The stability of a compressible fluid with variable transport properties in a horizontal chemical vapour deposition reactor

A linear stability analysis was performed to determine the point of onset of longitudinal rolls in a horizontal duct of rectangular cross-section with a heated bottom surface, approximating a typical horizontal chemical vapour deposition reactor. The fluid was considered to be compressible with temperature-dependent transport properties. It was found that nitrogen is a less stable carrier gas than helium. The effect of the temperature-dependent transport properties was to render less stable the flow in the duct with a bottom surface temperature of 700 K In comparison with the duct with the bottom surface at 1000 K. This interesting result emphasizes the importance of taking into account the temperature dependence of fluid properties. Comparison with the Boussinesq-fluid constant-properties model showed that that model can be considerably in error, depending on the reference conditions for property evaluation and on the particular carrier gas.