Membrane stack for a humidifier of a fuel cell system

Abstract

The invention relates to a membrane stack (1) for a humidifier of a fuel cell system. The membrane stack (1) comprises several membranes (2) stacked one on top of the other along a stacking direction (S), each membrane being gas-tight and moisture-permeable. A spacer element (3) is arranged between each pair of membranes (2, 2a, 2b) adjacent in the stacking direction (S). This spacer element rests against the two membranes (2, 2a, 2b), forming a gap (4) between them, such that the gap (4) creates a gas path (6, 6a, 6b) through which a gas (G, G1, G2) can flow.At least one of the spacer elements (3) comprises at least one wave structure (13) supported on the two adjacent membranes (2, 2a, 2b) with at least two waves (5) arranged offset from each other, or / and comprises at least one stud structure (12) supported on the two adjacent membranes (2, 2a, 2b) with a plurality of studs (8) arranged in the form of a grid (9), wherein the grid (9) has several grid rows (10) and several grid columns (11), and wherein the studs (8) of at least two adjacent grid rows (10) are arranged offset from each other.

Description

The invention relates to a membrane stack for a humidifier of a fuel cell system and to a humidifier with such a membrane stack.Conventional membrane stacks for humidifiers comprise membranes stacked on top of one another, each with a membrane layer which is impermeable to gas and permeable to moisture or water or water vapor. Between the individual membrane layers or membranes, an intermediate space is formed in each case, through which the gas can flow, i.e. forms a gas path. Thus, a membrane of the membrane stack formed in this way can be overflowed in the humidifier on one side in each case by a gas to be humidified, in particular air, and on the other side by a moist gas, in particular moist air. The two gases are in this case fluidically separated from one another by the respective membrane. Consequently, there is no material mixing of the two gases flowing through the humidifier and the membrane stack. However, the moisture of the moister gas can pass through the membrane layer and be absorbed by the drier gas for moistening it. The moisture of the two gases consequently balances one another when flowing through the membrane stack.Such humidifiers are frequently used in fuel cell systems, where a dry cathode supply air must be humidified before it is supplied to the fuel cell. The cathode supply air is to be humidified in order to avoid or at least delay drying out of the polymer electrolyte membranes typically used in a fuel cell. Such drying, which is to be avoided by means of the humidifier module, has a negative effect in particular on the durability of the polymer electrolyte membranes and the efficiency of the fuel cell.For the highest possible transfer rate of moisture through the respective membrane, it has proven advantageous to generate turbulences in the air flow of both the moist gas and the gas to be humidified. The more pronounced the sensitive turbulence, the greater the rate of transfer of water or moisture through the membrane.However, it has proven disadvantageous that with increasing turbulence, the pressure loss of the moist or respectively to be humidified gas guided through the membrane stack also increases in an undesired manner.It is therefore an object of the present invention to provide an improved embodiment for a membrane stack described at the beginning, in which the above-described problems are taken into account. In particular, a membrane stack is to be created which is distinguished by a high transfer rate of moisture or water from the moist gas to the gas to be humidified with a simultaneously low pressure loss in these gases.This object is achieved by the subject matters of the independent claims. Preferred embodiments are the subject of the dependent claims.The basic idea of the invention is therefore to stack the membranes of the membrane stack on top of one another and to arrange them at a distance from one another in that they are arranged alternately on a respective spacer element. Said spacer elements are thus arranged between two membranes adjacent in the stacking direction. In this case, an intermediate space formed by means of a spacer element between two membranes adjacent in the stacking direction forms in each case a gas path for the flow either with the moist gas or with the gas to be humidified.According to the invention, the spacer element comprises a corrugated structure with rows of knobs arranged offset with respect to one another and / or a knob structure with rows of knobs arranged offset with respect to one another, by means of which the spacer element is supported on the two membranes adjacent in the stacking direction.The spacer element thus functions not only as a mechanical stabilizer for the two adjacent membranes, but also as a turbulence generator for the gas flowing through the gas path, so that the transfer rate of moisture or water through the membrane is markedly improved. Due to the offset arrangement of said corrugations or rows of knobs which is essential to the invention, a particularly turbulent flow of the gas is achieved on the one hand, but at the same time the pressure drop occurring in the gas can be advantageously kept small.As a result, a membrane stack with a high water or moisture transfer rate from the moist gas to the gas to be humidified and with a simultaneously low pressure drop in at least one of these two gases, preferably in both gases, is realized in this way.According to the concept of the invention, a membrane stack according to the invention for a humidifier of a fuel cell system comprises a plurality of membranes which are stacked one on top of the other at a distance from one another along a stacking direction and are each formed so as to be gas-tight and moisture-permeable.In the present case, "gas-tight membrane" is to be understood as meaning that the membrane does not allow a gas to pass through the membrane. In the present case, "moisture-permeable membrane" is to be understood as meaning that the membrane allows the passage of moisture both in gas form, that is to say in particular in the form of water vapor, and in liquid form, in particular in the form of water vapor. In the case of gaseous moisture, the aforementioned gas tightness of the membrane can thus be canceled.A spacer element is arranged between each of two membranes adjacent in the stacking direction, which spacer element is supported at least in sections on the two membranes, forming an intermediate space between these two membranes, so that the intermediate space forms a gas path through which a moist gas or gas to be humidified can flow. According to the invention, one of the spacer elements has at least one corrugation structure supported on the two adjacent membranes, having at least two corrugations arranged offset from one another, and, alternatively or additionally, at least one nub structure supported on the two adjacent membranes, having a plurality of knobs arranged in the form of a grid. In the latter case, the grid of knobs has a plurality of grid lines and a plurality of grid columns, and the knobs of at least two adjacent grid lines are arranged offset with respect to one another.Expediently, the material of at least one spacer element can comprise a plastic, in particular a thermoplastic, or can be such a plastic or thermoplastic. Such a thermoplastic is in particular polyamide (PA), polypropylene (PP) or polyethylene (PE), optionally each with a filler.Preferably, the spacer element arranged between the two adjacent membranes in the interspace divides this interspace into a first subspace formed between the spacer element and a first of the two membranes and into a second subspace formed between the spacer element and a second of the two membranes. Thus, gas can be advantageously divided into two different volumes of the relevant intermediate space, which is associated with an increased moisture transfer.According to an advantageous development of the membrane stack according to the invention, the intermediate spaces formed along the stacking direction form first gas paths through which a moist first gas can flow and which extend along a first path direction, and second gas paths through which a second gas to be humidified can flow and which extend along a second path direction transversely, preferably orthogonally, to the first path direction. During operation of the membrane stack, moisture is thus transferred through the membrane. As a result, the moist gas is dehumidified and the moist gas to be humidified, i.e. the moisture content of the moist gas decreases and the moisture content of the gas to be humidified increases. In a further preferred variant, the first path direction can be arranged at an acute angle to the second path direction. Therefore, adjacent spacer elements in the stacking direction are preferably arranged rotated with respect to each other with respect to their path direction, in particular by 90°. Said further development allows an advantageous, because it is space-saving, flow through the membrane stack with the moist gas or with the gas to be humidified in the cross-flow. In this way, a particularly advantageous flow through the membrane stack in a cross-flow can be realized.Particularly expediently, the first gas paths can extend along a first path direction between two mutually opposite first outer sides of the membrane stack. Analogously, the second gas paths can extend along a second path direction between two mutually opposite second outer sides of the membrane stack.Particularly preferably, at least two waves of at least one wave structure arranged in a first gas path are arranged consecutively along the first path direction and offset with respect to one another in the second path direction. Alternatively or additionally, in this variant, at least two corrugations of at least one corrugation structure arranged in a second gas path are arranged consecutively along the second path direction and offset with respect to one another in the first path direction. If moist gas is conducted through the first gas paths and gas to be humidified is conducted through the second gas paths, or vice versa, an effective transfer of moisture from the moist gas to the gas to be humidified can take place in this way.According to an advantageous development, the wave structure has a plurality of waves which are successive along the first path direction. In this case, two adjacent waves along the first path direction are arranged offset with respect to one another in the second path direction. Alternatively or additionally, the wave structure in this refinement can have a plurality of waves which are successive along the second path direction, wherein then two waves which are adjacent along the second path direction are arranged offset with respect to one another in the first path direction. If moist gas is conducted through the first gas paths and gas to be humidified is conducted through the second gas paths, or vice versa, an effective transfer of moisture from the moist gas to the gas to be humidified can take place in this way.According to an advantageous further development, the corrugation structure has a spacing zone between two corrugations arranged offset with respect to one another, in which spacing zone the spacing element is arranged in a planar manner at a distance from the two membranes adjacent in the stacking direction. Expediently, the spacer element can be configured to be flat or / and planar in the spacer zones. In this way, a region is created in the relevant gas path in which no pressure loss, or only a negligibly small pressure loss, is generated in the gas.According to a further advantageous development, at least one spacer element can have at least two, preferably a plurality of, spacer zones which are arranged at a distance, in particular consecutively, in particular along the first or second path direction. The greater an area proportion of the corrugation structure(s) or of the nub structure(s) on the spacer element, the greater the water or moisture transfer rate achieved. The larger the surface area of the spacer zones on the spacer element, the smaller the pressure drop caused in the respective gas. By defining the respective area fractions, it is thus possible to adapt the moisture transfer rate and pressure drop in the gas which is passed through the membrane stack.According to an advantageous development, at least one wave arranged in a first gas path has a plurality of wave maxima and wave minima which alternate with one another along the second path direction. In this case, the wave is supported in the wave maxima at one (first) of the two adjacent membranes and is supported with the wave minima at one (second) of the two adjacent membranes. Preferably, the wave along the first path direction can have a sinusoidal geometry. Alternatively or additionally, in this refinement, at least one wave arranged in a second gas path has a plurality of wave maxima and wave minima which alternate one after the other along the first path direction. In this case, the wave structure is supported in the wave maxima on one (first) of the two adjacent membranes and with the wave minima on another (second) of the two adjacent membranes. Preferably, the wave along the second path direction can have a sinusoidal geometry. By means of said support of the shaft on the two membranes adjacent in the stacking direction, the membrane stack is effectively mechanically stiffened in the region of the respective gas path or intermediate space.According to a further advantageous development of the membrane stack according to the invention, the nub structure can have first knobs which are supported on the membrane adjacent in the stacking direction and can also have second knobs which are supported on the membrane adjacent in the opposite direction to the stacking direction. In this way, the membrane stack is mechanically stiffened in the region of the relevant intermediate space or gas path.Particularly preferably, the grid formed by the knobs can have a plurality of alternately successive first and second grid lines, wherein the first grid lines are arranged offset with respect to the second grid lines. As a result, particularly strong turbulence currents are generated.In a preferred embodiment, the knobs of a specific raster line or raster column along the first path direction can form a sinusoidal geometry with a plurality of knob maxima and knob minima that alternate with one another, in particular in a section along the first path direction. Alternatively or additionally, in this embodiment, the knobs of a specific raster line or raster column along the second path direction-in particular in a section along the second path direction-can form a sinusoidal geometry with a plurality of knob maxima and knob minima that alternate with one another.Particularly expediently, the raster lines of the knob structure of at least one spacer element arranged in a first gas path extend along the second path direction or along the first path direction. Particularly preferably, in this variant, the grid columns of the knob structure extend orthogonally to the grid rows. Alternatively or additionally, the raster lines of the knob structure of at least one spacer element arranged in a second gas path extend along the first path direction or along the second path direction. Particularly preferably, in this variant, the grid columns of the knob structure extend orthogonally to the grid rows.In a preferred embodiment of the membrane stack according to the invention, at least one aperture is formed in at least one spacer element, which aperture fluidically connects the first subspace formed between the spacer element and the (first) membrane adjacent in the stacking direction to the second subspace formed between the spacer element and the membrane adjacent opposite to the stacking direction. Particularly preferably, the at least one aperture opens at one end into a (first) surface facing the (first) membrane and at the other end into a (second) surface of the spacer element facing the (second) membrane. With the aid of said breakthrough, the gas flows in the two subspaces can be mixed in an advantageous manner.According to a further advantageous development, a plurality of such apertures can therefore be arranged in the at least one spacer element at a distance from one another and thus fluidically separated from one another. In this way, the mixing of the two subspaces explained above can be further increased.According to a preferred embodiment, the corrugated structure and / or the knob structure is arranged between two edge sections of the respective spacer element, which edge sections likewise extend in each case along the first or second path direction and are preferably embodied in a flat manner. If the spacer element is arranged in a first gas path, the two edge sections extend along the first path direction and delimit the gas path perpendicular to the first path direction, that is to say preferably along the second path direction. Particularly preferably, the two edge sections then lie opposite one another along the second path direction. If the spacer element is arranged in a second gas path, the two edge sections extend along the second path direction and delimit the second gas path perpendicular to the second path direction, that is to say preferably along the first path direction. Particularly preferably, the two edge sections then lie opposite one another along the first path direction.Particularly preferably, the two edge sections of a respective spacer element are firmly connected on both sides to the membrane adjacent in each case in the stacking direction. In this way, the spacer element is firmly connected to the two adjacent membranes. At the same time, a fluid-tight limitation of the respective intermediate space or gas path is achieved. The provision of separate sealing elements for sealing the gas paths or intermediate spaces can thus be dispensed with.A cohesive connection, in particular, can be realized by means of a suitable adhesive layer made of an adhesive or of an adhesive tape. This eliminates the customary folding of the membranes around the spacer element in conventional membrane stacks. At the same time, by means of the spacer element bonded to the membranes, a fluid-tight delimitation of the intermediate space or gas path is realized. The result is thus a membrane stack of technically simple construction and thus also cost-effectively produced.At least one adhesive connection is particularly expediently realized by means of an adhesive layer made of adhesive or made of an adhesive tape. This is particularly preferred for all adhesive connections present. In this way, the membrane stack can be assembled in a particularly simple manner, but mechanically stable.Particularly expediently, the edge sections can be configured in the form of strips. In this way, it is ensured that sufficient space is available along the direction of extension for the gas path formed in the region of the contact or spacing zone.According to a further advantageous development, at least one corrugation structure or knob structure of at least one first spacer element arranged in the first gas path extends perpendicular to the first path direction between two outer sides of the membrane stack delimiting the relevant intermediate space transversely, preferably perpendicularly, to the first path direction across the entire intermediate space or gas path. Alternatively or additionally, in this refinement, at least one corrugation structure or knob structure of at least one second spacer element arranged in the first gas path extends perpendicular to the second path direction between two outer sides of the membrane stack delimiting the relevant intermediate space transversely, preferably perpendicularly, to the second path direction across the entire intermediate space or gas path. In this way, said contact zone is provided in the entire path cross section of the respective gas path.According to an advantageous development, the membrane stack can have, in a cross section perpendicular to the axial direction, the geometry of a square with two mutually opposite first sides and with two mutually opposite second sides or the geometry of a rectangle with two mutually opposite narrow sides and two mutually opposite broad sides.The invention further relates to a humidifier for a fuel cell system of a motor vehicle or for a stationary fuel cell system. The humidifier comprises a housing surrounding a housing interior. Furthermore, the humidifier comprises a membrane stack according to the invention arranged in the housing interior and presented above. The advantages of the membrane stack according to the invention explained above are therefore transferred to the humidifier according to the invention.Further important features and advantages of the invention are evident from the dependent claims, from the drawings and from the associated description of the figures with reference to the drawings.It is understood that the features mentioned above and those still to be explained below can be used not only in the respectively specified combination, but also in other combinations or alone, without departing from the scope of the present invention.Preferred exemplary embodiments of the invention are illustrated in the drawings and are explained in more detail in the following description, wherein the same reference numerals refer to the same or similar or functionally the same components.They show, in each case schematically: FIG. 1 shows an example of a membrane stack 1 according to the invention in a perspective illustration, FIG. 2 shows a detailed illustration of FIG. 1 in the region of a plurality of membranes stacked one on top of the other, FIG. 3 is a sectional view of two membranes adjacent in the stacking direction, opposite in the stacking direction and delimiting the intermediate space along the stacking direction, and the spacer element arranged in the intermediate space, FIG. 4 shows a spacer element of the membrane stack shown in FIGS. 1 and 2 in a separate, perspective illustration, FIG. 5 shows a detailed illustration of FIG. 4 in the region of the wave structure, FIG. 6 is a representation illustrating the geometry of the wave structure of the spacer element according to FIGS. 1 to 5, FIG. 7 shows a further design variant of the example of the figure, in which the spacer element instead of a corrugated structure as in the example of FIGS. 1 to 6 instead has a knob-like structure with a plurality of knobs. FIG. 8 shows two membranes adjacent in the stacking direction, opposite in the stacking direction and delimiting the intermediate space along the stacking direction, and the spacer element according to FIG. 7 arranged in the intermediate space.FIG. 1 illustrates an example of a membrane stack 1 according to the invention in a perspective illustration. FIG. 2 is a detailed view of FIG. 1 in the region of a plurality of membranes 2 stacked one on top of the other. According to FIGS. 1 and 2, the membrane stack 1 comprises membranes 2 stacked at a distance from one another along a stacking direction S and each formed so as to be gas-tight and moisture-permeable.A spacer element 3 is arranged between each two membranes 2 adjacent in the stacking direction S, which spacer element is supported at least in sections on the two membranes 2, 2 forming an intermediate space 4 between these two membranes 2, 2. This is illustrated by the sectional illustration of FIG. 3, which shows a single such intermediate space 4 and two adjacent membranes 2, 2 lying opposite one another along the stacking direction S and delimiting the intermediate space 4 along the stacking direction S, and the spacer element 3 arranged in the intermediate space 4. The arrangement of the spacer element 3 in the intermediate space 4 and its support on the two membranes 2, 2 accordingly takes place in such a way that the intermediate space 4 forms a gas path 6 through which a gas G can flow. According to FIG. 3, each spacer element 3 arranged in an intermediate space 4 divides this intermediate space 4 into a first subspace 4 aformed between the spacer element 3 and a first 2 aof the two membranes 2, 2 and into a second subspace 4 bformed between the spacer element 3 and a second 2 bof the two membranes 2, 2.As shown in FIG. 3, apertures 14 can be formed in the spacer element 3 in the corrugated structure 13, which openings fluidically connect the first subspace 4 aformed between the spacer element 3 and the first membrane 2, 2 aadjacent in the stacking direction S to the second subspace 4 bformed between the spacer element 3 and the membrane 2, 2 badjacent opposite to the stacking direction S. Each aperture 14 opens at one end into a first surface 15 aof the spacer element 3 facing the first membrane 2 a, 2 and at the other end into a second surface 15 bof the spacer element 3 facing the second membrane 2 b, 2.As can be seen from the illustration in FIG. 2, the intermediate spaces 4 formed along the stacking direction S between adjacent membranes 2, 2 alternately form first gas paths 6 athat can be flowed through by a moist first gas G 1, G and second gas paths 6 bthat can be flowed through by a second gas G 2, G to be humidified. In this case, the first gas paths 6 aextend along a first path direction P 1 between two mutually opposite first outer sides 7 a, 7 aof the membrane stack 1 (cf. FIG. 1 ). Similarly, the second gas paths 6 bextend along a second path direction P 2 between two mutually opposite second outer sides 7 b, 7 bof the membrane stack 1. The two path directions P 1, P 2 both extend orthogonally to the stacking direction S.FIG. 4 shows a separate perspective illustration of one of the spacer elements 3 arranged in a first gas path 1. FIG. 5 is a detailed illustration of FIG. 4 In the example of FIGS. 1 to 5, the spacer elements 3 each have a wave structure 13 supported on the two adjacent membranes 2 a, 2 b, 2. The wave structure 13 in turn has a plurality of successive waves 5, which in the example of FIGS. 4 and 5 follow one another along the first path direction P 1. In this case, adjacent shafts 5 along the first path direction P 1 are arranged offset with respect to one another in the second path direction P 2.FIG. 6 shows a detail of a shaft of the shaft structure 13 according to FIGS. 4 and 5 in a separate illustration. The wave 5 shown has along the second path direction P 2 a plurality of wave maxima 16 and wave minima 17 alternately following one another. A combination of FIG. 6 with FIG. 3 illustrates that the wave 5 is supported in the wave maxima 16 on the membrane 2 aadjacent in the stacking direction and is supported with the wave minima 17 on the membrane 2 badjacent in the opposite direction to the stacking direction S.It can be seen from the illustration in FIG. 4 that the corrugation structure 13 can have a spacing zone 18 in each case along the first path direction P 1 between the individual corrugations 5, in which spacing zone the spacing element 3 is arranged in a planar manner at a distance from the two membranes 2 a, 2 badjacent in the stacking direction S.In the example of FIG. 4, the corrugation structure 13 has, by way of example, 11 corrugations 5 and 10 spacing zones 18. In the region of the spacing zones 18 there is no shaft 5. In the example, the individual distance zones 18 each extend along the second path direction P 2, i.e. perpendicular to the first path direction P 1, along which the gas G, G 1 flows through the first gas path 6 a.As can be seen from FIG. 4, the shafts 5 and the spacer zones 8 can be arranged between two flat edge sections 19 a, 19 bof the respective spacer element 3 which respectively likewise extend along the first path direction P 1. If, as shown in FIG. 4, the spacer element 3 is thus arranged in a first gas path 6 a, 6, the two edge sections 19 a, 19 bextend both in each case along the first path direction P 1 and delimit the first gas path 6 a, 6 along the second path direction P 2. Expediently, as shown in FIG. 3, the two edge sections 19 a, 19 bare then opposite one another along the second path direction P 2. If, on the other hand, the spacer element 3 is arranged in a second gas path 6 b(not shown in FIG. 4 ), the two edge sections 19 a, 19 bextend along the second path direction P 2 and delimit the second gas path 6 b, 6 along the first path direction P 1. Expediently, the two edge sections 19 a, 19 bare then opposite one another along the first path direction P 1 (not shown in FIG. 4 ).In both of the aforementioned cases, the two edge sections 19 a, 19 bof a respective spacer element 3 can be firmly connected on both sides in a materially bonded manner to the membrane 2 a, 2 aadjacent in each case in the stacking direction S (cf. also FIG. 4 for the first edge section 19 ashown there). A cohesive connection, in particular, can be realized by means of a suitable adhesive layer made of an adhesive or of an adhesive tape. Alternatively, a welded connection is conceivable. In both variants, the spacer element 3 is firmly connected to the two adjacent membranes 2, 2. As a result, a fluid-tight lateral delimitation of the respective intermediate space 4 or gas path 6, 6 a, 6 bis achieved.Particularly expediently, the edge sections 19 a, 13 bmay be configured in the form of strips, as shown in FIG. 4. In this way, it is ensured that sufficient space is available along the first or second path direction P 1, P 2 for the gas path 6 formed in the region between the two edge zones 19 a, 19 b.FIG. 7 shows a separate perspective illustration of a further design variant of a spacer element 3 arranged in a first gas path 6 a. FIG. 8 is an illustration corresponding to FIG. 3 with the spacer element 3 shown in FIG. 7.In the example of FIGS. 7 and 8, the spacer element 3 has a knob structure 12 with a plurality of knobs 8 arranged in the form of a grid 9. According to FIG. 8, the knob structure 12 or the grid 9 of knobs 8 has first knobs 8 awhich are supported on the membrane 2 aadjacent in the stacking direction S and second knobs 8 bwhich are supported on the membrane 3 adjacent in the opposite direction to the stacking direction S.As illustrated in FIG. 7, the grid 9 of knobs 8 has a plurality of grid lines 10 and a plurality of grid columns 11 of knobs 8. The raster lines 10 are formed by first and second raster lines 10 a, 10 b, which alternate in the first path direction P 1. Analogously, the raster columns 11 are formed by first and second raster columns 11 a, 11 b, which alternate in the second path direction P 2.The knobs 8 of a specific raster row 10 or raster column 11 can have a sinusoidal geometry along the first path direction P 1-in particular in a section along the first path direction P 1-with a plurality of knob maxima and knob minima that alternate with one another. In addition, the knobs 8 of a specific raster row 10 or raster column 11 along the first path direction P 2-in particular in a section along the second path direction P 2-can have a sinusoidal geometry with a plurality of knob maxima and knob minima that alternate with one another.As can be seen from FIG. 7, the knobs 8 forming the first raster lines 10 aare arranged offset along the second path direction P 2 with respect to the knobs 8 forming the second raster lines 10 b. Likewise, the knobs 8 forming the first raster columns 11 aare arranged offset along the first path direction P 1 with respect to the knobs 8 forming the second raster rows 10 b.In comparison with the above-explained spacer element 3 with knob structure 12 arranged in a first gas path 6 a, in the case of a spacer element 3 with knob structure 12 arranged in a second gas path 6 a, the grid columns 11 and the grid rows 10 are interchanged (not shown).The apertures 14 illustrated with reference to FIG. 3 and formed in a corrugated structure 13 can also be provided in a spacer element 3 having a knob structure 12 (not shown in the figures).Expediently, the material of a respective spacer element 3 can be a plastic, in particular a thermoplastic, in all the examples explained. Such a thermoplastic is, for example, polyamide (PA), polypropylene (PP) or polyethylene (PE), optionally each with a filler.

Claims

Membrane stack (1) for a humidifier of a fuel cell system, - with several membranes (2) which are stacked on top of one another at a distance from one another along a stacking direction (S), are each formed so as to be gas-tight and moisture-permeable, - wherein between each two membranes (2, 2a, 2b) adjacent in the stacking direction (S) is respectively arranged spacer element (3) which is supported on the two membranes (2, 2a, 2b) forming an intermediate space (4) between these two membranes (2, 2a, 2b), so that the intermediate space (4) forms a gas path (6, 6a, 6b) through which a gas (G, G1, G2) can flow, - wherein at least one of the spacer elements (3) forms at least one gas path (6, 6a, 6b) on the two adjacent membranes (2, 2a, 2b) supporting corrugation structure (13) having at least two corrugations (5) arranged offset with respect to one another and / or having at least one nub structure (12) supporting on the two adjacent membranes (2, 2a, 2b) having a plurality of knobs (8) arranged in the form of a grid (9), wherein the grid (9) comprises a plurality of grid rows (10) and a plurality of grid columns (11), and wherein the knobs (8) of at least two adjacent grid rows (10) are arranged offset with respect to one another.Membrane stack according to Claim 1, characterized in that the interstices (4) formed along the stacking direction (S) alternately form first gas paths (6a), through which a moist first gas (G, G1) can flow and which extend along a first path direction (P1), and second gas paths (6b), through which a second gas (G, G2) to be humidified can flow and which extend along a second path direction (P2) transversely, preferably orthogonally, to the first path direction (P1).Membrane stack according to Claim 2, characterized in that - the at least two corrugations (5, 5) of at least one corrugation structure (13) arranged in a first gas path (6a, 6) are arranged successively along the first path direction (P1) and offset with respect to one another in the second path direction (P2), or / and in that - the at least two corrugations (5, 5) of at least one corrugation structure (13) arranged in a second gas path (6b, 6) are arranged successively along the second path direction (P2) and offset with respect to one another in the first path direction (P1).Membrane stack according to Claim 3, characterized in that - the wave structure (13) has a plurality of waves (5) which are successive along the first path direction (P1) and in each case two waves (5) which are adjacent along the first path direction are arranged offset with respect to one another in the second path direction (P2), or / and in that - the wave structure (13) has a plurality of waves (5) which are successive along the second path direction (P2) and in each case two waves (5) which are adjacent along the second path direction are arranged offset with respect to one another in the first path direction (P1).Membrane stack according to one of the preceding claims, characterized in that the corrugated structure (13) has a spacing zone (18) between two shafts (5, 5) arranged offset with respect to one another, in which spacing zone the spacing element (3) (3) is arranged, in particular in a planar manner, at a distance from the two membranes (2, 2) adjacent in the stacking direction (S).Membrane stack (1) according to one of claims 2 to 5, - at least one wave (5) arranged in a first gas path (P1) has a plurality of wave maxima (16) and wave minima (17) arranged in alternating succession along the second path direction (P2), wherein the wave (5) is supported in the wave maxima (16) on a (first) (2a) of the two adjacent membranes (2a, 2b, 2) and with the wave minima (17) on a (second) (2b) of the two adjacent membranes (2a, 2b, 2); or in that - at least one wave (5) arranged in a second gas path (P2) has a plurality of wave maxima (16) and wave minima (17) arranged alternately one after the other along the first path direction (P1), wherein the wave structure (13) is supported in the wave maxima (16) on one (first) (2a) of the two adjacent membranes (2, 2) and with the wave minima (17) on one (second) (2b) of the two adjacent membranes (2a, 2b).Membrane stack according to one of the preceding claims, characterized in that the nub structure (12) has first knobs (8, 8a) which are supported on the membrane (2a, 2) adjacent in the stacking direction (S) and also has second knobs (8) which are supported on the membrane (2b, 2) adjacent in the opposite direction to the stacking direction (S).Membrane stack according to one of the preceding claims, characterized in that the grid (9) made of the knobs (8) has alternately successive first and second grid lines (10a, 10b), wherein the first grid lines (10a) are arranged offset with respect to the second grid lines (10b).Membrane stack according to one of the preceding claims, characterized in that - the raster lines (10) of the knob structure (8) of at least one spacer element (3) arranged in a first gas path (6a, 6) extend along the second path direction (P2); and / or in that - the raster lines (10) of the knob structure (8) of at least one spacer element (3) arranged in a first gas path (6a, 6) extend along the first path direction (P1).Membrane stack (1) according to one of the preceding claims, characterized in that - at least one aperture (14) is formed in at least one spacer element (3), which aperture fluidically connects a first subspace (4a) formed between the spacer element (3) and the (first) membrane (2, 2a) adjacent in the stacking direction (S) to the second subspace (4b) formed between the spacer element (3) and the membrane (2, 2b) adjacent opposite to the stacking direction (S), - preferably the at least one aperture (14) opens at one end into a (first) surface (15a) facing the (first) membrane (2a, 2) and at the other end into a (second) surface (15b) of the spacer element (3) facing the (second) membrane (2b, 2).Membrane stack according to claim 10, characterised in that in the at least one spacer element (3) a plurality of such apertures (14) is arranged at a distance from one another and thus fluidically separated from one another.Humidifier for a fuel cell system of a motor vehicle or for a stationary fuel cell system, - with a housing surrounding a housing interior; - with a membrane stack (1) according to one of the preceding claims arranged in the housing interior.

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