Direct Numerical Simulation of Hydrogen Boiling Using a Compressible Diffuse Interface Method with an Accurate Equation of State
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Hydrogen is a promising energy carrier for the green transition, with liquid hydrogen (LH2) offering high gravimetric energy density that makes it attractive for storage, transport and non-stationary applications. However, in addition to the high liquefaction costs, heat ingress during storage and transport causes significant boil-off losses, which remains a key challenge for widespread use of LH2. While boil-off in stationary storage primarily occurs through surface evaporation, mass transfer via boiling becomes important during active pressurization and sloshing events. Detailed experimental and modelling studies of LH2 boiling remain scarce, motivating the use of direct numerical simulations (DNS) in this work to improve the fundamental understanding of boiling phenomena in LH2. In this work, we use a compressible accurate conservative diffuse interface method with mass transfer to perform direct numerical simulations of LH₂ film boiling. At atmospheric pressure, liquid hydrogen boils at approximately 20 K, where thermophysical properties exhibit strong variations, and may even approach critical conditions (12.86 bar and 32.94 K) under unexpected pressurization events. To capture these effects, we couple the diffuse interface solver with a thermodynamics library implementing a quantum-corrected cubic equation of state for hydrogen. The model is fully compressible in both phases, with phase change represented as a relaxation term proportional to the difference in Gibbs free energy. We first validate the approach using two-dimensional water steam film boiling and then apply the solver to film boiling of hydrogen, highlighting key differences in boiling behaviour between the two fluids.
