Flow Regimes and Transitions in a Rapid Chemical Vapor Deposition Reactor Using Flow Visualization and Rayleigh Light Scattering

Abstract

Previous study of carrier gas flow in rapid chemical vapor deposition (RCVD) reactors has been limited mostly to numerical simulations and flow visualizations. In the present work flow regimes were observed and temperatures were measured in a vertical axisymmetric pedestal RCVD reactor using flow visualization and Rayleigh light scattering (RLS) for noninvasive temperature measurement. Flow visualizations revealed that the flow undergoes complex transitions between stable flow regimes as heating occurs. The two dominant stable flow regimes were buoyant stable (BS) and momentum stable (MS). RLS was used to determine the instantaneous carrier gas temperature at discrete points in the test section. The flow regimes and their transition points were easily recognized and agreed with flow visualization data. The flow visualizations and RLS tests showed identifiable trends in transition points between flow regimes and in the types of regimes encountered. These trends were dependent on Grashof number and Reynolds number.