Separator plate for an electrochemical system and electrochemical system

Abstract

Separator plate (18) for an electrochemical system (10), in particular for an electrolyzer, wherein the separator plate (18) has on at least a first side a plurality of channels (34) which can be flowed through in a longitudinal channel direction and which are each separated from each other at least sectionally by a web (36), wherein the channels (34) each have a plurality of flow cross-section-reduced areas (42), wherein the number of flow cross-section reduced areas (42) within a first half of a total channel length (L1) of each channel (34) is less than within a second half of the total channel length (L1).

Description

[0001] The invention relates to a separator plate for an electrochemical system and an electrochemical system, wherein the electrochemical system is in particular an electrolyzer.

[0002] The use of electrochemical systems and in particular electrolyzers is state of the art. A known basic principle of an electrolyzer design is described below using the methods disclosed here. Fig. 1 discussed.

[0003] However, it has been found that known electrochemical systems cannot always achieve the desired level of efficiency.

[0004] The present invention is therefore directed to the task of improving the efficiency of an electrochemical system.

[0005] This problem is solved by the subject matter of the independent claims. Advantageous further developments are specified in the dependent claims as well as in this description and these figures.

[0006] Accordingly, a separator plate for an electrochemical system is proposed, in particular for an electrolyzer, wherein the separator plate has on at least a first side a plurality of channels through which flow can occur in a channel longitudinal direction or a flow direction and which are each separated from one another at least in sections by a web, wherein the channels each have a plurality of regions with a reduced flow cross-section, wherein the number of regions with a reduced flow cross-section within a first half of a total channel length of each channel is smaller than within a second half of the total channel length.

[0007] According to the invention, it was recognized that the efficiencies of existing electrochemical systems can be impaired, particularly by the accumulation of resulting reaction products in areas that are subsequently no longer sufficiently accessible for the desired electrochemical reaction to occur. In particular, incoming reaction media can no longer reach these areas or can only reach them to a limited extent, so that a desired electrochemical reaction cannot be realized to the desired extent. This is particularly critical when the areas include catalyst materials for the electrochemical reaction.

[0008] In the case of electrolyzers, it has been recognized that catalyst layers in the anode region of an electrochemical cell, in particular, can be obscured by oxygen produced during the electrochemical reaction. Since water is typically used as the reaction medium along the anode, the oxygen concentration increases along the flow path and the achievable local efficiency thus increasingly decreases. The more oxygen is produced, or in other words, the higher the gas content, the more difficult it becomes for the supplied water to remove the oxygen. Likewise, it becomes more difficult for the water to penetrate a typically provided porous transport layer on its way to the anode or to the catalyst layer there. The increasing gas content also impairs the local viscosity of the water / oxygen mixture and thus its local flow behavior.

[0009] The invention therefore proposes structural modifications to separator plates that can at least partially mitigate such disadvantages. In particular, it is proposed to use the reduced-flow cross-section regions to achieve local increases in the flow velocity of a reaction medium guided along the surface of the separator plate. This can increase the probability that resulting reaction products are sufficiently transported away or, figuratively speaking, flushed away.

[0010] The fact that the reduced-flow cross-section regions are unevenly distributed along the entire channel length allows for the expected increase in the concentration of reaction products to be transported away in a flow direction along the channel's longitudinal axis. When the reaction medium flows along the separator plate from the first half toward the second half, the higher number of reduced-flow cross-section regions in the second half allows the expected increased concentration of reaction products to be reliably transported away, and / or a catalyst layer can still be reached past them.

[0011] The channels can each be encompassed by a flow region of the separator plate, within which at least one reaction medium can flow. The flow region can comprise a distribution field and a flow field known per se. The flow field can be the region that is at least partially or even largely opposite or concealed by a GDL and / or PTL explained below. In other words, the flow field can be located in an electrochemically active region of the electrochemical system or an electrochemical cell comprised thereby. A distribution field, on the other hand, can serve to supply the reaction medium to the flow field and / or to transport it away from it. Typically, no electrochemical reaction takes place within the distribution field.

[0012] The reduced-flow cross-section regions disclosed here can optionally be provided exclusively in the distribution field or, for example, in a larger number in the distribution field than in the flow region. This can take into account the fact that reaction products that may hinder the electrochemical reaction are expected to be predominantly present or accumulate in the distribution field.

[0013] The channels can generally be elongated. For example, a length can exceed a width of the channels by at least twenty or fifty times. The channels can, but do not have to, be straight. They can, for example, also run in a wave-like manner and / or with one or more curves and / or one or more angles. An embodiment with a meandering channel course is explained below.

[0014] The webs and channels can each be produced by a stamping process of a base body, in particular a metal one. The webs and channels can in particular be directly adjacent to one another and / or merge into one another. Preferably, a plurality of channels and webs positioned between them are provided, for example at least 20 or at least 100 channels. The webs can preferably separate the channels from one another along their entire length and / or preferably extend along their entire length between the channels. However, by means of optional channel-connecting regions explained below, an at least local fluid-conducting connection across the webs can be provided. In this case, the webs can be understood, for example, as structurally and / or spatially separating the channels, but locally connecting them in a fluid-conducting manner.

[0015] The channels can connect through-openings within the separator plate. In particular, they can extend between two through-openings and connect them in a fluid-conducting manner. In a conventional manner, a reaction medium can be passed through one through-opening, which can then pass into the channels and be guided by them toward the other through-opening.

[0016] The regions with reduced flow cross-section can be formed integrally from the separator plate or, in other words, introduced integrally into the material of the separator plate. They can be formed directly into a respective channel and / or merge directly into at least one channel side wall and / or a channel base. The channel base, which can also be referred to as the channel floor, can be a deepest region of a channel. It can be connected via channel side walls to an outer surface and / or an adjacent outermost or uppermost region of the first side of the separator plate. Such an outermost or uppermost region can in particular be formed by a web or be encompassed thereby. The channel side walls can adjoin the channel base on both sides, e.g. viewed in a cross-sectional view, wherein the cross-sectional plane can run orthogonally to the channel longitudinal direction.Any channel side wall may generally run along the channel's longitudinal direction.

[0017] The channel side walls can be aligned perpendicular or essentially perpendicular to the plane of the separator plate. The channel base is in particular aligned parallel or essentially parallel to the plane of the separator plate. The term “essentially” can, for example, include deviations from parallelism or orthogonality of up to 30°, up to 20°, up to 10° or up to 5°. The channel side walls can generally delimit the channel towards the flow plate. In the case of very small channel geometries, the side walls can also transition from the channel base to the web via two curved lines without containing any straight sections. In this case, the channel side wall can be the part that connects the channel base and the web.

[0018] The reduced-flow cross-section regions can span an entire channel width and / or extend between opposing channel side walls and connect them to one another. In particular, they can have a pronounced transverse extension with respect to a channel's longitudinal axis. Consequently, the reduced-flow cross-section regions can also be referred to as transverse ribs within a channel or form such transverse ribs.

[0019] According to a further embodiment, the first half of the total channel length lies upstream of the second half. Consequently, the smaller number of regions with reduced flow cross-sections also lies upstream, i.e., the number of regions with reduced flow cross-sections increases in the flow direction. The term "upstream" refers to the flow direction along the longitudinal direction of the channel. This flow direction can, in principle, be considered independent of any spatial orientation. In particular, this flow direction can also run vertically if the separator plate is oriented accordingly upright.

[0020] This embodiment assumes a predetermined flow direction along the channels. In particular, this can relate to a flow direction from a first through-opening toward a second through-opening, wherein these through-openings are fluidically connected by the channels.

[0021] According to one embodiment, the number of regions with reduced flow cross-section within the second half of the total channel length is at least 10% higher than within the first half of the total channel length, and in particular at least 20% higher, at least 35% higher, or at least twice as large. It has been shown that this effectively compensates for the influence of the increasing oxygen concentration during flow from the first to the second half.

[0022] Additionally or alternatively, the number of reduced flow area regions within the second half of the total channel length may not be more than four times higher or five times higher than within the first half of the total channel length (especially within a given channel). This limits the flow resistance generated by the reduced flow area regions within the second half, which in turn prevents any degradation of efficiency.

[0023] According to one embodiment, the number of areas with reduced flow cross-section within the first half and / or the second half of the total channel length is at least 5 and in particular at least 10. This allows impairments of the efficiency to be effectively limited.

[0024] According to one embodiment, the distance between successive regions with reduced flow cross-section (in particular of a respective channel) is inhomogeneous, at least within the second half of the total channel length. This takes into account the fact that the oxygen concentration is not expected to be constant, particularly within this second half, so that the distances can be adjusted accordingly.

[0025] In particular, the distance can decrease at least in sections when viewed in the longitudinal direction of the channel. Thus, within the second half of the total channel length, the concentration of the areas with reduced flow cross-section can increase at least in sections, particularly when viewed in one flow direction. This, in turn, takes into account the fact that the oxygen concentration increases, as expected, within the second half and further, particularly in the flow direction.

[0026] According to one embodiment, at least some of the positions of the reduced-flow cross-section regions of a respective channel, viewed along the entire channel length, deviate from the positions of the reduced-flow cross-section regions of at least one other channel. In particular, this can apply to channels that are immediately adjacent to one another. This can create a local pressure difference between the channels. In particular, the pressure in a first channel can be increased at the position of its reduced-flow cross-section region, whereas in the other channel at the same position the pressure remains constant and is lower in comparison. This can promote fluid flow from the first channel into the other channel. In other words, a transverse flow can be generated between the channels, in particular by overcoming a web located between these channels.This increases the ability to remove accumulating oxygen and, in particular, to flush a PTL, as explained below, free of oxygen.

[0027] According to one embodiment, the reduced-flow cross-section regions define a reduction in flow cross-section primarily in a vertical direction of a respective channel. A channel width, however, can preferably be constant or at least decrease to a lesser extent than the height of the channel. Such a configuration of the reduced-flow cross-section regions is advantageous from a manufacturing perspective.

[0028] The height direction can extend perpendicular to a plane of the separator plate and / or a center or base plane thereof. The plane can contain those areas of the separator plate that are not deformed, for example, during a stamping process. The width of a respective channel can extend perpendicular to the height direction as well as perpendicular to the channel's longitudinal axis.

[0029] According to one embodiment, the regions with reduced flow cross-sections, viewed along the channel's longitudinal direction, have a first section with increasing height and a second section with decreasing height. The first section is preferably located upstream of the second section and points, for example, toward a channel end within the first half, whereas the second section can point toward a channel end within the second half. Additionally or alternatively, the first section is preferably longer than the second section. In other words, the regions with reduced flow cross-sections can be mirror-asymmetrical with respect to their respective center plane orthogonal to a channel's longitudinal axis.

[0030] In this embodiment, the increase in height can be less steep than the decrease in height. This promotes flow over the area with reduced flow cross-section, limiting flow turbulence. Due to the reduced length of the second section, the size of the areas with reduced flow cross-section can be reduced, which can be advantageous from a manufacturing perspective.

[0031] In particular, the first section can be curved or flat, but preferably oblique or inclined. This also helps to limit flow turbulence.

[0032] The following comments on the first and second sections and their length ratios, and in particular their measurement as projected lengths, also apply accordingly in the present context.

[0033] In general, the reduced flow cross-section regions of a separator plate, for example in a width direction thereof, and / or of an individual channel can be of similar design or differ from one another. The width direction can, in particular, extend orthogonally to the channel longitudinal direction and / or correspond to a shorter dimension of a generally rectangular separator plate. In the latter case, the deviations can, in particular, be designed to take into account the increasing oxygen concentration along a flow direction. For example, with increasing local oxygen concentration, the reduced flow cross-section regions can be designed to reduce the flow cross-section to a correspondingly increasing extent and consequently increase local water pressure, in particular compared to downstream reduced flow cross-section regions.

[0034] According to one embodiment, at least some of the reduced-flow cross-section regions extend between a first channel side wall and a second channel side wall and rise, at least in sections, toward one of the first and second channel side walls. The channel side walls can extend along the channel's longitudinal axis and, in particular, run at an equal distance and / or parallel thereto. They can be connected by a channel base. This can, for example, run parallel to a plane of the separator plate's flat surface and / or comprise a lowest point of the channel, viewed in the vertical direction.

[0035] In other words, the height of the reduced-flow cross-section regions at a transition to the first channel side wall can be different from the height at a transition to the second channel side wall. Viewed in a cross-section in which the cross-sectional plane runs perpendicular to the channel's longitudinal axis, an outwardly and / or upwardly facing surface of the reduced-flow cross-section regions can be angled and / or obliquely correspondingly.

[0036] This rise and / or oblique course of the areas with reduced flow cross-section can in turn promote cross flows between adjacent channels.

[0037] According to one embodiment, at least some of the webs have at least one channel-connecting region. The channel-connecting region can also be referred to as a channel-connecting region. It can fluidly connect the two channels, which are separated from one another by the web and to which they are each adjacent, to one another. Thus, a fluid guided in a first channel can reach a second channel via the channel-connecting region and / or vice versa. The first and second channels are preferably separated from one another outside the channel-connecting region (or the channel-connecting regions) by the web. The channel-connecting region, in turn, promotes crossflows between adjacent channels, which is advantageous for the effective removal of the oxygen produced.

[0038] However, a channel-connecting region can also extend between different sections of one and the same channel. This particularly applies to channels that do not extend exclusively in a straight line. In this case, an adjacent web may not extend exclusively in a straight line, but may, for example, be adapted to the extension of one or both adjacent channels. This can result in at least one section of a web being arranged between two adjacent channel sections of one and the same channel. One example is a multiply curved and / or angled and, in particular, meandering channel and web course, as explained below using an exemplary embodiment.In such cases, the channel-connecting region can be formed, for example, in the web section arranged between two adjacent channel sections and, for example, establish a fluid connection crossing this web section between the adjacent channel sections.

[0039] The channel-connecting regions can each extend adjacent to or at a short distance from a region with a reduced flow cross-section. The distance can be considered in particular along a channel longitudinal axis. It can be, for example, less than 5 cm and in particular less than 2 cm. The region with a reduced flow cross-section can be formed in one of the channels or channel sections connected by the channel-connecting region. If the channel-connecting region is formed with a first and second section of the type explained above, in particular in a section with a greater length, the channel-connecting region can be positioned closer to the first section than to the second section. In particular, it can be positioned at least sectionally at the same position as the first section, viewed along the longitudinal axis.This allows the pressure increase generated by the first section to be efficiently converted into a cross flow along the channel connecting area.

[0040] In general, the channel-connecting region can form a local depression within a web, which preferably extends at an angle to a web's longitudinal axis and / or across the entire web width. However, the depression preferably remains above adjacent channel bottoms.

[0041] In particular, the channel-connecting region can have a first opening region, in which it opens into a first of the channels or channel sections separated by the web, and a second opening region, in which it opens into a second of the channels or channel sections separated by the web. The opening regions can be lowered relative to a web roof and / or a generally highest height level of the web, in particular in the direction of the channels into which they respectively open. For example, the opening regions can be located at least halfway up the channel. This enables low-resistance introduction and discharge of fluid in the channel-connecting regions.

[0042] In particular, the first and second outlet regions can be located at different heights. Consequently, the channel-connecting region can have a gradient. In particular, it can be beveled and / or angled accordingly between the outlet regions and / or have a downward curvature. This promotes flow through the adjacent component (e.g., the PTL).

[0043] According to one embodiment, the areas with reduced flow cross-section are arranged in such a way that cross-flow of the hydrogen generated on the back side of a single-layer separator plate is possible.

[0044] According to one embodiment, the separator plate is made of titanium or comprises titanium. Alternatively or additionally, the separator plate can have a material thickness of at least 0.2 mm. Alternatively or additionally, the separator plate can have a plurality of through-openings on both sides of a flow field that includes at least portions of the channels, each of which is fluidically connected to the flow field.

[0045] A separator plate having any of the above-mentioned features is particularly suitable for use in electrochemical systems and in particular in an electrolyzer.

[0046] The invention also relates to a separator plate for an electrochemical system, in particular for an electrolyzer, wherein the separator plate has, on at least a first side, a plurality of channels through which flow can occur in a channel longitudinal direction and which are each separated from one another by a web, wherein the channels each have a plurality of regions with a reduced flow cross-section, wherein the regions with a reduced flow cross-section have a first section with an increasing height and a second section with a decreasing height, wherein the first section lies upstream of the second section and has a greater length than the second section. The first and second sections can be separated from one another by a further section, in particular a section with a constant height.

[0047] Preferably, a length of each of the first and second sections is considered in a plane of the separator plate. This can correspond to a projected length, in particular as a result of an orthogonal projection of the respective section lengths into a common plane, and in particular into the plane of the separator plate. This also applies in the context of the previously discussed aspect and its analogous embodiment comprising first and second sections of the described type.

[0048] This separator plate can have all further embodiments and variants mentioned here, which are disclosed, for example, in connection with the separator plate explained above.

[0049] The invention also relates to a separator plate for an electrochemical system, in particular for an electrolyzer, wherein the separator plate has on at least a first side a plurality of channels through which flow can take place in a channel longitudinal direction and which are each separated from one another by a web, wherein the channels each have a plurality of regions with a reduced flow cross-section, wherein at least some of the regions with a reduced flow cross-section extend between a first channel side wall and a second channel side wall and rise at least in sections towards one of the first and second channel side walls.

[0050] This separator plate can also have all of the further embodiments and variants mentioned here, which are disclosed, for example, in connection with the separator plate explained first.

[0051] The invention also relates to a separator plate for an electrolyzer, wherein the separator plate has on at least one first side a plurality of channels through which flow can pass in a channel longitudinal direction and which are each separated from one another by a web, wherein the channels each have a plurality of regions with a reduced flow cross-section, wherein at least some of the webs have at least one channel-connecting region and the channel-connecting region has a first mouth region in which it opens into a first of the first channels separated by the web, and a second mouth region in which it opens into a second of the first channels separated by the web.

[0052] This separator plate can also have all of the further embodiments and variants mentioned here, which are disclosed, for example, in connection with the separator plate explained first.

[0053] Finally, the invention also relates to an electrochemical system, in particular an electrolyzer, comprising a plurality of separator plates, each of which is designed according to any of the aspects disclosed herein.

[0054] In particular, each separator plate can be installed in a single layer. In such a case, both outer sides or surfaces of the separator plate can be part of an electrochemical cell and / or carry reaction media for the electrochemical reaction. This enables a compact structure, particularly compared to a two-layer design, in which the facing inner sides of the two layers are not directly involved in the electrochemical reaction and, in particular, do not carry any participating reaction media.

[0055] Embodiments of the invention are explained below with reference to the accompanying schematic figures. Similar or equivalent features may be provided with the same reference symbols throughout the figures. Within a given figure, not all instances of a feature shown may be provided with the reference symbol associated with that feature. Fig. 1 shows the basic structure of an electrochemical system in the form of an electrolyzer according to an embodiment of the invention. Fig. Figure 2 shows a separator plate according to an embodiment of the invention, as used for example in the system of Fig. 1 can be used, but without a representation of areas with reduced flow cross-section. Fig. 3A-C show possible distributions of areas with reduced flow cross-section within a separator plate, such as the separator plate from Fig. 2. Fig. 4-8 show possible characteristics of areas with reduced flow cross-sections, as they can be found in a separator plate made of, for example, Fig. 1 can be trained. Fig. 9-10 show possible pressure distributions, such as those caused by areas with reduced flow cross-section, for example in the separator plate made of Fig. 1 can be generated. Fig. 11-12 are partial views of a separator plate such as Fig. 1, to explain characteristics and functions of the areas with reduced flow cross-sections. Fig. 13 shows a separator plate according to another embodiment of the invention.

[0056] Fig. Figure 1 shows an electrochemical system 10 according to an embodiment of the invention. The electrochemical system 10 is an electrolyzer. The basic structure of this electrolyzer explained here is known in principle. Modifications according to the invention disclosed here relate in particular to the design of the separator plate 18.

[0057] The electrolyzer comprises a stack of repeating component sequences, as explained below. The stack is arranged and clamped between two limiting plates 14.

[0058] Within the stack, bipolar plates 16 are provided, which consist of a separator plate 18, installed here in a single layer. The separator plate 18 is formed from a single metal sheet and in particular embossed and / or punched. Fig. 1, the wave shape of the separator plate 18 is intended to merely indicate the embossed structure of the channels, without representing a direction of the channels through the wave shape.

[0059] The separator plate 18 has mutually opposite, outwardly facing surfaces. These surfaces each form an anode side or a cathode side of the bipolar plate 16. More specifically, a first outwardly facing surface of the separator plate 18 lies opposite and in particular against a porous transport layer (PTL) 20. The PTL 20 comprises or consists of titanium or a titanium alloy in the form of a porous material, for example, a sintered material. The corresponding surface or side of the separator plate 18 forms an anode side of the bipolar plate 16.

[0060] The corresponding other outward-facing surface of the separator plate 18 of each bipolar plate 16 lies opposite and in particular abuts a gas diffusion layer (GDL) 22. The GDL 22 comprises or consists of carbon, and in particular of a carbon fleece. The corresponding surface or side of the separator plate 18 forms a cathode side of the bipolar plate 16.

[0061] Between a PTL 20 and adjacent GDL 22 there is arranged a catalyst carrier 24 which is coated with catalyst materials, see a Fig. 1 exemplary marked catalyst layer 26.

[0062] During operation of the electrolyzer, water is guided along the anode side of the bipolar plate 16. The water flow direction can be Fig. 1 for example, from vertical top to vertical bottom (or vice versa) or from right to left (or vice versa).

[0063] The water is split into oxygen, electrons, and positively charged hydrogen ions by interacting with a neighboring catalyst layer 26 and applying a voltage from a voltage source 28. The hydrogen ions diffuse to the cathode side, where they combine with the electrons to form hydrogen. To reach the catalyst layer 26, the water must penetrate an adjacent PTL 20.

[0064] The oxygen concentration increases progressively along the flow direction of the water as it flows past a separator plate 16. This results in the water being increasingly prevented from penetrating the PTL 20 and thus reaching the catalyst layer 26. This reduces the overall achievable efficiency of the electrolyzer.

[0065] Fig. 2 shows a single separator plate 18 as used in the system 10 of Fig. 1 can be used. In Fig. In Figure 2, an anode side of the separator plate 18 faces the viewer. The separator plate 18 comprises a plurality of through-openings 30, 32. More precisely, two hydrogen through-openings 32 are provided, each surrounded by a seal 33. The seal 33 prevents a fluid-conducting connection between the hydrogen through-openings 32 and the depicted anode side of the separator plate 18.

[0066] Furthermore, four water passages 30 are provided as an example. These are not sealed from the anode side shown and are thus fluidly connected to it.

[0067] In addition, a channel-web arrangement is embossed into the anode side, which forms a flow area for the water supplied via the water passage openings 30.

[0068] The channel-web arrangement comprises a plurality of channels 34 and webs 36 extending between them and separating the channels, in particular spatially and / or structurally. A direction of extension and thus also a respective longitudinal axis (not shown separately) of the channels 34 and webs 36 runs in Fig. 2 vertical, see the entered coordinate system having a vertical and horizontal axis V, H. Consequently, the channels 34 and webs 36 each extend between two opposite water passage openings 30.

[0069] The flow area is divided into a flow field 38, which is located in an electrochemically active region of the system 10 and in which the guided water participates in the electrochemical reaction of the electrolyzer. Furthermore, the flow area comprises distribution areas 40 in which no electrochemical reaction takes place. These distribution areas 40 are each assigned to one of the through-openings 30, 32 in order to connect them to the flow field 38 in a fluid-conducting manner.

[0070] In a conventional manner, the channels 34 and webs 36 form a complementary channel-web arrangement on the cathode side of the separator plate 18 facing away from the viewer. On this cathode side, the water passages 30 are fluidically sealed by seals 33, and the hydrogen passages 32 are fluidically connected to the flow area.

[0071] The structure of the separator plate 18 discussed above essentially corresponds to conventional examples of the prior art. However, the solution disclosed here provides modifications in the form of the flow cross-section-reduced regions 42, which in Fig. 2 are not entered separately and are explained below.

[0072] Based on the Fig. 3A-C, the positions of the flow cross-section-reduced areas 42 are explained. Fig. 3A-C each show sections of the flow area of ​​the separator plate 18 from Fig. 1 and in particular of its flow field 38. The anode side of the separator plate 18 is again considered. The longitudinal axes of the channels 34 and webs 36 again run vertically. A selected arrangement of two channels 34 and a web 36 extending therebetween is marked with a corresponding sequence of reference numerals. A flow direction S of the water runs vertically between two of the water passage openings 30, not separately shown in these figures.

[0073] The areas 42 with reduced flow cross-section are each indicated by dots and only selected ones are provided with a corresponding reference symbol.

[0074] In the case of Fig. 3A shows that the density of the flow cross-section-reduced regions 42 increases along a respective channel 34 in the flow direction S. More precisely, a distance between two immediately adjacent flow cross-section-reduced regions 42, viewed in the channel longitudinal direction, decreases increasingly along the flow direction S. This takes into account the fact that an oxygen concentration increases viewed in the flow direction S.

[0075] Fig. 3A also schematically indicates the position of a center axis M, which intersects the channels 34 at half their length. It can be seen that within a first lower half of the channels 34, i.e., along a first half of the total channel length L1, fewer regions 42 with reduced flow cross-section are provided than in the upper half. The lower half lies upstream of the upper half.

[0076] Fig. 3A also shows an optional variant in which the flow cross-section-reduced regions 42 of adjacent channels 34 are each positioned at the same positions along a channel longitudinal direction.

[0077] Fig. Figure 3B shows a variant in which the reduced-flow cross-section regions 42 of adjacent channels 34 are not positioned at the same positions along a channel's longitudinal direction. This can promote cross-flows between the channels 34, since the reduced-flow cross-section regions 42 can generate a significant pressure difference compared to an adjacent channel without a reduced-flow cross-section region 42 at the same longitudinal position. The distances along the channel's longitudinal axis between the individual reduced-flow cross-section regions are equal.

[0078] Fig. Figure 3C shows a variant in which the embodiments of the Fig. 3A and Fig. 3B are combined. Thus, the number of flow cross-section-reduced regions 42 increases along a respective channel longitudinal axis and in particular in a second downstream half of a total channel length L1, whereby, however, the positions of the flow cross-section-reduced regions 42 along the longitudinal axis are offset from a respective adjacent channel 34. This variant combines the advantages of the variants of Fig. 3A and Fig. 3B.

[0079] Fig. Figure 4 shows a partial sectional view through a single channel 34, wherein a region 42 with a reduced flow cross-section lies in the sectional plane. The sectional plane also contains a channel longitudinal axis L. A flow direction S is also shown, which runs essentially parallel to the channel longitudinal axis L. In addition, Fig. 4 a canal bottom 35 and a canal side wall 37 are marked.

[0080] A channel length extends along the longitudinal axis L. A channel width runs orthogonal to this and orthogonal to the image plane of Fig. 4. A channel height runs in Fig. 4 perpendicular to the canal bottom.

[0081] The area 42 with reduced flow cross-section has a first section 44 and a second section 46, wherein, viewed in the flow direction, the first section 44 is located upstream of the second section 46 and the sections 44, 46 are connected via a comparatively shorter section 43 with a constant height. In the example shown, the second section 44 has a greater length I1 compared to a length I2 of the first section 46, wherein the lengths I1, I2 are measured along the channel longitudinal axes L and as lengths projected into a plane or a plane parallel thereto. In the example, such a plane runs from Fig. 4 parallel to the flow direction S and is perpendicular to the plane of the sheet, as is clear from the illustrated extensions of the lengths I1, I2. In addition, the height increase of the first section 44 is less pronounced than in the case of the second section 46, i.e. the first section 44 is less steep and / or is less inclined. Finally, the first section 44 is curved and in particular concavely curved, whereas the second section 46 is optionally flat. With such a design, the flow of water from the channel 34 can be directed more intensively in the direction of the PTL. As a result, the PTL and the adjacent catalyst layer can be at least partially flushed free of oxygen accumulating therein, which increases the probability that the water conducted in the channel 34 reaches the adjacent catalyst layer to a greater extent.

[0082] Fig. 5 shows an alternative design of a flow cross-section reduced area 42 in a Fig. 4 analogous view. In this case, a longer first section 44 is provided, arranged upstream of a second section 46. However, this section is less curved and transitions more smoothly into a region 42 with a reduced flow cross-section. The same advantages apply as in the case of Fig. 4 can be achieved and the same length ratios are obtained, even if the lengths I1, I2 in Fig. 5 are not registered separately.

[0083] The Fig. 6-8 each show sectional views of a channel 34, in which the sectional plane is orthogonal to the channel's longitudinal axis L. Consequently, in these figures, the channel's longitudinal axis L (not shown separately) and also a flow direction S run orthogonally to the image plane. The views each show a channel 34 arranged between two webs 36. The channel 34 has a reduced flow cross-section region 42 that connects two opposite channel side walls 37.

[0084] Fig. Figure 6 shows a variant in which the flow cross-section-reduced region 42 has a convexly curved upper or outer side. This curvature can be formed at least in a highest region of the flow cross-section-reduced region 42, for example in a region to which Fig. 4 and Fig. 5 shows the reference number 42.

[0085] In Fig. 7, however, the corresponding outer or upper side is flat.

[0086] In Fig. 8, the outer or upper side is inclined. The area 42 with reduced flow cross-section thus merges into the opposite channel side walls 37 at different height positions. In particular, the variant of Fig. 8 promotes cross currents, as will be shown below with reference to Fig. 9 and Fig. 10 explained.

[0087] It is pointed out that the formation of a flow cross-section-reduced area according to the Fig. 4 and Fig. 5 with any variant of the Fig. 6-8 can be combined, but not necessarily. In particular, the cross-sectional shape can be Fig. 4 and / or Fig. 5 optionally with any of the Fig. 6-8 shown shapes or orientations of an outer or upper side. That is, the cross-sectional shape of Fig. 4 can optionally be combined with the design from Fig. 6 or Fig. 7 or Fig. 8. The cross-sectional shape of Fig. 5 can optionally also be designed with the Fig. 6 or Fig. 7 or Fig. 8 can be combined.

[0088] The Fig. 9 and Fig. 10 are partial sectional views through a separator plate 18, the section plane being analogous to the Fig. 6-8 and the view includes several adjacent webs 36 and channels 34.

[0089] In this case, the separator plate 18 is, for example, according to the variant of Fig. 3B or Fig. 3C. Accordingly, two of the channels 34 shown have two reduced flow cross-section regions 42 located in the sectional plane, whereas a further channel 34 positioned between these channels 34 does not have a reduced flow cross-section region 42 located in the sectional plane and thus positioned at the same longitudinal axis position.

[0090] The flow cross-section-reduced areas 42 are designed to be inclined, analogous to the variant of Fig. 8. The regions 42 with reduced flow cross-sections each generate a local pressure increase +P of the water conducted in the channels 34 as a result of the cross-section reduction. In comparison, the central channel 34 shown has a lower pressure -p at the same longitudinal axis position. This creates a differential pressure between the channels 34. This promotes cross-flows Q between the channels, which run transversely to the channel longitudinal axes and at least partially flow over webs 36 positioned between the channels 34. As shown, these cross-flows Q can in particular penetrate into the PTL and pass through it. Consequently, the PTL can be at least partially flushed free of oxygen accumulating therein, which increases the probability that the water conducted in the channels will reach a catalyst layer (not shown in this figure) to a greater extent.

[0091] Fig. 10 is one to Fig. 9 shows an analogous view, but in which channel-connecting areas 48 are additionally indicated. These promote fluid communication between the adjacent channels 34 across the webs 36. In particular, as shown, they lower the height of the webs 36, at least in sections, which promotes water overflow.

[0092] The Fig. 11 and Fig. 12 show partial perspective views of a separator plate 18. Shown is an exemplary pair of adjacent channels 34, which are separated from one another by a web 36. The channels 34 each have, by way of example, reduced-flow cross-section regions 42, which are arranged purely optionally at essentially identical positions along the respective channel longitudinal axes L. Viewed transversely to the channel longitudinal axes L, channel-connecting regions 48 are arranged adjacent to the reduced-flow cross-section regions 42. The channel-connecting regions 48 are located, by way of example, at the same positions along the longitudinal axes L as the reduced-flow cross-section regions 42.

[0093] For one of the channel-connecting regions 48, a first mouth region 50 is also shown, which opens into a first channel 34, and a second mouth region 52, which opens into the adjacent second channel 34.

[0094] Fig. 12 shows the partial section of the separator plate 18 from Fig. 11 in a flow-conducting state. It can be seen that the areas 42 with reduced flow cross-section, viewed in the flow direction S, again have an upstream first section 44 and a downstream second section 46. These sections 44, 46 can, for example, be designed according to any of the variants explained herein. At the upstream first section 44, as indicated by corresponding reference numerals and arrows, a local pressure increase of the water conducted in a respective channel 34 occurs. At the downstream second section 46, viewed in the flow direction S, in contrast, a local pressure drop occurs compared to the pressure at the upstream first section 44.

[0095] In the example shown, the channel-connecting regions 48 are designed such that the first orifice region 50 is located near the first section 44 of the correspondingly adjacent, reduced-flow cross-section region 42 of the first channel 34, and in particular, at least partially along a same section of the channel's longitudinal axis 34. The second orifice region 52, in contrast, is positioned adjacent to, and in particular in a same longitudinal axis section as, the second section 46 of the reduced-flow cross-section region 42 of the adjacent second channel 34. Thus, the channel-connecting region 48 connects regions within the channels 34 that have differing pressures, and in particular, an upstream region with increased pressure with a downstream region with reduced pressure. This promotes crossflows between the adjacent channels 34.These cross flows are also at least partially oriented in the flow direction S, which further reduces turbulence.

[0096] Fig. 13 shows a separator plate 18 in a Fig. 2 comparable view. This separator plate 18 differs from the variant in Fig. 2 with regard to a channel course in the flow field 38. In the following, only this difference will be discussed and all further explanations regarding Fig. 2 also apply accordingly to the variant of Fig. 13.

[0097] In Fig. 13, the channels 34 in the flow field 38 have a multiply angled and thus particularly meandering course. A channel longitudinal axis (not shown) also runs correspondingly multiply angled and particularly meandering. A selected channel 34 is shown in Fig. 13, wherein the proportions are schematically greatly exaggerated and not representative. It is understood that a plurality of such formed channels 34 are provided in the flow field 38. Furthermore, it is understood that adjacent channels 34 are in turn separated from each other by webs 36. Due to the meandering shape of the channels 34, the webs 36 extend at least in sections between two adjacent and in particular at least in sections parallel to each other channel sections 39. Two such channel sections 39 are shown in Fig. 13 is marked with a corresponding reference symbol as an example.

[0098] The channels 34 each have a plurality of reduced-flow cross-section regions 42, which are schematically indicated by dots and of which only selected ones are provided with a corresponding reference symbol. Furthermore, the webs 34 each have channel-connecting regions 48, which in this case—alternatively or in addition to adjacent channels 34—connect adjacent channel sections 39 to one another. Again, these channel-connecting regions 48 are preferably arranged close to or immediately adjacent to reduced-flow cross-section regions 42 in order to convert pressure increases generated there into cross-flows between the connected channel sections 39.

Claims

[1] Separator plate (18) for an electrochemical system (10), in particular for an electrolyzer, wherein the separator plate (18) has on at least one first side a plurality of channels (34) through which flow can take place in a channel longitudinal direction and which are each separated from one another at least in sections by a web (36), wherein the channels (34) each have a plurality of areas (42) with reduced flow cross-section, wherein the number of flow cross-section-reduced regions (42) within a first half of a total channel length (L1) of each channel (34) is less than within a second half of the total channel length (L1). [2] Separator plate (18) according to claim 1, wherein the first half is upstream of the second half. [3] Separator plate (18) according to claim 1 or 2, wherein the number of flow cross-section-reduced regions (42) within the second half of the total channel length (L1) is at least 10% higher than within the first half of the total channel length (L1) and in particular at least 20% higher or at least 35% higher. [4] Separator plate (18) according to one of the preceding claims, wherein the number of flow cross-section-reduced regions (42) within the first half and / or the second half of the total channel length (L1) is at least 5 and in particular at least 10. [5] Separator plate (18) according to one of the preceding claims, wherein at least within the second half of the total channel length (L1) the distance between successive flow cross-section-reduced regions (42) is inhomogeneous. [6] Separator plate (18) according to claim 5, wherein the distance decreases at least in sections when viewed in the longitudinal direction of the channel. [7] Separator plate (18) according to one of the preceding claims, wherein, viewed along the total channel length (L1), at least some of the positions of the flow cross-section-reduced regions (42) of a respective channel (34) deviate from the positions of the flow cross-section-reduced regions (42) of at least one other channel (34). [8] Separator plate (18) according to claim 7, wherein the at least one other channel (34) is an immediately adjacent channel (34). [9] Separator plate (18) according to one of the preceding claims, wherein the flow cross-section reduced regions (42) define a flow cross-section reduction primarily in a height direction of a respective channel (34). [10] Separator plate (18) according to one of the preceding claims, wherein the flow cross-section-reduced regions (42) have, viewed along the channel longitudinal direction, a first section (44) with increasing height and a second section (46) with decreasing height, wherein the first section (44) is located upstream of the second section (46) and has a greater length (I1) than the second section (46). [11] Separator plate (18) according to claim 10, wherein the first portion (44) is curved. [12] Separator plate (18) according to one of the preceding claims, wherein at least some of the flow cross-section-reduced regions (42) extend between a first channel side wall (37) and a second channel side wall (37) and rise at least in sections towards one of the first and second channel side walls (37). [13] Separator plate (18) according to one of the preceding claims, wherein at least some of the webs (36) have at least one channel-connecting region (48). [14] Separator plate (18) according to claim 13, wherein the channel-connecting region (48) has a first mouth region (50) in which it opens into a first of the channels (34) or channel sections (39) separated from the web (36), and a second mouth region (52) in which it opens into a second of the channels (34) or channel sections (39) separated from the web (36). [15] Separator plate (18) according to claim 14, wherein the first and second mouth regions (50, 52) are located at different height levels. [16] Separator plate (18) according to one of the preceding claims, comprising or consisting of titanium; and / or having a material thickness of at least 0.2 mm; and / or on both sides of a flow field (38) which comprises at least portions of the channels (34), having a plurality of through-openings (30, 32) which are each fluidically connected to the flow field (38). [17] Separator plate (18) for an electrochemical system (10), in particular for an electrolyzer, wherein the separator plate (18) has on at least one first side a plurality of channels (34) through which flow can take place in a channel longitudinal direction and which are each separated from one another by a web (36), wherein the channels (34) each have a plurality of areas (42) with reduced flow cross-section, wherein the flow cross-section-reduced regions (42) have a first section (44) with increasing height and a second section (46) with decreasing height, wherein the first section (44) lies upstream of the second section (46) and has a greater length (I1) than the second section (46). [18] Separator plate (18) for an electrochemical system (10), in particular for an electrolyzer, wherein the separator plate (18) has on at least one first side a plurality of channels (34) through which flow can take place in a channel longitudinal direction and which are each separated from one another by a web (36), wherein the channels (34) each have a plurality of areas (42) with reduced flow cross-section, wherein at least some of the flow cross-section-reduced regions (42) extend between a first channel side wall (37) and a second channel side wall (37) and rise at least in sections towards one of the first and second channel side walls (37). [19] Separator plate (18) for an electrolyzer, wherein the separator plate (18) has on at least one first side a plurality of channels (34) through which flow can take place in a channel longitudinal direction and which are each separated from one another by a web (36), wherein the channels (34) each have a plurality of areas (42) with reduced flow cross-section, wherein at least some of the webs (36) have at least one channel-connecting region (42), and the channel-connecting region (42) has a first mouth region (50) in which it opens into a first of the first channels (34) separated from the web (36), and a second mouth region (52) in which it opens into a second of the first channels (34) separated from the web (36). [20] Electrochemical system (10), in particular electrolyzer, comprising a plurality of separator plates (18) according to one of the preceding claims. [21] Electrochemical system (10) according to claim 20, wherein a respective separator plate (18) is installed in a single layer.

Images