This paper describes the numerical simulation of heat transfer in a system for growing corundum single-crystal plates (leucosapphire and ruby) of size 200 x 200 mm. A mathematical model accounting for the radiative and conductive heat transfer has been developed. Three-dimensional computations have been made with minor simplifications of the furnace geometry. The thermal fields at various positions of the crystal container and the effect of various setup units and their design on the temperature distribution are analyzed. The computed crystallization front shape is compared with the available experimental data. Numerical analysis was used to optimize the hot zone design. (c) 2005 Elsevier B.V. All rights reserved.