The purpose of this project is to examine several numerical simulation techniques which have been used for the development of 400 mm silicon single crystals. The temperature distribution in all of the hot zone (HZ) regions is calculated by global heat transfer analysis. The thermoelastic stress within a crystal is calculated based on the crystal temperature. The melt convection or argon gas flow is simultaneously solved by global heat transfer analysis. In this paper, we report our design and experiment results for an 18-in KZ configuration for 150 mm crystals. This configuration can be enlarged to 36-in. HZ for 300 mm crystal or 36-in. HZ for 400 mm crystals. For each of these HZ configurations, a global heat transfer numerical simulation is performed. These results show that a degradation in the thermal damage to the quartz crucible, the argon gas flow pattern, and the thermoelastic stress at the growth interface, are predicted to be functions of HZ size - the larger the configuration, the greater the degradation. In order to reduce the thermoelastic stress, the shape of the growth interface should be controlled to be as flat as possible