Convective Melting Modeling Approach for Phase Change Materials with Variable Boundary Heating

The present study conceives a numerical model for phase change materials following the apparent heat capacity method where the phase change occurs within a chosen temperature interval. A multiphysical modeling approach to satisfy the coupled momentum, energy and continuity conservation equations whilst avoiding numerical singularities is applied. By means of a 2D test-case geometry with variable boundary heating the influence of natural convection within the melted liquid zone is visualized. Corresponding non-dimensional governing equations are analysed to quantify the dominant contributing terms. It turns out that for sufficiently small Grashof number, or consequently small Rayleigh numbers the influence of natural convection can be neglected, thus simplyfing the problem substantially. The modeling approach has been adapted to a 2D-axisymmetric geometry within the scope of experimental validation. The simulation results and experimental data show reasonably good agreement. The model is numerically stable and suitable to facilitate design of latent heat storage systems.