Membrane stacking unit

Abstract

The invention relates to a membrane stacking unit (3) for a humidifier (1) for a fuel cell-powered vehicle. The membrane stacking unit (3) has a cuboid membrane stack (4) and two sealing frames (10a, 10b). The invention also relates to the humidifier (1) with a housing (2) and the membrane stacking unit (3).

Description

[0001] The invention relates to a membrane stack unit for a humidifier for a fuel cell-powered vehicle according to the preamble of claim 1. The invention also relates to the humidifier with the membrane stack unit.

[0002] A humidifier can be used, for example, in a fuel cell system to humidify dry air flowing to the fuel cell with moist air flowing from the fuel cell. The humidifier typically comprises a housing and a membrane stack made up of several flexible membranes. The membranes are stacked at a distance from one another in the membrane stack and glued together in such a way that four side surfaces of the membrane stack are connected to one another in pairs in an air-conducting manner and are hermetically separated from other side surfaces. This allows the dry air and the moist air to flow cross-flow through the membrane stack and exchange moisture or water vapor with each other via the membrane. To prevent the dry air and the moist air from mixing in the humidifier, the side surfaces through which flow occurs must be hermetically separated from one another.Typically, a cuboid, frame-like frame is used for this purpose, which is glued to the side surfaces of the membrane stack. The membrane stack and the frame together form a so-called membrane stack unit, which is then arranged in the housing. Gluing the frame to the membrane stack takes place after the membrane stack has been installed in the frame and can be very complex.

[0003] The object of the invention is therefore to provide an improved or at least alternative embodiment for a membrane stack unit of the generic type, in which the described disadvantages are overcome. The object of the invention is also to provide a corresponding humidifier with the membrane stack unit.

[0004] This object is achieved according to the invention by the subject matter of the independent claims. Advantageous embodiments are the subject matter of the dependent claims.

[0005] The present invention is based on the general idea of ​​forming the frame in several parts and from at least two frame panels and introducing an adhesive groove into the frame panels so that assembly can be simplified.

[0006] The membrane stack unit according to the invention is intended or designed for a humidifier for a fuel cell-powered vehicle. The membrane stack unit has a cuboid-shaped membrane stack with a plurality of flexible membranes stacked in a stacking direction. The membrane stack has four side surfaces through which air can flow and are aligned parallel to the stacking direction, and two end surfaces through which air cannot flow and are aligned transversely to the stacking direction. The membrane stack unit also has two sealing frames, and the sealing frames are assigned to two opposite side surfaces of the membrane stack. Each sealing frame has a circumferential sealing region and a circumferential region projecting perpendicularly from the sealing region. The sealing region surrounds the respective associated side surface at the edge and rests against it.The peripheral area is oriented toward the membrane stack and surrounds the membrane stack at its edges. According to the invention, the respective sealing frame has a recess surrounding the associated side surface at least on one surface of the sealing area facing the associated side surface. The respective recess is filled with an adhesive, and the respective sealing frame is sealed to the membrane stack via the adhesive.

[0007] The membrane stack can be formed from several flexible membranes, with the individual membranes arranged at a distance from one another. The membranes can be designed such that they are impermeable to air and permeable to moisture or water vapor. Flow-through spacers can be stacked between the membranes. The membrane and the spacers can be glued to one another in such a way that flow-through channels are formed between the membranes. The respective channels can connect two of the respective opposite side surfaces of the membrane stack in an air-conducting manner and be hermetically separated from two other of the respective opposite side surfaces of the membrane stack. The individual channels can alternately connect the respective opposite side surfaces in the stack direction in an air-conducting manner, such that the membrane stack as a whole can be flowed through in cross-flow.

[0008] The four side surfaces through which air can flow and the two end surfaces through which air cannot flow delimit the membrane stack to the outside and form the outer surface of the cuboid-shaped membrane stack. The two end surfaces are arranged opposite one another and can be formed by the respective last membranes in the stacking direction. Alternatively, the membrane stack unit can have two sealing plates, wherein the sealing plates rest on the respective last membranes in the stacking direction and, in particular, can be sealingly connected to the respective last membranes in the stacking direction. The sealing plates can then be surface-identical to the respective last membranes in the stacking direction and represent the end surfaces of the membrane stack. The sealing plates can, for example, be formed from plastic and, in particular, can be, for example, glued to the respective last membranes in the stacking direction.

[0009] The membrane stack unit has two - in particular exactly two - sealing frames. Each sealing frame is formed from the sealing area and the circumferential area. The sealing area and the circumferential area can be formed integrally with one another, merge integrally into one another, or be inseparably connected to one another. The sealing area can be formed by a flat or level frame. The sealing area can have an edge on the inside, and the circumferential area can be formed on the outside or opposite the edge. The circumferential area is formed perpendicular to the sealing area. As a result, the sealing frame can have an L-shaped cross-section. The sealing area rests against the respective associated side surface of the membrane stack. The circumferential area surrounds the membrane stack at the edge and is perpendicular to the associated side surface orarranged parallel to all surfaces of the membrane stack adjacent to the associated side surface—i.e., to the two end faces and the two adjacent side faces. The sealing frame can be molded from plastic, for example.

[0010] A recess for the adhesive is formed on the surface of the sealing area facing the associated side surface. The adhesive then seals and bonds the respective sealing frame to the membrane stack. The recess is formed all the way around the sealing frame and can completely surround the associated side surface. In particular, the recess can follow the frame-like shape of the sealing area. The adhesive can be any liquid or flowable adhesive that solidifies after application with or without additional treatment - i.e., treated or untreated. When assembling the sealing frame to the membrane stack, the adhesive can be introduced into the recess and then the sealing frame can be bonded to the membrane stack.A sufficient amount of adhesive can be applied through the recessed groove, thus ensuring a reliable bond between the sealing frame and the membrane block.

[0011] In one possible embodiment of the membrane stack unit, the respective recess can be formed by a groove. The groove can, in particular, be formed at a distance from an edge of the sealing region opposite the circumferential region. The groove can completely surround the associated side surface and be arranged at a distance from an edge of the sealing region opposite the circumferential region. The groove can also be arranged at a distance from the circumferential region. In other words, the groove can be delimited in front of the edge of the sealing region and / or from the circumferential region by a web. The groove is formed on the respective surface of the sealing region and can protrude into the sealing region. As a result, the groove can accommodate a sufficient amount of adhesive and the sealing frame can be securely connected or bonded to the membrane stack. The groove itself can have any cross-section.In particular, the groove may have a U-shaped cross-section.

[0012] In a possible further embodiment of the membrane stack unit, the respective recess can be formed by a groove that is open on one side. The groove can then be delimited by at least one web from an edge of the sealing area opposite the circumferential area and can be open to the circumferential area. In other words, the groove can be arranged at a distance from an edge of the sealing area opposite the circumferential area. The groove that is open on one side allows the excess adhesive to drain to the circumferential area and further into a gap formed between the circumferential area and the membrane stack. This allows the adhesive to distribute freely between the membrane stack and the sealing frame and simplifies the dosing of the adhesive. Furthermore, leakage of the excess adhesive onto the associated side surface and thus blocking of the air-conducting channels can be avoided.

[0013] The respective sealing frame can have at least one drainage groove for the excess adhesive to drain out of the recess. The drainage groove can be fluidically connected to the recess and lead from the respective recess to an edge of the sealing region opposite the circumferential region and thus to the side surface of the membrane stack. Alternatively, the drainage groove can be fluidically connected to the recess and lead from the respective recess to the circumferential region of the sealing frame and thus to a gap lying between the membrane stack and the circumferential region. The respective drainage groove can, for example, be aligned perpendicular to the respective recess. The excess adhesive can be drained out of the recess via the respective drainage groove, thereby enabling secure bonding of the sealing frame to the associated side surface.To evenly drain excess adhesive from the recess, several drainage grooves can be provided, which may be evenly or irregularly distributed around the surrounding recess. The multiple drainage grooves may be identical or different in shape.

[0014] In one possible embodiment of the membrane stack unit, the respective sealing frame can have at least one overflow groove surrounding the associated side surface. The overflow groove can be formed on the surface of the sealing area facing the associated side surface, spaced from the recess, and fluidly connected to the recess. The overflow groove can advantageously absorb the excess adhesive without the adhesive reaching the associated side surface.

[0015] The respective overflow groove can, for example, be located between the recess and an edge of the sealing area opposite the peripheral area. Alternatively, the respective overflow groove can be located between the recess and the peripheral area of ​​the sealing frame. It is understood that the respective sealing frame can also have two different or identical overflow grooves. The overflow grooves can then be formed in the form of a groove on both sides of the respective recess.

[0016] The respective recess and the respective overflow groove are fluidically connected to one another. For this purpose, a web formed between the recess and the overflow groove can be spaced from the associated side surface, thereby forming a gap between the web and the associated side surface. The respective recess and the respective overflow groove can then be fluidically connected to one another via the gap. Alternatively or additionally, at least one connecting groove can be formed in a web formed between the recess and the overflow groove. The recess and the respective overflow groove can then be fluidically connected to one another via the respective connecting groove.

[0017] In one possible embodiment of the membrane stack unit, it can be provided that the respective recess has at least two sections with different heights and / or different widths. In other words, the respective recess can vary in height and / or width along its longitudinal axis. As a result, the respective sealing frame can be adhesively bonded to the associated side surface or to the membrane stack in different sections using a different amount of adhesive. Analogously, the respective overflow groove can have at least two sections with different heights and / or different widths. In other words, the respective overflow groove can vary in height and / or width along its longitudinal axis. Appropriately, the design of the overflow groove can be adapted to the design of the recess or vice versa.

[0018] When manufacturing the membrane stack unit, the membrane block can be produced in a first step. For this purpose, the membranes and the permeable spacers are glued together and the sealing plates are placed on the last membranes in the stacking direction. The sealing plates can remain loosely placed on the last membranes in the stacking direction or, alternatively, can be glued to the last membranes in the stacking direction. This allows the cuboid membrane block to be produced with the four side surfaces through which air can flow and the two end surfaces through which air cannot flow. In a second step, the membrane stack can be pre-stressed and glued to the two sealing frames. For this purpose, the adhesive can be metered into the respective recess of the respective sealing frame beforehand and the respective sealing frame can then be glued to the respective assigned side surface.The respective recess can be overfilled, allowing the respective sealing frame and membrane stack to be connected without cavities. Excess adhesive can be displaced inward toward the associated side surface or outward toward the perimeter via the respective drain groove and / or the respective overflow groove and / or via the recess in the form of a groove open on one side.

[0019] The invention also relates to a humidifier for a fuel cell-powered vehicle for humidifying dry air with moist air. The humidifier can be provided in particular for a fuel cell system with a fuel cell. The dry air can then be the air flowing to the fuel cell and the moist air can be the air flowing from the fuel cell. The humidifier comprises a housing and the membrane stack unit described above. The membrane stack unit is accommodated in the housing, and the side surfaces of the membrane stack are at least partially sealed from one another within the housing by the two sealing frames. The two sealing frames can bear tightly against the housing, or additional seals can be arranged between the housing and the two sealing frames.This allows the respective air-permeable side surfaces of the membrane block to be hermetically separated from each other within the housing. If the membrane stack includes sealing plates, the sealing plates can also be tightly sealed against the housing. To avoid repetition, reference is made to the above explanations at this point.

[0020] Further important features and advantages of the invention emerge from the subclaims, from the drawings and from the associated description of the figures based on the drawings.

[0021] It is understood that the features mentioned above and those to be explained below can be used not only in the combination specified in each case, but also in other combinations or on their own, without departing from the scope of the present invention.

[0022] Preferred embodiments of the invention are illustrated in the drawings and explained in more detail in the following description, wherein like reference numerals refer to identical or similar or functionally identical components. Elements not directly visible are marked with dashed lines.

[0023] They show, schematically Fig. 1 a sectional view of a humidifier according to the invention with marked air flow; Fig. 2 is an exploded view of a membrane stack unit according to the invention for the humidifier according to the invention; Fig. 3 a view of a membrane block of the membrane stack unit according to the invention; Fig. 4 a view of a sealing frame of the membrane stack unit according to the invention in a first embodiment; Fig. 5 a view of the sealing frame of the membrane stack unit according to the invention in a second embodiment; Fig. 6 a sectional view of the membrane stack unit according to the invention with the sealing frame in a third embodiment; Fig. 7 a sectional view of the membrane stack unit according to the invention with the sealing frame in a fourth embodiment without the membrane stack; Fig. 8 a sectional view of the membrane stack unit according to the invention with the sealing frame in a fourth embodiment with the membrane stack.

[0024] Fig. Figure 1 shows a sectional view of a humidifier 1 according to the invention, in particular for a fuel cell system. The humidifier 1 comprises a two-part housing 2 and a membrane stack unit 3 according to the invention. The membrane stack unit 3 is accommodated in the housing 2.

[0025] The membrane stack unit 3 comprises a cuboid membrane stack 4 made up of a plurality of flexible membranes 5. The membranes 5 are stacked at a distance from one another in a stacking direction ST, for which purpose air-permeable spacers (not shown here) can be arranged between the individual membranes 5. The membranes 5 are glued to one another in such a way that a plurality of air-permeable channels 6 and 7 are formed between the membranes 5. The membrane stack 4 thus has four air-permeable side surfaces 6a, 6b, 7a, 7b arranged parallel to the stacking direction ST and through which air can flow, and two end surfaces 8a, 8b oriented transversely to the stacking direction ST and through which air cannot flow - not directly visible here and only indicated.

[0026] The respective side surfaces 6a and 6b are arranged opposite one another and connected to one another in an air-conducting manner by the respective channels 6. In contrast, the respective side surfaces 6a and 6b are hermetically separated from the channels 7. The respective side surfaces 7a and 7b are arranged opposite one another in a similar manner and connected to one another in an air-conducting manner by the respective channels 7. The respective side surfaces 7a and 7b are appropriately separated from the channels 6 in an air-tight manner. The channels 6 and 7 alternate in the stacking direction ST, so that dry air TL and moist air FL can flow through the membrane stack 4 in a cross-flow without mixing.

[0027] Dry air TL flows through channels 6, and moist air FL flows through channels 7. Membranes 5 are impermeable to air and permeable to moisture or water vapor, so that the dry air TL and the moist air FL can exchange moisture or water vapor with each other through membranes 5. The end faces 8a and 8b of membrane stack 4 are formed by two sealing plates 9a and 9b—not directly visible here and only indicated—which are firmly and sealingly connected to the respective last membranes 5 in the stacking direction ST. The sealing plates 9a and 9b can be glued to the respective last membranes 5 in the stacking direction ST, for example.

[0028] In addition, the membrane stack unit 3 comprises two sealing frames 10a and 10b, which in this embodiment are assigned to the side surfaces 6a and 6b through which the dry air TL flows. However, it is understood that the sealing frames 10a and 10b can also be assigned in the same way to the side surfaces 7a and 7b through which the moist air FL flows. The respective sealing frames 10a and 10b each have a sealing area 11 and a peripheral area 12, which are aligned perpendicular to one another. As a result, the respective sealing frames 10a and 10b have an approximately L-shaped cross-section. The respective sealing frames 10a and 10b are glued to the membrane stack 4 at the respective associated side surfaces 6a and 6b, as can be seen from Fig. 2 to Fig. 8 is explained in more detail.

[0029] The sealing area 11 of the respective sealing frame 10a or 10b is frame-shaped and surrounds the associated side surface 6a or 6b at the edge. The sealing frame 10a or 10b is bonded to the associated side surface 6a or 6b at the sealing area 11 using an adhesive 19. The peripheral area 12 is integrally formed on the sealing area 11 and protrudes from the membrane block 4. The peripheral area 12 surrounds the membrane block 4 at the edge.

[0030] The membrane stack unit 3 further comprises two circumferential seals 13a and 13b, which are clamped in a sealing manner between the respective sealing frames 10a and 10b or between the sealing areas 11 of the respective sealing frames 10a and 10b and the housing 2. The sealing frames 10a and 10b and the two seals 13a and 13b hermetically separate the two side surfaces 6a and 6b within the housing 2 from one another and from the remaining surfaces of the membrane stack 4. The two sealing plates 9a and 9b also hermetically separate the two side surfaces 7a and 7b within the housing 2. As a result, the dry air TL and the moist air FL flow through the housing 2 of the humidifier 1 without mixing and can exchange moisture or water vapor with each other within the membrane block 4 via the membranes 5.

[0031] The housing 2 is two-part and comprises a first housing part 2a and a second housing part 2b. The two housing parts 2a and 2b are connected to each other in an airtight manner. A first inlet 14a and a first outlet 14b for the dry air TL and a second inlet 15a and a second outlet 15b for the moist air FL are formed in the housing 2. The first inlet 14a is assigned to the side surface 6a and the first outlet 14b to the side surface 6b. Similarly, the second inlet 15a is assigned to the side surface 7a and the second outlet 15b to the side surface 7b. The sealing frames 10a and 10b, the seals 13a and 13b and the sealing plates 9a and 9b separate the side surfaces 6a, 6b, 7a, 7b as well as the respective inlets 14a and 15a and the respective outlets 14b and 15b in an airtight manner.

[0032] Fig. 2 shows an exploded view of the membrane stack unit 3 according to the invention for the humidifier 1 according to the invention. As already described above, the membrane stack unit 3 has the membrane stack 4 with the plurality of membranes 5. In Fig. 2, the end faces 8a and 8b, through which air can flow, with the two sealing plates 9a and 9b are particularly visible. The sealing plates 9a and 9b each have a ribbed structure 16, which serves to support the membrane stack unit 3 and to prevent excessive expansion of the membranes, particularly in the central regions. For this purpose, the sealing frames 10a and 10b each encompass the sealing plates 9a and 9b in an edge region and thus prevent the membrane stack 4 from expanding in the stacking direction ST or in the longitudinal direction. Furthermore, the two sealing frames 10a and 10b can be seen, which are glued to the side surfaces 6a and 6b of the membrane stack 4. The two seals 13a and 13b, which seal the membrane stack unit 3 to the housing 2, are arranged on the sealing frames 10a and 10b.

[0033] Fig. Figure 3 shows a view of the membrane block 4 of the membrane stack unit 3 according to the invention. As already described above, the membrane stack 4 comprises the plurality of membranes 5 and the sealing plates 9a and 9b. The individual membranes 5 are bonded to one another, and the respective last membranes 5 in the stacking direction ST are additionally bonded to the sealing plates 9a and 9b. The membrane block 4 thus forms a coherent, inseparable structural unit.

[0034] Fig. 4 shows a view of the sealing frame 10a or 10b of the membrane stack unit 3 according to the invention in a first embodiment. The sealing frame 10a or 10b has a recess 17 on a surface 18 facing the associated side surface 6a or 6b. The recess 17 is shaped in the form of a groove 17a and surrounds the respective associated side surface 6a or 6b of the membrane stack 4 at the edge. The recess 17 is formed between an edge 20 of the sealing region 11 opposite the circumferential region 12 and the circumferential region 12. The recess 17 is arranged at a distance from the edge 20 and from the circumferential region 12. In other words, the recess 17 is separated from the edge 20 by a web 24. The recess 17 is filled with the adhesive 19 and the respective sealing frame 10a or 10b can be glued to the associated side surface 6a or 6b by means of the adhesive 19.

[0035] Fig. 5 shows a view of the sealing frame 10a or 10b of the membrane stack unit 3 according to the invention in a second embodiment. In contrast to the first embodiment of the sealing frame 10a or 10b, the respective sealing frame 10a or 10b here has a plurality of drainage grooves 21 that lead from the recess 17—here the groove 17a—to the edge 20 or to the associated side surface 6a or 6b. The drainage grooves 21 are formed in the web 24 formed between the recess 17 and the edge 20. The excess adhesive 19 can drain via the drainage grooves 21 onto the associated side surface 6a or 6b, so that the recess 17 can be overfilled and the respective sealing frame 10a or 10b can be connected to the associated side surface 6a or 6b without voids. Otherwise, the first embodiment and the second embodiment of the respective sealing frame 10a and 10b are identical.

[0036] Fig. 6 shows a sectional view of the membrane stack unit 3 according to the invention with the sealing frame 10a or 10b in a third embodiment. In the third embodiment, the respective sealing frame 10a or 10b has, in addition to the recess 17 - here the groove 17a - and the plurality of drainage grooves 21, an overflow groove 22. The recess 17 and the drainage grooves 21 are identical to those shown in the second embodiment. The overflow groove 22 is formed between the recess 17 and the circulation region 12 at a distance from the recess 17 and the circulation region 12. The overflow groove 22 surrounds the respective associated side surface 6a or 6b of the membrane stack 4 or the recess 17. The recess 17 and the overflow groove 22 are expediently fluidically connected to one another. For this purpose, a web 23 formed between the overflow groove 22 and the recess 17 is formed at a distance from the side surface 6a or 6b, so that between the web 23 and the associated side surface 6a or 6b6b, a gap 25 is formed. For this purpose, the web 23 has a correspondingly adjusted height. Excess adhesive 19 can escape from the recess 17 through the gap 25 into the overflow groove 22 and / or through the respective drainage grooves 21 onto the associated side surface 7a or 7b.

[0037] Fig. 7 shows a sectional view of the membrane stack unit 3 according to the invention with the sealing frame 10a or 10b in a fourth embodiment and without the membrane stack 4. Fig.8 shows a sectional view of the membrane stack unit 3 according to the invention with the sealing frame 10a or 10b in a fourth embodiment and with the membrane stack 4. In the fourth embodiment, in contrast to the other embodiments, the recess 17 is shaped in the form of a groove 17b that is open on one side. The groove 17b is closed to the edge 20 of the sealing region 11 and open to the circulation region 12. This allows the excess adhesive 19 to flow from the recess 17 to the circulation region 12 and further into a gap 26 between the membrane stack 4 and the circulation region 12. Furthermore, in the fourth embodiment, the overflow groove 22 is formed between the edge 20 and the recess 17. The fluidic connection between the recess 17 and the overflow groove 22 is shaped identically to that in the third embodiment.

Claims

[1] Membrane stack unit (3) for a humidifier (1) for a fuel cell powered vehicle, - wherein the membrane stack unit (3) comprises a cuboid membrane stack (4) with a plurality of flexible membranes (5) stacked in a stacking direction (ST), - wherein the membrane stack (4) has four side surfaces (6a, 6b, 7a, 7b) through which air can flow and are aligned parallel to the stacking direction (ST) and two end surfaces (8a, 8b) through which air cannot flow and are aligned transversely to the stacking direction (ST), - wherein the membrane stack unit (3) has two sealing frames (10a, 10b) and the sealing frames (10a, 10b) are assigned to two opposite side surfaces (6a, 6b) of the membrane stack (4), - wherein the respective sealing frame (10a, 10b) has a circumferential sealing area (11) and the sealing area (11) runs around the edge of the respective associated side surface (6a, 6b) and bears against it, - wherein the respective sealing frame (10a, 10b) has a peripheral region (12) projecting perpendicularly from the sealing region (11), and the peripheral region (12) faces the membrane stack (4) and surrounds the membrane stack (4) at the edge, characterized by , - that the respective sealing frame (10a, 10b) has, at least on one surface (18) of the sealing region (11) facing the associated side surface (6a, 6b), a recess (17) surrounding the associated side surface (6a, 6b), and - that the respective recess (17) is filled with an adhesive (19) and the respective sealing frame (10a, 10b) is sealingly bonded to the membrane stack (4) via the adhesive (19). [2] Membrane stack unit (3) according to claim 1, characterized bythat the respective recess (17) is formed by a groove (17a), wherein the groove (17a) is formed at a distance from an edge (20) of the sealing region (11) opposite the circumferential region (12). [3] Membrane stack unit (3) according to claim 1, characterized by that the respective recess (17) is formed by a groove (17b) which is open on one side, wherein the groove (17b) is delimited by a web (24) from an edge (20) of the sealing area (11) opposite the peripheral area (12) and is open to the peripheral area (12). [4] Membrane stack unit (3) according to one of the preceding claims, characterized by , - that the respective sealing frame (10a, 10b) has at least one drainage groove (21) for draining the excess adhesive (19) from the recess (17) and the drainage groove (21) is fluidically connected to the recess (17), and - that the respective drainage groove (21) leads from the respective recess (17) to an edge (20) of the sealing area (11) opposite the circumferential area (12) and thereby to the side surface (6a, 6b) of the membrane stack (4). [5] Membrane stack unit (3) according to one of the preceding claims, characterized by , - that the respective sealing frame (10a, 10b) has at least one drainage groove (21) for draining the excess adhesive (19) from the recess (17) and the drainage groove (21) is fluidically connected to the recess (17), and - that the drainage groove (21) leads from the respective recess (17) to the circumferential area (12) of the sealing frame (10a, 10b) and thereby to a gap (26) lying between the membrane stack (4) and the circumferential area (12). [6] Membrane stack unit (3) according to one of the preceding claims, characterized by , - that the respective sealing frame (10a, 10b) has at least one overflow groove (22) surrounding the associated side surface (6a, 6b), and - that the overflow groove (22) on the surface (18) of the sealing region (11) facing the associated side surface (6a, 6b) is formed at a distance from the recess (17) and is fluidically connected to the recess (17). [7] Membrane stack unit (3) according to claim 6, characterized by , - that the respective overflow groove (22) lies between the recess (17) and an edge (20) of the sealing area (11) of the sealing frame (10a, 10b) opposite the circumferential area (12), or - that the respective overflow groove (22) lies between the recess (17) and the circumferential area (12) of the sealing frame (10a, 10b). [8] Membrane stack unit (3) according to claim 6 or 7, characterized by , - that a web (23) is formed between the recess (17) and the overflow groove (22), wherein the web (23) is spaced from the associated side surface (6a, 6b) and thereby a gap (25) is formed between the web (23) and the associated side surface (6a, 6b), and wherein the respective recess (17) and the respective overflow groove (22) are fluidically connected to one another via the gap (25), and / or - that a web (23) is formed between the recess (17) and the overflow groove (22) and at least one connecting groove is formed in the web (23), wherein the recess (17) and the overflow groove (22) are fluidically connected to one another via the respective connecting groove. [9] Membrane stack unit (3) according to one of the preceding claims, characterized by , - that the respective recess (17) has at least two sections with different heights and / or with different widths, and / or - that the respective overflow groove (22) has at least two sections with different heights and / or with different widths. [10] Humidifier (1) for a fuel cell powered vehicle for humidifying dry air (TL) with moist air (FL), - wherein the humidifier (1) comprises a housing (2) and the membrane stack unit (3) according to one of the preceding claims, - wherein the membrane stack unit (3) is accommodated in the housing (2) and the side surfaces (6a, 6b) of the membrane stack (4) within the housing (2) are at least partially sealed from one another by the two sealing frames (10a, 10b).

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