The thermodynamic properties of plasmas formed by air and water vapor mixtures is calculated in the temperature range from 500 to 12 000 K at atmospheric pressure and local thermodynamic equilibrium (LTE). The Gibbs free energy minimization method is used to determine the equilibrium composition of the plasmas which is necessary to calculate the thermodynamic properties. Then the thermodynamic properties are also used to calculate the density of energy and the power flow of plasmas concerned. The results are presented and discussed according to the rate of water vapor. The results of the density of energy and power flow show in particular that the increasing of the rate of water vapor in air can be interesting for power cut. This could improve the performance of plasma during current breaking in air.

equilibrium composition, Gibbs free energy, plasma, thermodynamic properties