HEAT-TRANSFER FROM A RAREFIED PLASMA-FLOW TO A METALLIC PARTICLE WITH HIGH SURFACE-TEMPERATURE

Analytical results are presented concerning heat transfer to a metallic spherical particle immersed in a plasma flow for the extreme case of free-molecule regime and thin plasma sheath. The results show that as the surface temperature of the heated particle is comparatively high, additional heat transfer mechanisms due to radiation heat loss and thermionic emission from the particle surface should be all taken into account in the calculation of heat transfer to the particle. Radiation heat loss becomes appreciable at wall temperatures lower than those at which significant thermionic emission occurs. As the plasma temperature is comparatively low, radiation heat loss even restricts the surface temperature of the particle to such a low value that the effect of thermionic emission on heat transfer can be ignored, The heat flux to the particle increases with increasing gas pressure or speed ratio, and decreases with increasing electron/heavy-particle temperature ratio for a fixed electron temperature of two-temperature plasmas.