Thermal analysis on filling process in hydrogen tank

When hydrogen is filled into a hydrogen tank, it is considered that the gas temperature in the tank rises considerably because the gas is pressurized to very high pressure. If the ultimate pressure is constant, the gas temperature is influenced by the heat exchange between the gas and the inner wall of the tank, filling time and filling methods. In this research, a numerical analysis of heat and fluid flow has been performed to investigate the behavior of pressure and gas temperature in the tank during and after the filling process when an adiabatic wall and an isothermal wall are variously arranged for each wall that composed the hydrogen tank. As a result, it is found that using an isothermal wall for the wall of the circumference is very effective to cooling of the gas in the tank. In addition, a numerical analysis considering the heat capacity of the wall and the heat exchange between the gas and the inner wall of the tank has been performed to clarify the behavior of pressure and gas temperature in the tank and wall temperature of the tank under a more realistic condition, and to compare its result with the numerical results under the condition in which an adiabatic wall and an isothermal wall are variously arranged. As a result, it is found that the behavior of pressure and gas temperature under the more realistic condition is very similar to those under the condition in which an isothermal wall is used for the wall of the circumference, and consequently when the behavior for a short time is shown, realistic behavior in the tank can be clarified even under the condition of an isothermal wall because the change in wall temperature is very small. Finally, the change in wall temperature under the more realistic condition is shown and consequently the behavior of the small increase of the wall temperature is clarified.