EFFECT OF INTERNAL RADIATIVE HEAT-TRANSFER ON THE CONVECTION IN CZ OXIDE MELT

A numerical study was carried out to investigate the effect of interna l radiative heat transfer on the convection in the Czochralski oxide m elt. Results were obtained for a wide range of the absorption coeffici ents of the melt. The flow and temperature fields showed a remarkable change with the variance in the absorption coefficient. In this study, we adopted two different kinds of boundary conditions for the radiati ve heat transfer at the melt surface, i.e., an opaque and a semitransp arent diffuse gray surface, and for each case, the influence of Marang oni convection was investigated. The optical characteristic of the mel t surface and the Marangoni effect greatly affected the convection and temperature field in the melt. When the surface was assumed to be sem itransparent, in the range of a small absorption coefficient, the smal ler the absorption coefficient was, the lesser the Marangoni effect be came, This was caused by the disappearance of the temperature gradient at the melt surface, and consequently the flow became as weak as in t he case without the Marangoni effect. These numerical results give a c lue for discussion on the effect of internal radiative heat transfer i n the melt of the Czochralski system.