Effective Thermophysical Constants of Thousands of Fluids─II: Lennard-Jones and Residual Entropy Scaling Parameters for Viscosity

High Resolution Image Download MS PowerPoint Slide In our previous work ( J. Chem. Eng. Data, 70, 2911–2946), we compiled, critically evaluated, and fitted the critical constants and acentric factors of 1541 pure fluids, based primarily on NIST REFPROP 10.0, NIST ThermoData Engine 10, and the Dortmund Data Bank 2023. That study represented the first part of a series aimed at determining effective thermophysical constants for thousands of fluids to enable reliable calculations of key thermophysical properties over wide pressure and temperature ranges within a simple model framework. This study constitutes the second part and focuses on determining more effective constants, Lennard-Jones (L-J) and residual entropy scaling (RES) parameters, for viscosity predictions below 60 MPa. The L-J parameters for dilute-gas viscosity were obtained either by anchoring to REFPROP 10.0 calculations or by estimation using newly developed symbolic regression (SR) correlations based on critical constants. The RES parameters for residual viscosity were determined by regression to experimental data or estimated using SR correlations depending solely on critical constants. The model uncertainty is estimated at 6% with fitted RES parameters and 18% (or much higher for those with high critical temperatures) with predicted ones. All obtained effective constants were critically assessed, and a software package is provided to facilitate the application of the model and the effective constants.