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] for an electrochemical m

[0002] 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.

[0003] 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.

[0004] 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.

[0005] 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.

[0006] 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. 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 this, i.e. an outer side of a second individual plate. In contrast, a cooling fluid is usually guided in an interior space defined by the inner sides of the individual plates.

[0007] 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 flow is sometimes only possible with increased flow resistance. This correspondingly reduces the cooling capacity of the separator plate and can therefore limit the performance of the electrochemical system.

[0008] An object of the present invention is therefore to improve the cooling capacity of a separator plate and thus a performance of an electrochemical system having a plurality of such separator plates.

[0009] 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.

[0010] Accordingly, a separator plate for an electrochemical system is proposed, wherein the separator plate comprises a first individual plate and a second individual plate, the inner sides of which face each other and together define a cooling fluid distribution structure, wherein the separator plate has at least one first through-opening for conducting 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, 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 have a first section,which opens into one of the first channels, and a second section which extends in the flow field, wherein the first section has a flow cross-section which is larger than a flow cross-section of the second section.

[0011] By widening the flow cross-section in the first section and consequently in the opening region of the second channels, the flow velocity there is deliberately reduced. This has the effect of limiting pressure losses in the cooling fluid, which would occur more frequently if the cooling fluid were transferred from the first to the second channels without corresponding widening. In other words, the invention provides for the flow in the opening region of the second channels to be deliberately slowed down by means of the cross-sectional widening. This is advantageous because in this opening region (i.e. in the first section of the second channels) a certain degree of turbulence within the coolant flow is unavoidable due to the fluid exchange taking place there and a significant change in direction that is typically present there.

[0012] The effect of limiting pressure loss is particularly pronounced when, as provided in embodiments, the second channels open into a curved and / or similarly widened region of the first channels. Such a design of the first channels further reduces the flow velocity.

[0013] The first channels can extend at least partially into the distribution region. The first channels can optionally continue in the flow field and / or adjoin channels in the flow field and / or merge into channels in the flow field. The first channels can have an optional curved section. For example, the distribution region can comprise a first section that includes 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 also comprises a second section that includes 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.The curved section of a respective first channel may have a flow cross-section that is larger than the flow cross-section of the first segment of the first channel.

[0014] The flow field can be characterized, for example, by all the webs and channels it encompasses being straight and running parallel to each other and parallel to a main flow direction of the cooling fluid through the flow field. Alternatively, the webs and channels could also be wave-shaped and run alongside each other with a similar wave shape and along the main flow direction (or even a main flow axis).

[0015] Additionally or alternatively, the flow field can be characterized by being located within an MEA reinforcement edge and, in particular, being surrounded and / or framed by it at least in sections. However, the flow field itself is preferably not opposite the MEA reinforcement edge, but rather the actually active region of the MEA, in particular in the form of its electrolyte membrane. Reference is made, for example, to DE 20 2020 106 459 U1, and in particular to Figure 3B, which shows an MEA with a reinforcement edge that frames an active region of the MEA. However, the situation can be different with regard to the less deeply shaped region at least partially associated with the flow field, in which the MEA reinforcement edge and the GDL overlap.

[0016] The first and second individual plates can each have a distribution region and a flow field for fluid guidance on their outer sides. A transition region can be arranged between the distribution region and the flow field, in which the webs have a lower height compared to both the distribution region and the flow field. The transition region can be counted partly as the distribution region and partly as the flow field. 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 one of its outer sides.

[0017] The first section of the second channels can be located at least partially outside the flow field and / or at least partially within the distribution area. However, it is also possible for both the first and second sections to be located entirely within the flow field. The second section of a second channel can be any (partial) section of the second channel in the flow field. Alternatively, this section can comprise the entire length of the second channel in the flow field.

[0018] The second channels can be fluidly connected to a respective first channel due to their opening. The second channels can be supplied with cooling fluid from or through the first channel into which they open, or, depending on the flow direction, supply the first channel with cooling fluid. Consequently, at least a portion of the cooling fluid from a first channel can be distributed to at least one second channel opening into it, or can be received and collected by the first channel from this second channel.

[0019] The second channels can each open into one of the first channels at one end of a respective first section. Starting from this end, each second channel can, for example, extend elongated and / or along a longitudinal axis toward a center of the flow field. This center can be a center along a main flow axis of the flow field, along which the cooling fluid flows through the flow field. Neither the first nor the second channels necessarily have to run in a straight line, although this can nevertheless be provided in principle.

[0020] The connection of the second channels to the first channels due to their converging enables branching of the cooling fluid distribution structure. This can, for example, enable the cooling fluid to be guided in the distribution area with a first number of channels and the cooling fluid to be guided in the flow field with a second, larger number of channels, wherein the larger number is formed at least partially as a result of the described branching.

[0021] The second channels can each flow into only one first channel. This means a limited number of feed points into or out of the second channels, which can reduce flow resistance. On the other hand, several second channels can flow into a first channel (e.g., two or more second channels). This allows for a particularly significant increase in the number of channels or a particularly pronounced branching of the type described above.

[0022] A further development provides that the flow cross-section of the first section is enlarged by at least 20% compared to the flow cross-section of the second section, and in particular by at least 30% or at least 40%. In particular, the flow cross-section of the first section can be enlarged by at least 60%, by at least 100%, or by at least 150% compared to the flow cross-section of the second section. To achieve compactness, however, the flow cross-section of the first section can be enlarged by no more than 200% compared to the flow cross-section of the second section, for example.

[0023] The flow cross-sectional area increase between the first and second sections can be uniform for each of the second channels or can vary between the second channels. Multiple groups of second channels can exist, with the flow cross-sectional area increase in each group being uniform in the respective first section, but the flow cross-sectional area increases between the groups differing from one another. Such degrees of freedom can achieve a space-optimized design of the cooling fluid distribution structure.

[0024] The first section can have a maximum flow cross-section of a respective second channel. This reduces the space required by the second channel, since the increased flow cross-section can, for example, be limited to the first section. The flow cross-section can continuously decrease from the first section to the second section, or at least not increase again. For example, the flow cross-section can be constant or continuously decrease at least over a certain length of a respective second channel. This can avoid significant cross-sectional changes, which could in turn cause turbulence and thus pressure losses.

[0025] According to one embodiment, the flow cross-section of the first section is significantly increased by increasing a width dimension of the second channel. The width dimension preferably runs in or parallel to a plane of the separator plate. Alternatively or additionally, the width can be measured perpendicular to a local main flow direction in or through a second channel.

[0026] In particular, an increase in the width dimension may exceed any increase in the maximum height of the first channel in its first section (e.g., be at least twice as large) and / or the maximum height of the first channel may be substantially constant. The height may be measured orthogonally to the plane of the planar surface and / or in a direction directed toward the correspondingly opposite individual plate.

[0027] Significantly increasing the flow cross-section by adjusting the width dimension can prevent or at least limit local height increases of the second individual plate, if structurally possible at all. According to one embodiment, a maximum height dimension of the first section and the second section differs by no more than 20%. The height dimension can run perpendicular to a plane of the separator plate's flat surface.

[0028] 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 herein. On the one hand, the planes 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 planes of the flat surface. However, with the latter approach, it is important to note that when considering distances, etc., the material thickness of only one of two plates under consideration is taken into account.

[0029] A further development provides that the respective opening of a second channel into 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 first channel.

[0030] At least some of the second channels can each be located in sections opposite a web formed on the inside of the first individual plate. For example, the second channels (and more precisely, a partial section thereof) can each cross a web formed on the inside of the first plate. This corresponds to an at least temporary change in the plane of the cooling fluid flow, for example, when the cooling fluid is guided from the first section of the second channels, flowing over the opposite web, further toward the second section or the flow field. However, a reverse flow direction from the flow field toward the first section is also possible.

[0031] 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 first 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.

[0032] In particular, in this context, it can be provided that at least some of the second channels each have a subsection that lies opposite a web formed on the inner side of the first individual plate. This subsection can fluidically connect the first and second sections of the respective second channel. Alternatively, the subsection can be encompassed by the first or second section, for example if it has analogous width dimensions thereto. It has been shown that the above-described possibility of changing planes and providing a subsection provides additional degrees of freedom in order to branch the cooling fluid distribution structure to a significant extent in the region of the transition between the distribution region and the flow field.

[0033] A flow cross-section of the partial section can also be larger than a flow cross-section of the second section. This particularly applies to an average value of the flow cross-section of the respective sections, wherein this average value is averaged, for example, over the length of a respective section. Consequently, the average value of the flow cross-section of the partial section can be larger than the average value of the flow cross-section of the second section.

[0034] Additionally or alternatively, a flow cross-section of a region of the first section that flows into the first channel and a flow cross-section of the partial section may not differ by more than 50%. In this case, the mean values ​​of the respective regions and sections can also be considered.

[0035] Due to the above relative ratios of the flow cross-sections, sufficiently effective flow decelerations can be achieved, but in particular without excessive cross-sectional jumps, which in turn could generate pressure losses.

[0036] According to a further development, the first section has a length which is less than 20 times, in particular 15 times, in particular 12 times, in particular 10 times, in particular 8 times the channel width in the second section.

[0037] Unless otherwise specified, height and width measurements can be taken to be measured at half the height of the structure in question.

[0038] In a further embodiment, at least some of the other second channels extend into the flow field and are each located opposite one of the first channels. This increases the degree of branching at the transition from the distribution region into the flow field. For example, these second channels can each be located opposite 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 first channels on the inside of the second individual plate, but also due to the corresponding direct opposition of at least some of the second and first channels. This increases the achievable cooling of the second individual plates.

[0039] In this context, it can be provided that these other second channels have a flow cross-section that essentially corresponds to a flow cross-section of a respective second section of the second channels. This can result in uniform flow conditions in the flow field.

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

[0041] The invention is explained below with reference to the accompanying schematic figures. The same reference numerals may be used throughout the figures for similar or equivalent features.

[0042] Figure 1 shows a perspective view of an electrochemical system with a plurality of stacked separator plates with membrane electrode units arranged between them.

[0043] 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.

[0044] Figure 3 shows a perspective partial view of the separator plate of the first embodiment in the region of a distribution area of ​​a first individual plate, in particular cathode plate, of the separator plate.

[0045] Figure 4 shows a perspective partial view of a separator plate according to the first embodiment in the region of a distribution area of ​​a second individual plate, in particular anode plate, of the separator plate.

[0046] Figure 5 shows a schematically highly simplified view of a part of a cooling fluid distribution structure inside the separator plate according to the first embodiment.

[0047] Figure 6 shows an orthogonal projection of the structural features of a part of the separator plate into a common plane.

[0048] Figure 1 shows an electrochemical system 1 of the type proposed here, comprising 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 referred to as the stacking direction. In the present example, the system 1 is a fuel cell stack. Each 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.

[0049] In alternative embodiments, 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 flowing onto 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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 area 20a can also be used as a

[0056] The fluid-carrying structures of the distribution areas 20a in Figure 2 are also defined by webs and channels extending between the webs and delimited by the webs.

[0057] 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 regions 20c which overlap with the distribution regions 20a, b of the individual plates 2a, 2b. This cooling fluid distribution structure 19 also has a flow field 17c which 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 complementarily shaped web-channel structures on the corresponding inner sides and thus complementarily shaped web-channel structures of the cooling fluid distribution structure 19. The two through openings 11b andThe 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.

[0058] 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.

[0059] 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 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.

[0060] Figure 3 shows a section of the outer side of the separator plate 2 according to one embodiment, with a view of the first individual plate 2b facing away from the viewer in Fig. 2, in particular a cathode plate, in the area outlined in dashed lines in Figure 2. The viewing angle is rotated compared to Figure 2, as can be seen from the indicated position of the through-opening 11c in Figure 3. Only a cut-off part of both the distribution region 20b and the flow field 17b is shown. In these, a fluid is guided from the through-opening 11c via a first distribution region 20b and through a web-channel structure 46b on the outer side of the first individual plate 2b. The web-channel structure 46b has a plurality of outwardly projecting webs 27b and channels 29b enclosed therebetween, 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.

[0061] On the inner side of the first individual plate 2b facing away from the viewer, the web-channel structure 46b forms complementarily 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.

[0062] The distribution region 20b comprises a first section 20bl, an optional 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. The segments 50, 54 and the curved section 52 directly follow one another 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 as analogous sections 20bl, 20b2 of the cooling fluid distribution structure 19.

[0063] The first segment 50 extends from an edge of the distribution region 20b near the through-opening 11c to the optional 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 54 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 54 merges directly into a web 27b of the flow field 17b or continues as such.

[0064] 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 the second segment 54 are also each straight. The curved section 52, however, does not have a completely straight section and preferably also does not have a section with a constant flow cross-section.

[0065] A flow cross-section of each first web 27b temporarily increases within a respective curved section 52. In the first and second segments 50, 54, each web 27b therefore has a smaller flow cross-section compared to the curved section 52.

[0066] Alternatively, however, the curved section 52 could be omitted and the first and second segments 50, 54 could merge directly into one another. This can also comprise a curved or angled transition. However, this transition can be characterized by no increase in flow cross-section or by a significantly smaller increase in flow cross-section compared to the curved section 52 disclosed here as an example. Figure 4 shows a section of the bipolar plate 2 with a view of the outer side of the second individual plate 2a, preferably an anode plate, in the area outlined in dashed lines from 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 region 20a and the flow field 17a are shown.In these channels, a fluid is guided from the through-opening 11b through the distribution area 20a and through a web-channel structure 46a on the outside of the second individual plate 2a. For example only, the web-channel structure 46a has several outwardly projecting webs 27a and channels 29a enclosed therebetween, selected ones of which are each provided with a corresponding reference symbol. The deepest regions of the channels 29a extend in the plane of the second individual plate 2a.

[0067] As shown, the webs 27a are optionally interrupted in sections along their longitudinal extent within the distribution area 20a, but can also extend continuously in the direction of the flow field 17a.

[0068] Furthermore, the webs 27a are optionally also interrupted near their transition to the flow field 17a, but can also extend at least partially continuously into the flow field 17a. Consequently, the webs 27a are not guided with a change of direction as in Fig. 3, nor are they guided continuously into the flow field 17a.

[0069] The number of webs 27a—at least together with the webs 28a—is greater in the flow field 17a than in the distribution area 20a. For example, additional webs 28a are provided in the flow field 17a, which would not merge into these webs 27a even if the webs 27a of the distribution area 20a were to extend continuously.

[0070] Figure 4 also shows that some of the webs 27a, 28a have widened first sections 33 in a transition region between the distribution region 20a and the flow field 17a. In the example shown, these first sections 33 are located in the distribution region 20a and transition into less widened second sections 35. The latter are located in the flow field 17a and run there in a straight line along a main flow axis S.

[0071] Fig. 5 shows a schematically highly simplified view of a first channel 27c and two second channels 30c opening into it of the cooling fluid distribution structure 19 formed between the individual plates 2a, b. The separator plate 2, which is only shown in detail, is rotated by 90° compared to Figures 3 and 4, which corresponds to an orientation analogous to Figure 2 (see also orientation of the main flow axis S in comparison to Fig. 4).

[0072] The cooling fluid distribution structure 19, in turn, has a distribution region 20c and a flow field 17c. The cooling fluid distribution structure 19 actually comprises a plurality of first and second channels 27c, 30c, which, however, is not shown in the schematically highly simplified Fig. 5. The first channel 27c is primarily defined by the inner side 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 first channel 27c has first and second segments 50, 54 and a curved section 52, each of which is formed as recesses on the inner side 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 of Fig. 3 forms a corresponding first channel 27c of the cooling fluid distribution structure 19 or is shaped complementarily thereto.

[0073] The first channel 27c preferably has a substantially or completely constant height, which, for example, runs orthogonally to the planar surface planes of the individual plates 2a, 2b. The width of the first channel 27c, however, varies along its length. Given the preferably constant height, this width variation is equivalent to a variation in the flow cross-section available to the cooling fluid in the first channel 27c.

[0074] Fig. 5 shows that the optional curved section 52 has a significantly greater width than the first and second segments 50, 54. This results in a significant widening of the flow cross-section in the curved section 52 and limited to this.

[0075] Furthermore, Fig. 5 clearly shows that the first and second segments 50, 54 extend at an angle relative to each other. The widened curved section 52 thus defines a region of change in direction of the first channel 27c and enables a redirection of the cooling fluid from the first segment 50 into the second segment 54, which is angled relative thereto.

[0076] Fig. 5 also shows a cooling fluid feed from (or into) the first channel 27c into (or from) the second channels 30c, shown in dashed lines. The second channels 30c are essentially defined by the inner side 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 shaped complementarily to a portion of the webs 27a, 28a. This particularly concerns a portion of the webs 27a, 28a in or near the flow field 17a of the second individual plate 2a and specifically webs 27a, 28a with a widened end section 33 (see Fig. 4). The second channels 30c are spaced apart by webs 34c, which form complementarily shaped channels 34a on the outer side of the second individual plate 2a (see Fig. 4).

[0077] The second channels 30c each have a widened first section 33c, which merges into a less widened second section 35c. It can be seen that the first sections 33c on the inside of the second individual plate 2a are opposite the curved section 52 on the inside of the first individual plate 2b. An open end of each first section 33c faces the curved section 52 and establishes a fluid-conducting connection between the first channel 27c and a respective second channel 30c. For example, two second channels 30c open into a respective first channel 27c, with each of the second channels 30c opening into only one first channel 27c. The first and second sections 33c, 35c run, for example, at an angle to one another. This enables the first section 33c to be brought close to a respective first channel 27c in a space-saving manner.

[0078] The first sections 33c have a (e.g., average or maximum) width bl. This is measured, for example, transversely to a local main flow direction along a second channel 30c in the region of the first section 33c. The width bl is greater than a width b2 of a respective second section 35c (e.g., again measured transversely to a local main flow direction along a second channel 30c in the region of a second section 35c). In the example shown, the width bl decreases continuously and steplessly from a respective first section 33c to the width b2. The initial width bl is, for example, approximately 1.5 times the width b2.

[0079] In contrast, a height of the second channels 30c measured orthogonally to the widths b1, b2 and to the planes of the individual plates 2a, 2b is essentially constant, particularly in their region 33c, or completely constant. Consequently, the widening of the first sections 33c to the width b1 results in an enlarged flow cross-section there compared to the second sections 35c.

[0080] Fig. 5 further shows that a length II of each first section 33c is significantly greater than the width b2 of the second section 35c. For example, the length II can be measured up to a position and / or the first section 33c can extend to a position where the flow field 17c begins and / or where the width b2 is present for the first time.

[0081] From Fig. 5 it can be seen that the length II in relation to the width b2 is less than 20 times, in particular 15 times, in particular 12 times, in particular 10 times and in particular 8 times.

[0082] Both the change in direction in the region of the curved section 52 and the fluid exchange between the first channel 27c and a second channel 30c opening into it cause turbulence in the cooling fluid flow. Through the optional widening of the flow cross-section in the curved section 52, but especially through the inventive widening of the flow cross-section in each first section 33c, the flow velocity in this area of ​​increased turbulence is specifically reduced, thus limiting pressure losses.

[0083] Fig. 6 shows an orthogonal projection of a section of separator plate 2, oriented analogously to Fig. 5, into a plane parallel to the planes of the individual plates 2a, 2b. The view corresponds to a view through the corresponding section of separator plate 2. The section shown corresponds approximately to an area that has the schematically illustrated structures from Fig. 5. Positions of the distribution regions 20a-c and flow fields 17a-c on the outer and inner sides of the first and second individual plates 2a, b are indicated. These overlap at least in sections.

[0084] Furthermore, the positions and dimensions of overlaps of the channel-web structures 46a, b as well as the cooling fluid distribution structure 19 defined by them can be seen.

[0085] Three first channels 27c of the cooling fluid distribution structure 19 are shown, each shaped complementarily to webs 27b on the outside of the first individual plate 2b. Also shown is the fluid-conducting connection of the optional curved section 52 of each first channel 27c to two second 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). Not all of the second channels 30c are marked with a corresponding reference symbol in Figure 6. For some of the second channels 30c, their widened first sections 33c and their reduced-width second sections 35c are marked.

[0086] For one of the second channels 30c, the widened first section 33c is shown hatched. The first section 33c thus extends from an opening region into the first channel 27c (see left end of the first section 33c in Fig. 6) to a position at which the reduced width b2 (see Fig. 5) of the second section 35c, which preferably continues into the flow field 17c, is present for the first time. The first section 33c also comprises a likewise widened subsection 37c. This subsection 37c, at least in sections, is not located opposite a channel on the inside of the first individual plate 2b, but rather opposite a web 29c formed there.

[0087] The cooling fluid guided along the second channels 30c thus flows over a web 29c on the inside of the first individual plate 2b in the partial section 37c, so that a flow cross-section for the cooling fluid in this area is provided exclusively in the second individual plate 2a.

[0088] Figure 6 also shows additional 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 3. The channels 28c are located opposite sections of the second channels 30c.

[0089] Figure 6 further shows that the second segment 54 of each first channel 27c is guided into the flow field 17c of the cooling fluid distribution structure 19 and continues there as a channel. This lies opposite a further second 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 further second channel 31c is an example of a different type of second channel 31c on the inside of the second individual plate 2a compared to the second channels 30c discussed above. In contrast to Figure 4, the first channel 27c has a step St at the beginning of the curved section 52, but the maximum height in the curved section 52 otherwise extends constantly. Finally, Figure 6 also shows two transfer angles W2, W3 between a respective first channel 27c (in particular its optional curved section 52) and one of the second channels 30c.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 by its first section 33c. The longitudinal axes LI, L2 preferably run centrally through the said sections or regions in the width direction. 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.

[0090] The second transition 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 of its first section 33c. In this case, the second channel 30c is considered which is positioned further away from the first segment 50 (not shown in the case of the uppermost channel 27c).

[0091] Due to the curvature of the curved section 52, the considered longitudinal axis L2' is positioned slightly differently than the longitudinal axis L2 of the first transfer angle W2. Consequently, to define the transfer angles W2, W3, a longitudinal axis LI of a local area of ​​the first channel 27c, and in particular of the curved section 52, is always used, which is intersected by the longitudinal axis L2 of the correspondingly considered second channel 30c.

[0092] In the example shown, the first transfer angle W2 is greater than the second transfer angle W3, e.g., by at least 5° or at least 10°. Both transfer angles W2 and W3 are less than 80°, in particular less than 70° or in particular less than 60°, but preferably greater than 40°.

[0093] For the sake of completeness, Fig. 6 also shows an angle Wl spanned by the first and second segments 50, 54 of a respective first channel 27c.

Claims

Patent claims 1. A separator plate (2) for an electrochemical system (1), comprising a first individual plate (2b) and a second individual plate (2a), the inner sides of which face one another and together define a cooling fluid distribution structure (19), wherein the separator plate (2) has at least one first through-opening (11a) for conducting 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) 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), wherein the inner side of the second individual plate (2a) has a plurality of webs (34c) and second channels (30c) formed therebetween,wherein at least some of the second channels (30c) each have a first section (33c) which opens into one of the first channels (27c) and a second section (35c) which is located in the, Flow field (17c), wherein the first section (33c) has a flow cross-section which is enlarged compared to a flow cross-section of the second section (35c).

2. Separator plate (2) according to claim 1, wherein the flow cross-section of the first section (33c) is increased by at least 20% compared to the flow cross-section of the second section (35c), and in particular by at least 30% or by at least 40%.

3. Separator plate (2) according to claim 1 or 2, wherein the flow cross-section of the first section (33c) is significantly increased by an increase in a width dimension (bl) of the second channel (30c), wherein the width dimension (bl) is in or parallel to a plane surface of the Separator plate (2) runs.

4. Separator plate (2) according to one of the preceding claims, wherein a maximum height dimension of the first portion (33c) and the second portion (35c) differ from each other by no more than 20%, wherein the height dimension runs perpendicular to a flat surface plane of the separator plate (2).

5. Separator plate (2) according to one of the preceding claims, wherein the respective opening of a second channel (30c) into one of the first channels (27c) comprises that an open end of the second channel (30c), which faces a contact plane between the first and second individual plates (2a, 2b), is opposite the first channel (27c).

6. Separator plate (2) according to one of the preceding claims, wherein at least some of the second channels (30c) are each partially opposite a web (29c) formed on the inside of the first individual plate (2b).

7. Separator plate (2) according to claim 6, wherein the at least some of the second channels (30c) each have a partial section (37c) which is opposite the web (29c) formed on the inside of the first individual plate (2b), wherein a flow cross section of the partial section (37c) is also enlarged compared to a flow cross section of the second section (35c).

8. Separator plate (2) according to one of the preceding claims, wherein a flow cross-section of a region of the first section (33c) opening into the first channel (27c) and a flow cross-section of the partial section (37c) differ from each other by no more than 50%.

9. Separator plate (2) according to one of the preceding claims, wherein the first section (33c) has a length (II) which is less than 20 times, in particular 15 times, in particular 12 times, in particular 10 times, in particular 8 times the channel width (b2) in the second section (35c).

10. Separator plate (2) according to one of the preceding claims, wherein at least some other of the second channels (30c) extend in the flow field (17c) and are located there opposite one of the first channels (27c).

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