Simulation And Experimental Study On The Whole Vehicle Cooling System Of Fuel Cell Vehicle

As a new energy vehicle with great development potential,fuel cell vehicle has become one of the research and development focuses in the automotive field due to its advantages of cleanness,high efficiency and high power density.However,the heat dissipation demand of fuel cell vehicle is much larger compared to the ordinary vehicle engine,thus poses a great challenge to the design of the cooling system for it.In response to the current situation,this thesis aims to establish a simulation model of cooling system for whole fuel cell vehicle.In addition,this work investigates the optimal structural parameters of the radiator which is the important components of the cooling system to satisfy the heat dissipation performance of the proposed system.Based on the thorough analysis of the heat dissipation process of the fuel cell system and the influencing factors which affect the whole vehicle heat dissipation,this thesis establishes a simulation model for the fuel cell thermal system based on the MATLAB/Simulink platform.Through the theoretical analysis of the fuel cell vehicle cooling system,the heat dissipation requirements of the fuel cell system are calculated.Also,this thesis analyzes the influence of the fuel cell stack coolant water outlet temperature,the water flow rate allocation during system operation to the cooling system along with the variation of the radiator coolant water outlet temperature over time by combing the PID controller.Then a simulation for the radiator of the whole vehicle cooling system are conducted,the simulation model is simplified based on the actual operating conditions and structure of the radiator.Then the geometrical model of the periodic louver fins is established and the effect of louver spacing of the fins,louver thickness and louver angle on the flow and heat transfer performance to the radiator are investigated with CFD.The optimal structural parameters are obtained.a wind tunnel experiment bench is set up to investigate the performance of the radiator with two structural parameters,and the influence of different structure parameter,air flow rate and air inlet temperature to the heat transfer as well as flow resistance characteristic are analyzed.Through the study above,following conclusions can be obtained: the output voltage of fuel cell stack increases with the increment of operating temperature and the thermal power decrease with the increment of operating temperature.The demand maximum flow rate of cooling water for the designed stack is 1.8kg/s,which is much larger than the demand for intercooler 0.069kg/s.The coolant outlet temperature is in consistent with inlet temperature when the flow rate is constant,i.e.it can meet the demand for the stack heat dissipation.When the stack output current varies with a step change,the stack temperature can maintain around the optimal value 80?.The maximum output power can be 15 kW.The simulation results of radiator indicate that the flow and heat transfer performance are in better condition when the louver angle is 22°and the thickness of the lover fin is 0.15 mm.The work which have been done in this paper has a certain guiding significance for the further optimization design of the PEMFC vehicle cooling system.