Heat Transfer Analysis And Parametric Study Of Charge-Discharge Cycle In Compressed Hydrogen Storage Tank

Hydrogen fuel cell vehicles are one of the important development directions of automotive electricization in the world,and hydrogen energy storage is one of the vital technologies.At present,compressed hydrogen storage is the most widely used method of on-board hydrogen storage in the world.The lumped parameter model studied in this paper is based on the simulation analysis of the actual charge-discharge cycle of compressed hydrogen storage tanks.Through research,it is found that the heat transfer coefficient calculated by the empirical formula can better simulate the thermal effect during the actual charge-discharge cycle of the compressed hydrogen storage tank.Firstly,based on the change of heat transfer characteristics of compressed hydrogen storage tank during charge-discharge cycle,and combined with mass conservation equation,momentum conservation equation,energy conservation equation and state equation of real gas,the theory model of charge-discharge cycle of compressed hydrogen storage tank is established.According to whether the tank wall of the compressed hydrogen storage tank system is considered,the model is divided into a single-zone single-temperature(hydrogen zone,hydrogen temperature)model,a dual-zone dual-temperature(hydrogen zone and tank wall zone,hydrogen temperature and tank wall temperature)model and triple-zone triple-temperature(hydrogen zone,tank wall liner zone and tank wall shell zone,hydrogen temperature,tank wall liner temperature and tank wall shell temperature)model.The lumped parameter models of single zone,dual zone and triple zone were built in MATLAB/Simulink,and the numerical solutions of each model were obtained.The analytical solutions of single zone and dual zone models were obtained by formula derivation.The distributed parameter model of dual zone was built in COMSOL and the numerical solution is obtained.Then the average mass flow rate and the average heat transfer coefficient were substituted into the single zone,dual zone and triple zone models,and the simulation results were compared with the experimental data to verify the feasibility of the lumped parameter model.Secondly,based on the dual zone lumped parameter model,the heat transfer during the charge-discharge cycle of compressed hydrogen storage tanks is analyzed in the paper.And the convective heat transfer between hydrogen and tank wall during filling,holding and defueling are mainly researched.And the relationship between the Nusselt number which can be used to reflect the convective heat transfer intensity and the heat transfer coefficient is obtained.The main convective heat transfer form in filling process is forced convection,which is related to the Reynolds number and the Prandtl number.And the main convective heat transfer form in the holding and the defueling process is natural convection which is related to the Prandtl number and the Grashof number.Then the heat transfer coefficients calculated based on the energy conservation equation or the empirical formula are respectively substituted into the dual zone lumped parameter model,which verifies that the simulated value of the empirical formula method is more consistent with the experimental value and the optimized model is obviously better than the model which uses average mass flow rate and average heat transfer coefficient to simulated.Finally,based on the lumped parameter model,the effects of various parameters on the thermal effects of the compressed hydrogen storage tank during the chargedischarge cycle are studied in the paper.,including initial conditions(filling temperature,mass flow rate,ambient temperature,initial pressure and initial temperature)and hydrogen tank structural parameters(the type of hydrogen tank and the size of hydrogen tank).Then,it is concluded that pre-cooling filling temperature,reducing the mass flow rate and increasing the initial pressure can well reduce the hydrogen temperature during the charge-discharge cycle of the compressed hydrogen storage tank.Through research,it is found that the heat transfer coefficient calculated by the empirical formula can better simulate the thermal effect during the actual chargedischarge cycle of the compressed hydrogen storage tank.