Investigation of flow and heat transfer in vertical CVD reactors

This study is concerned with a numerical method to study the flow in large-size vertical chemical vapor deposition (CVD) reactors. The governing equations that describe the transport phenomena in the reactors are constructed in axisymmetric, curvilinear coordinates to fit an irregular geometry. Discretization is carried out using a finite-volume method. Since grids are arranged in a nonstaggered manner, special treatments are undertaken for calculation of face velocities such that decoupling between the velocity and pressure is avoided. The calculation shows that the buoyancy force resulting from the heated susceptor may cause recirculating flow above the susceptor when the temperature is high enough, leading to reduction of heat transfer and nonuniform distribution of heat flux. The recirculation can be suppressed by rotating the susceptor. However, a different kind of recirculation, rotating in the direction opposite to the buoyancy-driven recirculation, may be formed at the outer edge of the susceptor. An effective way to remove these recirculating flows is to reduce the reactor pressure because the buoyancy force and centrifugal force are proportional to the square of the reactor pressure. It is also shown that multiple-flow solutions may exist in certain temperature and rotational speed ranges. Thus, the flow in the reactor may depend on the startup procedure.