Thermal stratification and self-pressurization in a cryogenic propellant storage tank considering capillary effect in low-gravity

Thermal stratification and self-pressurization in a propellant storage tank due to heat leakage from the wall are key issues of space fluid management. Under low-gravity conditions, the gas/liquid two-phase flow in a tank is complicated owing to the irregular interface morphology caused by the capillary effect. To clarify the heat and mass transfer process, the gas/liquid two-phase flow with the capillary effect accounted at the interface is systematically investigated by taking into account the volume of fluid (VOF) method for two-phase capturing and the Lee model for phase change. Spatial-temporal evolutions of thermal and pressure distributions and mass transfer rates at the interface in an axisymmetric scaling capsule tank of ethanol are studied depending on various gravity levels, liquid filling ratios, and boundary heat fluxes. The results show that the overall temperature, pressure, and thermal distributions inside the tank are significantly affected by the gravity level, liquid filling ratio, and boundary heat flux, while the pressure distributions are quite similar under different conditions. The influence of gravity levels mainly originated from various interface configurations due to the capillary effect. Therefore, the capillary effect plays an important role in the heat and mass transfer process in low-gravity environments.