Plasma Concentrations out of Equilibrium: N2 (Kinetic Method and Mass Action Law), Ar-CCl4 and Ar-H2-CCl4 (Mass Action Law)

Titre: Heat and Mass Transfer under Plasma Conditions Editeurs: P. Fauchais, University of Limoges, Limoges Cedex, France; J. van der Mullen, University of Eindhoven, Eindhoven, the Netherlands; J. Heberlein, University of Minnesota, Minneapolis, MinnesotaThe multi-temperature Gibbs free energy minimization (GFEM) method has been compared to the Pseudo Kinetic Method (PKM) to calculate the composition of a nitrogen plasma at atmospheric pressure. When introducing only two temperatures Te and Th with their ratio e = 2, the GFEM method overestimates by more than two orders of magnitude the density of N2+. However when calculating the kinetic rate coefficient at different temperatures the thermodynamic relationship between them and the equilibrium constant is no more fulfilled. That is why an intermediate temperature T* between Te and Th has been introduced linked to the ratio of the electrons flux to that of neutrals and e has been assumed to vary with the electron density ne, equilibrium (e = 1) being achieved either for nemax = 1022 or 1023 m-3. With nemax = 1022 m-3 the agreement between the results obtained with the PKM and the GFEM method is fairly good. That is why this latter method has been used to calculate the composition of complex mixtures of Ar-CCl4 and Ar-H2-CCl4. Below 6000 K where complex molecules exist the variation of e between 2.5 and 1.5 does not affect very much the composition which, however, depends strongly on v (v = Tv/Th