A new free volume model for dynamic viscosity and density of dense fluids versus pressure and temperature
Résumé
This article presents a model based on the free volume concept, which describes the variations of dynamic viscosity and density versus temperature and pressure for the dense fluids (density > 200 kg · m-3). This model involves 6 constants for each pure compound: 3 for viscosity and 4 for density (1 constant is common to both quantities). Moreover if the viscosity and the density are known at a pressure and temperature of reference, it is sufficient to use 4 constants per pure compound. If the density is assumed to be known the model fits the viscosity data with an average absolute deviation of 3.8% for 3297 data corresponding to 41 very different pure compounds (alkanes, alkylbenzenes, cycloalkanes, alcohols, carbon dioxide, refrigerants). If the pressure is lower than 110 MPa the average absolute deviation is 2.8% for viscosity (2977 points). The model gives also good results for water (3.6%). If the density is unknown, for pressures lower than 110 MPa the model represents viscosity with an average absolute deviation of 3.5% and for the density the average absolute deviation is 1.5%.