Numerical Analysis for Impurity Effects on Diffusive-convection Flow Fields by Physical Vapor Transport under Terrestrial and Microgravity Conditions: Applications to Mercurous Chloride

In this study, impurity effects on diffusive-convection flow fields by physical vapor transport under terrestrial and microgravity conditions were numerically analyzed for the mixture of Hg2Cl2-I2 system. The numerical analysis provides the essence of diffusive-convection flow as well as heat and mass transfer in the vapor phase during the physical vapor transport through velocity vector flow fields, streamlines, temperature, and concentration profiles. The total molar fluxes at the crystal regions were found to be much more sensitive to both the gravitational acceleration and the partial pressure of component I2 as an impurity. Our results showed that the solutal effect tended to stabilize the diffusive-convection flow with increasing the partial pressure of component I2. Under microgravity conditions below 10-3g0, the flow fields showed a one-dimensional parabolic flow structure indicating a diffusion-dominant mode. In other words, at the gravitational levels less than 10-3g0, the effects of convection would be negligible.