Air-cooled fuel cell cathode plate and method for enhancing heat and mass transfer and moisturizing effects

Abstract

The invention belongs to the related field of fuel cell technology, and discloses an air-cooled fuel cell cathode plate for enhancing heat and mass transfer and moisturizing effects, which comprises a cathode flow field, a main cooling flow field and an auxiliary cooling flow field, wherein a first channel comprising a plurality of air flow channels, a second channel comprising a plurality of main cooling flow channels and a third channel comprising at least one auxiliary cooling flow channel are sequentially arranged, and the third channel is designed to occupy a part of the sectional area of the first channel in the direction perpendicular to the air flowing direction; in addition, at least one turbulent flow structure is arranged in each of the first channel and the third channel. 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, low in mass transfer performance and too fast in water loss of the membrane electrode to cause a dry membrane phenomenon 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 cathode plate and method for enhancing heat and mass transfer 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 are usually formed by a cathode plate and an anode plate through a "back-to-back" design. The bipolar plate has the functions of supporting the membrane electrode, separating the cathode and anode, providing flow space for the cathode and cathode reactants, evenly distributing the cathode and cathode reaction gases, discharging the water and heat generated by the electrochemical reaction, and collecting and conducting current. Therefore, the bipolar plate of a fuel cell usually includes a cathode reactant flow channel, an anode reactant flow channel, and a cooling medium flow channel.

[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 on the one hand, the mass transfer capacity is poor because the flow direction of the gas along the flow channel is perpendicular to the direction of diffusion to the gas diffusion layer; on the other hand, 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 and mass transfer capacity and improving the moisture retention capacity of the membrane electrode have 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 CN115911442A discloses a bipolar plate for air-cooled fuel cells with double concave-convex channels, which increases the heat dissipation area by extending one section or both ends of the cathode plate outward and setting heat dissipation fins, thereby enhancing the heat dissipation capacity of the air-cooled fuel cell. However, 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. In addition, the mass transfer capacity and moisture retention capacity of the membrane electrode of the bipolar plate designed using this technology have not been improved.

[0007] Chinese patent document CN115275246A discloses an air-cooled fuel cell bipolar plate and an air-cooled fuel cell thereof, which reduces the loss of water in the membrane electrode and improves 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 structure has limited improvement in mass transfer and moisture retention capacity. If it is necessary to further improve the mass transfer and moisture retention capacity while strengthening the heat dissipation capacity, it is necessary to further improve the design of the bipolar plate flow field structure. Summary of the invention

[0008] 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 cathode plate and method with enhanced heat and mass transfer and moisturizing effects, wherein the overall structural composition, especially the setting method and working mechanism of the auxiliary cooling flow field and the spoiler structure, is studied and improved, and some key processing parameters are further designed. Accordingly, the technical problems of the existing air-cooled fuel cell such as insufficient heat dissipation capacity, poor mass transfer performance, and dry film phenomenon caused by rapid water loss of the membrane electrode can be solved simultaneously, thereby effectively improving the power generation efficiency and operation stability of the air-cooled fuel cell.

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

[0010] 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 first channel including a plurality of air flow channels for supplying air as a cathode reactant; the main cooling flow field is provided with a second channel including a plurality of main cooling flow channels, and the auxiliary cooling flow field is provided with a third channel including at least one auxiliary cooling flow channel, respectively for supplying air serving as a cooling medium; wherein the third channel is designed to occupy a part of the cross-sectional area of ​​the first channel in a direction perpendicular to the air flow;

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

[0012] 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 first channel, that is, all the air flow channels, perpendicular to the air flow direction is reduced, the flow rate of the cathode reactant flowing through all the air flow channels can be effectively reduced, and the moisture retention capacity of the membrane electrode is significantly improved; on the other hand, the third channel cooperates with the second 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 are effectively improved;

[0013] In addition, by arranging turbulent structures in the first channel and the third channel and assigning different functions, not only can the airflow angle in the reaction gas flow be changed and the disturbance of the reaction gas be enhanced, thereby effectively improving the mass transfer capacity of the reaction gas to the gas diffusion layer, but also the disturbance is enhanced and the heat transfer boundary layer is destroyed, 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, poor mass transfer performance, and excessive loss of water in the membrane electrode and the occurrence of dry film phenomenon in existing air-cooled fuel cells.

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

[0015] As a further preference, the ratio of the sum of the cross-sectional areas of the second channel and the third channel 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 preference, the cross-sectional area of ​​the second channel perpendicular to the gas flow direction is greater than the cross-sectional area 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 further preferred, the height difference H between the structural upper surface of the first channel and the structural upper surface of the third channel is preferably designed to be greater than 0.12 mm.

[0018] As a further preference, the horizontal distance D at the connection between the first channel and the third channel is preferably designed to be greater than 0.2 mm.

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

[0020] As a further preference, the cross section of the first channel is preferably designed as a special-shaped structure, and the cross section of the second channel is preferably designed as a trapezoidal structure.

[0021] As a further preference, the third channel is preferably formed by enclosing 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, which is 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; 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 general, the above technical solution conceived by the present invention has the following technical advantages compared with the prior art:

[0024] (1) The present invention fully combines the working characteristics and specific needs of air-cooled fuel cells, and through research and improvement of the overall structure of the cathode 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;

[0025] (2) The present invention also studies and improves the configuration and different functions of the flow disturbance structure as another key component. Not only can the flow angle in the reaction gas flow channel be changed and the disturbance of the reaction gas be enhanced, thereby improving the mass transfer capacity of the reaction gas to the gas diffusion layer, but the retention disturbance can also be enhanced in the auxiliary cooling flow 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. 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] (4) The cathode plate of the present invention has a compact structure and is easy to process and manufacture. The spoiler structure can be processed and formed in one step. Compared with the prior art, it can simultaneously solve the technical problems of insufficient heat dissipation capacity, poor mass transfer performance, and dry film phenomenon caused by rapid water loss of the membrane electrode in the existing air-cooled fuel cell, effectively improving the power generation efficiency and operating stability of the air-cooled fuel cell, thereby ensuring further improvement in the overall performance of the air-cooled fuel cell. 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 structural schematic diagram of a preferred embodiment of the present application that includes a first channel, a second channel, a third channel and a spoiler structure;

[0030] Figure 3 is a schematic diagram for exemplarily representing some key processing parameters of the first channel and the third channel;

[0031] Throughout the 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-spoiler structure. DETAILED DESCRIPTION

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] As analyzed in the previous "Background Technology" section, the bipolar plates of air-cooled fuel cells in the prior art cannot properly and simultaneously solve the technical problems of insufficient heat dissipation capacity, poor mass transfer performance and membrane electrode dry membrane. The present invention studies and improves the overall structural composition of the cathode plate, especially the setting method and working mechanism of the auxiliary cooling flow field and the 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 is a schematic diagram of the overall structure of the cathode plate of the air-cooled fuel cell provided in this application, Figure 2 It is a structural schematic diagram of a preferred embodiment of the present application which includes a first channel, a second channel, a third channel and a spoiler structure.

[0040] like Figure 2As shown in, 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, wherein the cathode reaction gas flow field is provided with a first channel 1 comprising a plurality of air flow channels for supplying air as a cathode reactant; the main cooling flow field is provided with a second channel 2 comprising a plurality of main cooling flow channels, and the auxiliary cooling flow field is provided with a third channel 3 comprising at least one auxiliary cooling flow channel, respectively for supplying air that also serves as a cooling medium; wherein 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 turbulent flow structure 4 is provided in each of the first channel 1 and the third channel 3, and the turbulent flow structure is used in the first channel 1 to enhance the disturbance and change the airflow angle of the cathode reactant and enhance the disturbance, thereby improving the mass transfer capacity of the cathode reactant to the gas diffusion layer, and at the same time in the third channel 3 to enhance the disturbance and increase 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 can preferably be bent, stamped, etc. to generate a plurality of cathode air channels, main cooling channels, and auxiliary cooling channels, thereby forming a first channel, a third channel, and a third channel, respectively. Among them, the cross section of the first channel is, for example, a special-shaped structure, the cross section of the second channel is, for example, a trapezoidal structure, and the third channel can preferably be formed by the boundaries of the first channel and the second 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 air-cooled fuel cell stack is assembled. In addition, both ends of the above-mentioned first channel, second channel, and third channel are directly connected to the external environment.

[0042] 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, through the design of auxiliary cooling channels, the overall cross-sectional area of ​​the second channel, that is, all air flow channels, perpendicular to the air flow direction is reduced, thereby reducing the cross-sectional area of ​​the air flow channel and increasing the flow resistance, reducing the air flow rate and flow rate participating 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 further improving the performance of the air-cooled fuel cell; on the other hand, through the design of auxiliary cooling channels, the fourth channel and the third channel cooperate with each other to increase the flow area of ​​the cooling medium and enhance the disturbance, thereby further improving the heat dissipation performance accordingly.

[0043] In addition, by arranging turbulent structures in the first channel and the third channel and assigning different functions, not only can the airflow angle in the reaction gas flow be changed and the disturbance of the reaction gas be enhanced, thereby effectively improving the mass transfer capacity of the reaction gas to the gas diffusion layer, but also the disturbance is enhanced and the heat transfer boundary layer is destroyed, 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, poor mass transfer performance, and excessive loss of water in the membrane electrode and the occurrence of dry film phenomenon in existing air-cooled fuel cells, and ultimately effectively improve the power generation efficiency and operation stability of the air-cooled fuel cell.

[0044] like Figure 3 As shown in, 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 greater than the cross-sectional area of ​​the third channel 3 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.

[0046] 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.

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

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

[0049] 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 first channel, which leads to insufficient cathode reaction gas supply.

[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, on the one hand, by designing auxiliary cooling channels, the heat exchange area of ​​the cooling fluid is increased; on the other hand, by setting a turbulent structure in the auxiliary cooling channel, the disturbance is enhanced to destroy the heat transfer boundary layer, thereby enhancing the heat dissipation performance of the air-cooled fuel cell and improving the performance of the air-cooled fuel cell.

[0052] Secondly, the present invention can enhance the mass transfer capacity of the air-cooled fuel cell by providing a turbulent flow structure in the cathode reaction gas flow channel of the air-cooled fuel cell, changing the air flow angle in the reaction gas flow channel and enhancing the disturbance of the reaction gas, thereby improving the mass transfer capacity 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 flow channel in the cathode reaction gas flow channel of the air-cooled fuel cell, thereby reducing the cross-sectional area of ​​the reaction gas flow channel and increasing the flow resistance, thereby reducing the air flow rate and flow rate participating in the electrochemical reaction, reducing the excess air carrying away the water generated by the electrochemical reaction, and improving the moisturizing capacity of the membrane electrode, thereby further improving the performance of the air-cooled fuel cell.

[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. An air-cooled fuel cell cathode plate with enhanced heat and mass transfer and moisturizing effects, characterized in that: 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 first channel (1) 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 second channel (2) comprising a plurality of main cooling flow channels, and the auxiliary cooling flow field is provided with a third channel (3) comprising at least one auxiliary cooling flow channel for allowing air serving as a cooling medium to flow; wherein 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 flow disturbance structure (4) is provided in each of the first channel (1) and the third channel (3). The flow disturbance structure is used in the first channel (1) to enhance the disturbance and change the air flow angle of the cathode reactant and enhance the disturbance, thereby improving the mass transfer capacity of the cathode reactant to the gas diffusion layer, and is used in the third channel (3) to enhance the disturbance and increase the fluid heat exchange area of ​​the cooling medium, thereby improving the heat transfer capacity.

2. The air-cooled fuel cell cathode plate according to 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 according to claim 1 or 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 preferably designed to be in the range of 1.5 to 5:

1.

4. The air-cooled fuel cell cathode plate according to any one of claims 1 to 3, characterized in that: Compared with the cross-sectional area of ​​the second channel (2) perpendicular to the gas flow direction and the cross-sectional area of ​​the third channel (3) 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 cathode plate according to claim 3 or 4, characterized in that: The height difference H between the structural upper surface of the first channel (1) and the structural upper surface of the third channel (3) is preferably designed to be greater than 0.12 mm.

6. The air-cooled fuel cell cathode plate according to any one of claims 3 to 5, characterized in that: The horizontal distance D between the first channel (1) and the third channel (3) at the connection point is preferably designed to be greater than 0.2 mm.

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

8. The air-cooled fuel cell cathode plate according to any one of claims 1 to 7, characterized in that: The cross section of the first channel (1) is preferably designed as a special-shaped structure, and the cross section of the second channel (2) is preferably designed as a trapezoidal structure.

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