Abstract Due to its high power density, the aviation sector is pushing towards its electrification by designing new propulsion systems based on cryogenic liquid hydrogen (LH2). From an engineering point of view, the efficient design of tanks constitutes one of the main challenges. They must guarantee efficient isolation of the hydrogen to avoid its evaporation and, at the same time, ensure reasonable weight and dimensions. Using numerical simulations is fundamental for studying heat transfer between the external environment and the liquid fuel. This work focuses on the simulation of multiphase liquid-gas flow to analyze the tank pressurization as a function of different external heat fluxes. A commercial CFD software is used to perform simulations. VOF simulations with the Lee mass transfer model are employed, and some critical numerical parameters are analyzed to provide information on the optimal values.