Thermal Effect Simulation And Performance Prediction Of Charge-discharge Processes In Compressed Hydrogen Storage Tank

A thermodynamic analysis during charge-discharge cycle within a compressed hydrogen storage tank is presented in this manuscript,aiming to know the variation of hydrogen temperature,hydrogen pressure and wall temperature with time.Besides,the contributions of the refueling parameters on them are also investigated.The thermodynamic model is obtained on the basis of the mass balance equation and energy balance equation.In this model,the compressed hydrogen storage system is divided into two parts: one is the gas zone,and the other is the wall zone.Herein,there are two different ways to deal with the effect of tank wall.By ignoring the effect of the tank wall,a single-zone model is obtained,and the single-zone analytical solution is deduced.In the other way,by taking the effect of the tank wall into consideration,a dual-zone model is built,and the corresponding dual-zone analytical solutions can also be deduced.Besides,the Matlab/Simulink software is used to build the lumped parameter model to simulate the thermodynamic behavior,thus a single-zone simulated solution and a dual-zone simulated solution are corresponding obtained.Moreover,the Matlab/Simulink software can also research the situation where the liner and the fiber reinforced plastic composites(CFPR)are considered separately,thus a triple-zone(gas zone,liner zone and CFPR zone)lumped parameter model is built.The results of the simulated solutions can be utilized to compare with the results of the analytical solutions,Thus,the validity of the thermodynamic model can be checked.On the basis of the single-zone analytical solutions,the effects of the refueling parameters on the pre-cooling hydrogen temperature,the filling mass and the state of charge(SOC)are investigated.To avoid the hydrogen temperature exceeding the 85 C,and ensure the safety during the refueling process,the hydrogen needs to be cooled in advance.However,setting the precooling temperature becomes a critical problem.To address this issue,a new analytical solution of pre-cooling temperature from the singlezone thermodynamic model is proposed,and the function relationships between the refueling parameters(initial temperature,initial pressure and filling time)and the precooling temperature are deduced respectively.The critical conditions where the hydrogen needs to be precooled can be calculated if setting the final hydrogen temperature as 85 C.It can be draw a conclusion that the hydrogen needs to be precooled in the occasion of the real initial temperature being higher than the critical initial temperature,the real initial pressure being lower than the critical initial pressure and the real filling time being less than the critical filling time.The effects of the refueling parameters on the filling mass are also researched,the analytical solution of filling mass can be deduced from the analytical solution of hydrogen temperature,and the filling mass can be expressed as the function relationship with the mass flow rate,initial hydrogen pressure and inflow temperature.The analytical solution of filling mass is utilized to fit the reference data,thus the corresponding quantitative formulae can be determined.By assuming the hydrogen density within a hydrogen cylinder is uniform,a new analytical model on SOC is presented on the basis of the analytical solution of filling mass,the parameters in the analytical model can be determined by the least square method.When studying the two-parameters effects of mass flow rate and inflow temperature on the SOC,the Nusselt Number and Reynolds number are utilized to modify the analytical model,it turns out to be the new modified model has a good ability to fit the reference data.