Accurate Density and Viscosity Modeling of Nonpolar Fluids Based on the “f-Theory” and a Noncubic Equation of State

Recently, the f-theory, a theory for viscosity modeling based on friction concepts of classical mechanics, has been introduced. This new theory allows accurate viscosity–pressure–temperature (g–p–T) modeling based on a van der Waals type of equation of state, one with a repulsive pressure term and an attractive pressure term. Thus, popular cubic equations of state (CEOS), such as the SRK and the PR, have been successfully applied to obtain accurate g–p–T models (even close to the critical region) of fluids such as n-alkanes, N2, CO2, etc.,andsomeoftheirmixtures.However,eventhoughithasbeenshownthataCEOS f-theory-based model can accurately reproduce the viscosity behavior of, at least, nonpolar fluids, the accuracy of the density predictions is still limited by the algebraic structure of the CEOS. In this work, a noncubic van der Waals type of equation of state is introduced for the accurate modeling of both the density and the viscosity behavior of selected nonpolar fluids. The achieved accuracy, for both the density and the viscosity fluid properties, is close to, or within, experimental uncertainty and applies to wide temperature and pressure ranges.