Simulation Research On PEMFC And Thermal Management System

In recent years,the proton exchange membrane fuel cell has developed rapidly and is one of the most promising new energy sources in the future.PEMFC is not only clean and efficient,products are pollution-free,but also has the characteristics of high endurance and high energy density.However,due to the physical and chemical characteristics of PEMFC,the freezing of residual liquid water inside the battery in a low-temperature environment will easily lead to cold start failure,and even directly destroy the proton exchange membrane.In a high-temperature environment,the battery’s operating temperature is too high,which will easily reduce the battery performance or even damage the proton exchange membrane.Therefore,the thermal management performance of PEMFC has become an important factor restricting the output performance and life of the battery.To ensure the successful cold start of PEMFC under a low-temperature environment and improve the high-temperature heat dissipation performance of the thermal management system,this paper mainly focuses on the modeling and thermal management system of PEMFC as follows:(1)First,according to the geometric model and mathematical model of PEMFC,physical fields such as hydrogen fuel cell,solid and fluid heat transfer,cathode and anode free and porous media flow,and laminar flow were introduced for coupling using COMSOL software to establish a three-dimensional non-isothermal PEMFC model.In this model,the cathode transfer coefficient that affects the current density and the empirical parameters that affect gas diffusion in porous media were corrected,and the simulation results and test results of the fuel cell model were calibrated as the basis for follow-up research.(2)Then,the distribution of the liquid water content generated by the battery under different working conditions was studied,and the influence of different transfer coefficients and effective diffusion coefficients on the formation of liquid water was analyzed.To solve the problem of cold start failure of PEMFC due to freezing of liquid water in a low-temperature environment,a two-dimensional non-isothermal porous medium evaporation model of the PEMFC cathode was established using COMSOL software to study the effect of dry air at different speeds and temperatures and porosity on the effect of residual liquid water purging.A two-dimensional non-isothermal porous medium ice melting model of PEMFC cathode was established to study the influence of gas and coolant with different speeds and temperatures on the heating and deicing effect.The optimal purging and auxiliary heating programs were obtained by combining energy consumption,start-up time,and control costs.(3)Finally,the influence of different coolant temperatures on the output performance of PEMFC was analyzed.Based on the geometric model of the tube-strip radiator,a three-dimensional CFD simulation model of the heat exchange core of the radiator was established.According to the actual parameters and boundary conditions of the radiator wind tunnel test,the model was simulated and calculated by Fluent software and compared with the test results for verification.The accurate and reliable model was selected from 12 CFD models for the next calculation and analysis.Further,the heat transfer factor,friction factor,and comprehensive factor were analyzed by changing the window angle,fin spacing,and wind speed to find out the best parameters of heat dissipation performance,and the structure of the radiator was optimized to improve the high-temperature heat dissipation capacity of the battery thermal management system.Thereby the performance and life of PEMFC in high-temperature environments were improved.