An Experimental Study of Heat Transfer and Particle Deposition for the Modified Chemical Vapor Deposition

An experimental study has been made of heat transfer and particle deposition for the Modified Chemical Vapor Deposition process. The tube wall temperature distributions and the rates and efficiencies of particle deposition were measured. Results indicate that the axial variation of the tube wall temperature is quasi-steady; i.e., the distributions fit onto one curve if the relative distance from the moving torch is used as the axial coordinate. Due to the repeated heating from the traversing torch, the wall temperature is shown to reach a minimum ahead of the torch. It is shown that the two-torch formulation suggested by Park and Choi (1994) is valid for predicting this minimum temperature. Comparison of the measurements of the wall temperature, the particle deposition efficiency, and the tapered entry length with calculations is in good agreement. Due to chemical reactions, the tube wall temperature increases as the flow rate of the carrier gas O₂ is increased. The rate of particle deposition also increases as the flow rate of the carrier gas O₂ is increased, but the efficiency decreases. The effect of torch speed on the tube wall temperature and on the particle deposition have also been determined.