Mixing rules for thermal plasma properties in mixtures of argon, air and metallic vapours

Modelling of electric arcs and thermal plasmas in mixtures of gases and vapours needs prior knowledge of rather large data banks corresponding to thermodynamic functions, transport coefficients and radiation properties. For a given pressure these data are functions of temperature and gas proportions in the mixture. In order to reduce the memory or because some properties of the mixtures are not known, some mixing laws can be useful. These mixing rules allow estimation of the properties of the mixtures when only the corresponding properties of the pure gases or vapours are known. In this paper we study several mixing rules for mixtures of argon or air with metallic vapours. Simple laws such as linear interpolations are compared with relations deduced from physical consideration and some general behaviour is given in conclusion: mixing rules for electrical conductivity, viscosity and net emission coefficient are good. For other properties the use of a mixing law may produce rather large errors.