An air-cooled fuel cell cathode plate and method for enhancing heat and mass transfer and moisture retention

Abstract

This application belongs to the field of fuel cell technology and discloses an air-cooled fuel cell cathode plate that enhances heat and mass transfer and moisture retention. The cathode plate includes a cathode flow field, a main cooling flow field, and an auxiliary cooling flow field. It sequentially comprises a first channel containing multiple air channels, a second channel containing multiple main cooling channels, and a third channel containing at least one auxiliary cooling channel. The third channel is designed to occupy a portion of the cross-sectional area of ​​the first channel in a direction perpendicular to the airflow. Furthermore, at least one turbulence-inducing structure is provided in both the first and third channels. The invention also discloses a corresponding method. This invention simultaneously solves the technical problems of insufficient heat dissipation capacity, low mass transfer performance, and rapid moisture loss from the membrane electrode assembly (MEA) leading to dry film phenomenon 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 cathode plate and method for enhancing heat and mass transfer and moisture retention. 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 is typically formed by a cathode plate and an anode plate in a back-to-back design. 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, carrying away the heat generated by the electrochemical reaction. However, further research shows that, on the one hand, because the gas flow direction along the channel is perpendicular to the direction of diffusion into the gas diffusion layer, the mass transfer capacity is poor; on the other hand, due to the excessively high air velocity within the cathode flow channel, the water generated by the electrochemical reaction is also rapidly lost, resulting in low water content in the membrane electrode assembly (MEA) and the occurrence of 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 and mass transfer capabilities and improving the moisture retention capacity of the MEA, starting from the flow field structure of the bipolar plate, has been a continuously tackling technical challenge 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 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 reaction zone of the bipolar plate, leading to a decrease in the effective area utilization of the bipolar plate and increasing its weight to some extent, which is detrimental to improving the volumetric power density and mass power density of the air-cooled fuel cell. Furthermore, the mass transfer capacity and moisture retention capacity of the membrane electrode assembly (MEA) are not improved when using this technology.

[0007] 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, improving the MEA's moisture retention capacity and thus enhancing the performance of the air-cooled fuel cell. However, this structure has limited improvement in mass transfer and moisture retention capacity. If further improvements in mass transfer and moisture retention capacity are needed while simultaneously enhancing heat dissipation, the design of the bipolar plate flow field structure requires further refinement. Summary of the Invention

[0008] To address one or more of the above-mentioned defects or needs in the existing technology, this invention provides an air-cooled fuel cell cathode plate and method that enhances heat and mass transfer 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 turbulence structure, and by further designing some key processing parameters, this invention can simultaneously solve the technical problems of insufficient heat dissipation capacity, low mass transfer performance, and dry film phenomenon caused by excessive moisture loss of the membrane electrode in existing air-cooled fuel cells, effectively improving the power generation efficiency and operational stability of air-cooled fuel cells.

[0009] To achieve the above objectives, according to one aspect of the present invention, an air-cooled fuel cell cathode plate with enhanced heat and mass transfer and moisture retention effects is provided, characterized in that:

[0010] 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 has a first channel containing multiple air channels for airflow as a cathode reactant. The main cooling flow field has a second channel containing multiple main cooling channels. The auxiliary cooling flow field has a third channel containing at least one auxiliary cooling channel for airflow as a cooling medium. The third channel is designed to occupy a portion of the cross-sectional area of ​​the first channel in a direction perpendicular to the airflow.

[0011] In addition, at least one turbulence structure is provided in both the first and third channels. In the first channel, the turbulence structure is used to enhance the disturbance and change the airflow angle of the cathode reactant, thereby improving the mass transfer capacity of the cathode reactant to the gas diffusion layer. In the third channel, it is used to enhance the disturbance and increase the fluid heat exchange area of ​​the cooling medium, thereby improving the heat transfer capacity.

[0012] Based on the above concept, while keeping the contact area between the entire cathode flow field and the gas diffusion layer constant, on the one hand, since the overall cross-sectional area of ​​the first channel, i.e., all air channels, perpendicular to the air flow direction is reduced, the flow rate of cathode reactants flowing through all air channels can be effectively reduced, significantly improving the moisture retention capacity of the membrane electrode assembly (MEA). On the other hand, the third channel, in conjunction with the second channel, can 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 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.

[0013] In addition, by setting up turbulence structures and assigning different functions in both the first and third channels, it is possible not only to change the airflow angle within the reactant gas flow and enhance the turbulence of the reactant gas, thereby effectively improving the mass transfer capacity of the reactant gas to the gas diffusion layer, but also to enhance the turbulence and destroy the heat transfer boundary layer, further increasing the heat exchange area of ​​the cooling medium, thereby effectively improving the heat transfer capacity. Accordingly, it can more comprehensively and efficiently solve the technical problems of insufficient heat dissipation capacity, low mass transfer performance, and excessive moisture loss from the membrane electrode leading to dry membrane phenomenon in existing air-cooled fuel cells.

[0014] As a further preferred embodiment, both ends of the first channel, the second channel, and the third channel are directly connected to the outside atmosphere.

[0015] As a further preferred embodiment, the ratio of the sum of the cross-sectional areas of the second and third channels perpendicular to the gas flow direction to the cross-sectional area of ​​the first channel perpendicular to the gas flow direction is preferably designed to be in the range of 1.5 to 5:1.

[0016] As a further preferred embodiment, the cross-sectional area of ​​the second channel perpendicular to the gas flow direction is larger than that of the third 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.

[0017] As a further preferred embodiment, the height difference H between the upper surface of the first channel and the upper surface of the third channel is preferably designed to be 0.12 mm or more.

[0018] As a further preferred embodiment, the horizontal distance D at the connection point between the first channel and the third channel is preferably designed to be 0.2 mm or more.

[0019] As a further preferred embodiment, the cathode plate is preferably made of a metal sheet or a composite sheet, and it also has a sealing channel.

[0020] As a further preferred embodiment, the cross-section of the first channel is preferably designed as an irregular structure, and the cross-section of the second channel is preferably designed as a trapezoidal structure.

[0021] As a further preferred embodiment, the third channel is preferably formed by the boundary between the first channel and the second channel.

[0022] According to another aspect of the present invention, a corresponding method is also provided, characterized in that, during operation, the flow rate of the air serving as the cathode reactant decreases, while the flow area of ​​the air serving as the cooling medium increases and the disturbance is enhanced; at the same time, the mass transfer capacity of the cathode reactant is improved, and the heat exchange area of ​​the cooling medium is increased.

[0023] In summary, the technical solutions conceived by this invention have the following main technical advantages compared with the prior art:

[0024] (1) This invention fully combines the working characteristics and specific requirements of air-cooled fuel cells. By studying and improving the overall structure of the cathode 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.

[0025] (2) The present invention also studies and improves the setting method and different functions of the turbulence structure, which is another key component. It can not only change the airflow angle in the reaction gas channel and enhance the turbulence of the reaction gas, thereby improving the mass transfer capacity of the reaction gas to the gas diffusion layer, but also enhance the retention turbulence in the auxiliary cooling channel, thereby further improving the heat transfer capacity.

[0026] (3) 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] (4) The cathode plate of the present invention has a compact structure and is easy to process and manufacture. The turbulence structure can be processed and formed in one step. Compared with the prior art, it can solve the technical problems of insufficient heat dissipation capacity, low mass transfer performance and dry membrane phenomenon caused by excessive moisture loss of membrane electrode in the existing air-cooled fuel cell. It effectively improves the power generation efficiency and operation stability of the air-cooled fuel cell, thereby ensuring 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 a preferred embodiment of the present application, which includes a first channel, a second channel, a third channel, and a turbulence structure.

[0030] Figure 3 This is a schematic diagram used to exemplify some key processing parameters of the first and third channels;

[0031] In all the accompanying drawings, the same reference numerals are used to denote the same elements or structures, wherein:

[0032] 1-First channel; 2-Second channel; 3-Third channel; 4-Breakthrough structure. Detailed Implementation

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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, low mass transfer performance, and dry membrane of the membrane electrode assembly. This invention studies and improves the overall structure of the cathode plate, especially the setting method and working mechanism of the auxiliary cooling flow field and turbulence structure, and further designs some key processing parameters, aiming to solve the above-mentioned technical problems of existing air-cooled fuel cells.

[0039] 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 a preferred embodiment of the present application, which includes a first channel, a second channel, a third channel, and a turbulence structure.

[0040] like Figure 2As shown, the cathode plate of the present invention includes a cathode reaction gas flow field, a main cooling flow field, and an auxiliary cooling flow field. The cathode reaction gas flow field includes a first channel 1 containing multiple air channels for airflow as a cathode reactant. The main cooling flow field includes a second channel 2 containing multiple main cooling channels. The auxiliary cooling flow field includes a third channel 3 containing at least one auxiliary cooling channel, both for airflow as a cooling medium. The third channel 3 is designed to occupy a portion of the cross-sectional area of ​​the first channel 1 in a direction perpendicular to the airflow. Furthermore, both the first channel 1 and the third channel 3 are provided with at least one turbulence structure 4. This turbulence structure in the first channel 1 enhances turbulence and changes the airflow angle of the cathode reactant, thereby improving the mass transfer capacity of the cathode reactant to the gas diffusion layer. Simultaneously, in the third channel 3, it enhances turbulence and increases the fluid heat exchange area of ​​the cooling medium, thereby improving the heat transfer capacity.

[0041] More specifically, according to a preferred embodiment of the present invention, the cathode plate is preferably formed by bending, stamping, or other processes to create a plurality of cathode air channels, main cooling channels, and auxiliary cooling channels, thereby forming a first channel, a third channel, and a fourth channel, respectively. The first channel has a cross-section that is, for example, an irregular shape; the second channel has a cross-section that is, for example, a trapezoidal shape; and the third channel is preferably formed by the boundaries of the first and second channels. This design aims to improve the strength of the electrode plate and prevent the cathode side from collapsing during the assembly of the air-cooled fuel cell stack. Furthermore, both ends of the first, second, and third channels are directly connected to the external environment.

[0042] 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 channels, perpendicular to the air flow direction is reduced. This reduces the cross-sectional area of ​​the air channels and increases the flow resistance, thereby reducing the air velocity and flow rate participating in the electrochemical reaction. It also reduces the amount of water generated by the electrochemical reaction carried away by excess air, improving the moisture retention capacity of the membrane electrode, and thus 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 the disturbance, thereby further improving the heat dissipation performance.

[0043] In addition, by setting up turbulence structures and assigning different functions in both the first and third channels, the airflow angle within the reactant gas flow can be changed and the turbulence of the reactant gas can be enhanced, thereby effectively improving the mass transfer capacity of the reactant gas to the gas diffusion layer. Furthermore, the enhanced turbulence and disruption of the heat transfer boundary layer further increase the heat exchange area of ​​the cooling medium, thus effectively improving the heat transfer capacity. Consequently, it can more comprehensively and efficiently solve the technical problems of insufficient heat dissipation capacity, low mass transfer performance, and excessive moisture loss from the membrane electrode leading to dry membrane phenomenon in existing air-cooled fuel cells, ultimately effectively improving the power generation efficiency and operational stability of air-cooled fuel cells.

[0044] like Figure 3 As shown, according to a preferred embodiment of the present invention, the ratio of the sum of the cross-sectional areas of the second channel 2 and the third channel 3 perpendicular to the gas flow direction to the cross-sectional area of ​​the first channel 1 perpendicular to the gas flow direction is preferably designed to be in the range of 1.5 to 5:1.

[0045] According to another preferred embodiment of the present invention, the cross-sectional area of ​​the second channel 2 perpendicular to the gas flow direction is larger than that of the third channel 3 perpendicular to the gas flow direction, and the ratio of the two is preferably designed to be 1.5 to 5:1.

[0046] 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.

[0047] According to a preferred embodiment of the present invention, the height distance H between the upper surface of the first channel 1 and the upper surface of the third channel 3 is preferably designed to be 0.12 mm or more.

[0048] According to another preferred embodiment of the present invention, the horizontal distance D at the connection between the first channel 1 and the third channel 3 is preferably designed to be 0.2 mm or more.

[0049] 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 first channel, which could lead to insufficient supply of cathode reaction gas.

[0050] In summary, the air-cooled fuel cell cathode plate and method according to the present invention have the following advantages compared with the prior art:

[0051] Firstly, by designing auxiliary cooling channels, the heat exchange area of ​​the cooling fluid is increased. Secondly, by setting up turbulence structures in the auxiliary cooling channels, the turbulence is enhanced and the heat transfer boundary layer is destroyed, thereby enhancing the heat dissipation performance of the air-cooled fuel cell and improving its performance.

[0052] Secondly, the present invention can enhance the mass transfer capability of air-cooled fuel cells. By setting a turbulence structure in the cathode reaction gas flow channel of the air-cooled fuel cell, the airflow angle in the reaction gas flow channel is changed and the turbulence of the reaction gas is enhanced, thereby improving the mass transfer capability of the reaction gas to the gas diffusion layer.

[0053] Finally, the present invention can also enhance the moisturizing effect of the bipolar plate of the air-cooled fuel cell. By adding an auxiliary cooling channel in the cathode reaction gas flow channel of the air-cooled fuel cell, the cross-sectional area of ​​the reaction gas flow channel is reduced and the flow resistance is increased. This reduces the air velocity and flow rate participating in the electrochemical reaction, reduces the amount of water generated by the electrochemical reaction carried away by excess air, and improves the moisturizing ability of the membrane electrode, thereby further improving the performance of the air-cooled fuel cell.

[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 cathode plate with enhanced heat and mass transfer and moisture retention effects, characterized in that: 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 has a first channel (1) containing multiple air channels for air flow as a cathode reactant. The main cooling flow field has a second channel (2) containing multiple main cooling channels. The auxiliary cooling flow field has a third channel (3) containing at least one auxiliary cooling channel for air flow as a cooling medium. The third channel (3) is designed to occupy a portion of the cross-sectional area of ​​the first channel (1) in a direction perpendicular to the air flow. In addition, at least one turbulence structure (4) is provided in both the first channel (1) and the third channel (3). The turbulence structure in the first channel (1) is used to enhance the turbulence and change the airflow angle of the cathode reactant, thereby improving the mass transfer capability of the cathode reactant to the gas diffusion layer. At the same time, in the third channel (3), it is used to enhance the turbulence and increase the fluid heat exchange area of ​​the cooling medium, thereby improving the heat transfer capability.

2. The air-cooled fuel cell cathode plate as described in claim 1, characterized in that, Both ends of the first channel (1), the second channel (2) and the third channel (3) are directly connected to the outside atmosphere.

3. The air-cooled fuel cell cathode plate as described in claim 2, characterized in that, The ratio of the sum of the cross-sectional areas of the second channel (2) and the third channel (3) perpendicular to the gas flow direction to the cross-sectional area of ​​the first channel (1) perpendicular to the gas flow direction is designed to be between 1.5 and 5:

1.

4. The air-cooled fuel cell cathode plate as described in claim 3, characterized in that, The cross-sectional area of ​​the second channel (2) perpendicular to the gas flow direction is larger than that of the third channel (3) 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 cathode plate as described in claim 4, characterized in that, The height difference H between the upper surface of the first channel (1) and the upper surface of the third channel (3) is designed to be 0.12 mm or more.

6. The air-cooled fuel cell cathode plate as described in claim 5, characterized in that, The horizontal distance D at the connection point between the first channel (1) and the third channel (3) is designed to be 0.2 mm or more.

7. The air-cooled fuel cell cathode plate according to any one of claims 1-6, characterized in that, The cathode plate is made of metal sheet or composite sheet, and it also has a sealed channel.

8. The air-cooled fuel cell cathode plate as described in claim 7, characterized in that, The cross-section of the first channel (1) is designed as an irregular structure, and the cross-section of the second channel (2) is designed as a trapezoidal structure.

9. A method for enhancing heat and mass transfer and moisture retention effects using an air-cooled fuel cell cathode plate as described in any one of claims 1-8, characterized in that, During operation, the flow rate of air, which is the cathode reactant, decreases, while the flow area of ​​air, which is the cooling medium, increases and the disturbance is enhanced. At the same time, the mass transfer capacity of the cathode reactant is improved, and the heat exchange area of ​​the cooling medium is increased.

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