Correlation of viscosity of dense gases with an equation of state.

Abstract

This research was undertaken with the objective of calculating the viscosity of pure gases and their mixtures using the Enskog theory together with a volume translated Peng-Robinson (TPR) equation of state. The TPR equation was used to predict the density which is an independent variable of the radial distribution function ($\chi$) involved in the Enskog equation. In the original Enskog equation,$$\eta=\eta\sb0b\sb0\rho(1/b\sb0\rho\chi + 0.800 + 0.7614(b\sb0\rho\chi))$$the radial distribution function $\chi$ was added to the $\eta\sb0 b\sb0\rho$ term and the constant 0.8 was treated as substance and temperature dependent in this research. The modified Enskog equation$$\eta = \eta\sb0(b\sb0\rho\chi)({1.000\over (b\sb0\rho\chi)} + H\sb{(T)} + 0.7614(b\sb0\rho\chi))$$was found to be satisfactory for the representation of the viscosity for real gases. Extensive comparisons of calculated viscosities with experimental data for pure gases were undertaken over a temperature range from 200 to 1000 K and a pressure range from 1 to 980 atm. The overall average absolute deviations for the viscosity of gas mixtures such as carbon dioxide-methane, argon-neon, carbon dioxide-krypton and hydrogen-nitrogen were less than one percent. The procedure for the prediction of the viscosities for mixtures is simple and straightforward. Only the critical parameters, the accentric factor, and the viscosity at low pressure for the gases are required.