CFD calculation of a phase change material using STAR-CCM+ for a passive safety system of a sodium-cooled fast reactor

The aim of the present study is to quantify the impact that local scale physics of phase change has on the overall heat transfer of the quasi-cubic modular element of an innovative Decay Heat Removal System (DHRS). To evaluate the capabilities of using a solid/liquid phase change material (PCM) to drive passive natural circulation to cool the core of a Sodium-cooled Fast Reactor (SFR), a CFD analysis was carried out using STAR-CCM+. The melting-solidification model that utilizes the Volume- Of-Fluid (VOF) enthalpy-porosity approach proved sufficient when liquid and solid phases are isotropic, homogeneous and remain in thermal equilibrium at the interface, however, demonstrated extreme sensitivity when considering variable density between the phases. A preliminary estimation for the placement of the thermocouples according to the calculations was made for a future experimental study of melting Zamak PCM to measure areas of highly convective motion, hot and cold spots, and the shape of the melting interface