Coupling residual entropy scaling and revised Enskog theory (REST): A predictive framework for multicomponent transport properties from dilute gas to dense liquid

Estimating transport properties such as viscosity and thermal conductivity is crucial for a wide range of applications. No theory has yet been presented that is capable of predicting these properties accurately across the entire fluid region. With transfer lengths determined from intermolecular potentials, Revised Enskog Theory (RET) has been shown to yield accurate predictions from dilute gas to the liquid–solid transition at high temperatures. We present a methodology coupling RET with residual entropy scaling (RES), called REST, where the residual entropy scaling is derived from the high-temperature limit of RET. With equilibrium properties from thermodynamic perturbation theory, REST is fully predictive for transport properties of multicomponent mixtures under conditions ranging from dilute gas to dense liquid. It has an average absolute relative deviation (AARD) of 5.30%, 7.07%, and 2.97% for the viscosity of argon, neon, and air, respectively, across the full fluid range. The AARD is 1.3%–4.3% for the viscosity of several binary mixtures containing CH4, CO2, H2, and N2 at temperatures down to 100 K and pressures up to 792 bars. For the CH4/H2 mixture, REST significantly outperforms the present industry standard, which combines empirical correlations for the pure components with extended corresponding states theory. For a range of binary mixtures containing CO2, CH4, O2, and N2, the thermal conductivity is predicted with AARDs of 2.9%–6.3% at pressures up to 200 bars and temperatures ranging from 104 to 425 K, which is within the experimental accuracy. REST combined with the SAFT-VR Sum equation of state predicts the transport properties of argon and neon throughout the entire fluid region using an interaction potential derived from ab initio calculations as the sole input.