Optimised humidifier

Abstract

The invention relates to a humidifier for a fuel cell, comprising a membrane stack through which an exhaust air flow discharged from the fuel cell device and a supply air flow supplied to the fuel cell device flow with moisture exchange in a cross-flow, and a housing which sealingly and preferably integrally accommodates and sealingly holds the membrane stack such that said cross-flow can run off at least substantially without leakage and mixing, wherein the housing of the humidifier consists of two housing halves which are to be joined together, the boundary surfaces to be joined thereof, along which the housing halves are sealingly joined, extend in several different planes and are designed such that sealing material already applied in preparation for joining is substantially not subjected to any shear stress during joining.

Description

[0001] OPTIMIZED HUMIDIFIER

[0002] The invention relates to a humidifier for a fuel cell that can be manufactured particularly efficiently and to an associated membrane stack that can also be manufactured particularly efficiently.

[0003] TECHNICAL BACKGROUND

[0004] To optimize the performance of polymer electrolyte membrane (PEM) fuel cells, good humidification of the polymer membrane is of great importance.

[0005] Last but not least, indirect humidification using selective membranes is used in the automotive industry to keep the water balance under control. In a membrane humidifier, the moist exhaust stream from the fuel cell and the dry fresh air stream are brought into contact via a semipermeable membrane to enable mass transfer from water to the dry side.

[0006] STATE OF THE ART

[0007] A humidifier for a fuel cell is already known from DE102020212596A1.

[0008] It consists of a membrane stack which is housed in a cuboid housing in such a way that it is cross-flown by an exhaust air flow AL taken away from the fuel cell device and an inlet air flow ZL fed to the fuel cell device. The housing and the membrane stack are arranged adjacent to one another in such a way that together they form a sealing channel system. For this purpose, four grooved guide strips are provided in the housing which, as the cuboid membrane stack is pushed in like a drawer, accommodate its corners and thus hold the membrane stack on four sides at a distance from the wall of the housing forming the shell, in order to create the sealing channel system.

[0009] However, the sealing channel system is only functional when a reliable seal has been created between each grooved sealing strip and the corner of the membrane stack it supports.

[0010] The production of such a seal requires some effort, especially if a seal is to be produced with a formless sealing compound that is intended to bond the gap to be sealed between the membrane stack and the grooved guide rail.

[0011] It is then necessary to subsequently introduce the formless sealing compound into the gap to be sealed between the corner of the membrane stack and the grooved guide strip using long tubular probes by inserting these probes into the gap to be sealed and withdrawing them while dispensing the formless sealing compound.

[0012] This process is time-consuming and relatively error-prone. OBJECT OF THE INVENTION

[0013] It is the object of the invention to create a humidifier for a fuel cell with a membrane stack accommodated in a housing, which can be manufactured significantly easier

[0014] THE INVENTIVE SOLUTION

[0015] According to the invention, a humidifier for a fuel cell is proposed, comprising a prismatic, preferably cube- or cuboid-shaped membrane stack. This membrane stack can be cross-flown through by an exhaust air stream AL discharged from the fuel cell device and a supply air stream ZL supplied to the fuel cell device, with moisture exchange.

[0016] The humidifier then comprises a housing which holds the membrane stack in a material-to-material manner (i.e. usually by gluing it) and seals it in such a way that the said cross flow can proceed at least essentially leak- and mixing-free.

[0017] The humidifier is characterized by the fact that its housing consists of two housing halves that are to be joined together. The interfaces to be joined, along which the housing halves are sealed against each other, run in several different planes and are designed in such a way that sealing materials applied in preparation for joining are essentially not exposed to any shear stress during joining. Instead, the parts to be joined can be brought together in such a way that the surfaces to be joined all approach each other with a movement that runs predominantly or essentially along the normal to the respective surface. A certain amount of movement parallel to the respective surface is unavoidable, but also harmless. The decisive factor is that the sealing materials applied in preparation for joining are not exposed to any shear stress that has more than an insignificant impact on them.Expressed somewhat differently, one can say that the direction of the approaching movement is advantageously a direction normal to a plane formed by the three highest points of the casing.

[0018] A shear stress that is harmful to the often formless sealing material already present at the intended sealing location, which tends to push the formless sealing material aside, away from the location where it is intended to perform its intended function, only occurs in the final phase of the joining movement and is therefore harmless. The same applies to a preformed seal; it too is protected from deformation or being pushed aside.

[0019] The described effect according to the invention is used both during installation of the membrane stack in the first housing half and during the subsequent closing of the housing by joining the two housing halves between which the membrane stack is located.

[0020] In general, one can say that, according to the invention, a new mounting direction of the membrane stack is ideally used that is not parallel to one of the 12 edges of the housing. PARTICULARLY PREFERRED DEVELOPMENTS

[0021] Ideally, the housing consists of two housing halves that are to be joined together, with each housing half comprising three housing side surfaces, each of which merges at one side edge into one of the other two side surfaces and at its other side edge into the other of the other two side surfaces. This particularly effectively promotes essentially shear-free assembly. Protection is preferably also claimed for this version independently of the preceding claim.

[0022] Ideally, the interfaces through which the sides of the two housing halves are sealed together are essentially flat and straight, even if the surrounding housing areas are curved outward. This allows for a particularly effective, essentially shear-free joining process.

[0023] Notwithstanding this, it is particularly advantageous if one or more side surfaces bulge outwards in the area between the edges that border them, thus creating space for an increase in the usable flow cross-section(s).

[0024] FURTHER OBJECT OF THE INVENTION

[0025] As already mentioned, in a membrane humidifier the moister exhaust gas stream from the fuel cell and the drier fresh air stream are brought into contact via a semi-permeable membrane to enable the transfer of water to the dry side. A single or just a few membranes are not enough if more than just insignificant air streams are to be processed. Instead, so-called membrane stacks are used. In these, numerous membranes are stacked on top of one another with flat spacers in between. These ensure that a gap remains open between a pair of immediately adjacent membranes, through which the moister exhaust gas stream or the drier fresh air stream can flow.

[0026] The gaps through which the exhaust gas flow and the fresh air flow alternate. Thus (apart from the first and last gaps), each gap through which a partial exhaust gas flow flows is bordered by two gaps through which a partial fresh air flow flows. The only boundary between the partial flows is the respective semipermeable membrane. This membrane allows the diffusion of moisture but keeps the gas flows separate from one another.

[0027] Each of these gaps is laterally delimited by two edge elements. Supported by flat spacers, the edge elements maintain a distance between two adjacent membranes. At the same time, they seal and prevent any unacceptable lateral flow.

[0028] Such spacers are often formed by defined shaped strips, each of which has to be glued, pressed or welded to the first and second membrane.

[0029] The previously known measures for assembling the edge elements or for connecting successive membranes to one another are complex. In view of this, the object of the invention is to create a membrane stack that can be assembled with less effort and whose assembly can preferably be easily automated.

[0030] OTHER INVENTIONAL SOLUTIONS

[0031] Another solution according to the invention, for which not only subordinate but also independent protection is claimed - also in terms of the procedure - consists in the following:

[0032] Additionally proposed is a humidification device in the form of a membrane stack for humidifying a drier gas stream with the aid of a moister gas stream, in which the gas streams are separated from one another by the semipermeable membranes of a membrane stack. As the name suggests, the membrane stack comprises several membranes, flat spacers, and pairs of edge elements forming a flow path between themselves and successive membranes.

[0033] According to the invention, it is characterized in that each of the edge elements consists of at least one bead of an originally formless sealing and / or adhesive material, in which a flat spacer is embedded.

[0034] This means that - unlike before - there is no longer any need to manufacture, cut, position and glue solid strips or the like. And there is also no need for the flat spacers to be attached separately. Instead, each of the edge elements can be formed in situ on or at the membrane from at least one bead of initially formless, i.e. pasty or doughy sealing and / or adhesive material. The flat spacer can also be attached very easily; it is simply embedded in the material while it is still wet. The handling of the formless sealing material, which can therefore be pumped to its place of use, can be easily automated.

[0035] The fact that we are referring to sealing and / or adhesive materials here is due to the fact that the transition is fluid with the material used in the invention. For the invention, (only) any material can be used that, after setting, forms a bonded connection with the membrane material that is resistant to inflation and under-inflation, and, on the other hand, forms a "body" that essentially blocks the passage of gas through it.

[0036] ESPECIALLY PREFERRED TRAINING

[0037] In a particularly preferred embodiment, each edge element is formed from two beads which have been joined together in a moist state, which can still be seen structurally in the edge element when magnified accordingly, even after it has set.

[0038] LIST OF FIGURES

[0039] Figure 1 shows a typical overall system in which the humidifier according to the invention is used. Figures 1a to 1c show a first embodiment of the invention in an exploded view.

[0040] Figures Id and le show a variant with a radiator mounted on the front.

[0041] Figures I f to 1L (Figures li and Ij not assigned) show a variant of the invention in which the membrane stack is prismatic and is housed according to the invention.

[0042] Figure 2 shows the first embodiment in assembled state, in perspective.

[0043] Figure 3 shows a section through the first embodiment along the line CC.

[0044] Figure 4 shows an enlarged section of Fig. 3

[0045] Figure 5 shows a second embodiment of the invention in an exploded view.

[0046] Figures 6 and 7 show the second embodiment in assembled state, in perspective, from different angles.

[0047] Figure 8 shows a section through the second embodiment.

[0048] Figure 9 shows an enlarged detail from Fig . 8 .

[0049] Figure 10 shows the first embodiment in assembled condition and visualizes the joining of the first and second housing halves even more clearly by the bold dash-dotted line.

[0050] Fig. 11 visualizes the first embodiment in assembled state from a different perspective and shows the cutting line of Fig. 12.

[0051] Figure 12 shows the section already indicated in Figure 11.

[0052] Fig. 13 to 15 visualize even more clearly the snap connection used optionally to connect the housing halves.

[0053] Figure 16 shows membrane modules that are about to be assembled stacked on top of each other.

[0054] Fig. 17 shows a finished module stack consisting of a number of membrane modules.

[0055] Figure 18 shows the production of a single membrane module.

[0056] Fig. 19 shows an enlarged section of Figure 16, i.e. several membrane modules that are about to be stacked on top of each other.

[0057] Fig. 20 shows the result of the assembly of the individual membrane modules on top of each other, ie an enlarged section of Figure 17.

[0058] Fig. 21 illustrates the very efficient assembly of a preferred embodiment.

[0059] THE TYPICAL LOCATION OF THE HUMIDIFIER

[0060] Fig. 1 shows the common basic components of a fuel cell drive and thus provides an overview of where the humidifier according to the invention is located in the system. The fuel cell stack A is fed from the hydrogen tank D via the hydrogen pump B and the ejector C. The air is supplied via the air filter E and the compressor F through the humidifier 1. In the humidifier 1, the supplied air flow exchanges moisture with the air flow discharged via the expander G. The electrical load fed by the fuel cell is referenced H; the components fan, air cooler, and coolant pump, which are not further referenced, can also be seen.

[0061] FIRST EMBODIMENT OF THE HUMIDIFIER

[0062] Figs. 1a to 1c show a first embodiment of the invention. Humidifier 1 is shown here in exploded form. Fig. 1b schematically shows membrane stack 2, the structure of which will be explained in more detail later. For a number of applications, it is advantageous, although not mandatory, for the membrane stack to take the shape of a cuboid or cube, ideally with side, end, and cover surfaces that are at least substantially perpendicular to each other at each edge.

[0063] According to the invention, the membrane stack is accommodated between two specially designed housing halves 3a, 3b, as shown, for example, in Figs. 1a and 1c. The first, here lower housing half consists of the bottom wall 4a. At its right side edge shown in Fig. 1c, it merges into the second end wall 5b and at its rear side edge shown in Fig. 1c, it merges into the second side wall 6b, which here forms the rear wall. In all of this, the second end wall 5b and the second side wall 6b also merge into one another along their common side edge. The transitions are preferably made integrally in one piece.

[0064] The complementary second, here upper housing half 3b, which is shown by way of example in Fig. 1a, consists of the cover wall 4b. At its left side edge shown in Fig. 1a, it merges into the first end wall 5a and at its front side edge shown in Fig. 1a, it merges into the second side wall 6a, which here forms the front wall. In all of this, the first end wall 5a and the first side wall 6a also merge into one another along their common side edge. Here, too, the transitions are preferably made in one piece.

[0065] This illustrates very clearly that the housing according to the claim consists of two housing halves which are to be joined together, each housing half of which comprises three housing side surfaces, each of which merges at one of its side edges into one of the other two side surfaces and at its other side edge into the other of the other two side surfaces.

[0066] With reference to Figures 1d and 1e, for which the housing connection by screwing initially plays no role, it should be noted at this point that a housing side surface does not necessarily have to be a solid surface, even if that is the preferred case. Instead, it can optionally also be a reduced housing side surface, such as the bare housing side surface frame 5bb in the variant of the first exemplary embodiment shown in Fig. 1d. The reduced sections of the housing side surface can be clearly seen here, which are designed, for example, as flange strips and can be used for flanging on a cooler. The flange strips here frame a window through which the membrane stack can be seen until the cooler 35 is finally flanged on. The term “housing side surface” should be understood accordingly broadly.

[0067] It should be noted that the said transitions could also be welded, clipped or screwed if the effort seems appropriate.

[0068] In all of this, it may be advantageous from a flow perspective if each of the end walls 5a, 5b has a smaller surface area than the corresponding side, cover and bottom surfaces, as shown in the figure, but this is not mandatory at this stage.

[0069] For various applications, it is particularly advantageous if the membrane stack is sealed against the inner surfaces by means of an initially formless sealing and / or adhesive compound (hereinafter referred to as "adhesive...") in such a way that it can be flowed through with a cross-flow of moisture exchange by an exhaust air flow AL led away from the fuel cell device and a supply air flow ZL fed to the fuel cell device.

[0070] For this purpose, during assembly, nine first adhesive beads 7 are initially applied, usually in any desired order, namely, for example, four first adhesive beads 7 along the side edges of the base wall 4a, three further first adhesive beads 7 along the remaining side edges of the second side wall 6b and finally two first adhesive beads along the second end wall 5b.

[0071] Alternatively, and this should be said in a general way and not limited to this specific exemplary embodiment, the membrane stack can also be provided with a "contour seal" or prefabricated seal in a defined shape, usually made of elastomer material, instead of adhesive beads 7 along its edges, which ensures its sealing against the inner surface of the housing halves. For example, a membrane stack which is created by stacking frames and which forms a groove on the side edges is suitable for carrying such a contour seal, see also Fig. 5, designated there by the reference number 21a.

[0072] According to the invention, the membrane stack 2 can now be installed in the second housing half 3b. For this purpose, it is inserted into the second housing half 3b with a movement which is composed of three superimposed movement components, each of which runs perpendicular to the surface plane of the membrane stack which is directly opposite a bottom, side or end wall of the second housing half. In this way, all the first adhesive beads 7 made of the still formless sealing material only come into contact with their counter surface on the membrane stack right at the end of the assembly process and thus essentially avoid shear stress. Namely a harmful shear stress which has the tendency to push the formless adhesive material or the preformed contour seal used instead in some cases to a disturbing extent, away from the place where it is intended to exert its intended effect.The same applies here, analogously, to a preformed seal. During assembly, the first housing half 3a, which here forms the cover, is provided with second adhesive beads 8 along its inner edges, i.e., the edges along which two walls forming it meet. Then, using a similar movement as already described, the first housing half is placed onto the assembly comprising the second housing half 3b and the membrane stack 2 until the two housing halves are joined to form a closed housing. This ensures that the second adhesive beads 8 are also essentially not subjected to any harmful shear stress, in the same sense as described above.

[0073] As can be clearly seen from Fig. 1a and 1c, the bottom, the lid and the two side walls are each provided with a connecting piece 9, 10, 11, 12.

[0074] As can also be clearly seen from Figs. 1a and 1c, the housing 3 resulting from the two housing halves does not have to have a shape that strictly follows the shape of the membrane stack, i.e. here, for example, it does not have to have a strict or at least predominantly cuboid shape. Quite the opposite, it is particularly advantageous if the base, cover, and side surfaces that form a connection nozzle are designed to be more than just slightly bulged outwards. This creates more voluminous and therefore improved flow paths, via which more efficient fluid transport can take place from the respective connection nozzle to the inlet or outlet surface of the membrane stack and vice versa. In addition, bulged surfaces have a higher deformation resistance to the applied internal pressure. This applies not only to this specific embodiment, but in general.Furthermore, the end walls, which do not form a connection piece or flow path, are preferably designed with a bulged shape, as can be seen in Fig. 1a, not only in this exemplary embodiment, but generally. It may be useful to additionally equip them with ribbing, usually on the inside - for example, honeycomb-shaped ribbing. The ribbing is a preferred means of supporting the membrane stack, which it requires in particular on its outermost plate, which could otherwise bulge due to the pressure difference.

[0075] Starting from Fig. 3 - and taking into account Fig. 12 and the associated Fig. 11, which clarifies the sectional plane - it is possible to understand quite well by means of an overall view of Figs. 1a to c and Fig. 2 how it comes about that the at least essentially cuboid-shaped membrane stack 2 is flowed through with moisture exchange in cross flow by an exhaust air flow AL led away from the fuel cell device and a supply air flow ZL fed to the fuel cell device.

[0076] It is advisable to feed the supply air flow ZL to the humidifier via the connection piece 10 and to discharge it again via the connection piece 11 after it has flowed through the membrane stack 2 via its gap channels, which run parallel to the plane of the drawing in Fig. 4. This means that the chamber 13 is fed by the connection piece 10 and the supply air flow ZL, which emerges humidified from the membrane stack again, collects in the chamber 14 before it is discharged via the connection piece 11. It is then advisable to feed the exhaust air flow AL to the humidifier via the connection piece 12 and to discharge it again via the connection piece 9 after it has flowed through the membrane stack 2 via its gap channels, which also run parallel to the plane of the drawing in Fig. 4.This means that the chamber 16 is fed from the connection piece 12 and the supply air flow ZL emerging drier from the membrane stack collects in the chamber 15 before being discharged via the connection piece 9.

[0077] 3 and 4 and FIGS. 13 to 15, and what also applies generally regardless of this exemplary embodiment, is that it is advantageous if at least one, better several and ideally all boundary surfaces along which the housing halves are joined to form a seal against a respective edge of the membrane stack which carries a seal. Preferably, but not exclusively, this is a seal made of initially formless sealing material. It is particularly advantageous if the housing halves 3a and 3b which abut one another along the boundary surface form a tongue and groove connection 18, 19 at least locally (otherwise predominantly or over the entire length), ideally as a snap connection. This can be designed in such a way that it also ensures positive locking in the joining direction.This ensures that the housing halves 3a and 3b assume and permanently maintain a perfect position relative to each other. The seal now only needs to seal the joint at the interface between the housing halves and the chambers it is intended to contact.

[0078] Ideally, the housing halves form groove-like, often V-shaped recesses on the inside along the separating surfaces, into which the seal running along the edge of the membrane stack is pressed – regardless of whether it is an elastomer seal with a defined shape from the outset or a seal made of an initially formless sealing material. This optional measure significantly improves the reliability of the seal.

[0079] It is also noteworthy that where an edge of the membrane stack 2 meets the inner surface of a housing half, away from the housing separation surfaces, a groove-like recess 20 is preferably provided, into which the seal—of whatever type—is inserted along the edge of the membrane stack. This applies not only to this specific embodiment, but generally.

[0080] It is also noteworthy that the aforementioned tongue and groove or snap connection 18, 19 is optionally designed (but not only applicable to this specific embodiment) such that the tongue 19 snaps into the groove 18 in such a way that, during assembly, the gap between the meeting interfaces of the housing halves 3a and 3b, and thus the groove-like recess 20, is defined or enlarged, thereby facilitating the distribution of the adhesive. At this point, it is worth taking another careful look at Fig. 4. It can be seen that, for this purpose, the tongue 19 is optionally provided with a small lateral extension, which projects obliquely upwards and outwards in Fig. 4 and snaps into a lateral recess in the outer groove wall 18.

[0081] In general, the snap-on connection, combined with the adhesive, replaces another form-fitting connection in the form of screw connections, which saves time during assembly. It is equally general that the housing components can alternatively be joined by plastic welding, particularly laser welding.

[0082] SECOND EXAMPLE OF THE HUMIDIFIER

[0083] Figure 5 shows a second, slightly different embodiment. It is fundamentally closely related to the first embodiment, so everything stated for that embodiment also applies to this embodiment, unless otherwise indicated in the following descriptions.

[0084] A key difference is that the seal 21, which seals the joints at the interface between the housing halves, is not made of adhesive in this embodiment, but is a prefabricated seal, usually made of an elastomer with a defined shape. It is a seal that can also be referred to as a "contour seal." In many cases, this usually cord-like seal is characterized by the fact that it consists of two, usually parallel, end sections that taper in a V-shape toward their free ends. These end sections are connected at their wide ends by two sealing sections arranged in a plane perpendicular to them.

[0085] What the humidifier 1 shown in the exploded state in Fig. 5 looks like when fully assembled can be clearly seen in Figs. 5, 6 and 7. It can be clearly seen that the first and second housing halves 3a and 3b comprise housing side surfaces which by no means have to be flat, but can be bulged. However, each housing side surface of one housing half forms, where it meets a housing side surface of the other housing half, a flat interface that is at least in the form of a strip. Each housing half is thus equipped with six flat, strip-like interfaces, of which two always run parallel three times, whereby the said two parallel interfaces are located on different housing side surfaces.

[0086] It can be clearly seen from Figs. 6 and 7 that the mutually abutting interfaces of the housing halves are screwed together. For this purpose, along the interfaces of the first and second housing parts 3a, 3b, preferably only local thickenings 22 are provided to form a screw-in nut, and preferably only local thickenings to form a through hole 23.

[0087] Fig. 8 shows a similar situation to Fig. 3 for the second embodiment, so that what is said there also applies to Fig. 8.

[0088] Of particular interest is the enlarged detail from Fig. 8, which is shown here as Fig. 9. The special feature that can be seen here is the fact that the flanges provided for screwing, which form the interfaces here, optionally (and not only valid for this specific exemplary embodiment) have seal receiving grooves 24 and 25, which accommodate the contour seal 21, which can be clearly seen in Fig. 5, between them in the assembled state. One of these two grooves is preferably deeper; it accommodates the contour seal during pre-assembly and holds it in position during assembly. The other of the two grooves is preferably shallower; the previously protruding part of the contour seal 21 fits into it - favored by the type of assembly according to the invention - and thus ensures optimal tightness. Figs. 1h to 1L show a membrane stack according to the invention which has a prismatic design.This membrane stack is manufactured in the same way as described in this invention for the cuboid membrane stack. It is also installed according to the invention. Fig. 1f shows the still empty lower housing half 3a. It is constructed as described above.

[0089] A special feature is that each housing half has a sealing rib DR where it rests against an edge of the membrane stack outside a corner, which can carry a pre-formed seal or a sealing bead that initially lacks a fixed shape.

[0090] Furthermore, what was said above for the other embodiments applies here accordingly.

[0091] EXAMPLE OF THE MEMBRANE STACK

[0092] The finished membrane stack 2 looks as illustrated in Fig. 17. The membrane stack is preferably cubic or cuboid-shaped, but could also have a hexagonal or octagonal shape or a columnar shape.

[0093] As Fig. 16 illustrates, the membrane stack according to the invention is constructed from a number of stacked humidification modules 27, the design of which will be discussed in more detail below.

[0094] Figure 18 shows the structure of a humidification module. It consists of a semipermeable, in this case water vapor-permeable, membrane 28. In this exemplary embodiment, it is part of a rectangular or cubic membrane stack.

[0095] On the first side of the membrane 28, here its upper side, a bead 29 of initially formless, pasty adhesive or sealing material has been applied along the side edge, which is located here at the 3 o'clock position. Another such bead is provided along the side edge, which is located here at the 9 o'clock position.

[0096] A flat spacer in the form of the grid 30 is embedded in these two beads 29.

[0097] The grid 30 often consists of a large number of intersecting bars 31 and 32. As a rule, the bars are connected to one another at the intersection points. Ideally, the bars 31, 32 are made of plastic, sometimes also of corrosion-protected metal. Preferably, the flat spacer (cf. 30) is embedded in the track 29 in such a way that its upper bars protrude slightly, or 25% to 50%, from the track 29. This can serve to improve union with the counter-track, which will be explained shortly. The grid 30, which forms the spacer, is positioned in such a way that its bars 31 and 32 always meet the tracks 29 at only one angle and therefore never coincide with the tracks over their entire length.

[0098] On the second side of the membrane, here the underside, two additional beads 33 are provided along the side edge of the membrane 28, but offset—namely, along the side edges located at the 6 o'clock and 12 o'clock positions. Taken together, the components explained so far form a humidification module 27.

[0099] As can be clearly seen in Fig. 19, a plurality of such humidification modules 27 are stacked one upon another to form a membrane stack according to the invention. This stacking takes place while the beads 29 of sealing and / or adhesive compound are still wet, i.e., deformable and sticky.

[0100] It is important that the individual, successive humidification modules 27 are each installed rotated by 90° about their vertical axis. In this way, the beads 33 attached to the second side, i.e. here on the underside of the next membrane 28, are combined with the beads 29 attached to the first side, i.e. here the top side of the previous membrane 28, and from now on form a common lateral boundary and seal. This results in the complete embedding 34 of the respective grid 30. At the same time, each grid 30 specifies the maximum distance between two immediately consecutive membranes, which can be clearly seen in Fig. 20, which shows a section of a membrane stack according to the invention.

[0101] From Fig. 20 it can also be clearly seen how the described assembly of the humidification modules 27 has created alternating channels between two immediately consecutive membranes through which the exhaust air AL and the supply air ZL can flow in cross flow, exchanging moisture or water vapor via the semi-permeable membrane 28 located between them.

[0102] Fig. 21 shows a particularly clever way of mass producing the invention. First, a semipermeable membrane 28 is cut to size, preferably in the form of a rectangular strip. The cut is large enough that several humidification modules can later be individually cut from it. Parallel, but spaced-apart, beads 29 are pulled across the entire cut on top, along the edges explained above, which are located at the 9 o'clock and 3 o'clock positions. Then, a grid 30 cut to a corresponding size is embedded in the said beads. The "sandwich" is then cut several times, here horizontally perpendicular to the beads 29.

[0103] Each of the resulting membrane sections is then provided with the additional beads discussed above on its second side. This creates several humidification modules. These are then assembled as previously explained.

[0104] General

[0105] The technology used here can also be used beneficially in other applications where two material flows need to enter into a diffusive exchange, such as in cases of dialysis or, for example, the removal of alcohol from a liquid, to name just a few examples. Therefore, in due course, protection will also be claimed for material exchangers of a general nature, as follows:

[0106] Protection is also claimed for a material exchanger with a membrane stack through which an outflow discharged from another source and an inflow flow into the material exchange in cross-flow, and with a housing which receives and holds the membrane stack in a sealing and preferably material-locking manner so that the said cross-flow can proceed essentially leak-free and mixing-free, characterized in that its housing consists of two housing halves which are to be joined together, the interfaces to be joined, along which the housing halves are joined to form a seal against one another, run in several different planes and are designed in such a way that sealing materials already applied in preparation for joining are essentially not subjected to any shear stress during joining.

[0107] Protection is further claimed for a material exchanger, preferably according to claim 1, with a membrane stack through which an outflow discharged elsewhere and an inflow flow pass in cross-flow, and a housing which receives and holds the membrane stack in a sealing manner, preferably in a material-locking manner, so that the said cross-flow can flow at least essentially leak- and mixing-free, characterized in that the housing consists of two housing halves which are to be joined together, each housing half comprising three housing side surfaces, each of which merges at one of its side edges into one of the other two side surfaces and at its other side edge into the other of the other two side surfaces.

[0108] Protection is also claimed for a device as described so far in the dependent claims, but with reference back to the two objects previously described in this chapter, i.e. without restriction to a fuel cell or its humidifier. LIST OF REFERENCE SYMBOLS

[0109] 1 humidifier

[0110] 2 membrane stacks

[0111] 3 housings

[0112] 3a first housing half

[0113] 3b second housing half

[0114] 4a floor wall

[0115] 4b Cover wall

[0116] 5a first end wall

[0117] 5b second end wall

[0118] 5bb housing side frame

[0119] 6a first side wall

[0120] 6b second side wall

[0121] 7 first adhesive beads

[0122] 8 second adhesive beads

[0123] 9 connecting pieces

[0124] 10 connecting pieces

[0125] 11 connecting pieces

[0126] 12 connecting pieces

[0127] 13 Chamber

[0128] 14 chamber

[0129] 15 chambers

[0130] 16 chamber

[0131] 17 Interface along which the housing halves meet

[0132] 18 grooves

[0133] 19 spring

[0134] 20 groove-like depression

[0135] 21 Housing seal

[0136] 21a Contour seal of the membrane stack

[0137] 22 Thickening to form a screw-in nut

[0138] 23 Thickening to form a through hole

[0139] 24 Seal receiving groove in one housing half 25 Seal receiving groove in the other housing half

[0140] 26 not assigned

[0141] 27 Humidification module

[0142] 28 Membran

[0143] 29 Caterpillar

[0144] 30 grids (design of a flat spacer)

[0145] 31 Spacer rod

[0146] 32 spacer rod

[0147] 33 more caterpillars

[0148] 34 Embedding

[0149] 35 coolers

[0150] A fuel cell stack

[0151] B Hydrogen pump

[0152] C Ej ector

[0153] D hydrogen tank

[0154] E air filter

[0155] F compressor

[0156] G Expander

[0157] H electrical load

[0158] AL exhaust air flow

[0159] ZL supply air flow

[0160] DR sealing rib

Claims

CLAIMS 1. Humidifier (1) for a fuel cell with a membrane stack (2) through which an exhaust air stream (AL) discharged from the fuel cell device and an inlet air stream (ZL) supplied to the fuel cell device flow in cross-flow with moisture exchange, and a housing (3) which receives and holds the membrane stack (2) in a sealing and preferably material-locking manner so that the said cross-flow can flow at least essentially leak-free and mixing-free, characterized in that its housing (3) consists of two housing halves (3a, 3b) to be joined together, the interfaces to be joined, along which the housing halves (3a, 3b) are joined to form a seal against one another, run in several different planes and are designed so that sealing materials already applied in preparation for joining are essentially not exposed to any shear stress during joining.

2. Humidifier (1) for a fuel cell, preferably according to Claim 1, with a membrane stack (2) through which an exhaust air flow (AL) discharged from the fuel cell device and a supply air flow (ZL) supplied to the fuel cell device flow under moisture exchange in cross-flow, and a housing (3) which receives and holds the membrane stack (2) in a sealing and preferably materially bonded manner in such a way that the said cross-flow can proceed at least substantially leak-free and mixing-free, characterized in that the housing (3) consists of two housing halves (3a, 3b) which are to be joined together, each housing half (3a; 3b) comprising three housing side surfaces, each of which merges at one of its side edges into one of the other two side surfaces and at its other side edge into the other of the other two side surfaces.

3. Humidifier (1) for a fuel cell according to claim 1, characterized in that the boundary surfaces via which the side surfaces of the two housing halves (3a, 3b) are sealingly connected to one another are substantially flat and straight, even if the surrounding housing regions are curved outwards.

4. Humidifier (1) for a fuel cell according to one of the preceding claims, characterized in that one or more side surfaces bulge outwards in the region between the edges delimiting them.

5. Humidifier (1) for a fuel cell according to one of the preceding claims, characterized in that the membrane stack (2) is a cube or cuboid or a prism.

6. Humidifier (1) for a fuel cell according to one of the preceding claims, characterized in that four of the Side surfaces or walls (5a, 5b, 6a, 6b) each carry a connecting piece (9; 10; 11; 12) for connecting an inlet or outlet hose.

7. Humidifier (1) for a fuel cell according to claim 5, characterized in that the side surface (5a; 5b; 6a; 6b) carrying a connecting piece (9; 10; 11; 12) bulges outwards in order to create an enlarged flow connection between the connecting piece (9; 10; 11; 12) and the end surface (5a; 5b; 6a; 6b) of the membrane stack (2) which is fluidically associated with it.

8. Humidification device in the form of a membrane stack (2) for humidifying a drier gas stream with the aid of a moister gas stream, in that the gas streams are guided past one another separately through the semi-permeable membranes (28) of a membrane stack (2), with a plurality of membranes (28), flat spacers (30) and edge elements forming a flow path in pairs between themselves and successive membranes (28), characterized in that each of the edge elements consists of at least one bead (29; 33) made of a sealing and / or adhesive material, in which a flat spacer (30) is embedded.

9. Humidification device according to claim 8, characterized in that the flat spacers are grids (30) made of intersecting bars (31, 32).

10. Humidifying device according to claim 8 or 9, characterized in that the rods (31; 32), the ends of which are embedded in the tracks (29; 33), meet the tracks (29; 33) at an angle.

11. Humidifying device according to one of claims 8 to 10, characterized in that the rods (31, 32), the ends of which are embedded in the tracks (29; 33), meet the tracks (29, 33) at an angle.

12. Humidifying device according to one of claims 8 to 11, characterized in that each edge element consists of two beads (29; 33) which have been combined with each other in a moist state.

13. Humidifying device according to one of claims 8 to 12, characterized in that each edge element has a cross-section perpendicular to its longitudinal axis which is larger than the cross-section of a rod (31; 32) embedded by it perpendicular to its longitudinal axis.

14. A method for producing a humidifying device according to one of the preceding claims, characterized by the following steps: Production of a humidification module (27) by Cutting a semipermeable membrane (28), preferably in the form of a rectangular strip; Applying two spaced-apart beads (29; 33) of formless sealing and / or adhesive material along two parallel edges of the semipermeable membrane (28) on its first side, preferably the top side; Inserting a flat spacer (30) into the still wet adhesive beads (29); Applying two spaced-apart beads (33) of formless sealing and / or adhesive material along two other parallel edges of the semipermeable membrane (28) on its second side, preferably its underside, thus forming a humidification module (27); Assembly of several such humidification modules (27) by stacking them on top of each other in such a way that the underside beads (33) of a subsequent humidification module (27), in which no flat spacer (30) is inserted, are combined, while still wet, with the upper side beads (29) of the preceding humidification module (27), in which a flat spacer (30) is inserted.

15. Method according to the immediately preceding claim, characterized in that the semipermeable membrane (28) is first cut to size so that it forms a blank for a plurality of humidification modules (27), wherein two spaced-apart beads (29) are applied along two parallel edges of the semipermeable membrane (28), over the entire length of the blank, and then a flat spacer (30) is inserted into the beads (29), the surface extension of which corresponds at least substantially to the blank.

16. Method according to claim 14 or 15, characterized in that the assembly unit comprising the blank and the flat spacer (30) joined by means of the beads (29) is divided several times into sections, each of which corresponds to a humidification module (27).

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