Calculation of thermodynamic properties and transport coefficients of SF6-PTFE-Cu mixtures

The nozzle ablation and contact corrosion of power switchgear (such as high voltage SF6 circuit breaker) will lead to the generation of PTFE and copper vapor, which will affect the physical parameters of arc plasma and the breaking characteristics of SF6 circuit breaker. Therefore, based on the Gibbs free energy minimization method, the local thermodynamic equilibrium (LTE) composition of SF6-PTFE-Cu gas mixtures at different temperatures is obtained. We calculated the thermodynamic properties and transport coefficients of SF
6
-PTFE-Cu gas mixtures in the temperature range of 300K ~ 30000k and the pressure range of 0.1~0.8MPa. Different gas pressures, SF
6
/PTFE mixing ratios, copper proportions have certain influence on the thermodynamic properties and transport coefficient of the gas mixtures. The addition of PTFE has a great influence on these physical parameters. The addition of a small amount of copper will not lead to obvious changes in properties. However, when the mole fraction of copper exceeds 10%, the thermodynamic properties and transport coefficients will change significantly. Increasing the gas pressure will increase the transport coefficient, particularly in high temperature areas. The calculated results provide essential statistics for further researches of plasma behavior by using MHD arc model.