Dewatering element for dewatering a fuel cell stack

Abstract

The present invention relates to a dewatering element (100) for dewatering a fuel cell stack (200). The dewatering element (100) comprises: - a main body (101), wherein a cutout (103) for operating medium to flow through is formed in the main body (101), wherein the main body (101) forms a structured surface (107) at the edge (105) of the cutout (103), the structured surface comprising a multiplicity of structural elements (111) which are elevated in relation to a base (109) of the edge in the direction of the cutout.

Description

[0001] Description

[0002] Drainage element for draining a fuel cell stack

[0003] The presented invention relates to a drainage element for draining a fuel cell stack, a fuel cell stack and a fuel cell system according to the appended claims.

[0004] State of the art

[0005] In fuel cell systems, liquid water can form during operation, particularly in the area between the last fuel cells and the end plates of a fuel cell stack.

[0006] An accumulation of liquid water can damage a fuel cell stack.

[0007] Disclosure of the invention

[0008] Within the scope of the invention presented, a drainage element, a fuel cell stack, and a fuel cell system are presented. Further features and details of the invention emerge from the respective subclaims, the description, and the drawings. Features and details 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 of the individual aspects of the invention, reference is always made to each other. The invention presented serves, in particular, to provide a possibility for a robust fuel cell system.

[0009] According to a first aspect of the presented invention, a drainage element for draining a fuel cell stack is presented.

[0010] The drainage element comprises a base body, wherein a recess for flowing through 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 relative to a base of the edge in the direction of the recess.

[0011] In the context of the invention presented, a base of an edge is understood to be a region of the main body of the drainage element presented that is uniformly or flat and unprocessed, or in which no structural elements are formed. The structural elements rise from 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 some areas or forms a partially closed surface.

[0012] The presented invention is based on a drainage element that is arranged on the respective last or uppermost / lowest fuel cells of a fuel cell stack and that comprises a recess that has an edge or periphery, the surface of which is structured, in particular frayed or has gaps.

[0013] The structural elements extend from a base at the edge of the recess toward the recess, particularly toward the center of the recess. Therefore, the structural elements are particularly flat or level with the rest of the base body. Liquid water accumulating during operation of the fuel cell stack is drawn into the structured surface of the drainage element due to capillary forces, thus minimizing the accumulation of liquid water on the fuel cells.

[0014] In particular, it is provided that the drainage element is arranged on the outlet side, for example on an anode outlet channel.

[0015] It can be provided that the drainage element consists of a metal or a metal alloy.

[0016] A drainage element made of metal, such as aluminum, has proven to be particularly robust and durable.

[0017] Furthermore, a metallic drainage element transfers heat energy from a respective fuel cell stack particularly well to liquid water adhering to the drainage element, so that it evaporates quickly.

[0018] It can further be provided that the drainage element comprises an interface for engaging in a channel for guiding operating medium through a fuel cell stack.

[0019] To arrange or secure the drainage element to a channel, an interface can be provided, which is configured, for example, to penetrate into the channel and partially enclose it or partially accommodate the channel. Accordingly, the interface can be shaped according to the geometry of the channel and clamp the drainage element to the channel.

[0020] The structural elements can be angular or wavy.

[0021] Angular structural elements, in particular, have proven particularly suitable for providing capillary force. Furthermore, angular structural elements provide a particularly large surface area on which a correspondingly large amount of liquid water can accumulate and evaporate.

[0022] Wave-shaped structural elements have proven 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 water evaporates through a wall heat transfer from the fuel cell stack to the liquid water.

[0023] It may be provided that the structural elements are triangular.

[0024] Triangular structural elements have proven particularly suitable for providing capillary force and a large surface area for collecting liquid water.

[0025] In particular, triangular structural elements cause water droplets impacting the structural elements to be diverted into narrow spaces formed between the respective triangles, where high capillary forces prevail.

[0026] Furthermore, narrow spaces between two triangles form pockets in which liquid water can collect harmlessly for the fuel cell stack and possibly evaporate later.

[0027] It may further be provided that the structural elements comprise equilateral triangles.

[0028] Equilateral triangles form symmetrical pockets in which a particularly high capillary force prevails.

[0029] It can also be provided that the structural elements have a height between 0.1 mm and 0.7 mm. In particular, triangles with a height between 0.3 mm and 0.5 mm have proven particularly suitable for use in the proposed drainage element.

[0030] According to a second aspect, the presented invention relates to a fuel cell stack for a fuel cell system.

[0031] The proposed fuel cell stack comprises a plurality of fuel cells stacked on top of one another and end plates arranged at opposite ends of the fuel cell stack, wherein a number of channels for guiding operating media extend through the fuel cell stack, and wherein a possible embodiment of the proposed drainage 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.

[0032] Due to the drainage element presented, an accumulation of liquid water between the respective last fuel cells or

[0033] The edge fuel cells and the respective end plates of the fuel cell stack presented here are minimized. Accordingly, the fuel cell stack presented here is particularly robust, failure-resistant, and durable.

[0034] It can be provided that the recess of the drainage element overlies a channel for the flow of operating medium in a respective last fuel cell, wherein a cross section of the recess of the drainage element is smaller than a cross section of the overlaid channel.

[0035] By overlaying a channel of a fuel cell with the drainage element, structural elements of the drainage element in particular protrude into a mass flow flowing through the respective channels, so that liquid water in the mass flow impacts the structural elements and accumulates there.

[0036] In particular, the structural elements can swirl the mass flow due to their shape, so that the entire mass flow or a large part of the mass flow comes into contact with the flow element and at least a large part of the liquid water in the mass flow accumulates in the structural elements and evaporates.

[0037] It can be provided that the structured surface of the edge of the recess overlies the channel in a range between 0.1 mm and 0.7 mm.

[0038] In particular, structural elements with a height between 0.3 mm and 0.5 mm have proven to be particularly suitable for use in the drainage element presented.

[0039] It can further be provided that the base body overlies the respective channel in addition to the structured surface in a range between 0.2 mm and 0.9 mm.

[0040] Through an area in which the base body itself overlies a channel, the channel is greatly reduced in size, so that the structural elements protrude far into the channel and a particularly large amount of the mass flow flowing through the channel comes into contact with the structural elements.

[0041] In particular, it can be provided that the base itself or the base protrudes approximately 0.7 mm into a channel, and that structural elements are connected to it, protruding 0.5 mm into the channel. The structural elements can be triangular, e.g., isosceles.

[0042] Alternatively or additionally, the base itself or the base can protrude approximately 0.5 mm into a channel, followed by structural elements that protrude 0.3 mm into the channel. The structural elements can, in particular, be wave-shaped.

[0043] According to a third aspect, the presented invention relates to a fuel cell system for converting energy, wherein the fuel cell system comprises a possible embodiment of the presented fuel cell stack. Advantages described in detail for the drainage element for draining 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 energy according to the third aspect of the invention.

[0044] Further advantages, features, and details of the invention will become apparent from the following description, which describes exemplary embodiments of the invention in detail with reference to the drawings. The features mentioned in the claims and in the description may be essential to the invention individually or in any combination.

[0045] They show:

[0046] Figure 1 is a schematic representation of a possible design of the drainage element presented,

[0047] Figure 2 shows a schematic representation of a possible design of the presented fuel cell stack,

[0048] Figure 3 shows a schematic representation of a possible design of the presented fuel cell system.

[0049] Figure 1 shows a drainage element 100 for draining a fuel cell stack.

[0050] The drainage element 100 comprises a base body 101.

[0051] A recess 103 for the flow of operating media is formed in the base body 101.

[0052] At the edge 105 of the recess 103, a structured surface 107 is formed, which comprises a plurality of structural elements 111 raised relative to a base 109 of the edge 105. The structural elements 111 are shown here as triangular, by way of example, and have the effect that liquid water collects there due to the capillary force acting or building up between the structural elements 111 and evaporates efficiently due to the particularly large surface area created by the structural elements 111.

[0053] Figure 2 shows a fuel cell stack 200 for a fuel cell system.

[0054] 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.

[0055] A sealing element 205 is arranged on the fuel cell 201.

[0056] A drainage element 100 according to Figure 1 is arranged on an anode outlet channel 207.

[0057] In the present case, the drainage element runs, for example, flush with the sealing element 205. For this purpose, a receptacle for receiving, in particular for positively receiving, the drainage element 100 is formed in the sealing element 205.

[0058] Figure 3 shows a fuel cell system 300 for converting energy.

[0059] The fuel cell system comprises the fuel cell stack 200 according to Figure 2 and a number of auxiliary units 301 for supplying the fuel cell stack 200 with operating media.

Claims

Claims 1 . Drainage element (100) for draining water from a fuel cell stack (200), the drainage element (100) comprising: a base body (101), the base body (101) having a recess (103) formed therein for the operating medium to flow through, the base body (101) forming a structured surface (107) at the edge (105) of the recess (103), the structured surface comprising a plurality of structural elements (111) raised relative to a base (109) of the edge in the direction of the recess.

2. Drainage element (100) according to claim 1, characterized in that the drainage element (100) consists of a metal or a metal alloy.

3. Drainage element (100) according to claim 1 or 2, characterized in that the drainage element (100) comprises an interface for engaging in a channel for guiding operating medium through a fuel cell stack (200).

4. Drainage element (100) according to one of the preceding claims, characterized in that the structural elements (111) are angular or wavy.

5. Drainage element (100) according to one of the preceding claims, characterized in that the structural elements (111) are triangular 6. Drainage element (100) according to one of the preceding claims, characterized in that the structural elements (111) comprise equilateral triangles 7. Drainage 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 high 8. A fuel cell stack (200) for a fuel cell system (300), the fuel cell stack (200) comprising: - a multitude of stacked fuel cells (201), - 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 drainage element (100) according to one of claims 1 to 7 is arranged on at least one channel (207) of the number of channels (203, 207) of a fuel cell (201) arranged at one end of the fuel cell stack (200).

9. Fuel cell stack (200) according to claim 8, characterized in that the structured surface (107) of the edge of the recess (103) overlies the channel in a range between 0.1 mm and 0.7 mm.

10. Fuel cell stack (200) according to claim 9, characterized in that the base body (101) overlies the respective channel in addition to the structured surface (107) in a range between 0.2 mm and 0.9 mm.

11. Fuel cell system (300) for converting energy, wherein the fuel cell system (300) comprises a fuel cell stack (200) according to one of claims 8 to 10.

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