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In our previous work (J. Chem. Eng. Data 2021, 66, 1385–1398), a residual entropy scaling (RES) approach was developed to link viscosity to residual entropy using a 4-term power function for 39 refrigerants. In a further research (Int. J. Thermophys. 2022, 43, 183), this RES approach was extended to 124 pure fluids containing fluids from light gases (hydrogen and helium) to dense fluids (e. g., heavy hydrocarbons) and fluids with strong association force (e. g., water). In these previous researches, the model was developed by manual optimization of the power function. The average absolute relative deviation (AARD) of experimental data from the RES model is approximately 3.36%, which is higher than the 2.74% obtained with the various models in REFPROP 10.0. In the present work, the power function was optimized by iteratively fitting the global (fluid independent power terms) and local parameters (fluid-specific and group-specific parameters), and screening the experimental data. The resulting equation has only three terms instead of four. Most notably, the AARD of the new RES model is reduced down to 2.76%; this is very close to the various multi-parameter models in REFPROP 10.0, while the average relative deviation (ARD) amounts to 0.03%, which is smaller than to REFPROP 10.0’s 0.7%.

Schlagwörter: residual entropy scaling, viscosity, model, pure fluids, mixtures