The Melt–Crystal Interface in the Production of Monocrystalline Sapphire via Heat Exchanger Method—Numerical Simulation Aspects

In this work, selected numerical simulation aspects are analyzed in terms of their effect on predictions of the m-c interface. The fixed-grid enthalpy porosity phase change model, which is highly attractive in the field of modeling sapphire crystallization processes, is examined for its sensitivity to the mushy zone parameter as well as the grid resolution. A further focus is set to the simulation of thermal transport including internal radiation in the crystal and the melt via the finite volume method. Depending on the purpose of the investigation, different requirements on the angular resolutions are relevant. While most of the m-c interface as well as the temperature distribution remain practically unchanged at reasonable resolutions, a high sensitivity of the m-c interface in the near-wall region is demonstrated. This sensitivity is also observed in terms of radiative transport and, hence, the total heat transfer.