Free volume vacancy behaviour and dynamic viscosity of diesel fuels with additives at elevated temperature and pressure: thermo-occupancy function

The reported pressure-volume-temperature (PVT) data of five different diesel fuels at T = 297.95-373.06 K and P = 0.1-457.2 MPa were described by the Simha-Somcynsky (SS) equation of state (eos). From the equilibrium condition imposed on the eos, the hole fraction, h = h (P, T), a form of free volume measure, was computed. Furthermore, our physically-based correlation implicating the thermo-occupancy function, Y-h = Y-h(h, T), in terms of a function of h = h (P, T) and T has been extended in this study to estimate the dynamic viscosity, eta, for the mixtures of commercially available fuels. The model bridges a direct relation from an equilibrium property, h, to the transport process, eta, of the system and predicts the viscosity with the range from 0.15% to 0.31%. Newly designates 'viscoholibility' function defined as the derivative of logarithm of viscosity with respect to hole fraction has been discussed. It has an exponential decaying behaviour with respect to h. [Received: February 24, 2021; Accepted: May 14, 2021]