Powder Temperature Effect on Heat Transfer Property for Nano Powder Synthesis Using Thermal Plasma

Researches an interaction between thermal plasma and immersed powder has been studied from the early 1980s. In the early 1980s, they dealt with simple heat conduction model on spherical conductor inside hot gases, but in current state, they dealt with complex physical phenomena like turbulence effect on thermal plasma – powder interaction. For the study of thermal plasma – immersed powder energy transfer mechanism in high Knudsen number condition, in which is the effect of charged particle heating on immersed powder is the dominant case, the evaluation of charge balance on powder surface is essential. The researches on high Knudsen number condition has been intensively studied in low pressure plasma spray process, however this dissertation studied nano powder synthesis process and consider thermionic emission on the powder surface to evaluate the charge balance model and energy transfer properties on powder surface during the powder inflight time, which was not considered in previous researches. DC plasma torch and immersed powder simulation code was equipped to evaluate the effect of thermionic emission on the powder surface to powder surface charge balance model and energy transfer properties. Use of the immersed powder simulation code regarding thermionic powder emissions confirmed the possibility of overestimating the thermal plasma – powder energy transfer To confirm simulation results, modified test particle experiment condition was used on nano powder synthesis system. Comparative studies of experimental results and simulation results support the reliability of simulation code and confirm the thermionic electron emission effect on thermal plasma – powder energy transfer properties Results of this dissertation about thermal plasma – immersed powder energy transfer during the inflight time will contribute toward to evaluation powder heat transfer in thermal plasma process and predict the dust behavior in low pressure process