Thermodynamic and transport properties in non-equilibrium argon, oxygen and nitrogen thermal plasmas

Abstract

Thermal plasma processes and devices have been extensively studied and designed using modeling approach in the last two decades. Still, knowledge of thermodynamic and transport properties is one of the major needs in the modeling of thermal plasma processes. Computation of these properties is usually carried out through the approximated solution of the Boltzmann's equation using the Chapman–Enskog's method. While local thermodynamic equilibrium (LTE) was assumed in the past calculations, the development and use of more sophisticated plasma diagnostics have shown that this assumption often fails in thermal plasmas: for thermal non-equilibrium plasmas, the kinetic electron temperature T e is then assumed to be different from that of heavy species T h, chemical equilibrium being achieved. Non-equilibrium thermodynamic and transport property calculations of argon, nitrogen and oxygen plasmas at atmospheric pressure for electron temperature up to 45,000 K are here presented. Transport properties have been obtained using numerical codes developed by the authors which implement the Devoto's electron and heavy particles decoupling approach. Variation of composition, specific volume, specific enthalpy, specific heat, thermal conductivity, electrical conductivity and viscosity as a function of electron temperature and different degrees of non-equilibrium are reported. Results are compared with available data from published reports to check the accuracy of the developed codes.