A method for using an air-cooled fuel cell bipolar plate to enhance heat exchange and humidification.

Abstract

This application belongs to the field of fuel cell technology and discloses an air-cooled fuel cell bipolar plate with enhanced heat exchange and moisture retention. It includes an anode plate and a cathode plate arranged back-to-back. The anode plate includes an anode flow field with a first channel containing multiple hydrogen flow channels. The cathode plate includes a cathode reactant gas flow field, a main cooling flow field, and an auxiliary cooling flow field, with a second channel containing multiple air flow channels, a third channel containing multiple main cooling flow channels, and a fourth channel containing at least one auxiliary cooling flow channel sequentially arranged. 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. The invention also discloses a corresponding method. This invention simultaneously solves the technical problems of insufficient heat dissipation capacity and rapid moisture loss from the membrane electrode assembly (MEA) leading to dry membrane phenomena in existing air-cooled fuel cells, thereby effectively improving the power generation efficiency and operational stability of air-cooled fuel cells.

Description

Technical Field

[0001] This invention belongs to the field of fuel cell technology, and more specifically, relates to an air-cooled fuel cell bipolar plate and method for enhancing heat exchange and humidification effects. Background Technology

[0002] Fuel cells are typically composed of multiple stacked cell units. Each cell unit consists of bipolar plates, membrane electrode assemblies, oxygen (or air) as the cathode reactant, hydrogen as the anode reactant, and a cooling medium. Oxygen (or air) and hydrogen undergo an electrochemical reaction in the presence of a catalyst to generate electricity, while the cooling medium removes the waste heat generated by the electrochemical reaction. Air-cooled fuel cells directly use air as both the cathode reactant and the cooling medium, offering advantages such as simple structure, high energy conversion efficiency, cleanliness, high power density, and long lifespan. They show great promise for applications in portable power supplies and drones.

[0003] As one of the core components of a fuel cell, the bipolar plate serves multiple functions, including supporting the membrane electrode assembly, separating the cathode and anode, providing flow space for the reactants at the cathode and anode, uniformly distributing the reactant gases at the cathode and anode, discharging water and heat generated by the electrochemical reaction, and collecting and conducting current. Therefore, a fuel cell bipolar plate typically includes cathode reactant channels, anode reactant channels, and cooling medium channels.

[0004] For air-cooled fuel cells, excess air is used directly as both the cathode reactant and the cooling medium. Currently, most air-cooled fuel cell bipolar plates have an open, flat, direct-flow cathode flow field, meaning the cathode flow channel runs through the entire bipolar plate, with the inlet and outlet directly connected to the atmospheric environment. This flow channel structure is simple and facilitates rapid airflow to remove the heat generated by the electrochemical reaction. However, further research shows that due to the excessively high air velocity within the cathode flow channel, the water generated by the electrochemical reaction also flows out rapidly, resulting in low water content in the membrane electrode assembly (MEA) and causing a dry membrane phenomenon, which severely affects the performance of air-cooled fuel cells. To improve the performance of air-cooled fuel cells, enhancing their heat dissipation capacity and improving the moisture retention capacity of the MEA, starting from the flow field structure of the bipolar plate, has been a continuously challenging technical problem in the industry.

[0005] Patent searches revealed that existing technologies have proposed several solutions to the aforementioned technical challenges, as detailed below:

[0006] Chinese patent document CN107681176A discloses a bipolar plate for an air-cooled fuel cell with corrugated heat sinks. By adding heat sinks, the heat dissipation area is increased, enhancing the heat dissipation capacity of the air-cooled fuel cell. However, this patented technology requires fixing the heat sinks onto the bipolar plate before processing, which complicates the manufacturing process and increases flow resistance. Furthermore, the bipolar plate processed using this technology cannot alleviate the dry film phenomenon that may occur at the cathode of an air-cooled fuel cell.

[0007] Chinese patent document CN115911442A discloses a bipolar plate for a dual-concave-convex channel air-cooled fuel cell. This method increases the heat dissipation area and enhances the heat dissipation capacity of the air-cooled fuel cell by extending one or both ends of the cathode plate outwards and adding heat dissipation fins. However, this technology requires additional heat dissipation fins outside the bipolar plate's reaction zone, which reduces the effective area utilization of the bipolar plate and also increases its weight to some extent, hindering the improvement of the volumetric 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 its air-cooled fuel cell. By designing the cathode flow channel interface as an inverted trapezoid with a small opening and a wide bottom, the loss of moisture in the membrane electrode assembly (MEA) can be reduced to a certain extent, improving the MEA's moisture retention capacity and thus enhancing the performance of the air-cooled fuel cell. However, the improvement in moisture retention capacity by this structure is limited. If it is necessary to further improve the moisture retention capacity while enhancing the heat dissipation capacity, the design of the bipolar plate flow field structure needs to be further improved. Summary of the Invention

[0009] To address one or more of the above-mentioned defects or needs in the prior art, this invention provides an air-cooled fuel cell bipolar plate and method for enhancing heat exchange and moisture retention. By studying and improving its overall structural composition, especially the setting method and working mechanism of the auxiliary cooling flow field, and further designing some key processing parameters, this invention can simultaneously solve the technical problems of insufficient heat dissipation capacity and excessive moisture loss from the membrane electrode leading to dry membrane phenomenon in existing air-cooled fuel cells, effectively improving the power generation efficiency and operational stability of air-cooled fuel cells.

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

[0011] The anode plate includes an anode flow field, in which a first channel containing multiple hydrogen flow channels is provided for the flow of hydrogen as an anode reactant.

[0012] The cathode plate includes a cathode reaction gas flow field, a main cooling flow field, and an auxiliary cooling flow field. The cathode reaction gas flow field is provided with a second channel containing multiple air channels for air to flow as cathode reactants. The main cooling flow field is provided with a third channel containing multiple main cooling channels. The auxiliary cooling flow field is provided with a fourth channel containing at least one auxiliary cooling channel for air to flow as cooling medium.

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

[0014] Based on the above design, while keeping the contact area between the entire cathode flow field and the gas diffusion layer constant, on the one hand, the overall cross-sectional area of ​​the second channel, i.e., all air channels, perpendicular to the air flow direction is reduced, which can effectively reduce the flow rate of cathode reactants flowing through all air channels and significantly improve the moisture retention capacity of the membrane electrode. On the other hand, the fourth channel works in conjunction with the third channel to increase the flow area of ​​the cooling medium and enhance the disturbance, thereby further improving the heat dissipation performance. In this way, the heat dissipation performance and moisture retention capacity of the air-cooled fuel cell stack can be improved simultaneously, effectively enhancing the power generation efficiency and operational stability of the air-cooled fuel cell.

[0015] As a further preferred embodiment, the two ends of the first channel are respectively connected to a hydrogen inlet and a hydrogen outlet, and the two ends of the second, third, and fourth channels are all directly connected to the outside atmosphere.

[0016] As a further preferred embodiment, the ratio of the sum of the cross-sectional areas of the third and fourth channels 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 preferred embodiment, the cross-sectional area of ​​the third channel perpendicular to the gas flow direction is larger than that 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 a further preferred embodiment, the height difference H between the upper surface of the second channel and the upper surface of the fourth channel is preferably designed to be 0.15 mm or more.

[0019] As a further preferred embodiment, the horizontal distance D at the connection point between the second channel and the fourth channel is preferably designed to be 0.2 mm or more.

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

[0021] As a further preferred embodiment, the first channel is preferably designed as a wave-shaped structure or a DC channel structure, the cross-section of the second channel is preferably designed as an irregular structure, and the cross-section of the third channel is preferably designed as a trapezoidal structure.

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

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

[0024] In summary, the technical solutions conceived by this invention have the following main technical advantages compared with the prior art:

[0025] (1) This invention fully combines the working characteristics and specific requirements of air-cooled natural gas batteries. By studying and improving the overall structure of the bipolar plate, especially the setting method 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 and reduce the air flow of the cathode flow field, thereby effectively improving 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. Many actual tests have shown that these key processing parameters can ensure a better balance between improving the power generation efficiency and operation stability of the air-cooled fuel cell, and ensure that the technical problems of insufficient heat dissipation performance and dry film phenomenon in existing similar products can be solved simultaneously.

[0027] (3) The bipolar plate structure of the present invention is compact and 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 velocity and flow rate participating in the electrochemical reaction, reducing the amount of water generated by the electrochemical reaction carried away by excess air, and improving the moisture retention capacity of the membrane electrode. Thus, compared with the prior art, it can ensure further improvement of the overall performance of the air-cooled fuel cell. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the overall structure of the cathode plate of the air-cooled fuel cell provided in this application;

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

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

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

[0032] Figure 5 This is a schematic diagram used to exemplify some key processing parameters of the second and fourth channels;

[0033] In all the accompanying 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 Implementation

[0035] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0036] It should be understood that expressions such as "comprising" and "may include" as 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 "comprising" and / or "having" may be interpreted as indicating a specific characteristic, number, operation, constituent element, component, or combination thereof, but should 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,” “upper,” “lower,” “front,” “rear,” “left,” “right,” “vertical,” “horizontal,” “inner,” “outer,” “clockwise,” “counterclockwise,” “axial,” “radial,” and “circumferential” indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0038] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0039] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0040] As analyzed in the "Background Technology" section above, the bipolar plates of existing air-cooled fuel cells cannot adequately solve the technical problems of insufficient heat dissipation capacity and dry membrane of membrane electrode assembly simultaneously. This invention studies and improves the overall structure of the bipolar plate, especially the setting method and working mechanism of the auxiliary cooling flow field, and further designs some key processing parameters, aiming to solve the above-mentioned technical problems of existing air-cooled fuel cells.

[0041] Figure 1 This is a schematic diagram of the overall structure of the cathode plate of the air-cooled fuel cell provided in this application. Figure 2 This is a 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 processing, the anode plate 1 and cathode plate 2 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 sealing channels, while the cathode plate 2 specifically includes a cathode flow field, a main cooling flow field, an auxiliary cooling flow field, and sealing channels. During the assembly of an air-cooled fuel cell, the surfaces of the anode plate 1 and the cathode plate 2 are respectively bonded and stacked with the anode side and cathode side of the air-cooled membrane electrode assembly.

[0042] like Figure 3 As shown, the fuel cell cathode plate of the present invention can preferably be produced by stamping or other processes to generate several hydrogen flow channels, forming a first channel. The first channel may be equipped with a turbulence structure or a gas distribution structure as needed, and the inlet and outlet of the first channel are respectively connected to a hydrogen inlet and a hydrogen outlet.

[0043] like Figure 4As shown, 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. The cathode flow field is provided with a second channel 4 containing multiple air channels for airflow as a cathode reactant. The main cooling flow field is provided with a third channel 5 containing multiple main cooling channels. The auxiliary cooling flow field is provided with a fourth channel 6 containing at least one auxiliary cooling channel for airflow as a cooling medium. 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 airflow.

[0044] More specifically, according to a preferred embodiment of the present invention, the cathode plate 2 is preferably formed by bending, stamping, or other processes to create a plurality of cathode air flow channels, main cooling flow channels, and auxiliary cooling flow channels, thereby forming a second channel, a third channel, and a fourth channel, respectively. The cross-section of the second channel is, for example, an irregular shape; the cross-section of the third channel is, for example, a trapezoidal shape; and the fourth channel is preferably formed by the boundaries of the second and third channels. This design aims to improve the strength of the electrode plate and prevent the cathode side from collapsing during fuel cell stack assembly. Furthermore, both ends of the aforementioned second, third, and fourth channels are directly connected to the external environment.

[0045] Based on the above design, while keeping the contact area between the cathode flow field and the gas diffusion layer constant, on the one hand, by designing auxiliary cooling channels, the overall cross-sectional area of ​​the second channel (i.e., all air flow channels) perpendicular to the air flow direction is reduced. This decreases the cross-sectional area of ​​the air flow channels and increases flow resistance, lowering the air velocity and flow rate participating in the electrochemical reaction. This reduces the amount of water generated by the electrochemical reaction carried away by excess air, improving the moisture retention capacity of the membrane electrode assembly (MEA), thereby further improving the performance of the air-cooled fuel cell. On the other hand, by designing auxiliary cooling channels, the fourth channel works in conjunction with the third channel to increase the flow area of ​​the cooling medium and enhance turbulence, thus further improving heat dissipation performance. In this way, the heat dissipation performance and the moisture retention capacity of the MEA of the air-cooled fuel cell stack can be improved simultaneously, effectively enhancing the power generation efficiency and operational stability of the air-cooled fuel cell.

[0046] like Figure 5 As shown, 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 larger than that of the fourth channel 6 perpendicular to the gas flow direction, and the ratio of the two is preferably designed to be 1.5 to 5:1.

[0048] Through the above specific design, numerous actual tests have shown that, while ensuring a sufficient supply of cathode air, the heat exchange area has also been maximized, thereby achieving a better balance between improving the power generation efficiency and operational stability of air-cooled fuel cells.

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

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

[0051] Through the above specific design, numerous actual tests have shown that not only can the cathode plate have sufficient support strength, but it also effectively avoids excessive flow resistance in the second channel, which could lead to insufficient supply of cathode reaction gas.

[0052] Furthermore, according to another preferred embodiment of the present invention, the connection between the second channel and the fourth channel can be designed as 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 connections can be selected for bonding according to actual needs.

[0053] In summary, the air-cooled fuel cell bipolar plate and method of the present invention not only effectively increase the heat exchange area of ​​the cooling fluid and enhance turbulence and heat transfer, but also simultaneously reduce the cross-sectional area of ​​the cathode reaction gas flow channel and increase the flow resistance, while reducing the air velocity and flow rate in the reaction gas flow channel, thus reducing the amount of water generated by the electrochemical reaction carried away by excess air and helping to improve the moisture retention capacity of the membrane electrode assembly. 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 operational stability of the fuel cell, thus possessing good practical value and application prospects.

[0054] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A wind-cooled fuel cell bipolar plate with enhanced heat exchange and humidification 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) includes an anode flow field, in which a first channel (3) containing multiple hydrogen flow channels is provided for the flow of hydrogen as an anode reactant; The cathode plate (2) includes a cathode reaction gas flow field, a main cooling flow field and an auxiliary cooling flow field. The cathode reaction gas flow field is provided with a second channel (4) containing multiple air channels for air flow as cathode reactants. The main cooling flow field is provided with a third channel (5) containing multiple main cooling channels. The auxiliary cooling flow field is provided with a fourth channel (6) containing at least one auxiliary cooling channel for air flow as cooling medium. 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 airflow.

2. The air-cooled fuel cell bipolar plate as described in claim 1, characterized in that, The two ends of the first channel (3) are connected to the hydrogen inlet and the hydrogen outlet, respectively, 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 as described in claim 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 designed to be between 1.5 and 5:

1.

4. The air-cooled fuel cell bipolar plate as described in claim 3, characterized in that, The cross-sectional area of ​​the third channel (5) perpendicular to the gas flow direction is larger than that of the fourth channel (6) perpendicular to the gas flow direction, and the ratio of the two is designed to be between 1.5 and 5:

1.

5. The air-cooled fuel cell bipolar plate as described in claim 4, characterized in that, The height difference H between the upper surface of the second channel (4) and the upper surface of the fourth channel (6) is designed to be 0.15 mm or more.

6. The air-cooled fuel cell bipolar plate as described in claim 5, characterized in that, The horizontal distance D at the connection point between the second channel (4) and the fourth channel (6) is designed to be 0.2 mm or more.

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

8. The air-cooled fuel cell bipolar plate as described in claim 7, characterized in that, The first channel (3) is designed as a wave-shaped structure or a DC channel structure, the cross-section of the second channel (4) is designed as an irregular structure, and the cross-section of the third channel (5) is designed as a trapezoidal structure.

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

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