A Reference Multiparameter Viscosity Equation for Propane with an Optimized Functional Form

A multiparameter viscosity equation for propane, valid in wide temperature and pressure ranges, was developed through an optimization technique for the functional form. The obtained results are very satisfactory, showing an average absolute deviation of 0.28% for the currently available 1024 primary data points. This is a significant improvement with respect to the reference equation available in the literature. As usual, both the development and the evaluation of the viscosity equation requires a highly accurate equation of state in order to convert the independent variables used for the experimental data, in most applications, (T,P), into the independent variables of the viscosity equation, (T,ρ). The heuristic technique used to develop the equation allows to select consistent data sets and thus it is a powerful tool for screening the available experimental data. The present limit for the accuracy achievable in the representation of the viscosity surface of a pure fluid is set by the uncertainty level of the experimental data rather than by the effectiveness of the proposed modeling method.