ANALYSIS OF SELF-PRESSURIZATION PHENOMENON IN A CRYOGENIC FLUID STORAGE TANK WITH VOF METHOD

The self-pressurization phenomenon is studied numerically with the Volume of Fluid (VOF) method in a cryogenic fluid tank. Heat and mass transfer modelling is used for the phase change calculation at the interface. Transient simulations of the vaporization and pressure rise in a cylindrical liquid hydrogen tank are performed. The computations are carried out by using the CFD software package, Ansys Fluent, and an in-house developed code to calculate the source term associated with the phase change. Effects of the heat flux, fill level and gravity acceleration are investigated. Numerical results indicate that the pressure starts to rise after a certain time of sidewall heating and pressure rises gradually once the vaporization occurs. The rise rate increases as time elapses and is larger at higher heat flux at the same time. Multiple loops are observed in the fluid flow and thermal stratification is developed. The stratification degree is nearly the same for different fill levels at the same heat flux while the pressure rise rate increases as the fill fraction becomes larger. High temperature area appears when the fluid mixing becomes weaker as gravity acceleration decreases. Heat transfer turns to nucleate boiling at the wall from convection. as evaporation occurs at the interface.