Drainage element for draining a fuel cell stack

Abstract

The presented invention relates to a drainage element (100) for draining a fuel cell stack (200). The drainage element (100) comprises: - a base body (101), wherein a recess (103) for the flow of operating medium is formed in the base body (101), wherein the base body (101) forms a structured surface (107) at the edge (105) of the recess (103), wherein the structured surface comprises a plurality of structural elements (111) raised relative to a base (109) of the edge in the direction of the recess.

Description

The present invention relates to a dewatering element for dewatering a fuel cell stack, a fuel cell stack and a fuel cell system according to the appended claims.Prior ArtIn fuel cell systems, liquid water may form during operation, which accumulates particularly in the region between respective last fuel cells and respective end plates of a fuel cell stack.A collection of liquid water may damage a fuel cell stack.Disclosure of the InventionIn the context of the present invention, a dewatering element, a fuel cell stack and a fuel cell system are provided. Further features and details of the invention are evident from the respective dependent claims, the description and the drawings. Features and details which are described in connection with the drainage element according to the invention naturally also apply in connection with the fuel cell stack according to the invention or the fuel cell system according to the invention and vice versa, so that with regard to the disclosure reference is or can always be made to the individual aspects of the invention in a mutually alternating manner.The present invention serves in particular to provide a possibility for a robust fuel cell system.According to a first aspect of the present invention, a dewatering element for dewatering a fuel cell stack is provided.The dewatering element comprises a base body, wherein a recess for flowing operating medium is formed in the base body, wherein the base body forms a structured surface at the edge of the recess, and wherein the structured surface comprises a plurality of structural elements raised in the direction of the recess with respect to a base of the edge.In the context of the present invention, a base of an edge is understood to mean a region of the base body of the present dewatering element that runs uniformly or flat and is unprocessed or in which no structural elements form. The structural elements rise out of the base or on the base. Accordingly, the base of the edge is completely closed or forms a closed surface, while the structured surface is open in regions or forms an only partially closed surface.The present invention is based on a drainage element that is arranged on respective last or uppermost / lowermost fuel cells of a fuel cell stack and that comprises a recess that has an edge or circumference, the surface of which is structured, in particular frayed or has gaps.The structural elements extend from a base at the edge of the recess in the direction of the recess, in particular a center of the recess. Therefore, the structural elements are in particular planar or flat with the remaining base body.Liquid water produced during operation of the fuel cell stack is drawn into the structured surface on the surface of the dewatering element on account of capillary forces, with the result that accumulation of liquid water on the fuel cells is minimized.It is provided in particular that the dewatering element is arranged on the outlet side, for example on an anode outlet channel.It can be provided that the dewatering element consists of a metal or a metal alloy.A dewatering member made of metal such as, for example. Aluminum has proven to be particularly robust or durable.Furthermore, a metallic dewatering element transfers heat energy from a respective fuel cell stack particularly well to liquid water adhering to the dewatering element, so that the latter vaporizes quickly.It can furthermore be provided that the dewatering element comprises an interface for engaging into a channel for conducting operating medium through a fuel cell stack.For arranging or securing the dewatering element on a channel, a cut position can be provided which is configured, for example, to penetrate into the channel and enclose it in regions or to accommodate the channel in regions. Accordingly, the interface can be shaped according to a geometry of the channel and clamp the dewatering element to the channel.It can be provided that the structural elements are angular or wave-shaped.In particular angular structural elements have proven to be particularly suitable for providing a capillary force.Furthermore, angular structural elements require a particularly large surface area, on which a correspondingly large amount of liquid water can collect and evaporate.Wavy structural elements have proven to be particularly suitable for slowing down a flow through the recess, so that the residence time of liquid water on the structured surface is extended and this evaporates through a wall heat transition from the fuel cell stack to the liquid water.It can be provided that the structural elements are triangular.Triangular structural members have been found to be particularly suitable for providing capillary force and a large surface area for collecting liquid water.In particular, triangular structural elements bring about a discharge of water drops impinging on the structural elements in narrow points formed between respective triangles, where high capillary forces prevail.Furthermore, constrictions formed between two triangles form pockets in which liquid water for the fuel cell stack can collect harmlessly and, if appropriate, evaporate later.It can furthermore be provided that the structural elements comprise equilateral triangles.Equilateral triangles form symmetrical pockets in which a particularly high capillary force prevails.It can furthermore be provided that the structural elements are between 0.1 mm and 0.7 mm high.In particular, triangles having a height of between 0.3 mm and 0.5 mm have proven to be particularly suitable for use in the proposed dewatering element.According to a second aspect, the present invention relates to a fuel cell stack for a fuel cell system.The fuel cell stack presented comprises a plurality of fuel cells stacked one on top of the other and end plates arranged at opposite ends of the fuel cell stack, wherein a number of channels for conducting operating media extend through the fuel cell stack, and wherein a possible configuration of the presented dewatering element is arranged on at least one channel of the number of channels of a fuel cell arranged at one end of the fuel cell stack.Due to the proposed dewatering element, an accumulation of liquid water between respective last fuel cells or edge fuel cells and respective end plates of the proposed fuel cell stack is minimized. Accordingly, the fuel cell stack presented is particularly robust, fault-resistant and durable.It can be provided that the recess of the dewatering element overlaps a channel for the flow of operating medium in a respective last fuel cell, wherein a cross section of the recess of the dewatering element is smaller than a cross section of the overlapped channel.As a result of a superposition of a channel of a fuel cell by the dewatering element, structural elements of the dewatering element in particular project into a mass flow flowing through the respective channels, such that liquid water present in the mass flow impinges on the structural elements and accumulates there.In particular, the structural elements can swirl the mass flow due to their shape, so that the entire mass flow or a major part of the mass flow comes into contact with the flow element and at least a major part of liquid water located in the mass flow accumulates in the structural elements and evaporates.It can be provided that the structured surface of the edge of the recess overlaps the channel in a range between 0.1 mm and 0.7 mm.In particular, structural elements having a height of between 0.3 mm and 0.5 mm have proven to be particularly suitable for use in the proposed dewatering element.It can furthermore be provided that the base body overlaps the respective channel in addition to the structured surface in a range between 0.2 mm and 0.9 mm.By means of a region in which the base body itself overlaps a channel, the channel is greatly reduced in size, so that the structural elements project far into the channel and a particularly large amount of mass flow flowing through the channel comes into contact with the structural elements.In particular, it can be provided that the base body itself or the base projects approximately 0.7 mm far into a channel and that structural elements are connected thereto which project 0.5 mm far into the channel. In this case, the structural elements can be triangular, for example isosceles.Alternatively or additionally, it can be provided that the base body itself or the base projects approximately 0.5 mm far into a channel and that structural elements are connected thereto which project 0.3 mm far into the channel. In this case, the structural elements can be in particular wave-shaped.According to a third aspect, the present invention relates to a fuel cell system for converting energy, the fuel cell system including a possible configuration of the present fuel cell stack.Advantages described in detail with respect to the dewatering member for dewatering a fuel cell stack according to the first aspect of the invention apply equally to the fuel cell stack for a fuel cell system according to the second aspect of the invention and the fuel cell system for converting power according to the third aspect of the invention.Further advantages, features and details of the invention will become apparent from the following description, in which exemplary embodiments of the invention are described in detail with reference to the drawings. The features mentioned in the claims and in the description can be essential to the invention individually or in any combination.The following are shown: FIG. 1 shows a schematic illustration of a possible configuration of the dewatering element presented, FIG. 2 shows a schematic illustration of a possible configuration of the fuel cell stack presented, FIG. 3 shows a schematic illustration of a possible configuration of the fuel cell system presented.FIG. 1 shows a dewatering element 100 for dewatering a fuel cell stack.The dewatering element 100 comprises a base body 101. A recess 103 for flowing operating media through is formed in the base body 101.A structured surface 107 is formed on the edge 105 of the recess 103, which comprises a plurality of structural elements 111 raised with respect to a base 109 of the edge 105.The structural elements 111 are shown triangularly in the present case by way of example and have the effect that liquid water accumulates there on account of capillary force applied between the structural elements 111 or building up and evaporates efficiently on account of a surface area which is particularly large due to the structural elements 111.Referring to FIG. 2, a fuel cell stack 200 for a fuel cell system is shown.In the present case, a last, for example uppermost, fuel cell 201 of the fuel cell stack 200 can be seen, in which a number of channels 203 are formed.A sealing element 205 is arranged on the fuel cell 201.A dewatering element 100 according to FIG. 1 is arranged on an anode outlet channel 207.In the present case, the dewatering element runs, for example, flat with the sealing element 205. For this purpose, a receptacle is formed in the sealing element 205 for receiving, in particular for positively receiving, the dewatering element 100.FIG. 3 illustrates a fuel cell system 300 for converting energy.The fuel cell system comprises the fuel cell stack 200 according to FIG. 2 and a number of ancillary units 301 for supplying the fuel cell stack 200 with operating media.

Claims

Dewatering element (100) for dewatering a fuel cell stack (200), wherein the dewatering element (100) comprises: - a base body (101), wherein a recess (103) for flowing operating medium is formed in the base body (101), wherein the base body (101) forms a structured surface (107) at the edge (105) of the recess (103), wherein the structured surface comprises a plurality of structural elements (111) raised in the direction of the recess with respect to a base (109) of the edge.Dewatering element (100) according to Claim 1, characterized in that the dewatering element (100) consists of a metal or a metal alloy.The dewatering element (100) of claim 1 or 2, characterized in that the dewatering element (100) comprises an interface for engaging a channel for guiding operating medium through a fuel cell stack (200).Dewatering element (100) according to one of the preceding claims, characterized in that the structural elements (111) are angular or wave-shaped.Dewatering element (100) according to one of the preceding claims, characterized in that the structural elements (111) are triangularDewatering element (100) according to one of the preceding claims, characterized in that the structural elements (111) comprise equilateral trianglesDewatering element (100) according to one of the preceding claims, characterized in that the structural elements (111) are between 0.1 mm and 0.7 mm highA fuel cell stack (200) for a fuel cell system (300), the fuel cell stack (200) comprising: - a plurality of fuel cells (201) stacked on each other, - end plates arranged at opposite ends of the fuel cell stack (200), wherein a number of channels (203, 207) for guiding operating media extend through the fuel cell stack (200), wherein a dewatering element (100) according to any one of claims 1 to 7 is arranged at at least one channel (207) of the number of channels (203, 207) of a fuel cell (201) arranged at an end of the fuel cell stack (200).Fuel cell stack (200) according to claim 8, characterised in that the structured surface (107) of the edge of the recess (103) overlaps the channel in a range between 0.1 mm and 0.7 mm.Fuel cell stack (200) according to Claim 9, characterized in that the main body (101) overlaps the respective channel in addition to the structured surface (107) in a range between 0.2 mm and 0.9 mm.A fuel cell system (300) for converting energy, the fuel cell system (300) comprising a fuel cell stack (200) according to any one of claims 8 to 10.

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