Diffusion and Thermal Diffusion in Ne–CO2

Abstract

Values of the thermal diffusion factor αT and the ordinary diffusion coefficient D for Ne–CO2 mixtures have been measured over a temperature range of about −78° to 350°C by using the radioactive tracer C14O2. The thermal diffusion factor exhibits an unusual negative temperature dependence similar to that for Ar–CO2 mixtures. The data for Ne–CO2 are in good agreement with relations between measurable quantities, derived from the Chapman-Enskog theory, which are independent of the choice of force law. The experimental values have been compared with values calculated from the theory using the Lennard-Jones (12–6) potential. The agreement is good for D but very poor for αT. A corresponding states treatment based on the general form of the relations of the Chapman-Enskog theory has been used to correlate the thermal diffusion factor of Ne–CO2 with those of He–CO2 and Ar–CO2 mixtures. Therefore it appears as if the discrepancy between the theoretical values and the observed values is due primarily to the force model.