Electrode Heat Transfer in Thermal Plasmas

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In order to evidence heat transfer phenomena at the anode boundary layr of arc plasma, the boundary layr was observed by using laser scattering method and Langmuir probe method.The conditions of free-burning argon arc were roughly divided into two regions : a low current region (50A) and a high current region (150A). In the case of low current region, electron temperature increased with approaching the anode in arc axis, but heavy particle temperature decreased. This suggested that the anode boundary layr under this condition remarkably deviated from LTE (Local Thermodynamic Equilibrium). On the other hand, in the case of high current region, electron temperature approximately corresponded with heavy particle temperature at the degree of about 12000 K.This suggested that the boundary layr under this condition preserved the similar state of LTE.Langmuir probe measurements indicated that the anode fall for the low current region was positive, but one for the high current region was negative.It was concluded that the physical structures of the anode boundary layr were governed by heavy particle temperature close to the anode surface and the heavy particle temperature was influenced strongly by the arc current density.