Free-volume theory coupled with modified group-contribution PC-SAFT for predicting the viscosities. I. Non-associated compounds and their mixtures

Abstract The modified group contribution PC-SAFT (Fluid Phase Equilibria, 2016.430: p. 33–46, https://doi.org/10.1016/j.fluid.2016.09.020 ) has been combined with the Free Volume theory (FVT) to estimate fluid viscosities. The proposed model does not require critical constants or acentric factor of fluid as input parameters, while the correlation of the FVT parameter triplet is used to estimate the viscosity of n-alkanes, (up to n-C64H130), aromatics, non-aromatic hydrocarbons and small gases. The universal FVT parameters working with mg-SAFT for n-alkanes were used to predict the viscosity of heavy molecules at extreme pressure condition (up to 5000 bar). For all cases, an overall average relative deviation is around 3% compared to experimental data. The new approach empowers mg-SAFT with new predictive ability, allowing to simultaneously calculate fluid phase equilibria and viscosity with the same degree of accuracy. In addition, a new, simple and effective mixing rule was also proposed. It can yield very satisfactory predictions for liquid viscosity of several binary and multi-component mixtures from atmospheric to high pressure, with an overall average deviation of 2.46% for 87 considered mixtures.