HEAT-TRANSFER AROUND A SPHERICAL-PARTICLE LEVITATED IN ARGON PLASMA-JET

This paper concerns momentum and heat transfer to a nonevaporating oxi dized steel spherical particle (diameter 6.5 mm-8 mm) levitated at hig h Reynolds number in argon turbulent plasma jet flowing into cold air. The rapid rotation of the particle in the plasma Bow ensures the stab ility of the levitation phenomenon over a wide range of plasma torch p arameters. We use a dimensional analysis to describe the momentum tran sfer and the equilibrium levitation height data. The convective heat t ransfer coefficient was further estimated from gas and particle equili brium temperature at the front stagnation point or from the analysis o f the transient temperature signal for a particle abruptly immersed an d levitated in the plasma jet. Particle rotation is shown to determine the heat transfer rate ill a nonuniform plasma flow.