Modelling radiative heat transfer to closed LH2 storage

The paper presents a model of heat and mass transfer in a closed, vacuum-insulated liquid hydrogen (LH2) storage tank under conditions of radiation heat exchange. A three-dimensional Computational Fluid Dynamics model includes the Volume of Fluid method to track the liquid and gaseous phase interface, the Discrete Ordinate radiation model, and Large Eddy Simulation for turbulence modelling. The NIST database is used to define thermodynamic properties of LH2 and gaseous hydrogen to allow for an accurate representation of both phases under quasi-steady equilibrium conditions with non-uniform temperature distribution. The simulations are validated against experimental data from NASA (Technical Note TN-D-4171), where a 9-inch spherical dewar vessel, half-filled with liquid hydrogen, is subjected to radiative heat flux from two hemispherical electric radiant heaters maintained at a constant temperature. The simulated results are in good agreement with the experimental pressure and temperature transients at the several sensor locations. The simulations allowed insight into the radiative heat exchange with liquid hydrogen storage. Correct pressure and temperature dynamics were obtained under certain radiative heat flux distribution between the lower and upper tank hemispheres, which was only possible when the variable radiation emissivity of the tank surface as a function of temperature was accounted for, along with heat conduction in the inner tank wall. The simulations demonstrate the importance of accounting for the accurate thermal and radiation properties of materials used in vacuum-insulated liquid hydrogen vessels, which can affect the accuracy of predictions for liquid hydrogen storage parameters.