Chapman–Enskog theory has long provided an accurate description of the transport properties of dilute gas mixtures. At elevated densities, revised Enskog theory (RET) provides a framework for describing the departure of the transport properties from their dilute-gas values. Various methods of adapting RET for the description of real fluids have been proposed in the literature. The methods have in common that they incorporate one or more length scales to describe molecular interactions. With few exceptions, the required length scales have been estimated from experimental transport property data. In this work, we introduce two transfer lengths that describe the residual transport of momentum and energy. We derive a model called the exchange-weighted closest approach (EWCA), which links the transfer lengths to the intermolecular potential. Combining the EWCA model with Mie potentials fitted to experimental equilibrium properties yields accurate predictions for several real fluids, including a binary mixture. At higher temperatures, the theory is accurate at surprisingly high densities, even up to the liquid–solid transition of argon. We demonstrate how the transfer lengths can be computed from experimental data or correlations for the transport properties. The transfer lengths obtained in this manner are in good agreement with those obtained from the EWCA model paired with an accurate ab initio potential for argon. The results suggest that kinetic theory, after further developments, can become a predictive theory also for liquids.
