Air-cooled fuel cell stack and method for testing temperature and humidity of cathode flow field thereof

Abstract

The application discloses a kind of air-cooled fuel cell stacks and its cathode flow field temperature and humidity test method, it is related to fuel cell field, including shell, shell inside movable installation has lower end plate and upper end plate, lower end plate and upper end plate mutually close side are movably installed with insulating plate, two insulating plates mutually close side movably installs with current collecting plate, fixedly installed with cover plate on the current collecting plate located bottom side, cover plate and the current collecting plate between top side movably installs with multiple bipolar plate.The application can replace cathode flow field structure without disassembling stack, cathode flow field is not fixed, different flow field can be selected for different use environment, for stack experiment, since not disassembling stack, multiple experiments can ensure that other operating conditions in stack are not affected;When disassembling, such as assembly force change, air impurities and other conditions interference are introduced.

Description

Technical Field

[0001] This invention relates to the field of fuel cell technology, and in particular to a stack of an air-cooled fuel cell and a method for testing the temperature and humidity of its cathode flow field. Background Technology

[0002] A fuel cell is a chemical device that directly converts the chemical energy of fuel into electrical energy; it is also known as an electrochemical generator.

[0003] In existing technologies, replacing the cathode flow field of a fuel cell requires cumbersome disassembly of the bipolar plates. The fixed cathode flow field of the bipolar plates makes it difficult to meet the usage requirements of the cathode bipolar plates under all operating conditions. For experimental testing, it is impossible to guarantee that the force on the stack is consistent after each disassembly of the stack, which leads to errors. Replacing the cathode flow field bipolar plates requires reprocessing, which is costly. Existing humidity testing modules are bulky, difficult to arrange in narrow flow channels, and expensive. Therefore, there is a need for a method to test the temperature and humidity of the cathode flow field of an air-cooled fuel cell stack and its cathode flow field to meet people's needs. Summary of the Invention

[0004] The purpose of this invention is to provide a method for testing the temperature and humidity of the cathode flow field of an air-cooled fuel cell stack, in order to solve the problems mentioned in the background art, such as the cumbersome disassembly of bipolar plates when the cathode flow field of a fuel cell needs to be replaced, the fixed cathode flow field of the bipolar plates making it difficult to meet the usage requirements of the cathode bipolar plates under all operating conditions, the inability to ensure consistent stress on the stack after each disassembly in experimental testing of different flow fields of the air-cooled stack due to errors, the need for reprocessing when replacing the cathode flow field bipolar plates, the high cost, and the large size of existing humidity testing modules, which are difficult to arrange in narrow flow channels and are also expensive.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a stack of an air-cooled fuel cell and a method for testing the temperature and humidity of its cathode flow field, comprising a shell, wherein a lower end plate and an upper end plate are movably installed inside the shell, an insulating plate is movably installed on the side of the lower end plate and the upper end plate that are close to each other, a current collector is movably installed on the side of the two insulating plates that are close to each other, a cover plate is fixedly installed on the current collector located on the bottom side, and a plurality of bipolar plates are movably installed between the cover plate and the current collector located on the top side.

[0006] Preferably, the bipolar plate has multiple wedge-shaped openings on its bottom side and a through groove on its top side, with flow field blocks movably installed in each of the multiple wedge-shaped openings.

[0007] Preferably, test contacts and heating blocks are fixedly installed on the inclined surface of the flow field block, and the two test contacts and heating blocks are a pair.

[0008] Preferably, a membrane electrode is movably installed between two adjacent bipolar plates, and the specifications of the membrane electrode are the same as those of the bipolar plates.

[0009] Preferably, two inlet / outlet ports are fixedly installed on the top side of the upper end plate.

[0010] Preferably, a fan is fixedly mounted on the side of the housing.

[0011] Preferably, the bipolar plate has a 1x1mm inspection socket.

[0012] Preferably, the measurement unit, composed of test contacts and heating blocks arranged on the first and second flow field blocks, can measure the cathode temperature and humidity distribution inside the fuel cell stack. The principle is as follows:

[0013] The flow channel region is divided into a flow test area and a flow field area. The flow test area is located at the airflow inlet and is not in direct contact with the MEA. There is no water or heat generated by the electrochemical reaction that changes the temperature and humidity of this area. Therefore, the temperature and humidity here are approximately the ambient temperature and humidity. The specific heat capacity of the air under these conditions can be directly obtained from a table. Thus, the following formula is obtained:

[0014] Q=C×Qm×ΔT(1)

[0015] In the above formula, Q is the heat generated, which is determined by the power of the selected heating element and is a known quantity per unit time. The specific heat capacity C can be obtained by looking up a table of ambient temperature and humidity. ΔT is the temperature difference between the two thermocouples. At this time, the gas mass flow rate Qm in each flow channel can be calculated.

[0016] As can be seen from Formula 1, the gas mass flow rate Qm in each flow channel has been obtained, the temperature difference ΔT is a known quantity, and the local temperature T is also measured by thermocouples. Therefore, the specific heat capacity at different locations in different flow channels can be calculated, and the local humidity can be obtained by looking up the table.

[0017] The beneficial effects of this invention are:

[0018] In this invention, the cathode flow field structure can be replaced without disassembling the fuel cell stack. The cathode flow field is not fixed, and different flow fields can be selected for different operating environments. For fuel cell stack experiments, since the fuel cell stack does not need to be disassembled, it can be ensured that other operating conditions inside the fuel cell stack are not affected by conditions such as changes in assembly force and air impurities introduced during disassembly during multiple experiments.

[0019] In this invention, the flow field architecture can be arbitrarily changed for the same bipolar plate, reducing the cost of repeatedly designing and processing bipolar plates. The flow field structure does not participate in current collection and does not affect the internal resistance and stress conditions of the fuel cell stack.

[0020] In this invention, the temperature distribution, humidity distribution and gas mass flow rate inside the cathode flow field of an air-cooled fuel cell stack can be measured using low-cost small heating elements and thermocouples. Attached Figure Description

[0021] Figure 1 This is a three-dimensional structural schematic diagram of the stack of an air-cooled fuel cell and its cathode flow field temperature and humidity testing method proposed in this invention.

[0022] Figure 2 This is a side view of the stack of an air-cooled fuel cell and its cathode flow field temperature and humidity testing method proposed in this invention.

[0023] Figure 3 This is a schematic diagram of the membrane electrode assembly of a stack of an air-cooled fuel cell and its cathode flow field temperature and humidity testing method proposed in this invention.

[0024] Figure 4 This is a schematic diagram of the wedge-shaped opening portion of the stack of an air-cooled fuel cell and its cathode flow field temperature and humidity testing method proposed in this invention.

[0025] Figure 5 This is a schematic diagram of the bipolar plate portion of the stack of an air-cooled fuel cell and its cathode flow field temperature and humidity testing method proposed in this invention.

[0026] Figure 6 This is a schematic diagram of the flow field block portion of the stack of an air-cooled fuel cell and its cathode flow field temperature and humidity testing method proposed in this invention.

[0027] In the diagram: 100, outer casing; 200, lower end plate; 201, upper end plate; 202, inlet / outlet; 203, insulating plate; 300, current collector; 301, cover plate; 302, bipolar plate; 303, wedge-shaped opening; 304, through slot; 305, flow field block; 306, membrane electrode; 307, test contact; 308, heating block; 400, fan. Detailed Implementation

[0028] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0029] Reference Figure 1-6A stack of an air-cooled fuel cell and a method for testing the temperature and humidity of its cathode flow field are disclosed. The stack includes a housing 100. A lower end plate 200 and an upper end plate 201 are movably installed within the housing 100. Insulating plates 203 are movably installed on the sides of the lower and upper end plates 201 that are close to each other. A current collector 300 is movably installed on the side of the two insulating plates 203 that are close to each other. A cover plate 301 is fixedly installed on the current collector 300 located on the bottom side. Multiple bipolar plates 302 are movably installed between the cover plate 301 and the current collector 300 located on the top side. The main body of the cold fuel cell cathode bipolar plate is designed to be separate from the flow field, and the flow field is detachable. The fuel cell cathode bipolar plate and the flow field block adopt a counter-current wedge design. The bipolar plates use separate sealing rings, and the flow field block uses a method for quantitatively measuring temperature and humidity. The bipolar plate features test module wiring slots to control the temperature and gas flow rate in each channel. The design separates the flow field from the fuel cell stack, allowing for easy and flexible modification of the air-cooled fuel cell stack flow field. The flow field block can be directly extracted and replaced without disassembling the stack. The wedge-shaped inlet, from wide to narrow, aligns with the airflow direction, creating a self-locking effect during operation and preventing flow field detachment from affecting stack performance. The bipolar plate has 1x1mm inspection holes for direct insertion of inspection lines to test single-cell voltage. The flow field block has two thermocouple holes and one small heating element hole, allowing for the measurement of local temperature data. Simultaneously, the temperature difference between the two thermocouples on each test module can qualitatively characterize humidity changes. The wiring slots are non-through to prevent airflow loss from the fan.

[0030] In an optional embodiment: the bipolar plate 302 has a plurality of wedge-shaped openings 303 on its bottom side and a through groove 304 on its top side, and a flow field block 305 is movably installed in each of the plurality of wedge-shaped openings 303.

[0031] It should be noted that the cathode flow field block designed according to the requirements is inserted into different sockets along the wedge-shaped socket according to the designed cathode flow field requirements to complete the fuel cell stack assembly, so as to meet the requirements of different operating conditions or experimental schemes for the cathode flow field of the fuel cell stack. At the same time, the direction from the wide opening to the narrow opening of the wedge-shaped socket is in the direction of airflow. During use, the wind force will produce a self-locking effect to prevent the movement of the flow field block from interfering with the performance of the fuel cell stack.

[0032] In an optional embodiment: test contacts 307 and heating blocks 308 are fixedly installed on the inclined surface of the flow field block 305, and the two test contacts 307 and heating blocks 308 are a pair.

[0033] It should be noted that the flow field block has two thermocouple sockets and one small heating element socket, and local temperature data can be measured by reading the values.

[0034] In an optional embodiment, a membrane electrode 306 is movably mounted between two adjacent bipolar plates 302.

[0035] In an optional embodiment, two inlet / outlet nozzles 202 are fixedly installed on the top side of the upper end plate 201.

[0036] In an optional embodiment, a fan 400 is fixedly mounted on the side of the housing 100.

[0037] It should be noted that the fan is fixed to the housing with bolts, and then the housing is fixed to the end plate with threads.

[0038] In an optional embodiment, the bipolar plate 302 has a 1x1mm inspection socket.

[0039] It should be noted that the bipolar plate has a 1x1mm inspection socket, which makes it convenient to directly insert the inspection line to test the voltage of a single battery.

[0040] In an optional embodiment: the measuring unit composed of the test contact 307 and the heating block 308 arranged on the first flow field block 305 and the second flow field block can measure the cathode temperature distribution and humidity distribution inside the fuel cell stack. The principle is as follows:

[0041] The flow channel region is divided into a flow test area and a flow field area. The flow test area is located at the airflow inlet and is not in direct contact with the MEA. There is no water or heat generated by the electrochemical reaction that changes the temperature and humidity of this area. Therefore, the temperature and humidity here are approximately the ambient temperature and humidity. The specific heat capacity of the air under these conditions can be directly obtained from a table. Thus, the following formula is obtained:

[0042] Q=C×Qm×ΔT(1)

[0043] In the above formula, Q is the heat generated, which is determined by the power of the selected heating element and is a known quantity per unit time. The specific heat capacity C can be obtained by looking up a table of ambient temperature and humidity. ΔT is the temperature difference between the two thermocouples. At this time, the gas mass flow rate Qm in each flow channel can be calculated.

[0044] As can be seen from formula (1), the gas mass flow rate Qm in each flow channel has been obtained, the temperature difference ΔT is a known quantity, and the local temperature T is also measured by thermocouples. Therefore, the specific heat capacity at different locations in different flow channels can be calculated, and the local humidity can be obtained by looking up the table.

[0045] Working principle of this invention:

[0046] Install the main body of the fuel cell stack: The fuel cell stack is installed in the following order: air inlet end plate - insulation plate - current collector plate - multiple single cell units (bipolar plate - membrane electrode - bipolar plate) - current collector plate - insulation plate - blind end plate, with the middle sealed by a sealing ring and fastened with bolts;

[0047] Install the fan: Secure the fan to the housing with bolts, and then secure the housing to the end plate with threads;

[0048] Insertion flow field structure: The cathode flow field block designed according to the requirements is inserted into different sockets along the wedge-shaped socket according to the designed cathode flow field requirements to complete the fuel cell stack assembly, so as to meet the requirements of different operating conditions or experimental schemes for the cathode flow field of the fuel cell stack. At the same time, the direction from the wide opening to the narrow opening of the wedge-shaped socket is in the direction of airflow. During use, the self-locking effect is generated due to the wind force. The movement of the wall flow field block will interfere with the performance of the fuel cell stack.

[0049] Other structural installations: Insert inspection lines, air pipes, and other external equipment;

[0050] The air-cooled fuel cell cathode bipolar plate features a design that separates the main body from the flow field, allowing for detachment of the flow field. The fuel cell cathode bipolar plate and flow field block employ a counter-flow wedge design. The bipolar plate uses a separate sealing ring, while the flow field block allows for quantitative measurement of temperature, humidity, and gas flow velocity in each channel. The bipolar plate has test module wiring channels, separating the flow field from the fuel cell stack. This design allows for easy and convenient modification of the air-cooled fuel cell stack flow field. The flow field block can be directly removed and replaced without disassembling the stack. Furthermore, the wedge-shaped inlet's wide-to-narrow direction aligns with the airflow, creating a self-locking effect during operation and preventing flow field detachment from affecting stack performance. The bipolar plate has 1x1mm inspection holes for direct insertion of inspection lines to test single-cell voltage. The flow field block has two thermocouple holes and one small heating element hole, allowing for the measurement of local temperature data. Simultaneously, the temperature difference between the two thermocouples on each test module can qualitatively characterize humidity trends. The wiring channels are non-through to prevent airflow loss from the fan.

[0051] The cathode flow field structure can be changed without disassembling the fuel cell stack, saving tedious disassembly work. At the same time, since the fuel cell stack does not need to be disassembled, there is no force interference or external impurity interference to the fuel cell stack during the disassembly process, which enhances the performance stability of the fuel cell stack and is of great benefit to the use and experimental comparison of the fuel cell stack.

[0052] Because air-cooled fuel cell stacks have poor thermal stability and airflow distribution uniformity, they require high-quality cathode flow fields. Even the flow field structure at different locations of the bipolar plate has different requirements. Therefore, in cathode design and experimentation, it is necessary to repeatedly design and manufacture different bipolar plates to verify the rationality of the design and optimize the cathode structure, which imposes a huge cost burden on design and manufacturing. Therefore, adopting a cathode-separated design only requires one bipolar plate of the fuel cell stack and a matching flow field block, which can verify and optimize different flow field distribution designs, greatly reducing R&D costs.

[0053] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A stack of an air-cooled fuel cell, comprising a casing (100), characterized in that: A lower end plate (200) and an upper end plate (201) are movably installed inside the outer casing (100). An insulating plate (203) is movably installed on the side of the lower end plate (200) and the upper end plate (201) that are close to each other. A current collector (300) is movably installed on the side of the two insulating plates (203) that are close to each other. A cover plate (301) is fixedly installed on the current collector (300) located on the bottom side. Multiple bipolar plates (302) are movably installed between the cover plate (301) and the current collector (300) located on the top side. The bipolar plate (302) has multiple wedge-shaped openings (303) on its bottom side and a through groove (304) on its top side. Flow field blocks (305) are movably installed in each of the multiple wedge-shaped openings (303). Test contacts (307) and heating blocks (308) are fixedly installed on the inclined surfaces of the flow field blocks (305). Two test contacts (307) and heating blocks (308) are a pair. A membrane electrode (306) is movably installed between two adjacent bipolar plates (302), and the specifications of the membrane electrode (306) are the same as those of the bipolar plates (302); Two inlet / outlet nozzles (202) are fixedly installed on the top side of the upper end plate (201). A fan (400) is fixedly mounted on the side of the housing (100). The bipolar plate (302) has a 1x1mm inspection socket.

2. A method for testing the temperature and humidity of the cathode flow field in a fuel cell stack as described in claim 1, characterized in that: The temperature and humidity distribution of the cathode inside the fuel cell can be measured by the measurement unit consisting of the test contact (307) and the heating block (308) set on the flow field block (305). The principle is as follows: The flow channel region is divided into a flow test area and a flow field area. The flow test area is located at the airflow inlet and does not directly contact the MEA. There is no water or heat generated by electrochemical reactions that alters the temperature and humidity of this area. Therefore, the temperature and humidity here are approximately the ambient temperature and humidity. The specific heat capacity of the air under these conditions can be obtained directly from the table using the following formula: Q = C × Qm × ΔT (1) In the above formula, Q is the heat output, which is determined by the power of the selected heating element and is a known quantity per unit time. The specific heat capacity C can be obtained by looking up a table of ambient temperature and humidity. ΔT is the temperature difference between the two thermocouples, and Qm is the gas mass flow rate.

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