THERMODYNAMIC AND TRANSPORT-PROPERTIES OF ARGON HELIUM PLASMAS AT ATMOSPHERIC-PRESSURE

Because of the importance of having reliable transport coefficients fo r argon/helium mixtures available, viscosities and thermal conductivit ies of such mixtures at atmospheric pressure have been recalculated fo r molar fractions of helium ranging from 0 to 1 in steps of 0.1 and fo r temperatures varying from 1000 to 20,000 K. We have found that the v iscosities of Ar/He gas mixtures in the temperature range from 1000 to 10,000 K strongly depend on the values which are used to describe the interaction potentials between argon and helium atoms. For example, a n anomalous behavior has been found, indicating higher values of the v iscosity of Ar/He mixtures compared to those of pure argon or pure hel ium in a temperature range from 6000 to 10,000 K if one data set for A r-He interatomic potentials is used, while this anomalous behavior dis appears if other data sets are used. Our calculations of thermal condu ctivities of Ar/He plasmas have shown that the temperature dependences of thermal conductivities of mixtures are almost the same for differe nt sources of interatomic potentials between argon and helium atoms. A n anomalous behavior has been found indicating higher values of the th ermal conductivities of Ar/He mixtures compared to those of pure argon or pure helium in a temperature range from 11,000 to 15,000 K, regard less of which data set is used for Ar-He interatomic potentials. Calcu lating and analyzing the data of the thermal conductivities for molar fractions of helium from 90% to 100% in step changes of 1% indicates t hat this anomalous behavior is due to the contributions not only from heavy species but also from electrons and chemical reactions. The elec tron thermal conductivity, as well as the reactional thermal conductiv ity, decrease with increasing helium molar fractions from 90% to 100%, while the heavy particle thermal conductivity becomes higher with inc reasing helium molar fraction. The peak of the reactional conductivity will be reduced to 30% and shifted to lower temperatures (from 12,000 to 11,000 K) when the helium molar fractions increase from 92% to 99% . The data presented in this paper are considered to be the most relia ble property data available for Ar-He mixtures.