DE102015004953A1 - Humidifier for a fuel cell system, fuel cell system and vehicle having a fuel cell system - Google Patents

Abstract

The invention relates to a humidifier for a fuel cell system, which is designed for humidifying a medium which can be introduced into a fuel cell stack of the fuel cell system. The humidifier comprises a plurality of hollow-fiber membranes surrounding an inflow region (24) on the circumference. In the inflow region (24), a support structure (40) with at least one passage opening (44) is arranged. About the at least one passage opening (44), the hollow fiber membranes are acted upon by a moistening medium. The at least one Durchtrittsöfnung (44) has in a longitudinal direction (36) of the inflow region (24) has a length which is greater than half a length of a portion of the hollow fiber membranes in which the hollow fiber membranes abut the support structure (40). Furthermore, the invention relates to a fuel cell system with such a humidifier and a vehicle with a fuel cell system.

Description

The invention relates to a humidifier for a fuel cell system, which is designed for humidifying a medium which can be introduced into a fuel cell stack of the fuel cell system. The humidifier comprises a plurality of hollow-fiber membranes, which surround an inflow region on the circumference. In the inflow region, a support structure is arranged, which has at least one passage opening. About the at least one passage opening, the hollow fiber membranes can be acted upon with a humidifying medium, which is introduced into the inflow region. Furthermore, the invention relates to a fuel cell system with such a humidifier and a vehicle with a fuel cell system.

The DE 103 32 493 A1 describes a humidifier for a fuel cell system in which individual hollow fiber membranes are interconnected by a net-like matrix material. The hollow fiber membranes in this case form a mat-like composite, which is wound in the humidifier on a hollow body. The hollow body is in this case a tube with a plurality of passage openings. Via these passage openings, a moistening medium can come into contact with the hollow-fiber membranes through which the gas stream to be moistened flows.

Furthermore, the describes US Pat. No. 6,755,399 B2 a humidifier in which a humidifying medium is passed through hollow fiber membranes of a fiber bundle, which serves in a fuel cell system for humidifying supplied air from a fuel cell stack. The dry supply air to be humidified in this case enters the humidifier at a first end of the fiber bundle and then flows in countercurrent to the humidification medium flowing through the hollow fibers to the other end of the humidifier. However, some of the dry supply air to be humidified flows already at the first end into a bypass tube, which is arranged centrally in the fiber bundle. On the way to the second end passes through openings which are arranged in the bypass pipe, dry supply air from the bypass pipe and then flows around the hollow fiber membranes. So the dry supply air is to be evenly distributed in the fiber bundle.

However, such a bypass tube is unfavorable in view of the flow of the fiber bundle.

Object of the present invention is therefore to provide a humidifier of the type mentioned, a fuel cell system with such a humidifier and a vehicle with such a fuel cell system, by means of which a particularly good humidification of the medium to be humidified can be achieved.

This object is achieved by a humidifier having the features of patent claim 1, a fuel cell system having the features of patent claim 9 and by a vehicle having the features of patent claim 10. Advantageous embodiments with expedient developments of the invention are specified in the dependent claims.

In the case of the humidifier according to the invention, the at least one through-opening, as seen in a longitudinal direction of the inflow region, has a length which is greater than half the length of a partial region of the hollow-fiber membranes in which the hollow-fiber membranes rest against the support structure. By means of this passage opening or passage openings extending over a comparatively long length of the inflow region, a flow of the humidifying medium which is distributed particularly well over the length of the humidifier can be realized. In addition, a support structure with at least one passage opening of great length can be produced in a particularly simple and cost-effective manner, since components available as standard can be used. This is accompanied by improved manufacturability, reduced production time and reduced production costs.

With such a humidifier, which has at least one elongate passage opening, a particularly effective transfer of the humidifying medium into the region of the humidifier can be achieved, in which the hollow-fiber membranes are arranged and surround the inflow region. The moistening medium then flows around the hollow fibers formed by the membranes, through which flows the medium to be humidified. In this way, a particularly good and uniform humidification of the medium to be humidified can be achieved.

Preferably, the length of the at least one passage opening corresponds to the length of the partial area or is at least 70 percent to 95 percent of the length of the partial area. Thus, a particularly unhindered transfer of the humidifying medium from the inflow region into the space occupied by the hollow-fiber membranes and surrounding the inflow region of the humidifier can be ensured.

The support structure may be formed as a tube which has a plurality of slots forming the at least one passage opening. Such a tube with elongated slots provides a particularly stable support structure and thus ensures a high dimensional stability of the inflow area. The Tube may in particular be formed circular cylindrical and have to increase the stability end portions in which a wall of the tube is formed continuously, so having no slots. However, the support structure or the pipe can also have a polygonal cross section, in particular in cases in which the housing of the humidifier also has a polygonal cross section. Furthermore, not only one but two or more support structures or tubes can be provided.

The stability of the tube can be further increased if the webs which delimit the respective slots have at least one stiffening element. Such reinforced webs can be achieved with high robustness of the tube, a good transfer of the moistening medium in the space around the support structure in which the hollow fiber membranes are located.

The stiffening element of the respective web can be formed as a rib, which extends from the respective web in the radial direction a little way towards the center of the tube. A wall region of the tube which encompasses the respective web and the rib can have a T-shaped cross section, which gives the tube a particularly high stability.

In an alternative embodiment, the support structure may be formed as a profile part, through which at least two chambers are formed in the inflow region, which can be flowed through by the moistening medium in the longitudinal direction of the inflow region. Here, the at least one passage opening is provided by an open side of the respective chamber. Such a profile part is particularly simple and inexpensive to manufacture, and it can be formed in particular by extrusion.

The profile part may have a plurality of walls bounding the chambers, which extend from a center of the profile part in the radial direction up to the hollow fiber membranes resting against the profile part. The walls may in this case form an X or a Y in cross section, or the cross section may be formed in the manner of a six-ray or six-pointed star with rays of preferably constant thickness. In such a star-shaped profile part with six beams correspondingly six durchströmbare chambers are formed, which have the open side in the radial direction. Such a particularly stable profile part makes it particularly easy to provide a particularly large length of the passage openings.

Also, by means of the profile part can each very easily provide the same size chambers, which is advantageous for a uniform distribution of the humidifying medium.

As a further advantage, it has been shown that the support structure is formed as a helical spring whose turns are in contact with the hollow fiber membranes. In this case, the inflow region is designed in the manner of a channel whose walls are formed by the hollow-fiber membranes, these walls being supported by the turns of the helical spring. In such an embodiment of the support structure loosely arranged side by side hollow fiber membranes can be used instead of interconnected, in particular interwoven, hollow fiber membranes. In fact, the support structure designed in the manner of a helical spring prevents individual hollow fibers from reaching the inflow region through the passage openings, for instance by sagging.

Such an advantageous support of the hollow-fiber membranes can also be achieved if the support structure is provided by a plurality of rings. The rings can also be connected to each other by rods and together with the rods form an intrinsically rigid grid, which gives the inflow region its dimensional stability. Alternatively, a plurality of rods may be provided, which extend in the longitudinal direction of the inflow region and which are interconnected by means of an intrinsically rigid grid. Such a grid or network then has the passage openings with the long length.

The hollow-fiber membranes preferably form a bundle, which is arranged in a housing of the humidifier. In this case, the housing preferably has a housing wall which rests on an outer side of the bundle in a downstream region which is viewed in an inflow direction of the moistening medium in the inflow region. On the other hand, in an upstream portion (seen in the inflow direction), the housing wall is spaced from the outside of the bundle. By means of such a design of the housing wall, it is possible to achieve that the moistening medium initially reaches the downstream subregion of the inflow region and from there enters radially into the space in which the hollow-fiber membranes forming the bundle are located. From this end region of the bundle, the moistening medium then flows countercurrently, ie along the hollow-fiber membranes, to the upstream subregion in which the housing wall is spaced from the outside of the bundle. Such a guide of the humidifying medium in countercurrent leads to a particularly good humidification of the medium to be humidified.

For a uniform flow of the moistening medium, it is advantageous if the bundle formed by the hollow-fiber membranes is substantially round, ie has a circular-cylindrical shape with the inflow region as the-preferably central-channel.

The fuel cell system according to the invention, which can be used in particular in a vehicle, comprises a humidifier according to the invention. In this case, preferably, the exhaust gas of a cathode of a fuel cell stack of the fuel cell system can be introduced into the inflow region of the humidifier. In this case, the exhaust gas of the cathode is preferably usable for moistening an oxidizing agent which can be supplied to the cathode of the fuel cell stack as the medium to be humidified. In that case, the oxidizing agent to be humidified, for example air or oxygen, flows through the hollow-fiber membranes. This is cheaper than applying the hollow fiber membranes with the exhaust gas of the cathode, which contains liquid water. Otherwise, the liquid water could clog the - usually quite fine - hollow-fiber membranes, especially if the water freezes. The latter could also lead to damage to the hollow fiber membranes, which is reliably avoided in the present case.

Such a fuel cell system may include a plurality of other, in particular for fuel cell systems of vehicles usual components, which need not be explained in detail in the present case.

The vehicle according to the invention comprises a fuel cell system according to the invention.

The advantages and preferred embodiments described for the humidifier according to the invention also apply to the fuel cell system according to the invention and to the vehicle according to the invention.

The features and feature combinations mentioned above in the description as well as the features and feature combinations mentioned below in the description of the figures and / or in the figures alone can be used not only in the respectively specified combination but also in other combinations or in isolation, without the scope of To leave invention. Thus, embodiments are also included and disclosed by the invention, which are not explicitly shown or explained in the figures, however, emerge and can be produced by separated combinations of features from the embodiments explained.

Further advantages, features and details of the invention will become apparent from the claims, the following description of preferred embodiments and from the drawings. Showing:

1 a fuel cell system of a vehicle, wherein a humidifier for humidifying supply air for a cathode of a fuel cell stack of the fuel cell system is shown in perspective, which has a helical spring as a support structure for a trained in the humidifier, channel-shaped inflow region;

2 in perspective, an alternative support structure, which is designed as a tube with elongated slots;

3 in a sectional view of another, suitable as a support structure tube in which stiffening ribs are provided on webs of the tube;

4 perspective another alternative support structure, which is designed as a star-shaped extrusion profile; and

5 schematizes the flow paths of supply air to be humidified by a variant of the humidifier.

From a fuel cell system 10 a vehicle is in 1 a humidifier 12 which serves to humidify an oxidant to be provided for the fuel cell reaction. This oxidizing agent may be, for example, oxygen or air. The in the humidifier 12 humidified air is sent via a pipe 14 a cathode 16 a fuel cell stack 18 of the fuel cell system 10 fed. An anode 20 of the fuel cell stack 18 may be used as fuel for those in the fuel cell stack 18 occurring fuel cell reaction are supplied to hydrogen. In the present case, the exhaust gas of the cathode 16 containing the product water formed in the fuel cell reaction, the humidifier 12 fed as humectant. A dedicated exhaust pipe 22 is in 1 shown schematically.

That over the exhaust pipe 22 the humidifier 12 supplied, moist exhaust gas of the cathode 16 flows into a channel-shaped inflow area 24 of the humidifier 12 one. The inflow area 24 is from (in 1 not shown) hollow fiber membranes 26 surrounded (compare 5 ). Through these hollow fiber membranes 26 flows to be humidified supply air, which is the cathode 16 over the line 14 is supplied. The hollow fiber membranes 26 form a circular cylindrical bundle, in the center of which the channel-shaped inflow region 24 located. The the Bundle forming hollow fiber membranes 26 So are in a room 28 arranged, which the inflow area 24 encloses annularly.

At their ends are the hollow fiber membranes 26 through closure elements 30 . 32 passed, which are formed from a potting compound. In the input-side closure element 30 is a central entrance 34 provided, via which the exhaust gas serving as humidifying agent in the inflow region 24 which comes as in the room 28 centrally arranged channel is formed. An inflow direction of the exhaust gas into the inflow region 24 is in 1 through an arrow 36 illustrated. Through this arrow 36 is at the same time a longitudinal direction of the inflow area 24 indicated, which with a longitudinal axis of the humidifier 12 coincides.

The second, end-side closure element 32 has no outlet for that through the inflow area 24 in the humidifier 12 but it is also in an inflow area 24 end closing central area 38 closed trained. As a result, this first flows in the axial direction of the humidifier 12 in the direction of the arrow 36 in the inflow area 24 inflowing exhaust gas radially from the inflow region 24 out. Here it flows around the membranes on the outside, which form the hollow fibers, and it finds the moisture transfer from the wet exhaust gas to the through the hollow fiber membranes 26 flowing dry supply air instead.

At the in 1 shown variant of the humidifier 12 is in the inflow area 24 as a support structure 40 a coil spring 42 intended. At the turns of the coil spring 42 are the subregions of the hollow fiber membranes 26 at which in the room 28 are arranged, which in the axial direction through the closure elements 30 . 32 is limited. The spiral windings of the coil spring 42 prevent the subregions of the hollow-fiber membranes 26 in the inflow area 24 can pass through, for example, by hanging the sections. An alignment of the hollow fiber membranes 26 namely corresponds to the by the arrow 36 indicated longitudinal direction of the inflow 24 ,

By between the turns of the coil spring 42 provided, by material of the coil spring 42 free portions is formed a single passage opening, which in the longitudinal direction of the inflow 24 Seen has a length which the distance between the closure elements 30 . 32 and thus the subregion of the hollow-fiber membranes 26 corresponds, in which this at the support structure 40 issue. Through this passage opening of particularly large length, the exhaust gas can be particularly good in the hollow fiber membranes 26 containing space 28 reach.

In 2 is an alternative, for placement in the inflow area 24 provided support structure 40 shown. In the 2 shown support structure 40 is formed as a tube, wherein a plurality of passage openings in the form of elongated slots 44 in which the tube forming material is provided. These slots 44 extend almost the entire length of the tube, which is substantially the length of the humidifier 12 equivalent. In respective end areas 46 However, the tube is formed circumferentially closed.

That between the slots 44 existing material of the pipe forms webs 48 which the slots 44 limit laterally. In such a tube as a support structure 40 corresponds to the length of the slots 44 in the direction of the arrow 36 indicated longitudinal direction of the humidifier 12 essentially the length of the hollow fiber membranes 26 , However, depending on the design of the peripherally closed end regions 46 Occur that the length of the slots 44 only between 70 percent to 95 percent of the length of the section of the hollow-fiber membranes 26 corresponds, in which the hollow fiber membranes 26 are in contact with the pipe.

In the 3 shown support structure 40 is also designed as a pipe, but here are the webs 48 which the slots 44 border laterally, by ribs 50 strengthened. These ribs 50 serve as stiffening elements for the webs 48 and thus for the tubular support structure 40 all in all. In the present case, the ribs extend 50 from the jetties 48 starting a little way to a center 52 of the inflow area 24 , The through the bridges 48 and the ribs 50 formed areas of the tube formed as a support structure 40 are at the in 3 variant shown in cross-section T-shaped, with a height of the rib 50 , So their extension in the radial direction of the inflow 24 can be greater than a width of the bridge 48 , So its extension in the circumferential direction of the tube.

At the in 4 shown support structure 40 it is an extrusion profile, ie a profile part formed by extrusion. This in 4 Profile part shown has three crossing each other at the same angle walls 54 which form in cross-section a six-pointed star with rays of constant thickness. A center 56 the profile part thus forms the crossing point of the three walls 54 , By such a profile part is the inflow area 24 in the present six chambers 58 divided, their open, so not from the walls 54 limited, sides which form passages for the exhaust gas. About this also over the substantially entire length of the humidifier 12 extending passages then passes during operation of the humidifier 12 the exhaust into the room 28 with the hollow fiber membranes 26 ,

Such, formed by extrusion profile part, which in alternative embodiments, fewer or more walls 54 and correspondingly fewer or more chambers 58 can be particularly easy to provide in terms of manufacturing costs and process management.

At the in 5 shown variant of the humidifier 12 the exhaust gas flows in the direction of the arrow 36 in the inflow area 24 one. However, this is the end by the central area 38 the closure element 32 locked. Accordingly, the exhaust gas flows in particular in the vicinity of the closure element 32 in the radial direction from the inflow region 24 out. In this, seen in the inflow of the exhaust gas downstream portion, however, is a housing wall 60 a housing of the humidifier 12 on an outside of the bundle, which is the hollow fiber membranes 26 form. The corresponding subarea 62 the housing wall 60 is in 5 on the hollow fiber membranes 26 shown adjacent.

In an upstream section 64 is, however, the housing wall 60 from an outside of the bundle of hollow fiber membranes 26 spaced. Accordingly, in this subarea 64 the exhaust gas also directly from the inflow area 24 in the radial direction through the bundle of hollow-fiber membranes 26 pass. The part of the exhaust gas, but which at the downstream end of the inflow 24 is deflected, flows in countercurrent to that through the hollow fiber membranes 26 flowing supply air to the sub-area 64 the housing wall 60 which is from the bundle of hollow fiber membranes 26 is spaced.

Corresponding, this counterflow indicating flow arrows 66 are in 5 illustrated for illustration. The flow of the exhaust gas through the humidifier 12 at least partially in countercurrent can lead to a particularly good transmission of moisture from the exhaust gas to the supply air to be humidified.

Especially with a variant of the humidifier 12 in which the hollow fiber membranes 26 woven together or otherwise connected, the inflow can 24 merely by winding up the hollow fiber membranes 26 be formed around a trained as a cavity center of the bundle. Then, an inner tube as a support structure completely eliminated, and the hollow fiber membranes 26 need in the inflow area 24 not to be supported.

Alternatively, a support of the bundle of hollow fiber membranes 26 from the inside, ie in the inflow area 24 , via rings or an intrinsically stiff net or grid or via individual rods, which are connected to one another via a - preferably intrinsically rigid - network.

LIST OF REFERENCE NUMBERS

10

The fuel cell system

12

humidifier

14

management

16

cathode

18

fuel cell stack

20

anode

22

exhaust pipe

24

inflow

26

Hollow fiber membrane

28

room

30

closure element

32

closure element

34

inlet

36

arrow

38

Central area

40

support structure

42

coil spring

44

slot

46

end

48

web

50

rib

52

center

54

wall

56

center

58

chamber

60

housing wall

62

subregion

64

subregion

66

flow arrow

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 10332493 A1 [0002]
• US 6755399 B2 [0003]

Claims (10)

Humidifier for a fuel cell system ( 10 ), which is used for moistening a fuel cell stack ( 18 ) of the fuel cell system ( 10 ) is introduced medium having a plurality of hollow fiber membranes ( 26 ), which has an inflow area ( 24 ) surrounded circumferentially, wherein in the inflow ( 24 ) a support structure ( 40 ) with at least one passage opening ( 44 ) is arranged, wherein over the at least one passage opening ( 44 ) the hollow fiber membranes ( 26 ) can be acted upon by a moistening medium, characterized in that the at least one passage opening ( 44 ) in a longitudinal direction ( 36 ) of the inflow area ( 24 ) has a length which is greater than half a length of a portion of the hollow fiber membranes ( 26 ) in which the hollow fiber membranes ( 26 ) on the support structure ( 40 ) issue. Humidifier according to claim 1, characterized in that the length of the at least one passage opening ( 44 ) corresponds to the length of the partial area or is 70% to 95% of the length of the partial area. Humidifier according to claim 1 or 2, characterized in that the support structure ( 40 ) is formed as a tube, which has a plurality of the at least one passage opening ( 44 ) has forming slots. Humidifier according to claim 3, characterized in that the respective slots delimiting webs ( 48 ) at least one, in particular as from the respective web ( 48 ) in the radial direction towards the center ( 52 ) of the tube extending rib ( 50 ) have trained, stiffening element. Humidifier according to claim 1 or 2, characterized in that the support structure ( 40 ) is formed as, in particular formed by extrusion, profile part, through which in the inflow ( 24 ) at least two of the moistening medium in the longitudinal direction ( 36 ) of the inflow area ( 24 ) throughflowable chambers ( 58 ), wherein an open side of the respective chamber ( 58 ) the at least one passage opening is provided. Humidifier according to claim 5, characterized in that the profile part a plurality of the chambers ( 58 ) delimiting walls ( 54 ) extending from a center ( 56 ) of the profile part in the radial direction up to the voltage applied to the profile part hollow-fiber membranes ( 26 ). Humidifier according to claim 1 or 2, characterized in that the support structure ( 40 ) - as a coil spring ( 42 ) or - provided by a plurality of rings or - formed by an intrinsically stiff grid or - is formed by a plurality of rods which are interconnected by means of a rigid mesh. Humidifier according to one of claims 1 to 7, characterized in that the, in particular interconnected, hollow-fiber membranes ( 26 ), in particular a substantially round, bundle, which in a housing of the humidifier ( 12 ), wherein the housing is a housing wall ( 60 ), which in one in an inflow ( 36 ) of the humidifying medium into the inflow area ( 24 ) seen downstream portion ( 62 ) abuts an outer side of the bundle and in an upstream portion ( 64 ) is spaced from the outside. Fuel cell system, in particular for a vehicle, with a humidifier ( 12 ) according to one of claims 1 to 8, wherein the exhaust gas of a cathode ( 16 ) of a fuel cell stack ( 18 ) of the fuel cell system ( 10 ) into the inflow area ( 24 ) of the humidifier ( 12 ) and for moistening one of the cathodes ( 16 ) of the fuel cell stack ( 18 ) supplyable oxidizing agent is used as the medium to be humidified. Vehicle with a fuel cell system ( 10 ) according to claim 9.

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