EFFECTS OF CONVECTION ON PHYSICAL VAPOR TRANSPORT OF HG2CL2 IN THE PRESENCE OF KR - PART I: UNDER MICROGRAVITY ENVIRONMENTS

Special attention in the role of convection in vapor crystal growth has been paid since some single crystals under microgravity environments less than 1 g0 exhibits a diffusive-convection mode and much uniformity in front of the crystal regions than a normal gravity acceleration of 1 g0. The total molar fluxes show asymmetrical patterns in interfacial distribution, which indicates the occurrence of either one single or more than one convective cell. As the gravitational level decreases form 1 g0 down to 1.0 × 10−4 g0, the intensity of convection, indicative of the maximum molar fluxes, is reduced significantly for ΔT = 30 K and 90 K. The total molar fluxes decay first order exponentially with the partial pressure of component B, PB (Torr) for 20 Torr ≤ PB ≤ 300 Torr, and two gravity accelerations of gy = 1 g0 and 0.1 g0.