Air-cooled fuel cell bipolar plate for enhancing heat exchange and moisturizing effects and method

Abstract

The invention belongs to the related field of fuel cell technology, and discloses an air-cooled fuel cell bipolar plate capable of enhancing heat exchange and moisturizing effects, the air-cooled fuel cell bipolar plate comprises an anode plate and a cathode plate which are arranged back to back, the anode plate comprises an anode flow field, and a first channel comprising a plurality of hydrogen flow channels is arranged in the anode flow field; the cathode plate comprises a cathode reaction gas flow field, a main cooling flow field and an auxiliary cooling flow field, and a second channel comprising a plurality of air flow channels, a third channel comprising a plurality of main cooling flow channels and a fourth channel comprising at least one auxiliary cooling flow channel are sequentially arranged in the cathode reaction gas flow field, the main cooling flow field and the auxiliary cooling flow field. And the fourth channel is designed to occupy a part of the sectional area of the second channel in the direction perpendicular to the air flowing direction. The invention further discloses a corresponding method. According to the air-cooled fuel cell, the technical problems that the existing air-cooled fuel cell is insufficient in heat dissipation capability and the membrane electrode has a dry membrane phenomenon due to too fast water loss and the like can be solved at the same time, and the power generation efficiency and the operation stability of the air-cooled fuel cell are correspondingly and effectively improved.

Description

Technical Field

[0001] The present invention belongs to the field related to fuel cell technology, and more specifically, relates to an air-cooled fuel cell bipolar plate and method for enhancing heat exchange and moisturizing effects. Background Art

[0002] Fuel cells are usually stacked with multiple unit cells, each of which is composed of bipolar plates, membrane electrodes, cathode reactant oxygen (or air), anode reactant hydrogen and cooling medium. Oxygen (or air) and hydrogen react electrochemically under the action of catalysts to generate electricity, and the cooling medium takes away the waste heat generated by the electrochemical reaction. Air-cooled fuel cells directly use air as both the cathode reactant and cooling medium, and have the characteristics of simple structure, high energy conversion efficiency, clean and pollution-free, high power density, and long life. They have good application prospects in portable power supplies and drones.

[0003] As one of the core components of fuel cells, bipolar plates have the functions of supporting membrane electrodes, separating cathodes and anodes, providing flow space for cathode and cathode reactants, evenly distributing cathode and cathode reaction gases, discharging water and heat generated by electrochemical reactions, collecting and conducting current, etc. Therefore, fuel cell bipolar plates usually include cathode reactant flow channels, anode reactant flow channels, and cooling medium flow channels.

[0004] For air-cooled fuel cells, excess air is directly used as both the cathode reactant and the cooling medium. At present, the cathode flow field of most air-cooled fuel cell bipolar plates is an open flat flow channel, that is, the cathode flow channel runs through the entire bipolar plate, and the flow channel inlet and outlet are directly connected to the atmosphere. This flow channel structure is simple, which is conducive to the rapid flow of air and takes away the heat generated by the electrochemical reaction. However, further research shows that due to the excessively fast air flow rate in the cathode flow channel, the water generated by the electrochemical reaction will also be lost quickly, resulting in less water content in the membrane electrode, the dry film phenomenon, and seriously affecting the performance of the air-cooled fuel cell. In order to improve the performance of air-cooled fuel cells, starting from the flow field structure of the bipolar plate, enhancing its heat dissipation capacity and improving the moisture retention capacity of the membrane electrode has always been a technical problem that the industry continues to tackle.

[0005] Patent search found that the prior art has proposed some solutions to the above technical problems, which are analyzed as follows:

[0006] Chinese patent document CN107681176A discloses an air-cooled fuel cell bipolar plate with corrugated heat sinks, which increases the heat dissipation area by adding heat sinks, thereby enhancing the heat dissipation capacity of the air-cooled fuel cell. However, the patented technology requires the heat sink to be fixed to the plate before the bipolar plate is processed, which results in a complex processing process and increased flow resistance. At the same time, the bipolar plate processed by this technology cannot alleviate the dry film phenomenon that may occur in the cathode of the air-cooled fuel cell.

[0007] Chinese patent document CN115911442A discloses a dual concave-convex channel air-cooled fuel cell bipolar plate, which increases the heat dissipation area by extending one section or both ends of the cathode plate outward and setting heat dissipation fins to enhance the heat dissipation capacity of the air-cooled fuel cell. This technology requires additional heat dissipation fins to be set outside the reaction area of ​​the bipolar plate, resulting in a decrease in the effective area utilization rate of the bipolar plate, and also increases the weight of the bipolar plate to a certain extent, which is not conducive to improving the volume power density and mass power density of the air-cooled fuel cell.

[0008] Chinese patent document CN115275246A discloses an air-cooled fuel cell bipolar plate and an air-cooled fuel cell thereof, which can reduce the loss of water in the membrane electrode to a certain extent and improve the moisture retention capacity of the membrane electrode by designing the cathode flow channel interface into an inverted trapezoid with a small opening and a wide bottom surface, thereby improving the performance of the air-cooled fuel cell. However, the improvement of the moisture retention capacity of the structure is limited. If it is necessary to further improve the moisture retention capacity and strengthen the heat dissipation capacity, it is necessary to further improve the design of the bipolar plate flow field structure. Summary of the invention

[0009] In response to one or more of the above defects or needs of the prior art, the present invention provides an air-cooled fuel cell bipolar plate and method for enhancing heat exchange and moisturizing effects, wherein the overall structural composition, especially the setting method and working mechanism of the auxiliary cooling flow field, is studied and improved, and some key processing parameters are further designed. Accordingly, technical problems such as insufficient heat dissipation capacity of existing air-cooled fuel cells and dry film phenomenon caused by rapid water loss of membrane electrodes can be solved simultaneously, thereby effectively improving the power generation efficiency and operation stability of air-cooled fuel cells.

[0010] To achieve the above object, according to one aspect of the present invention, there is provided an air-cooled fuel cell bipolar plate with enhanced heat exchange and moisturizing effects, the bipolar plate comprising an anode plate and a cathode plate arranged back to back, characterized in that:

[0011] The anode plate comprises an anode flow field, wherein a first channel comprising a plurality of hydrogen flow channels is provided in the anode flow field for allowing hydrogen gas as an anode reactant to flow;

[0012] The cathode plate comprises a cathode reaction gas flow field, a main cooling flow field and an auxiliary cooling flow field, wherein the cathode reaction gas flow field is provided with a second channel including a plurality of air flow channels for supplying air as a cathode reactant; the main cooling flow field is provided with a third channel including a plurality of main cooling flow channels, and the auxiliary cooling flow field is provided with a fourth channel including at least one auxiliary cooling flow channel, which are respectively used for supplying air serving as a cooling medium;

[0013] In addition, the fourth channel is designed to occupy a portion of the cross-sectional area of ​​the second channel in a direction perpendicular to the air flow.

[0014] Through the above conception, when the contact area between the entire cathode flow field and the gas diffusion layer remains unchanged, on the one hand, since the overall cross-sectional area of ​​the second channel, that is, all air flow channels, perpendicular to the air flow direction is reduced, the flow rate of cathode reactants flowing through all air flow channels can be effectively reduced, and the moisture retention capacity of the membrane electrode is significantly improved; on the other hand, the fourth channel cooperates with the third channel to increase the flow area of ​​the cooling medium and enhance the disturbance, and the heat dissipation performance is further improved accordingly; in this way, the heat dissipation performance of the air-cooled fuel cell stack and the moisture retention capacity of the membrane electrode can be improved simultaneously, and the power generation efficiency and operation stability of the air-cooled fuel cell can be effectively improved.

[0015] As a further preference, both ends of the first channel are respectively connected to the hydrogen inlet and the hydrogen outlet, and both ends of the second channel, the third channel and the fourth channel are directly connected to the outside atmosphere.

[0016] As a further preference, the ratio of the sum of the cross-sectional areas of the third channel and the fourth channel perpendicular to the gas flow direction to the cross-sectional area of ​​the second channel perpendicular to the gas flow direction is preferably designed to be in the range of 1.5 to 5:1.

[0017] As a further preference, the cross-sectional area of ​​the third channel perpendicular to the gas flow direction is greater than the cross-sectional area of ​​the fourth channel perpendicular to the gas flow direction, and the ratio of the two is preferably designed to be in the range of 1.5 to 5:1.

[0018] As further preferred, a height difference H between the structural upper surface of the second channel and the structural upper surface of the fourth channel is preferably designed to be greater than 0.15 mm.

[0019] As a further preference, the horizontal distance D at the connection between the second channel and the fourth channel is preferably designed to be greater than 0.2 mm.

[0020] As further preferred, the anode plate and the cathode plate are preferably made of metal plates or composite plates, and each of them further has a sealing channel.

[0021] As further preferred, the first channel is preferably designed as a wavy structure or a straight channel structure, the cross section of the second channel is preferably designed as a special-shaped structure, and the cross section of the third channel is preferably designed as a trapezoidal structure.

[0022] As a further preference, the fourth channel is preferably formed by enclosing the boundary between the second channel and the third channel.

[0023] According to another aspect of the present invention, a corresponding method is provided, characterized in that during operation, the flow rate of air as a cathode reactant is reduced, while the flow area of ​​air as a cooling medium is increased and the disturbance is enhanced.

[0024] In general, the above technical solution conceived by the present invention has the following technical advantages compared with the prior art:

[0025] (1) The present invention fully combines the working characteristics and specific needs of air-cooled natural gas batteries, and through research and improvement of the overall structure of the bipolar plate, especially the setting mode and working mechanism of the auxiliary cooling flow field, it can not only increase the flow area of ​​the cooling flow field and enhance the disturbance, but also reduce the working cross-sectional area of ​​the cathode flow field, reduce the air flow rate of the cathode flow field, and thus effectively improve the moisture retention capacity of the membrane electrode;

[0026] (2) The present invention also involves further design of some key processing parameters of the cathode plate. More actual tests have shown that these key processing parameters can ensure a better balance between improving the power generation efficiency and operating stability of the air-cooled fuel cell, and can simultaneously solve the technical problems of insufficient heat dissipation performance and dry film phenomenon in existing similar products;

[0027] (3) The bipolar plate of the present invention has a compact structure and is easy to process and manufacture. It can effectively reduce the cross-sectional area of ​​the cathode reaction gas flow channel and increase the flow resistance by adding auxiliary cooling flow, thereby reducing the air flow rate and flow rate involved in the electrochemical reaction, reducing the excess air carrying away the water generated by the electrochemical reaction, and improving the moisture retention capacity of the membrane electrode, thereby ensuring that the overall performance of the air-cooled fuel cell is further improved compared with the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the overall structure of the cathode plate of the air-cooled fuel cell provided by the present application;

[0029] Figure 2 It is a schematic diagram of the overall structure of the anode plate of the air-cooled fuel cell provided in the present application;

[0030] Figure 3is a schematic diagram of a structure including a first channel according to a preferred embodiment of the present application;

[0031] Figure 4 It is a structural schematic diagram of a preferred embodiment of the present application that includes a second channel, a third channel and a fourth channel;

[0032] Figure 5 is a schematic diagram for exemplarily representing some key processing parameters of the second channel and the fourth channel;

[0033] Throughout the drawings, the same reference numerals are used to denote the same elements or structures, wherein:

[0034] 1- anode plate; 2- cathode plate; 3- first channel; 4- second channel; 5- third channel; 6- fourth channel. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0036] It should be understood that expressions such as "include" and "may include" used in this application indicate the existence of the disclosed functions, operations or constituent elements, and do not limit one or more additional functions, operations and constituent elements. In this application, terms such as "include" and / or "have" may be interpreted as indicating specific characteristics, numbers, operations, constituent elements, components or combinations thereof, but may not be interpreted as excluding the existence or possibility of adding one or more other characteristics, numbers, operations, constituent elements, components or combinations thereof.

[0037] It should be understood that the terms "center", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0038] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0039] In this application, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0040] As analyzed in the previous "Background Technology" section, the bipolar plates of the air-cooled fuel cells in the prior art cannot properly and simultaneously solve the technical problems of insufficient heat dissipation capacity and membrane electrode dry film. The present invention aims to solve the above-mentioned technical problems of the existing air-cooled fuel cells by studying and improving the overall structural composition of the bipolar plates, especially the setting method and working mechanism of the auxiliary cooling flow field, and further designing some key processing parameters.

[0041] Figure 1 is a schematic diagram of the overall structure of the cathode plate of the air-cooled fuel cell provided in this application, Figure 2 Schematic diagram of the overall structure of the anode plate of the air-cooled fuel cell provided in this application. Figure 1 and Figure 2 As shown, after the anode plate 1 and the cathode plate 2 are processed, they are bonded together, for example, back to back. The anode plate 1 specifically includes a hydrogen inlet, a hydrogen outlet, an anode flow field, and a sealing groove, etc., and the cathode plate 2 specifically includes a cathode flow field, a main cooling flow field, an auxiliary cooling flow field, and a sealing groove, etc. When the air-cooled fuel cell is assembled, the surface of the anode plate 1 and the surface of the cathode plate 2 are respectively stacked with the anode side and the cathode side of the air-cooled membrane electrode.

[0042] like Figure 3 As shown, the fuel cell cathode plate of the present invention can preferably use a stamping process to generate a plurality of hydrogen flow channels to form a first channel. A flow disturbance structure or a gas distribution structure can be provided in the first channel as required, and the inlet and outlet of the first channel are respectively connected to the hydrogen inlet and the hydrogen outlet.

[0043] like Figure 4As shown in, the cathode plate 2 of the present invention includes a cathode reaction gas flow field, a main cooling flow field and an auxiliary cooling flow field, wherein the cathode flow field is provided with a second channel 4 comprising a plurality of air flow channels for supplying air serving as a cathode reactant; the main cooling flow field is provided with a third channel 5 comprising a plurality of main cooling flow channels, and the auxiliary cooling flow field is provided with a fourth channel 6 comprising at least one auxiliary cooling flow channel, respectively for supplying air serving as a cooling medium; in addition, the fourth channel 6 is designed to occupy a portion of the cross-sectional area of ​​the second channel 4 in a direction perpendicular to the air flow.

[0044] More specifically, according to a preferred embodiment of the present invention, the cathode plate 2 can preferably be bent, stamped, etc. to generate a plurality of cathode air channels, main cooling channels, and auxiliary cooling channels, thereby forming a second channel, a third channel, and a fourth channel, respectively. Among them, the cross section of the second channel is, for example, a special-shaped structure, the cross section of the third channel is, for example, a trapezoidal structure, and the fourth channel can preferably be formed by the boundaries of the second channel and the third channel. The purpose of designing such a structure is to improve the strength of the plate and avoid the cathode side from being compressed and collapsed when the fuel cell stack is assembled. In addition, both ends of the second channel, the third channel, and the fourth channel are directly connected to the external environment.

[0045] Through the above conception, under the condition that the contact area between the entire cathode flow field and the gas diffusion layer remains unchanged, on the one hand, by designing the auxiliary cooling channel, the overall cross-sectional area of ​​the second channel, that is, all the air flow channels, perpendicular to the air flow direction is reduced, the cross-sectional area of ​​the air flow channel is reduced and the flow resistance is increased, the air velocity and flow rate involved in the electrochemical reaction are reduced, and the excess air carries away the water generated by the electrochemical reaction, and the moisture retention capacity of the membrane electrode is improved, thereby further improving the performance of the air-cooled fuel cell; on the other hand, by designing the auxiliary cooling channel, the fourth channel cooperates with the third channel to increase the flow area of ​​the cooling medium and enhance the disturbance, and correspondingly further improves the heat dissipation performance. In this way, the heat dissipation performance of the air-cooled fuel cell stack and the moisture retention capacity of the membrane electrode can be improved simultaneously, effectively improving the power generation efficiency and operation stability of the air-cooled fuel cell.

[0046] like Figure 5 As shown in, according to a preferred embodiment of the present invention, the ratio of the sum of the cross-sectional areas of the third channel 5 and the fourth channel 6 perpendicular to the gas flow direction to the cross-sectional area of ​​the second channel 4 perpendicular to the gas flow direction is preferably designed to be in the range of 1.5 to 5:1.

[0047] According to another preferred embodiment of the present invention, the cross-sectional area of ​​the third channel 5 perpendicular to the gas flow direction is greater than the cross-sectional area of ​​the fourth channel 6 perpendicular to the gas flow direction, and the ratio of the two is preferably designed to be in the range of 1.5 to 5:1.

[0048] Through the above specific design, more actual tests have shown that while ensuring sufficient cathode air supply, the heat exchange area has been increased as much as possible, which can achieve a better balance between improving the power generation efficiency and operating stability of the air-cooled fuel cell.

[0049] According to a preferred embodiment of the present invention, a height distance H between a structural upper surface of the second channel 4 and a structural upper surface of the fourth channel 6 is preferably designed to be greater than 0.15 mm.

[0050] According to another preferred embodiment of the present invention, the horizontal distance D between the second channel 4 and the fourth channel 6 is preferably designed to be greater than 0.2 mm.

[0051] Through the above specific design, many actual tests have shown that it can not only ensure that the cathode plate has sufficient supporting strength, but also effectively avoid excessive flow resistance in the second channel, which leads to insufficient cathode reaction gas supply.

[0052] In addition, according to another preferred embodiment of the present invention, the connection between the second channel and the fourth channel is designed to be a bonding area for the cathode plate and the anode plate, and the bonding process includes but is not limited to laser welding. It should be noted that since there are multiple connections between the second channel and the fourth channel, during the bipolar plate bonding process, several of the numerous connections can be selected for bonding according to actual needs.

[0053] In summary, the air-cooled fuel cell bipolar plate and method according to the present invention can not only effectively increase the cooling fluid heat exchange area, enhance disturbance and strengthen heat exchange, but also simultaneously reduce the cross-sectional area of ​​the cathode reaction gas flow channel and increase the flow resistance, while reducing the air flow rate and flow rate in the reaction gas flow channel, reducing the excess air from carrying away the water generated by the electrochemical reaction, and helping to improve the moisture retention capacity of the membrane electrode. The air-cooled fuel cell bipolar plate of the present invention has a compact structure, is easy to process and manufacture, and effectively improves the power generation efficiency and operating stability of the fuel cell, and thus has good practical value and application prospects.

[0054] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A bipolar plate for an air-cooled fuel cell with enhanced heat exchange and moisturizing effects, the bipolar plate comprising an anode plate (1) and a cathode plate (2) arranged back to back, characterized in that: The anode plate (1) comprises an anode flow field, wherein a first channel (3) comprising a plurality of hydrogen flow channels is provided in the anode flow field for allowing hydrogen as an anode reactant to flow; The cathode plate (2) comprises a cathode reaction gas flow field, a main cooling flow field and an auxiliary cooling flow field, wherein the cathode reaction gas flow field is provided with a second channel (4) comprising a plurality of air flow channels for allowing air serving as a cathode reactant to flow; the main cooling flow field is provided with a third channel (5) comprising a plurality of main cooling flow channels, and the auxiliary cooling flow field is provided with a fourth channel (6) comprising at least one auxiliary cooling flow channel, each of which is used to allow air serving as a cooling medium to flow; Furthermore, the fourth channel (6) is designed to occupy a portion of the cross-sectional area of ​​the second channel (4) in a direction perpendicular to the air flow.

2. The air-cooled fuel cell bipolar plate according to claim 1, characterized in that: The two ends of the first channel (3) are respectively connected to the hydrogen inlet and the hydrogen outlet, and the two ends of the second channel (4), the third channel (5) and the fourth channel (6) are directly connected to the outside atmosphere.

3. The air-cooled fuel cell bipolar plate according to claim 1 or 2, characterized in that: The ratio of the sum of the cross-sectional areas of the third channel (5) and the fourth channel (6) perpendicular to the gas flow direction to the cross-sectional area of ​​the second channel (4) perpendicular to the gas flow direction is preferably designed to be in the range of 1.5 to 5:

1.

4. The air-cooled fuel cell bipolar plate according to any one of claims 1 to 3, characterized in that: Compared with the cross-sectional area of ​​the third channel (5) perpendicular to the gas flow direction and the cross-sectional area of ​​the fourth channel (6) perpendicular to the gas flow direction, the former is larger than the latter and the ratio of the two is preferably designed to be in the range of 1.5 to 5:

1.

5. The air-cooled fuel cell bipolar plate according to claim 3 or 4, characterized in that: The height difference H between the structural upper surface of the second channel (4) and the structural upper surface of the fourth channel (6) is preferably designed to be greater than 0.15 mm.

6. The air-cooled fuel cell bipolar plate according to any one of claims 3 to 5, characterized in that: The horizontal distance D between the second channel (4) and the fourth channel (6) at the connection point is preferably designed to be greater than 0.2 mm.

7. The air-cooled fuel cell bipolar plate according to any one of claims 1 to 6, characterized in that: The anode plate (1) and the cathode plate (2) are preferably made of metal plates or composite plates, and each of them has a sealing channel.

8. The air-cooled fuel cell bipolar plate according to any one of claims 1 to 7, characterized in that: The first channel (3) is preferably designed as a wave-shaped structure or a straight channel structure, the cross section of the second channel (4) is preferably designed as a special-shaped structure, and the cross section of the third channel (5) is preferably designed as a trapezoidal structure.

9. A method for enhancing heat exchange and moisturizing effects by using the air-cooled fuel cell bipolar plate according to any one of claims 1 to 8, characterized in that: During operation, the flow velocity and flow rate of the air as the cathode reactant decrease, while the flow area of ​​the air as the cooling medium increases and the disturbance increases.

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