Predicting the Viscosity of Pure Light Hydrocarbons

8. E. EAKIN R. T. ELLINGTON MEMBERS AIME The following equation, which describes the viscosity of methane, ethane, propane and n-butane in the vapor, liquid and dense-fluid regions for densities up to 2.4 times the critical density, is presented. . fJ= fJ-o .• + A(e7 .mP e-"··P-) where A = 32.80 0.1637 (M), micropoises, fJ-v .• = gas viscosity at atmospheric pressure and the fluid temperature, micropoises, p = density of the fluid, gm/ cc, and M = molecular weight The atmospheric-pressure viscosity can be represented satisfactorily by Sutherland's equation for which values of the necessary constants are given. The equation represents the data on these materials over the entire region with a standard deviation of 1.6 per cent for 288 points. Except in the immediate vicinity of the critical density , the largest difference between predicted and observed viscosity was 4.3 per cent. To facilitate calculations, the equation is presented as a single curve of fJfJ-u' . evaluated for a gas of zero molecular weight. By modification of the co-ordinates, the curve becomes a straight line. The factor for converting the curve value of fJfJ-u'. to that for the actual gas is a linear fun ction of molecular weight, and is also plotted.