International Journal of Thermophysics, Vol. 22, No. 1, 2001 Viscosity of Natural-Gas Mixtures: Measurements and Prediction 1 M. J. Assael, 2, 3 N. K. Dalaouti, 2 and V. Vesovic 4 New measurements of the viscosity of a natural-gas mixture are reported. The measurements were performed in a vibrating-wire viscometer, in the temperature range from 313 to 455 K at a pressure close to atmospheric and in the temperature range from 240 to 353 K at pressures up to 15 MPa. The uncertainty of the reported measurements is estimated to be \1 0. The data were employed to validate further an existing method of predicting the viscosity of mixtures at high pressures. KEY WORDS: natural gas; vibrating wire; viscosity. 1. INTRODUCTION Although natural gas is widely used for both domestic and industrial use, very few measurements of its viscosity have been reported in the open liter- ature [13]. The available data sets are further restricted, since in only a few cases are all the details of the experimental setup published, thus making it very difficult to judge the uncertainty and reliability of the published data. To our knowledge, only two investigators [1, 2] have reported measure- ments of the viscosity of natural-gas mixtures obtained in a well-charac- terized apparatus with an adequate uncertainty. The present measurements attempt to fill this gap. Natural gas is a multicomponent fluid mixture, and the behavior of natural-gas transport properties thus represents a challenging test for devel- opments in kinetic theory. The development of predictive methodology to 61 0195-928X010100-006119.500  2001 Plenum Publishing Corporation 1 Paper presented at the Fourteenth Symposium on Thermophysical Properties, June 2530, 2000, Boulder, Colorado, U.S.A. 2 Faculty of Chemical Engineering, Aristotle University, 54006 Thessaloniki, Greece. 3 To whom correspondence should be addressed. 4 TH Huxley School of Environment, Earth Sciences and Engineering, Imperial College, London SW7 2BP, United Kingdom.