CALCULATIONS OF RADIATION TRANSFER IN SF6 PLASMAS USING THE METHOD OF PARTIAL CHARACTERISTICS

Radiation emission and absorption in SF6 are plasmas are important energy transfer processes. Exact calculations, though possible in principle, are usually impossible in practice because of the need to treat about 400 spectral lines and also continuum radiation spanning wavelengths from 10 nm to 10 mu m. From calculated spectral absorptivities at 300 000 radiation frequency points for SF6 plasmas of 1, 5 and 10 bar from 300 K to 35 000 K, we have calculated two integrals over radiation frequency. These integrals, designated Som and Delta Sim are used in the approximate method of 'partial characteristics', as formulated by Sevast'yanenko. The validity of this method of partial characteristics has been demonstrated by comparing exact calculations with the approximate calculations to evaluate radiation intensities, radiation fluxes and divergence of radiation fluxes for specified temperature profiles. Agreement to within 20% is obtained with exact calculations, but with a reduction of computation time of about four orders of magnitude. Furthermore, the new method has been used to evaluate net emission of radiation as a function of position in an algorithm to predict temperature profiles of wall stabilized arcs of any given current. Fair agreement is obtained between predicted and experimental values of central are temperatures and electric field strengths as a function of current for SF6 arcs of radius 0.25 cm at a pressure of 1 bar.