Assessment of turbulence models for evaporation and stratification in cryogenic storage tanks

According to the International Energy Agency, the use of renewable energy sources

will increase significantly towards 2050. Green energy carriers are essential for large-

scale storage and transport to manage the intermittency of wind and solar and meet

future energy demands. Liquefied hydrogen ( LH2) is emerging as a promising candidate

for large-scale applications, being a carbon-free energy carrier with sufficiently high

density.

To design efficient and safe venting systems for LH2 tanks for filling, storage and

transport, it is crucial to predict the evaporation rate and the temperature of the resultant

gas phase. This depends on the heat ingress, which varies with the type and size of

the tank. The presence of convective regions in the tank, which may propagate to a

turbulent flow regime, will increase the evaporation rate.

Previous work has mainly focused on pressurization in closed tanks, with no clear

trends in turbulence model selection. This work performs 2D Computational Fluid

Dynamics simulations of the gas phase in a vented LH2 tank using various RANS

turbulence models. Model selection is found to have a large impact on the boil-off rate,

and the addition of a buoyancy production term in the turbulence transport equations

is found to dampen turbulence. The vertical temperature profiles and average boil-off

rates are compared with experimental data.