Conjugate heat transfer and particle deposition in the modified chemical vapor deposition process: Effects of torch speed and solid layer

Abstract

A study has been carried out for the conjugate heat transfer and particle deposition that occur during the modified chemical vapor deposition (MCVD) process. The analysis includes thermophoretic particle transport in the gas flow and heat transfer through the solid layer; the effects of variable properties in both the gas and the solid regions are included. A notable feature of the study is the inclusion of the effects of periodic heating due to the repeated traversing of the torch and the effects of the increasing solid layer thickness as the particles deposit. A new concept uses a two torch formulation to simulate the torch heating from both the present and the previous passes. This formulation is able to predict the minimum wall temperature in front of the torch, which is closely related to the deposition efficiency. Localized heating of the moving torch is studied using the heat flux boundary condition on the tube wall. The calculated surface temperature distribution and the deposition efficiency are in good agreement with experimental data. Of particular interest are the effects of torch speed and solid layer thickness on the efficiency, the rate of deposition of the particles and the taper length.