Thermodynamic and transport properties of a ternary Ar-H2-He mixture out of equilibrium up to 30000 K at atmospheric pressure

This paper is devoted to a study of the effect of the non-equilibrium parameter theta = T-e/T-h on the plasma composition and thermodynamic and transport properties of ternary mixtures Ar-H-2-He, which are commonly used in dc plasma spraying. Calculations are performed in the temperature range 300-30 000 K and at atmospheric pressure. First, to calculate the non-equilibrium composition, two techniques are used: the equilibrium constant (van de Sanden) and pseudo-kinetic methods. Second, the specific heat at constant pressure is obtained by a five-point numerical differentiation of the specific mass enthalpy. Third, the most recent data of potential interactions or elastic differential cross sections are carefully examined in order to choose the most appropriate ones to determine the collision integrals. Finally a convergence study of transport coefficients (thermal conductivity, viscosity and electrical conductivity) is conducted to evaluate the influence of the non-equilibrium parameter theta on this convergence. It has to be pointed out that the latter has a non-negligible influence on transport coefficients.