A simple generalized viscosity model for natural gas components and their mixtures based on free-volume theory

Abstract

This work presents a generalized viscosity model for both the gaseous and dense fluids based on free-volume theory (FVT). The characteristic parameters of FVT were reduced using the Lennard-Jones molecular parameters: the potential strength (σ) and the atomic diameter (ε), and the reduced parameters were correlated with the molecular weight of fluids. The generalized viscosity model has only 6 constant coefficients, which were determined by 5573 experimental viscosity data of 8 basic natural gas components. It indicates that the generalized viscosity model can represent the viscosity of 8 basic natural gas components well with the average absolute relative deviation (AARD) of 2.27%. To check the predictive ability of the generalized model, the viscosity of 7 natural gas components not used in the equation fitting were calculated using the model, comparisons were made to the calculated results of the specific equations in REFPROP 10.0 software with the AARD of 3.92%. Furthermore, 2147 experimental viscosity data of 14 natural gas mixtures were compared to the calculated result of the generalized model, good agreement was found with a total AARD of 3.40%. It is shown that the generalized model provides a simple and reliable way for the viscosity calculation of natural gas.