On the Determination of High-pressure Mass-diffusion Coefficients for Binary Mixtures

Abstract

A model for high-pressure binary diffusion coefficient calculation is proposed based on considerations originating from recasting both the low pressure kinetic theory and the Stokes-Einstein infinite dilution expressions into forms consistent with corresponding states theory. These considerations lead to an ansatz that is an expression reflecting departures from the kinetic theory relationship through a division factor that is a function of the reduced species density and that becomes unity in the limit of low pressure gases. Available high pressure data sets extracted from the literature are used to derive correlations for the factor that are eventually categorized according to the species system. The typical uncertainty in these correlations is estimated as 10 to 15 %, with a maximum uncertainty of about 30% for the high density regime.