Transport properties of carbon dioxide+ethane and methane+ethane mixtures in the extended critical region

A practical representation for the transport coefficients of pure fluids and binary mixtures in and beyond the critical region of liquid-vapor equilibria is presented. The crossover expressions for the thermal conductivity, the binary diffusion coefficient, the thermal diffusion coefficient, and the thermal diffusion ratio incorporate scaling laws near the critical point and are transformed to regular background values far away from the critical point. In the limits of pure components, the crossover expression for the thermal conductivity of binary mixtures is transformed to the crossover expression for the thermal conductivity of pure fluids. For the calculation of the regular backgrounds transport properties of pure fluids, we use dense fluid contributions obtained from independently fitting pure fluid data and a dilute gas contribution from Chapman–Enskog theory. A comparison is made with thermal conductivity data for pure carbon dioxide, methane, ethane, and carbon dioxide+ethane and methane+ethane mixtures.