Air-cooled fuel cell cathode plate and air-cooled fuel cell

Abstract

The present invention discloses an air-cooled fuel cell cathode plate, relating to the field of fuel cell technology. The cathode plate plate may include: a cathode plate body, the cathode plate body being provided with a cathode plate flow channel for air circulation; the cross-sectional area of ​​the cathode plate flow channel changes along the direction of air flow within the cathode plate flow channel. The present invention also discloses an air-cooled fuel cell including the air-cooled fuel cell cathode plate. The present invention can improve fuel cell performance without increasing material and process costs.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel cells, and in particular to an air-cooled fuel cell cathode plate and an air-cooled fuel cell. Background Art

[0002] Fuel cells are environmentally friendly, highly efficient, and long-lasting power generation devices. For example, in a proton exchange membrane fuel cell (PEMFC), fuel gas (hydrogen) enters the cell from the anode. Hydrogen atoms lose electrons at the anode and become protons. These protons then travel through the proton exchange membrane inside the cell to the cathode. Simultaneously, electrons travel through an external circuit to the cathode. At the cathode, the protons and electrons combine with oxygen to form water.

[0003] An air-cooled fuel cell is a power generation device that converts the chemical energy in fuel and oxidant directly into electrical energy through a catalytic reaction. Thermal management uses a high-performance fan as a heat sink. Currently, increasing the rated power of a single air-cooled fuel cell stack is a technical challenge for the entire industry. Due to limitations such as the thermal management boundaries of air-cooled fuel cells, the rated power of mainstream air-cooled fuel cell stacks in the domestic market is currently below 5kW, resulting in a relatively high cost for air-cooled fuel cell systems. Given existing engineering and material technologies, the system cost per kilowatt remains high.

[0004] Currently, the cathode plate flow path of conventional air-cooled fuel cells is typically a straight flow path. Both cathode reactant gas and cooling gas are supplied by fans. The reactant gas enters the catalyst layer through the cathode gas diffusion layer for reaction, and the heat generated must be reversed through the gas diffusion layer and continuously absorbed by the air. As the gas flows, the temperature in the membrane electrode increases continuously. High temperatures can easily cause the proton exchange membrane to dry out, leading to rapid degradation of fuel cell performance. To ensure the stack operates at the appropriate temperature, an excess of air is required for cooling. However, due to the low specific heat capacity of air, a very high excess coefficient is required. Summary of the Invention

[0005] The purpose of the present invention is to provide an air-cooled fuel cell cathode plate and an air-cooled fuel cell to solve the problems existing in the above-mentioned prior art and to improve the performance of the fuel cell without increasing material costs and process costs.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] The present invention provides an air-cooled fuel cell cathode plate, comprising a cathode plate body, wherein the cathode plate body is provided with a cathode plate flow channel for air circulation; the cross-sectional area of ​​the cathode plate flow channel changes along the air flow direction in the cathode plate flow channel.

[0008] Preferably, the cathode plate flow channel is a Venturi flow channel, and the Venturi flow channel includes an inlet section, a contraction section, a throat section, a diffusion section and a straight mouth section arranged in sequence along the air flow direction; wherein the inlet section, the throat section and the straight mouth section are all straight sections with the same cross-sectional area along the air flow direction, the cross-sectional area of ​​the contraction section gradually decreases along the air flow direction, and the cross-sectional area at the end of the diffusion section is larger than the cross-sectional area at the front end of the diffusion section.

[0009] Preferably, the length of the entrance section is L1, L1≤5a1, wherein a1 is the width of the entrance section.

[0010] Preferably, the contraction angle of the contraction section is λ1, and λ1≤21°.

[0011] Preferably, the length of the throat section is L2, L2≤3a2, wherein a2 is the width of the throat section.

[0012] Preferably, the diffusion section is a straight line section, and the expansion angle of the diffusion section is β, β≤7°;

[0013] Alternatively, the diffusion section is a curved section, wherein the curved section is a convex or concave curved section, and the curved section meets the following conditions:

[0014]

[0015] Where: ζ is the local loss coefficient, λ is the resistance coefficient along the way, θ is the expansion angle, K is the coefficient of the expansion angle, and A2 / A1 is the expansion area ratio.

[0016] Preferably, the length of the straight section is L3, L3≤10a3, wherein a3 is the width of the straight section.

[0017] Preferably, a plurality of cathode plate flow channels are arranged side by side on the cathode plate body, and each of the cathode plate flow channels is a cathode plate flow channel that is arranged symmetrically on the left and right.

[0018] Preferably, the cathode plate body is a graphite cathode plate or a metal cathode plate, the graphite cathode plate is a graphite cathode plate formed by CNC milling or die pressing, and the metal cathode plate can be laser welded with a metal anode plate to form a metal bipolar plate.

[0019] The present invention also provides an air-cooled fuel cell, comprising the above-mentioned air-cooled fuel cell cathode plate.

[0020] Compared with the prior art, the present invention has achieved the following beneficial technical effects:

[0021] 1. The cathode plate body of the present invention has the same manufacturing process as the conventional direct current cathode plate, without increasing the cost. By changing the cross-sectional area of ​​the cathode plate flow channel, the heat exchange efficiency is improved, the rated power point is increased, and higher economic benefits are achieved.

[0022] 2. The present invention can reduce the power of the radiator, thereby reducing the parasitic power of the entire fuel cell system and improving the efficiency of the fuel cell system.

[0023] 3. The present invention increases the gas pressure on the cathode side, increases the diffusion amount of oxygen in the gas diffusion layer, and improves the reaction efficiency of the fuel cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0025] Figure 1 This is a diagram of a single battery integration in an embodiment of the present invention;

[0026] Figure 2 A side view of a cathode plate of an air-cooled fuel cell according to an embodiment of the present invention;

[0027] Figure 3 Schematic diagram of the flow distribution of the cathode plate of an air-cooled fuel cell in an embodiment of the present invention;

[0028] Figure 4 A detailed diagram of the Venturi flow in an embodiment of the present invention;

[0029] Figure 5 is a schematic diagram of a straight diffusion section in an embodiment of the present invention;

[0030] Figure 6 Schematic diagram of a convex diffusion section in an embodiment of the present invention;

[0031] Figure 7 Schematic diagram of a concave diffusion section in an embodiment of the present invention;

[0032] Among them, 100 is the cathode plate of the air-cooled fuel cell, 101 is the cathode plate body, 102 is the Venturi flow channel, 1021 is the inlet section, 1022 is the contraction section, 1023 is the throat section, 1024 is the diffusion section, 1025 is the straight mouth section, 103 is the flow channel ridge, 104 is the anode manifold hole, 200 is the proton exchange membrane, 300 is the cathode diffusion layer, and 400 is the anode diffusion layer. DETAILED DESCRIPTION

[0033] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0034] The purpose of the present invention is to provide an air-cooled fuel cell cathode plate and an air-cooled fuel cell to solve the problems existing in the above-mentioned prior art and to improve the performance of the fuel cell without increasing material costs and process costs.

[0035] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0036] Example 1

[0037] like Figure 1-Figure 7 As shown, this embodiment provides an air-cooled fuel cell cathode plate 100, including a cathode plate body 101, on which a cathode plate flow channel for air circulation is provided; the cross-sectional area of ​​the cathode plate flow channel changes along the air flow direction in the cathode plate flow channel.

[0038] The cathode plate body 101 of this embodiment has the same manufacturing process as the conventional direct current cathode plate, without increasing the cost. By changing the cross-sectional area of ​​the cathode plate flow channel, the heat exchange efficiency is improved, the rated power point is increased, and higher economic benefits are achieved.

[0039] In this embodiment, the cathode plate flow channel is preferably a Venturi flow channel 102, or a flow channel whose cross-sectional area changes in the form of gradual contraction or gradual expansion; wherein the Venturi flow channel 102 is a flow channel made according to the Venturi effect, which is also called the Venturi effect. This phenomenon is named after its discoverer, Italian physicist Giovanni Battista Venturi. This effect is manifested in that when a restricted flow passes through a reduced flow cross-section, the flow velocity of the fluid increases, and its flow velocity is inversely proportional to the flow cross-section; and according to Bernoulli's principle, the increase in flow velocity is accompanied by a decrease in fluid pressure, which is the common Venturi phenomenon. In layman's terms, this effect refers to the generation of low pressure near a high-speed flowing fluid, thereby generating an adsorption effect. This effect can be used to make the Venturi flow channel 102.

[0040] Specifically, the Venturi flow channel 102 includes an inlet section 1021, a contraction section 1022, a throat section 1023, a diffusion section 1024 and a straight mouth section 1025, which are arranged in sequence along the air flow direction; wherein, the inlet section 1021, the throat section 1023 and the straight mouth section 1025 are all straight sections whose cross-sectional areas do not change along the air flow direction, the cross-sectional area of ​​the contraction section 1022 gradually decreases along the air flow direction, and the cross-sectional area of ​​the end of the diffusion section 1024 (the end close to the straight mouth section 1025) is larger than the cross-sectional area of ​​the front end of the diffusion section 1024.

[0041] In this embodiment, the cross-sectional area of ​​the diffuser section 1024 at the expansion end continuously increases, and the gas flow rate significantly decreases. However, since the potential function remains constant, the pressure of the gas in the converging portion continuously decreases. The gas encounters resistance in the inlet direction. Furthermore, since the gas diffuses to both sides, as it flows through the gradually expanding pipe flow channel, the gradual increase in the pipe cross-sectional area causes the flow rate to decrease along the flow direction, while the pressure increases. Furthermore, due to the influence of viscosity, near the wall, the flow rate is low, so the momentum is insufficient to overcome the reverse pressure. Consequently, backflow occurs near the wall, causing vortices and energy loss. The larger the diffusion angle of the diffuser section, the greater the energy loss caused by the vortices. This causes the gas flow pattern to gradually transform from unidirectional laminar flow to chaotic, turbulent flow in all directions. Turbulent flow allows the gas to remain in the flow channel longer and diffuse into the diffusion layer, increasing the number of molecules undergoing electrochemical reactions per unit time, thereby increasing the output power of the fuel cell. Through fluid simulation (CFD) calculations and physical verification, the rated power point of a single cell with the same reaction area can be increased by about 8.2%, thereby improving the performance of the air-cooled fuel cell.

[0042] For an incompressible fluid, the Bernoulli equation is:

[0043]

[0044] Where p is the static pressure, v is the flow velocity, Φ is the potential function, and ρ is the fluid density;

[0045] For compressible fluids, the Bernoulli equation is:

[0046]

[0047] Where p is the static pressure, v is the flow velocity, Φ is the potential function, γ is the isentropic index, and ρ is the fluid density.

[0048] In this embodiment, the length of the entrance section 1021 is L1, L1≤5a1, where a1 is the width of the entrance section 1021.

[0049] In this embodiment, the contraction angle of the contraction section 1022 is λ1, and λ1≤21°.

[0050] In this embodiment, the length of the throat section 1023 is L2, L2≤3a2, where a2 is the width of the throat section 1023.

[0051] In this embodiment, the diffusion section 1024 may be a straight line section, and the expansion angle of the diffusion section 1024 is β, β≤7°;

[0052] Alternatively, the diffusion section 1024 is a curved section, specifically, the curved section is a convex or concave curved section, wherein, Figure 6 As shown in the figure, the convex curve segment is a curve segment that bulges toward the middle on both sides, such as Figure 7 As shown, the concave curve segment is a curve segment whose middle part is concave toward both sides; further, the curve segment also meets the following conditions:

[0053]

[0054] Where: ζ is the local loss coefficient, λ is the resistance coefficient along the way, θ is the expansion angle, K is the coefficient of the expansion angle, and A2 / A1 is the expansion area ratio.

[0055] As a preferred implementation, in this embodiment, the diffusion section 1024 is preferably a straight line segment or a concave curve segment.

[0056] In this embodiment, the length of the straight section 1025 is L3, L3≤10a3, where a3 is the width of the straight section 1025.

[0057] In this embodiment, a plurality of cathode plate flow channels are arranged side by side on the cathode plate body 101 , and each of the cathode plate flow channels is bilaterally symmetrical (or mirror image) in arrangement.

[0058] In this embodiment, the cathode plate body 101 is a graphite cathode plate or a metal cathode plate. The graphite cathode plate is a graphite cathode plate formed by CNC milling or die pressing. The metal cathode plate can be laser welded with a metal anode plate to form a metal bipolar plate.

[0059] The cathode plate of the present invention can also be applied to the application scenarios of air-cooled plates of various other materials; and the present invention can be combined with improving the moisture retention rate of the cathode side gas diffusion layer to achieve improved fuel cell performance without increasing the manufacturing cost and process cost of the gas diffusion layer (GDL).

[0060] Specifically, the method for improving the moisture retention rate of the cathode side gas diffusion layer in the present invention is as follows: reducing the proportion of polymer: the carbon black paper used as the base of the gas diffusion layer is formed by uniformly dispersing carbon powder and polymer binder and then hot pressing to form a sheet with a smooth surface, wherein the mass ratio of polymer to carbon powder is between 20:80 and 45:55; the carbon powder can be selected from activated carbon, carbon black, acetylene black or a mixture thereof, and the specific surface area of ​​the carbon powder is 50m 2 / g-2000m 2 / g; the polymer can be selected from fluororesins, such as PTFE, polyvinylidene 1,1-difluoride, etc. This fluororesin can also be used as a hydrophobic treatment agent for carbon black paper, thereby simplifying the subsequent hydrophobic treatment process, reducing costs, and changing the ratio of the gas diffusion layer.

[0061] The specific working principle of the present invention is as follows:

[0062] Air enters the inlet section 1021 under the action of the radiator (fan);

[0063] As the air further reaches the contraction section 1022, the flow rate increases and the pressure decreases;

[0064] The air further reaches the throat section 1023, where the flow rate is the highest and the pressure is the lowest;

[0065] When the air further reaches the diffuser section 1024, the high-speed flow of the fluid generates a large number of vortices on both sides of the pipe, commonly known as "eddies", which generate low pressure nearby, thereby producing an adsorption effect. The media on both sides of the flow channel can have a longer retention time, thereby extending the heat exchange time and improving the heat exchange efficiency.

[0066] The air further reaches the straight opening section 1025. Under the constraint of the straight opening section 1025, the fluid changes from turbulent flow to flat flow, and the gas flows out of the flow channel, thereby minimizing the parasitic power of the entire flow channel body.

[0067] The present invention further provides an air-cooled fuel cell, comprising the above-mentioned air-cooled fuel cell cathode plate 100 .

[0068] It should be noted that it is obvious to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention. Therefore, from all perspectives, the embodiments should be regarded as illustrative and non-restrictive, and the scope of the present invention is defined by the appended claims rather than the foregoing description. It is intended that all changes that fall within the meaning and range of equivalents of the claims be included in the present invention, and any reference signs in the claims should not be construed as limiting the claims to which they relate.

[0069] The present invention uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only intended to help understand the method and core concept of the present invention. At the same time, those skilled in the art will find that the specific implementation methods and application scopes may vary based on the concept of the present invention. In summary, the contents of this specification should not be construed as limiting the present invention.

Claims

1. A cathode plate for an air-cooled fuel cell, comprising a cathode plate body, wherein the cathode plate body is provided with a cathode plate flow channel for air circulation; characterized in that: The cross-sectional area of ​​the cathode plate flow channel changes along the direction of air flow in the cathode plate flow channel; The cathode plate flow channel is a Venturi flow channel, which includes an inlet section, a contraction section, a throat section, a diffusion section, and a straight section arranged in sequence along the air flow direction; wherein the inlet section, the throat section, and the straight section are all straight sections with the same cross-sectional area along the air flow direction, the cross-sectional area of ​​the contraction section gradually decreases along the air flow direction, and the cross-sectional area at the end of the diffusion section is larger than the cross-sectional area at the front end of the diffusion section; The length of the entrance section is L1, L1≤5a1, where a1 is the width of the entrance section; The contraction angle of the contraction section is λ1, and λ1≤21°.

2. The air-cooled fuel cell cathode plate according to claim 1, characterized in that: The length of the throat section is L2, L2≤3a2, where a2 is the width of the throat section.

3. The air-cooled fuel cell cathode plate according to claim 1, characterized in that: The diffusion section is a straight line section, and the expansion angle of the diffusion section is β, β≤7°; Alternatively, the diffusion section is a curved section, wherein the curved section is a convex or concave curved section, and the curved section meets the following conditions: Where: ζ is the local loss coefficient, λ is the resistance coefficient along the way, θ is the expansion angle, K is the coefficient of the expansion angle, and A2 / A1 is the expansion area ratio.

4. The air-cooled fuel cell cathode plate according to claim 1, characterized in that: The length of the straight section is L3, L3≤10a3, wherein a3 is the width of the straight section.

5. The air-cooled fuel cell cathode plate according to claim 1, characterized in that: A plurality of cathode plate flow channels are arranged side by side on the cathode plate body, and each of the cathode plate flow channels is a cathode plate flow channel arranged symmetrically on the left and right.

6. The air-cooled fuel cell cathode plate according to claim 1, characterized in that: The cathode plate body is a graphite cathode plate or a metal cathode plate. The graphite cathode plate is a graphite cathode plate formed by CNC milling or die pressing. The metal cathode plate can be laser welded with a metal anode plate to form a metal bipolar plate.

7. An air-cooled fuel cell, characterized in that: The invention comprises an air-cooled fuel cell cathode plate as described in any one of claims 1 to 6.

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