Chemical vapor decomposition (CVD) is one of the important techniques in the fabrication of semiconductor and compound semiconductor materials which are crucial in high speed electronics and supercomputer technology. Barrel reactor is a commercial CVD reactor operating at atmospheric pressure or reduced pressure. Unfortunately, uniformity in film deposition is a real concern in this reactor. The flow patterns are three dimensional asymmetric. The objectives of this proposed work are as follows. The first is to use state-of-the-art finite element techniques in computational fluid dynamics to solve for the complex reactive flows in a barrel reactor. Different finite element methods lead to different consistent mass matrices. The goal is to find an algorithm which provides an "optimal" consistent mass matrix with minimum numerical diffusion and spurious oscillation. The developed algorithm will be used to study the effects of gas flow rates, suspector rotating speed, gas nozzle locations, substrate temperature and operating pressure on the deposition rate and uniformity of existing reactors. It can also be used as a design tool for new gas distribution system and reactor design.