TREATMENT OF THERMOPHORETIC DEPOSITION IN TUBE FLOW FOR MATERIALS PROCESSING APPLICATIONS

摘要

Material processing techniques based on vapor or particle transport involve a number of interrelated hydrodynamic and thermal effects. For cases with large temperature gradients or small (nano) particles, thermal gradients can induce motion referred to as thermophoresis. Thermophoresis directly impacts material quality and production rates for chemical vapor deposition (CVD) and related processes. A simple yet useful geometry for the study of thermophoretic deposition is axial tube flow. This geometry is particularly useful as it closely represents one process used to produce fiber optic preforms. While considerable research has been conducted on thermophoretic deposition, a global description and understanding of the phenomena is still difficult. This paper will first review the analytical study of thermophoretic deposition. Starting with the simple Graetz problem the development of more complex solutions to the governing Navier-Stokes equations will be detailed from the literature. Next, the creation of a coupled, two code Eulerian approach to solve this problem will be presented. Finally, the results of numerical case studies performed by the author will be discussed. These results will be used to compare and contrast the influence of different factors.