Viscosity prediction of pure fluids and mixtures in a corresponding-states framework

A three-parameter corresponding-states (CS) model is here developed importing methods formerly studied for the volumetric representation of fluids. Two fluids of the same conformal family are chosen both for their third parameter, here defined, and for the availability of viscosity-dedicated equations. On the basis of the three-parameter CS model form of Teja et al for volumetric properties, the reduced viscosity of a third fluid of the family is obtained in reduced pressure and temperature. A new scaling factor is assumed to replace the Pitzer acentric factor as a third parameter; it is generated from saturated-liquid-viscosity experimental data. These are then the only model inputs, allowing the model to calculate viscosity predictively over the whole pressure, density, temperature (p, p, T) domain. The conversion of the independent variables from (p, T) to (p, T), necessary only for the reference fluids, is obtained through volumetric-dedicated equations of state. The model is here applied to hydrocarbons and hydrofluorocarbon refrigerants, including fluoropropanes, with a prediction accuracy comparable with those of the reference fluid equations. Given the predictive nature of the model and the scatter of the experimental data sets, the mean accuracy obtained is very good and particularly satisfactory for technical application requirements.