Thermal behavior of a solid particle in an arc discharge during transient cooling conditions

Abstract

The thermal behavior of a tungsten particle has been studied in an argon arc discharge during transient extinction conditions. At the beginning of the transient process, the particle is electrically neutral and is at the cathode voltage. During this period of time, it is observed that the thermionic cooling effect plays a major role in the heat transfer mechanisms. Within the limits of the solid surface and surrounding gas temperatures investigated, which varied between 3600 and 3300 K for the surface and between 8000 and 6000 K for the argon gas, the heat transfer rates by convection and radiation are of the same magnitude but opposite in sign. Each of them amounts to less than 10% of the heat loss rate induced by thermionic emission. Besides the theoretical aspect of the study, the cooling effect observed (about 6 × 104 K s−1) may be of interest for improving solid surface properties, provided that the solid particle possesses characteristic thermionic emission properties.