An Optimal Method for the Computation of the Parameter Rs of the Net Emission Coefficient Approximation Approach for Determining the Electrical and Thermal Characteristics of Plasma Arcs
Résumé
Large-scale industrial plasma torches and processes use primarily high-current electric arcs. Therefore, their basic design must inevitably account for radiative transfer which becomes the prevailing heat loss mechanism at high currents. This heavily increases the complexity of the governing equations. Many approximate approaches have been proposed. The present work relies on the method of approximate average net emission coefficient (NEC) using the isothermal sphere approximation with a radius Rs to solve semi-analytically the Ellenbaas-Heller equation and compares it with exact calculations obtained using an iterative method. To our knowledge no study has provided yet a method to determine the most accurate value of Rs. In this paper, we present an optimal method for determining the best value of Rs that leads to the best agreement between the approximate and the exact methods. As a result, the complete electric characteristic has been obtained for hydrogen at 1 bar in a detailed case study.