Viscosity calculation of supercritical gases based on the Rainwater-Friend theory and the modified Enskog theory

A new correlation function for the calculation of viscosity for five typical supercritical gases is presented using the Rainwater-Friend and modified Enskog theory. It is shown that by using accurate values for the thermal pressure and co-volume in the modified Enskog theory, this correlation function is suitable for calculation of the viscosity of supercritical gases, without any density and temperature limitation. For this purpose, two new correlation functions for the calculation of the thermal pressure coefficient and co-volume are presented. It is also shown that the covolume in the modified Enskog theory depends not only on temperature, but also on density. The accuracy of the calculated viscosity is about 1%, which is much better than the previous work. It is also shown that the modified Enskog theory can be extended to very high density-temperature ranges by choosing correct values for the thermal pressure and co-volume.