Coupled radiation, conduction, and Joule heating in argon thermal plasmas

A model is developed to study the coupled energy transfer mechanisms and to predict the temperature profiles in axisymmetric atmospheric argon plasmas. The steady-state energy balance equation, including radiation, conduction, and electric heating, is solved iteratively. Radiative transfer is computed from a Monte Carlo method fed by up to date high-resolution spectroscopic data and accurately predicted line profiles. The model is first validated through comparisons with experimental results obtained via emission spectroscopy from a Maecker-type, direct current, wall-stabilized argon plasma. Different techniques were used for the measurement of temperature and electron number density profiles and to assess the local equilibrium character of this plasma. It is shown that radiative losses leads to a significant decrease of the temperature level and that self-absorption inside the plasma column is very important. The contribution of different spectral domains to radiative transfer is analyzed, and a parametric study is conducted by varying the arc current intensity.