Viscosity prediction of pure refrigerants applying the residual entropy scaling theory coupled with a “Generalized Chart” parametrization method for the Statistical Associating Fluid Theory

Abstract

The residual entropy scaling (RES) theory integrated with different thermodynamic Equation of States (EoS) have obtained several accurate and simple viscosity models of working fluids, which is crucial for designing and optimizing of the energy utilization system. However, the influence of parameterization methods on RES’s viscosity calculations is rarely mentioned in a systematic way. Hence, a robust parameterization method based on generalized relation between the Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) EoS’s input parameters of 11 pure refrigerants (including hydrocarbons (HCs), CO2, hydrofluorocarbons (HFCs), hydrofluoroolefins (HFOs)) and their critical properties is introduced and coupled with a robust formulation of the reduced viscosity term in RES theory recently proposed by Dehlouz et al. Accurate vapor pressure calculations and near-constant difference between calculated liquid densities and high-accuracy correlation model in saturated state could be obtained with this parameterization method. Viscosities in vapor and liquid phases are exactly reproduced with an overall error of 3.14% applying the model proposed in this work, which is comparable to those from three RES models in literature and the extended corresponding states (ECS) model with overall errors of 3.36%, 3.22%, 3.41% and 1.77%, respectively. In addition, the divergence behavior in dilute region and the component-specific curves of dimensionless reduced viscosity and entropy variables are improved than other RES models under study to a certain extent. Meanwhile, as a supplement, the limitation of the above RES models on predicting viscosities in the near critical region is also discussed in detail.