Thermodynamic Properties and Transport Coefficients of SF6-N2 Arc Plasma

The thermodynamic properties and transport coefficients of SF6-N2 mixture were calculated within the temperature range of 300K to 30000K and pressure range of 0.1 to 1.6MPa. This study focused on investigating the influence of different N2 ratios and gas pressures on the physical properties of SF6-N2 mixed gas. The composition of particles in the arc plasma was determined based on the principle of minimizing Gibbs free energy, and the thermodynamic parameters and transport coefficients were determined using standard thermodynamic equations and Chapman-Enskog theory. It was observed that the addition of N2 had a certain impact on the specific heat and thermal conductivity of the mixture, primarily influenced by the decomposition of N2 molecules and differences in ionization levels of sulfur, fluorine, and nitrogen atoms. Increasing gas pressure led to an increase in transport coefficients, particularly within the elevated temperature range. Additionally, higher pressures inhibited ionization and dissociation reactions within the plasma, thus impeding the evolution of macroscopic plasma parameters to a certain extent. The calculated results provide fundamental data for magnetohydrodynamic arc plasma modeling and serve as a reference for the design of environmentally friendly high-voltage circuit breakers. Several examples are presented in the paper.