Viscosity surface for mixtures of methane and ethane

Abstract

The viscosity surface for methane-ethane mixtures has been correlated as a function of composition, density and temperature. The correlation is based on measurements, made at the National Institute of Standards and Technology, using a torsionally oscillating quartz crystal viscometer, which have been reported previously. The viscosity data cover the composition range including both pure fluids and three of their binary mixtures and include temperatures from 100 to 320K with pressures to 30 MPa. The correlation comprises contributions from the dilute gas state, based entirely on Chapman-Enskog mixture theory and an empirical excess function. The excess function exploits corresponding states arguments and, with suitable reductions of the viscosity, density and temperature, the data are seen to conform closely to a single function of the reduced quantities. The very steep rise of viscosity at high densities is described by a simple rational polynomial and this is added to another polynomial in reduced density and temperature to completely represent the reduced excess viscosity. For the 624 experimental points which were considered, the average absolute deviation from the correlation is less than 1.5%.