Study On Temperature Distribution Law In Solid Oxide Fuel Cell Based On Heat Preservation Method

With the increasingly serious environmental and energy problems,Solid Oxide Fuel Cell(SOFC),as a clean and efficient energy conversion device,also has the advantages of strong fuel adaptability,all-solid-state and modularity,and has gradually become the focus of research in the era of energy transition.However,the working temperature of SOFC is high(usually 600-800 °C),and in the process of SOFC application,due to uneven heat transfer and material property differences,the temperature distribution in the cell is uneven,resulting in thermal stress,which restricts the stability and durability of SOFC.Therefore,it is necessary to study the temperature distribution law and its constraints in SOFC,which provides a reference for the optimal design of temperature field in SOFC application process.In this thesis,a new test method is proposed for the experimental characterization of the temperature distribution law during SOFC preheating and stable operation,and then the temperature distribution law in the SOFC single cell and the three-piece short stack is experimentally characterized by this method,and the main work content and conclusions are as follows:First of all,aiming at the problem that there is a huge gap between the internal temperature field of the cell and the actual stack operation when the electric furnace is used to maintain the working temperature during the SOFC single cell and short stack test,this thesis proposes a test method for cell insulation through heat transfer analysis,in order to obtain the temperature distribution law in the actual stack by single cell or short stack test.Based on this method,the SOFC single cell and short stack temperature distribution test bench was built,and the arrangement of the assembly and test thermocouple of the large-size single cell and the three-piece short stack was completed,and the experimental results showed that the performance output of the large-size single cell and short stack of the experimental system was acceptable,and the insertion of the thermocouple had little effect on the cell performance.Then,based on the test method of cell insulation,the temperature distribution law of SOFC single cell and short stack during stable operation is experimentally studied,and the temperature distribution law of flat SOFC single cell and short stack during stable operation is studied by combining experimental parameters such as current density,flow field structure and air excess coefficient.The experimental results show that the overall temperature rise of SOFC single cell and short stack increases significantly before and after the insulation method,and when the single cell is discharged at 24 A constant current,the average temperature in the cell is about10 °C and 30 °C higher than the furnace temperature,respectively,which indicates that the external insulation of the cell can effectively reduce the heat transfer between the cell and the furnace,reduce the influence of the electric furnace on the temperature distribution in the cell,and it is expected to obtain a temperature distribution law similar to that in the actual stack.When the short stack is discharged at 30 A,the overall temperature rises by about 100°C,so the actual stack may have a temperature much higher than the expected temperature during the application process,which shows the importance of temperature monitoring and cell thermal management for the stable operation of SOFC stacks.After that,the heating law of SOFC short stack during the preheating process was experimentally studied by means of heat preservation,and the SOFC preheating rate and temperature distribution of the preheating process were analyzed by combining the parameters such as the preheating gas heating rate(furnace heating rate)and the amount of preheating gas.The experimental results show that when the thermal insulation method is used and the hot air preheating short stack is introduced,the cell heating curve is "S" shaped,that is,the heating trend is slow first,then fast and finally approaching,which is similar to the heating curve of the hot gas preheating cell obtained by numerical simulation in the literature,indicating that the insulation method proposed in this thesis can be used to study the internal temperature rise and temperature distribution law of the pile using the hot gas preheating method,especially in the initial stage and the final imminent stage.Finally,a numerical model of flat plate SOFC unit is established,and the influence of manifold thickness on the temperature distribution in SOFC is studied based on this model.The numerical simulation results show that with the increase of the thickness of the manifold,the temperature gradient in the cell gradually decreases,except for the gas inlet area,there is still a large temperature gradient,the temperature gradient in other areas of the cell gradually decreases,and the temperature curve along the length of the cell gradually flattens.When the current collector thickness is increased from 0.6mm to 18.0mm,the temperature difference from the center area of the cathode and anode flow channel to the gas outlet area of the cell is reduced from25 K to 5K,and the maximum temperature of the cell is also reduced from 1125 K to1088K;combined with the experimental test results,the thickness of the test cell manifold is large(18.0mm),which may affect the temperature test.