THERMAL-CONVECTION IN PHYSICAL VAPOR TRANSPORT OF MERCUROUS CHLORIDE (HG2CL2) FOR RECTANGULAR ENCLOSURES

The convective Bow structures in the physical vapour transport process for mercurous chloride (Hg2Cl2) are investigated for two-dimensional rectangular enclosures at various aspect ratios (width-to-transport le ngth) and two different wall boundary conditions: conducting and insul ating. For a low aspect ratio of 0.124, the core of the flow is domina ted by a unicellular convective structure at a Rayleigh number 1.51 x 10(4) for conducting walls. For increasing Rayleigh number, the flow f ield bifurcates to asymmetric multicells. In contrast to conducting wa ll boundary conditions, the insulating wall boundary conditions tend t o suppress the formation of secondary cells. As the aspect ratio decre ases, the Rayleigh number at which transient convective flow arises de creases.