Computational and experimental methods were used to investigate the production of bulk polysilicon via a horizontal tubular CVD reactor. Experiments were conducted to study the effect of cooling gas on the system process while keeping the process gas flow rate at zero. A numerical model was also developed to simulate the process. Simulation results were compared to the experimental data to examine the effect of cooling gas on temperature distributions of the silicon tube and the inner quartz tube, as well as the effect of different process gas flow rates on heating power input and silicon tube temperature. Using the numerical simulation method, the investigation has also been conducted to reveal the correlation between the polysilicon production rate and the process gas flow rate, mass fraction of the silane gas in hydrogen and the temperature of the substrate silicon tube. This study has demonstrated the feasibility of high production rate for polysilicon in the new reactor. (C) 2002 Elsevier Science B.V. All rights reserved.