gap 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.

Furthermore, the separator plates usually each have at least one through-opening through which the media can be fed to the electrochemical cells or membrane electrode assemblies (MEAs) arranged between adjacent separator plates of the stack or from these can be led away.

From such a through-opening, a respective fluid is guided by means of the structures described above into a respective first distribution area and from there into a flow field opposite the active area of the cell or MEA. After flowing through the active area, the fluid is fed back to an outlet through-opening via a second distribution area, also called a collection area. An example of this can be found in DE 20 2016 107 302 Ul.

It is known to guide 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 guide a second fluid, e.g. a reaction gas, on a second outer side of the separator plate facing away from it, i.e. an outer side of a second individual plate. In contrast, a cooling fluid is usually guided in an interior space delimited by the inner sides of the individual plates. The media are usually guided through the system using external pumping services.

The fluid-conducting structures on the respective outer sides of the individual plates form complementary structures on their inner sides, which guide the cooling fluid. However, it has been shown that with previous solutions, the cooling fluid guidance is sometimes only possible under increased flow resistance. This places higher demands on the external pumping power. This reduces the cooling capacity of the separator plate accordingly and can consequently lead to limitations in the overall performance of the electrochemical system.

An object of the present invention is therefore to improve the cooling capacity of a separator plate and thus a total performance of an electrochemical system with a plurality of such separator plates.

This object is achieved by the subject matter of claim 1. Advantageous further developments are specified in the dependent claims as well as in this description and in the figures.

Accordingly, a separator plate for an electrochemical system is proposed, comprising a first single plate and a second single plate, the inner sides of which face one another and together delimit a cooling fluid distribution structure, wherein the separator plate has at least one first through-opening for passing a cooling fluid through the separator plate and the cooling fluid distribution structure has at least one distribution region and a flow field, wherein the inner side of the first individual plate has a plurality of webs and first channels formed therebetween, wherein the first channels each define at least one continuous fluid connection from the distribution region into the flow field and each have a curved section, wherein the distribution region comprises a first section which comprises first segments of the first channels, wherein the first segments define a fluid connection between the through-opening and the curved section of a respective first channel, wherein the distribution region comprises a second section which comprises second segments of the first channels, wherein the second segments each define a fluid connection between the curved section of a respective first channel and the flow field, wherein the inner side of the second individual plate has a plurality of webs and second channels formed therebetween, wherein at least some of the second channels each open into a curved section of one of the first channels and extend from the respective curved section through the second section of the distribution region into the flow field.

With the solution disclosed here, it is possible to limit the high flow resistances in a transition area between the distribution area and the flow field as well as the space requirement of this transition area.

It is known that various fluid connections must be established in this transition region in order to connect a typically higher number of channels in the flow field with a typically lower number of channels in the distribution region in a fluid-conducting manner. Previously known transition regions often have a large number of differently positioned and dimensioned fluid connections between the channels. The number of channels in the distribution region to which the channels of the flow field are each connected in a fluid-conducting manner can also vary greatly between the channels of the flow field. In other words, the channels of the flow field can have different numbers of feed points.

These previously generally inhomogeneous fluid connections within the transition area often result in increased turbulence of the cooling fluid. id flow and/or inhomogeneous supply of the channels of the flow field with cooling fluid. This can result in local pressure fluctuations and in particular in excessive pressure losses of the cooling fluid flow.

In addition, increased flow resistance and resulting pressure losses can occur with previous solutions because channels of the flow field are sometimes brought to and connected to channels of the distribution area at almost right angles.

By opening the second channels into the curved section, the angles that are spanned between the connected channels can be reduced. In particular, connections with angles of significantly less than 90° can be realized. In addition, it was recognized and is also partially implemented in more detail by the following embodiments that the fluid-conducting connection to the curved section enables more homogeneous connections within the transition area and reduces the space required in the transition area.

In particular, in view of their respective main extension lengths, the first channels can be assigned primarily to the distribution area and the second channels primarily to the flow field, even if they partly extend into the other of the distribution area and the flow field and/or are continued there.

In the solution disclosed here, it can be provided that the inside of the first individual plate in the distribution area has only first channels or at least twice as many first channels of the type disclosed here compared to optional other channels. Additionally or alternatively, the inside of the second individual plate in the flow field can only comprise second channels of the type disclosed here. All second channels can therefore be connected to a curved section or open into such a section. According to the embodiments below, however, second channels can also be provided which are opposite the second segments of the first channels or any continuations thereof.

One variant provides exactly two second channels which are fluidically connected to a curved section of a respective first channel and a second channel which is opposite the second segment of the same and/or a possible continuation thereof. The above variants regarding the number and connection of first and second channels have in common that they each enable a space-saving branching of the channels at the transition from the distribution area to the flow field and a correspondingly efficient cooling of the flow field. However, this is achieved with a reduced total number of connection points between the channels compared to existing solutions, which results in better utilization of the available installation space.

The first channels may optionally continue in the flow field and/or connect to channels in the flow field and/or merge into channels in the flow field.

The curved section can generally be used to bring about a change in the direction of a respective first channel when it runs from an area close to the through-opening in the direction of the flow field. For this purpose, it can be sufficient if one of the flanks of the respective first channel runs in a curved manner in the curved section, but both flanks of the respective first channel can also run in a curved manner in the curved section. The two flanks can be curved in the curved section at least in sections in the same direction and/or curved in sections in different directions. The curvatures of both flanks can extend over sections of the curved section of equal length, in particular over the entire curved section, or over sections of the curved section of different lengths.

As is also the case in the prior art, the through-opening and the flow field of the separator plate are generally dimensioned differently and/or the through-opening is offset relative to a center of the flow field when viewed in a width direction of the separator plate. The width direction of the separator plate can extend parallel to a plane of the individual plates and orthogonal to a longitudinal axis of the individual plates and/or orthogonal to a flow direction through the flow field. In order to guide a plurality of channels from the through-opening to the flow field, these cannot always run in a straight line within the distribution area due to the described different dimensioning and/or positioning. The curved section, which according to one embodiment is the only curved section of the first channels, enables a targeted change in direction of the first channels in order to be able to connect any starting positions of the first channels near the through-opening with any end positions of the first channels near the flow field. However, it is also possible for the first Channels have at least one further curved section, for example in their course between the through opening and the curved section mentioned here.

The segments and the curved section of each first channel can each directly adjoin one another and/or directly merge into one another. The first channels optionally have no further segments and sections within the distribution area, apart from the first and second segments and the curved section disclosed here.

The second segments, in particular end sections thereof remote from the curved region, can each run parallel to a main flow direction of the cooling fluid through the flow field and/or open into channel sections in the flow field which have such a parallel extension. The main flow direction can run in a longitudinal direction of the separator plate and/or be straight, preferably completely straight. The first segment of each first channel can run at an angle to the main flow direction.

At least regions of the curved section, in particular regions of the curved section facing the flow field, as well as the second segments of the first channels for cooling fluid, can have a smaller depth compared to both the first segments of the first channels and the cooling fluid channels of the flow field. This can be advantageous with regard to the space required by the MEA, MEA reinforcement edge and GDL. For this purpose, a step can be provided in the region of the curved section, for example.

The first and second individual plates can each also have a distribution area and a flow field for fluid guidance on their outer sides. The first individual plate can form a cathode plate and/or can carry oxygen or air as a first fluid on its outer side. The second individual plate can form an anode plate and/or can carry hydrogen as a second fluid on its outer side.

According to a further development, the respective opening of a second channel into the curved section of one of the first channels comprises that an open end of the second channel, which faces a contact plane between the first and second individual plates, is opposite the curved section of the first channel. The second channels can be fluid-conducting as a result of the opening. tend to be connected to the bend section. The second channels can be fed with cooling fluid from or through the bend section or, depending on the flow direction, feed the bend section with cooling fluid. Consequently, at least a portion of the cooling fluid from the bend section can be distributed to the second channels or received and collected by the bend section from the second channels.

It can be provided that at least some of the second channels each open into only one of the first channels. This means a limited number of feed points into or out of the second channels, which can reduce flow resistance.

According to one embodiment, more than one second channel and in particular exactly two second channels open into a curved section of a respective first channel. This enables a space-saving increase in the number of channels or a space-saving branching of the channels at the transition between the distribution area and the flow field.

In a further development, in an orthogonal projection of the first and second channels into the plane of the separator plate, the second channel closest to the first segments and the first channel span a first transfer angle which is less than 80°, in particular less than 70°, in particular less than 60°. Preferably, the smallest spanned angle that can be entered is considered.

Alternatively or additionally, it can be provided that in an orthogonal projection of the first and second channels into the plane of the separator plate, a second channel located further away from the first segments and the first channel span a second transfer angle that is smaller than the first transfer angle, in particular at least 5°, preferably at least 10° smaller. Preferably, the smallest enrollable spanned angle is considered.

The transfer angles enable a spatially compact fluid-conducting connection of the second channels to a respective first channel. At the same time, flow resistances due to the at least partial change in flow direction when fluid passes between the channels are limited, as connections > 90° can be prevented.

According to one embodiment, at least some of the second channels which open into the curved section are each partially located on a on the inside of the first plates opposite a web formed on the inside. For example, the second channels (and more precisely a section thereof) can cross a web formed on the inside of the first plate. This corresponds to an at least temporary change of level of the cooling fluid guide when the cooling fluid is guided, for example, from the curved section into the second channels and from these, flowing over the opposite web, further in the direction of the flow field. However, a reverse flow direction from the flow field into the distribution area is also possible.

A change of level of the cooling fluid guide can be understood as a change of flow levels of the cooling fluid distribution structure in such a way that a change is made from an area in which a flow cross section of the cooling fluid distribution structure extends significantly in a flow space for the cooling fluid spanned by the second individual plate to an area in which a flow cross section of the cooling fluid distribution structure extends significantly in a flow space for the cooling fluid spanned by the second individual plate, or vice versa.

According to one embodiment, the second channels each have a first section which opens into a curved section of one of the first channels, a second section which lies opposite a web formed on the inside of the first plate, and a third section which runs in the flow field, wherein the second section connects the first and third sections in a fluid-conducting manner.

It has been shown that the possibility of changing levels described above and also the above-mentioned sections of the second channels provide additional degrees of freedom in order to branch the cooling fluid distribution structure in the region of the transition between the distribution region and the flow field to a desired extent in a space-saving manner.

A further aspect provides that at least some of the other second channels formed on the inside of the second individual plate are located within the flow field opposite one of the first channels formed on the inside of the first individual plate. For example, these second channels can each be located opposite a second segment of a first channel of the type described above and/or a continuation of a first channel into the flow field. Thus, the cooling fluid can be guided not only as a result of the above-described opening of the second channels into the curved section on the inside of the second individual plate, but also by the corresponding direct opposition of at least a portion of the second and first channels. This increases the achievable cooling of the second individual plates.

According to a further development, the first segment and the second segment of each first channel are inclined relative to each other by a maximum of 80°, preferably by a maximum of 60° and in particular by a maximum of 45°.

In this case, the smallest possible cutting angle that can be entered can be considered. In particular, the smallest possible cutting angle that can be entered between the, for example, extended longitudinal axes of the first and second segments can be considered. A corresponding limitation of the relative angle of the first and second segments to a maximum of 80° limits the extent of the change in direction through the curved section and, accordingly, the associated flow resistance.

Alternatively or additionally, the first and second segments of each first channel can be inclined by at least 20° and in particular at least 40° relative to one another. This enables a sufficiently large change in direction through the curved section to enable a fluid-conducting connection of the first channels to different positions of the flow field.

In a further embodiment, the curved section has a flow cross-section that is larger than a flow cross-section of the first and/or second segment.

For example, the curved section of the first channel, particularly at the point of its largest cross section, can have a flow cross section that is at least 1.5 times as large and in particular at least twice as large as the flow cross section of the first segment of the first channel. For example, the flow cross section can be at least 1.8 times or at least 2.2 times or between 2 and 2.5 times as large as the flow cross section of the first segment. It has been shown that by means of such widening of the flow cross section in the curved region, the above-described effect according to the invention can be achieved particularly reliably. Additionally or alternatively, the curved section of the first channel can have a flow cross-section that is at least twice as large, preferably at least three times as large, as the flow cross-section of the second segment of the first channel. For example, the flow cross-section of the curved section can be at least 2 times, at least 2.5 times or at least 3.5 times as large, in particular between 3 and 4 times as large, as the flow cross-section of the second segment. Consequently, the flow cross-section can decrease again after widening in the curved section. The curved section can thus form a locally and in particular locally limited widened area of each first channel with respect to the flow cross-section. This means that a targeted reduction in the flow velocity as a result of the cross-sectional widening, as explained below, can also only take place in a correspondingly locally limited manner.

Widening the flow cross-section of the bend region can limit pressure losses compared to a case without corresponding widening. It was recognized that the fluid exchange between each bend region and the second channels increases turbulence of the cooling fluid flow in the bend section. However, by widening the flow cross-section, the cooling fluid flow is deliberately slowed down, which limits pressure losses due to the increased turbulence.

The flow cross-section of the first and second segments can in principle be similar, but can also be different from one another. In particular, the flow cross-section of the first segment can be larger than the flow cross-section of the second segment. This enables a fluid-conducting connection of the second segment to a channel of the flow field that has a similar or similarly reduced flow cross-section compared to the first segment.

A further embodiment provides that the flow cross-section of the curved section is at least twice as large, at least two and a half times as large or at least three times as large, in particular between three and three and a half times as large, compared to a channel of the flow field to which the first channel is fluidically connected (and/or into which the first channel merges or in whose form the first channel is continued as a channel of the flow field). This also underlines that the expansion of the flow cross-section can take place locally in the curved section in order to prevent unnecessary pressure losses outside the curved section. A further development provides that the flow cross-section of the curved section is increased significantly compared to the flow cross-section of the first segment (and optionally also of the second segment) by increasing a width dimension of the first channel. The width dimension preferably runs in or parallel to a flat surface plane of the separator plate and/or along or in a width direction explained above.

In particular, an increase in the width dimension may exceed any increase in the height of the first channel within the curved portion (for example, be at least twice as large) and/or the height of the first channel may be substantially constant. The height may be measured orthogonal to the planar surface plane and/or in a direction pointing toward the corresponding opposing single plate.

Significantly increasing the flow cross-section by adjusting the width dimension can prevent or at least limit increases in the height of the individual plates in the area of the curved section, if this is structurally possible at all.

In a manner known per se, the plane of the flat surface 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 an embossing or deep-drawing process to form the web-channel structures or beads described here. On the one hand, the plane of the flat surface 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 plane of the flat surface. With the latter approach, however, it must be ensured that when considering distances or the like, the material thickness of only one of the two plates considered is taken into account.

The first and second segments can be essentially or completely straight. A substantially straight extension can be understood to mean extensions with a slight and/or only partially present curvature. However, this possible curvature is preferably significantly smaller than a curvature of the curved section. For example, it is not more than 20% of the curvature of the curved section.

The curved section can be continuously curved or, with other In other words, no section extending in a straight line. The curvature of the curved section can be constant or can vary along the length of the curved section. The flow cross-section of the curved section can vary continuously along its length. Alternatively, any section of the curved section with a constant flow cross-section can be shorter (e.g. at most half as long) than one or more sections with a varying flow cross-section. Preferably, the flow cross-section in the curved section increases or decreases continuously. An exception to this can arise from the aforementioned optional stage.

A further development provides that in at least some of the first channels, the first segment is at least four times or at least ten times as long as the curved section. This part or, in other words, this group of first channels can extend away from outer side edges of the distribution area and/or the flow field, for example when viewed in a width direction explained above. Instead, this part of the first channels can extend in a central region within the distribution area, again preferably viewed in the width direction, and/or can encompass this central region.

The invention also relates to an electrochemical system having a plurality of separator plates according to any aspect described herein.

The invention is explained below with reference to the attached schematic figures. The same reference numerals can be used across the figures for similar or equivalent features.

Figure 1 shows a perspective view of an electrochemical system with a plurality of stacked separator plates with membrane electrode units arranged between them.

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.

Figure 3 shows a perspective partial view of the separator plate of the first embodiment in the region of a distribution region of a first individual plate, in particular cathode plate, of the separator plate. Figure 3a is an enlarged detail view of a section of Figure 3.

Figure 4 shows a perspective partial view of a separator plate according to a first embodiment in the region of a distribution region of a second individual plate, in particular anode plate, of the separator plate.

Figure 5 shows a schematically highly simplified view of a part of a cooling fluid distribution structure in the interior of the separator plate according to the first embodiment.

Figure 6 shows an orthogonal projection of the structural features of a part of the separator plate into a common plane.

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 stack 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 unit (MEA) 10 is arranged between adjacent separator plates 2 of the stack 6 (see also 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 guided on or through the separator plates in an electrolyzer, an electrochemical compressor or a redox flow battery can differ from the media used for a fuel cell system.

The z-axis 7, together with an x-axis 8 and a y-axis 9, clamps 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 fed to the system 1 and through which media can be removed from the system 1. These media that can be fed 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.

Figure 2 shows in perspective two adjacent separator plates 2 or bipolar plates, which can be included in an electrochemical system of the type of system 1 from Figure 1. The separator plates 2 correspond to an example from the prior art. However, the properties and features explained below in relation to this can also apply to the separator plates 2 according to the invention disclosed here or can be provided for them, unless otherwise mentioned or apparent.

Fig. 2 also shows a known membrane electrode unit (MEA) 10 arranged between these adjacent separator plates 2, wherein the MEA 10 in Fig. 2 is largely covered 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 covers the other individual plate 2b. The individual plates 2a, 2b can each be made from a metal sheet, e.g. from a stainless steel sheet. The individual plates 2a, 2b can, for example, be welded to one another, e.g. by laser welding connections or only be connected when the stack is stacked. In particular, the design of fluid-conducting structures on the outside of the individual plate 2a facing the viewer can differ in Fig. 2 from the structures according to the invention in the other figures below.

The individual plates 2a, 2b have through-openings which are aligned with one another and 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 which 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 through the lines formed by the through openings 11b, 11c. 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 with reaction gas and to discharge the reaction products from the stack 6.

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.

Adjacent to the electrochemically active region 18 of the MEA, the individual plate 2a facing the viewer has a flow field 17a with structures for guiding a reaction medium along the outside of the individual plate 2a on its outside facing the viewer. These structures are designed in Figure 2 in the form of a large number of webs and channels running between the webs and delimited by the webs. On the outside of the separator plate 2 facing the viewer, the individual plate 2a facing the viewer also has two distribution regions 20a. The distribution areas 20a each comprise structures that are designed to distribute a medium introduced from a first of the two through openings 11b into one of the distribution areas 20a via the active area 18 by means of the flow field 17a or to collect or bundle a medium flowing from the active area 18 or from the flow field 17a to the second of the through openings 11b. In the latter case, the collecting distribution area 20a can also be referred to as a collecting area. The fluid-conducting structures of the distribution areas 20a are also provided in Figure 2 by webs and channels running between the webs and delimited by the webs.

Without this being shown separately in Figure 2, a cooling fluid distribution structure 19 formed and/or enclosed between the individual plates 2a, 2b also has distribution areas which coincide with the distribution areas. surfaces 20a of the individual plates 2a, 2b overlap. This cooling fluid distribution structure also has 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. The web-channel structures on the outer sides of the individual plates 2a, 2b form complementary web-channel structures on the corresponding inner sides and thus complementary web-channel structures of the cooling fluid distribution structure 19.

The two through-openings 11b or the lines formed by the through-openings 11b through the plate stack of the system 1 are each in fluid communication with one another via passages 13b in sealing beads 12b, via the distribution structures of the distribution areas 20a 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 in the sense of this disclosure. A fluid guided along the outside 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.

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, 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 in the sense 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.

The through-openings 11a, however, or the lines formed by the through-openings 11a through the plate stack of the system 1, are each in fluid communication with one another via a cavity enclosed or surrounded by the individual plates 2a, 2b, which forms the cooling fluid distribution structure 19. This is again done, for example, by means of 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 passage openings, which is particularly obvious from their average cross-sectional size in comparison to the other passage openings 11b, 11c.

Figure 3 shows a section of the outside of the bipolar plate 2 according to an embodiment with a view of the first individual plate 2b facing away from the viewer in Figure 2, in particular a cathode plate, in the dashed area of Figure 2. The viewing angle is rotated compared to Figure 2, as can be seen from the position of the through-opening 11c shown in Figure 3. Only a cut-off part of both the distribution area 20b and the flow field 17b is shown. A fluid is guided into the flow field 17b from the through-opening 11c via the first distribution area 20b and guided by a web-channel structure 46b on the outside of the first individual plate 2b. The web-channel structure 46b has several outwardly projecting webs 27b and channels 29b enclosed between them, only selected ones of which are provided with a corresponding reference symbol. The deepest areas of the channels 29b run in the plane of the first individual plate 2b.

On the inner side of the first individual plate 2b facing away from the viewer, the web-channel structure 46b forms complementary shaped webs and channels of the cooling fluid distribution structure 19, see Figures 5 and 6 discussed below. More precisely, the webs 27b of the web-channel structure 46b form cooling fluid-carrying channels of the cooling fluid distribution structure 19, whereas the channels 29b of the web-channel structure 46b form webs of the cooling fluid distribution structure 19.

The distribution area 20b comprises a first section 20bl, a curved section 52 and a second section 20b2. In the first section 20bl, the webs 27b of the web-channel structure 46b have a first segment 50. In the second section 20b2, the webs 27b have a second segment 54, see the enlarged detailed view from Fig. 3a. The segments 50, 54 and the curved section 52 follow one another directly and merge directly into one another. On the inside, the corresponding segments of a complementarily shaped channel 27c of the cooling fluid distribution structure 19 can carry cooling fluid. The sections 20bl, 20b2 are present on the inside of the first individual plate 2b as analogous sections 20bl, 20b2 of the distribution area 20c of the cooling fluid distribution structure 19.

The first segment 50 extends from an edge of the distribution area 20b near the through opening 11c to the curved section 52. The Curved section 52 is generally positioned closer to the flow field 17b than to the through-opening 11c. The second segment 54 extends from the curved section 52 to the flow field 17b. At least one end section of the second segment 52 pointing away from the curved section 52 can run parallel to a main flow direction (not shown) vertical in Fig. 3 through the flow field 17b. The second segment 52 merges directly into a web 27b of the flow field 17b or is continued as such.

The flow field 17b can be characterized, for example, in that all of the webs 27b and channels 29b included therein are straight and run parallel to one another and parallel to the main flow direction. Alternatively, the webs 27b and channels 29b could also be wave-shaped and run next to one another and along the main flow direction with a similar wave shape. In addition, the webs 27b and channels 29b in the flow field 17b have a constant flow cross-section and/or a substantially constant height. In the distribution area 20b, not all of these requirements can be met.

Additionally or alternatively, and not limited to the specific details of this embodiment, the flow field 17b can be characterized in that it lies within an MEA reinforcement edge and in particular is surrounded and/or framed by it at least in sections. However, the flow field 17b itself is not opposite the MEA reinforcement edge, but rather the actually active area of the MEA, in particular in the form of its electrolyte membrane. Reference is made by way of example to DE 20 2020 106 459 Ul and in particular to Figure 3B, which shows an MEA with a reinforcement edge that frames an active area of the MEA.

In the majority of the first webs 27b, the first segment 50 is significantly longer than the curved section 52. The first segment 50 and also the second segment 52 are also each straight. The curved section 52, on the other hand, does not have a completely straight section or a section with a constant flow cross-section.

As explained below with reference to Figure 5, a flow cross-section of each first web 27b preferably increases temporarily within the respective curved section 52. In the first and second segments 50, 52, each web 27b therefore has a smaller flow cross-section compared to the curved section 52. Fig. 3a is an enlarged detailed view of a section outlined in dashed lines in Fig. 3. The curved section 52 and its enlarged dimensions compared to the partially visible first segment 50 and second segment 54 can again be seen. A step 53 is only optionally shown in Fig. 3a, which is also indicated in Fig. 3. Via this step 53, the areas of the curved section 52 facing the flow field 17c (on the inside), as well as the second segments 54 of the first channels 27c, can have a lower height both compared to the first segments 50 of the first channels 27c and compared to the channels of the flow field 17b. Conversely, on the outside shown in Fig. 3a, the corresponding webs 27b on the side of the step 53 facing the flow field 17b are designed to be lower. This can be advantageous in terms of the space requirements of MEA, MEA reinforcement edge and GDL.

For the sake of completeness, it should be mentioned that Fig. 3a also shows that additional webs 28b extend in the flow field 17b opposite the distribution region 20b. This is equivalent to a channel 29b on the outside of the first individual plate 2b branching into further channels 31b in the transition between the distribution region 20b and the flow field 17b.

Figure 4 shows a section of the bipolar plate 2 with a view of the outside of the second individual plate 2a, preferably an anode plate, in the dashed area in Figure 2. The viewing angle is rotated compared to Figure 2, as can be seen from the indicated position of the through-opening 11b in Figure 4. Only a cut-off part of the distribution area 20a and the flow field 17a are shown. A fluid is guided into the flow field 17a from the through-opening 11b via the distribution area 20a and guided by a web-channel structure 46a on the outside of the second individual plate 2a. Merely as an example, the web-channel structure 46a has several outwardly projecting webs 27a and channels 29a enclosed between them, selected ones of which are each provided with a corresponding reference symbol. The deepest areas of the channels 29a run in the plane of the second individual plate 2a.

As shown, the webs 27a are optionally interrupted in sections along their longitudinal extension within the distribution region 20a, but can also extend continuously in the direction of the flow field 17a.

Furthermore, the webs 27a are optionally interrupted near their transition to the flow field 17a, but can also extend continuously into the flow field 17a. The webs 27a are therefore not guided continuously into the flow field 17a with a change of direction as in Fig. 3.

The number of webs 27a is greater in the flow field 17a than in the distribution area 20a. For example, additional webs 28b are provided in the flow field 17a, which would not merge into these webs 27a even in the case of an alternative continuous extension of the webs 27a of the distribution area 20a.

Figure 4 also shows, by way of example, that some of the webs 27a, 28a have enlarged end sections 33 in a transition region between the distribution region 20a and the flow field 17a. This is explained in more detail below with reference to Fig. 6.

Fig. 5 shows a highly simplified schematic of a channel 27c of the cooling fluid distribution structure 19 formed between the individual plates 2a, b. The separator plate 2, which is only shown in part, is rotated by 90° compared to Figures 3 and 4, which corresponds to an orientation analogous to Figure 2. The cooling fluid distribution structure 19 in turn has a distribution area 20c and a flow field 17c. The cooling fluid distribution structure 19 actually comprises a plurality of channels 27c, which is not shown in the highly simplified schematic of Fig. 5.

The channel 27c is essentially limited by the inside of one of the webs 27b of the first individual plate 2b (see Fig. 3) or, in other words, is shaped complementarily to such a web 27b. Accordingly, the channel 27c has first and second segments 50, 54 and a curved section 52, which are each designed as recesses on the inside of the first individual plate 2b that are complementary to the segments 50, 54 and the curved section 52 of the webs 27b. Each of the webs 27b from Fig. 3 forms a corresponding channel 27c of the cooling fluid distribution structure 19 or is shaped complementarily thereto.

The channel 27c preferably has a substantially or completely constant height, which runs, for example, orthogonal to the planar surface planes of the individual plates 2a, 2b. Preferably, however, the width of the channel 27c varies along its course. In view of the preferably constant height, this variation in width is equivalent to a variation in a flow cross-section available to the cooling fluid in the channel 27c. Fig. 5 shows that the first segment 50 has a width bl. The curved section 52 has a significantly larger width b2 in comparison, whereby in particular a maximum and/or an average width of the curved section 52 can be considered. A width b3 of the second segment 54 lies between the widths bl and b2 of the first segment 50 or the curved section 52. This results in an expansion of the flow cross-section in the curved section 52 and limited to this.

Furthermore, it is clear from Fig. 5 that the first and second segments 50, 54 extend at an angle W1 relative to one another. This angle W1 is defined as the smallest intersection angle of the extended longitudinal axes La, Lb of the first and second segments 50, 54. The widened curved section 52 consequently defines an area of a change in direction of the first channel 27c and enables the cooling fluid to be diverted from the first segment 50 into the second segment 54, which is angled relative thereto.

Fig. 5 also shows an optional cooling fluid feed from (or into) the curved section 52 into (or from) second channels 30c shown in dashed lines. The second channels 30c are essentially limited by the inside of a portion of the webs 27a, 28a of the second individual plate 2a (see Fig. 4). In other words, the second channels 30c are formed complementarily to a portion of these webs 27a, 28a. This particularly relates to a portion of the webs 27a, 28a in or near the flow field 17a of the second individual plate 2a.

Accordingly, the second channels 30c optionally have enlarged end sections 33 analogous to those in Fig. 4. These end sections 33 are not shown significantly enlarged in Fig. 5 due to the schematic representation. It can be seen that these end sections 33 on the inside of the second individual plate 2a are opposite the curved section 52 on the inside of the first individual plate 2b and open into it. An open end of every second channel 30c faces the curved section 52 and establishes a fluid-conducting connection between the first channel 27c and a respective second channel 30c.

Both the change in direction in the area of the curved section 52 and the optional fluid exchange between the first channel 27c and the second channels 30c cause turbulence in the cooling fluid flow. By widening the flow cross-section in the curved section 52, the flow velocity in this section of increased turbulence is specifically reduced, which limits the pressure losses that occur. Fig. 6 shows an orthogonal projection of a section of the separator plate 2, which is oriented analogously to Fig. 5, in a plane parallel to the planes of the individual plates 2a, 2b. The view corresponds to a view through the corresponding section of the separator plate 2. The section shown corresponds approximately to an area that has the schematically shown structures from Fig. 5. Positions of the distribution areas 20a-c and flow fields 17a-c on the outer and inner sides of the first and second individual plates 2a, b are entered. These overlap at least in sections.

Furthermore, one can see the positions and extents of overlaps of the channel-web structures 46a, b as well as the cooling fluid distribution structure 19 jointly delimited thereby.

Three channels 27c of the cooling fluid distribution structure 19 are shown, each of which is shaped complementarily to webs 27b on the outside of the first individual plate 2b. For the middle of the channels 27c, the widened curved region 52 is shown hatched, with the hatched lines marking areas that are below half the channel height by way of example. Furthermore, the fluid-conducting connection of the curved region 52 of each channel 27c to two channels 30c on the inside of the second individual plate 2a (shaped complementarily to webs 27a on the outside of the second individual plate 2a) can be seen. Not all of the second channels 30c are marked with a corresponding reference symbol in Figure 6.

For the uppermost first channel 27c, transfer areas between the first and second channels 27c, 30c are hatched. In the case of the upper two channels 30c, the hatching marks an area in which open ends of the second channels 30c are opposite the curved area 52 and the channels 30 consequently open into the curved area 52.

Figure 6 also shows further channels 28c on the inside of the first individual plate 2b. These are part of the cooling fluid distribution structure 19 and are shaped complementarily to the webs 28b on the outside of this first individual plate 2b, see Figure 3a. The channels 28c are located opposite sections of the second channels 30c.

More specifically, the second channels 30c each comprise a first portion 30cl which opens into one of the curved portions 52 and a third portion 30c3 which is opposite a corresponding channel 28c. The first and third sections 30cl, 30c3 are connected by a second section 30c2. This is not located, at least in sections, opposite a channel on the inside of the first individual plate 2b, but rather opposite a web 29c formed there.

The cooling fluid guided along the second channels 30c thus flows over a section of a web 29c on the inside of the first individual plate 2b, so that a flow cross-section for the cooling fluid in this area is provided exclusively in the second individual plate 2a. The second channels are therefore fed from the curved section 52 with a change in level or can feed cooling fluid into it by means of the change in level.

The webs 29c discussed above on the inner sides of the first and second individual plates 2a, 2b can be designated more specifically with 29c-2a and 29-2b and are additionally marked with these reference symbols 29c-2a, 29-2b in Figure 6. The webs 29c-2a are formed on the inner side of the second individual plate 2a and the webs 29c-2b on the inner side of the first individual plate 2b.

Furthermore, Figure 6 shows that the second segment 54 of each channel 27c is led into the flow field 17c of the cooling fluid distribution structure 19 and continues there as a channel. This is opposite a channel 31c on the inside of the second individual plate 2a, which is shaped complementarily to one of the webs 28a on the outside of this second individual plate 2a (see Figure 4). The channel 31c is an example of a different type of second channel on the inside of the second individual plate 2a from the second channels 30c mentioned. More precisely, the two uppermost second channels 30c in Figure 6 form examples of at least some of the second channels in the sense of the claims that open into the curved section 52. The channels 31c, on the other hand, are examples of some of the other second channels in the sense of the claims that run in the flow field 17c and there are each opposite a first channel 27c or its continuation in the flow field 17c.

Fig. 6 shows a preferred variant in which a first channel 27c is connected in its curved section 52 to exactly two second channels 30c in a fluid-conducting manner and which is located exactly opposite another second channel 31c in the flow field 17c. With such a branching of the cooling fluid distribution structure 19 at the transition to the flow field 17c, efficient cooling can be achieved by means of the flow field 17c, although the branching requires little space. The second channels 30c, 31c are also only connected to exactly one first channel 27c or are located opposite it. This reduces the number of transfer points of the cooling fluid for each of the channels 27c, 30c, 31c, which limits flow resistances in the coolant guide.

Finally, Figure 6 also shows two transfer angles W2, W3 between a channel 27c or its curved section 52 and one of the second channels 30c, which open into the curved section 52. The first transfer angle W2 is enclosed by a longitudinal axis LI of the curved section 52 and a longitudinal axis L2 of the second channel 30c and in particular of its end region 33. The longitudinal axes LI, L2 preferably run centrally in the width direction through the said sections or regions. The second channel 30c that is positioned closer to the first segment 50 (not shown in Figure 6 in the case of the uppermost channel 27c) is considered. Furthermore, the smallest achievable intersection angle between the longitudinal axes LI, L2 is considered.

The second transfer angle W3 is spanned between the longitudinal axis LI' of the curved section 52 and the longitudinal axis L2' of the other second channel 30c and in particular by its end region 33. In this case, the second channel 30c is considered which is positioned further away from the first segment 50, which is not shown in the case of the uppermost channel 27c.

Due to the curvature of the curved section 52 but also of the second channel 30c, the longitudinal axes LI', L2' considered are aligned slightly differently than the longitudinal axes LI, L2 of the first transfer angle W2. To define the transfer angles W2, W3, a longitudinal axis LI, LI' of a local area of the curved section 52 is therefore always used, which is intersected by the longitudinal axis L2 of the correspondingly considered second channel 30c.

It should be mentioned again that a longitudinal axis LI, LI' of a corresponding local region can run in the width direction centrally in this local region, wherein the width direction can correspond to a width dimension of the first channel 27c. Likewise, the considered longitudinal axes LI', L2' of the second channels 30c can each run in the width direction or along a channel width centrally within the second channels 30c and in particular from their optionally enlarged end sections 33.

In the example shown, the first transfer angle W2 is larger than the second transfer angle W3. Both transfer angles W2, W3 are smaller than 80°, but preferably larger than 40°. This reduces flow resistance in comparison to a right-angled connection of channels of the flow field 17c to channels of the distribution area 20c, which is common in the prior art. At the same time, however, sufficient branching is still possible to realize the increased number of channels in the flow field 17c.

For the sake of completeness, Fig. 6 again shows the angle Wl, as explained above using Figure 5.

Claims

patent claims 1. Separator plate (2) for an electrochemical system, comprising a first individual plate (2b) and a second individual plate (2a), the inner sides of which face each other and together delimit a cooling fluid distribution structure (19), wherein the separator plate (2) has at least one first through-opening (11a) for passing a cooling fluid through the separator plate (2) and the cooling fluid distribution structure (19) has at least one distribution region (20c) and a flow field (17c), wherein the inner side of the first individual plate (2b) has a plurality of webs (29c, 29c-2b) and first channels (27c) formed therebetween, wherein the first channels (27c) each define at least one continuous fluid connection from the distribution region (20c) into the flow field (17c) and each have a curved section (52), wherein the distribution region (20c) has a first section (20bl) which comprises first segments (50) of the first channels (27c), wherein the first segments (27c) define a fluid connection between the through-opening (11a) and the curved section (52) of a respective first channel (27c), wherein the distribution region (20c) comprises a second section (20b2) which comprises second segments (54) of the first channels (27c), wherein the second segments (54) each define a fluid connection between the curved section (52) of a respective first channel (27c) and the flow field (17c), wherein the inside of the second individual plate (2a) has a plurality of webs (29c, 29c-2a) and second channels (30c) formed therebetween, wherein at least some of the second channels (30c) each open into a curved section (52) of one of the first channels (27c) and extend from the respective curved section (52) extend through the second portion (20b2) of the distribution region (20c) into the flow field (17c). 2. Separator plate (2) according to claim 1, wherein the respective opening of a second channel (30c) into the curved section (52) of one of the first channels (27c) comprises that an open end of the second channel (27c), which faces a contact plane between the first and second individual plates (2a, 2b), is opposite the curved section (52) of the first channel (27c). 3. Separator plate (2) according to claim 1 or 2, wherein at least some of the second channels (30c) each open into only one of the first channels (27c). 4. Separator plate (2) according to one of the preceding claims, wherein more than one second channel (30c) opens into a curved section (52) of a respective first channel (27c), and in particular exactly two second channels (30c) open. 5. Separator plate (2) according to one of the preceding claims, wherein in orthogonal projection of the first and second channels (27c, 30c) into the planar surface plane of the separator plate (2), the second channel (30c) closest to the first segments (50) and the first channel (27c) span a first transfer angle (W2) which is less than 80°, in particular less than 70°, in particular less than 60°. 6. Separator plate (2) according to the preceding claim, wherein, in the case of orthogonal projection of the first and second channels (27c, 30c) into the plane of the separator plate (2), the first channel (27c) and a second channel (30c) located further away from the first segments (50) span a second transfer angle (W3) which is smaller than the first transfer angle (W2), in particular smaller by at least 5°, preferably smaller by at least 10°. 7. Separator plate (2) according to one of the preceding claims, wherein the at least some of the second channels (30c) each lie in sections opposite a web (29c, 29c-2b) formed on the inside of the first individual plate (2b); and/or wherein the second channels (30c) each have a first section (30cl) which opens into a curved section (52) of one of the first channels (27c), a second section (30c2) which lies opposite a web (29c, 29c-2b) formed on the inside of the first individual plate (2b), and a third section (30c3) which runs in the flow field (17c), wherein the second section (30c2) connects the first and third sections (30cl, 30c3) in a fluid-conducting manner. 8. Separator plate (2) according to one of the preceding claims, wherein at least some other of the second channels (31c) extend in the flow field (17c) and are located there opposite one of the first channels (27c). 9. Separator plate (2) according to one of the preceding claims, wherein the first segment and the second segment of each first channel are inclined relative to each other by a maximum of 80°, preferably by a maximum of 60° and in particular by a maximum of 45°. 10. Separator plate (2) according to one of the preceding claims, wherein the curved section (52) has a flow cross-section which is enlarged compared to a flow cross-section of the first and/or second segment (50, 54). 11. Separator plate (2) according to one of the preceding claims, wherein the first and second segments (50, 54) are substantially or completely straight. 12. Separator plate (2) according to one of the preceding claims, wherein in at least some of the first channels (27c) the first segment (50) is at least four times or at least ten times as long as the curved section (52).