Viscosity of NaCl Aqueous Solution under Supercritical Conditions: A Molecular Dynamics Simulation

Abstract

Reverse nonequilibrium molecular dynamics (RNEMD) simulation has been carried out to study the concentration dependence of the viscosity of sodium chloride aqueous solution under supercritical conditions. This simulation predicts the viscosities of pure water at two supercritical conditions with deviations from experimental values within 3 %. The calculated viscosity of sodium chloride solution increases with increasing concentration. The simulated viscosities are also compared with an empirical correlation derived based on experimental values at subcritical conditions. However, with the same increment of concentration, the viscosity of sodium chloride aqueous solution increases much slower than that at subcritical conditions. For example, at a concentration of 2.886 mol·kg−1 and at conditions of 700 K, 600 kg·m−3 and 700 K, 700 kg·m−3, the viscosities of supercritical sodium chloride aqueous solution increase 8 % and 11 %, respectively, when compared with pure water, while the predicted increment of viscosities by the empirical correlation is about 50 % .