A new representation of the viscosity of propane includes a zero-density correlation and an initial-density dependence correlation based on the kinetic theory of dilute gases and on the Rainwater–Friend theory. The higher density contributions of the residual viscosity in the representation are formed by a combination of double polynomials in density and reciprocal temperature, and a free-volume term with a temperature-dependent close-packed density. The full surface correlation is based on a set of primary experimental data selected as a result of a critical assessment of the available information from 37 original viscosity studies. The review refers to 96 citations altogether. The validity of the representation extends from the triple point to 600 K and 100 MPa in accordance with the modified Benedict–Webb–Rubin equation of state. The uncertainty of the representation varies from ±0.4% for the viscosity of the dilute gas phase between room temperature and 600 K, to about ±2.5% for the range 100–475 K up to about 30 MPa, and to about ±4% for points outside this range. Tables of the viscosity according to the representative equations at selected temperatures and pressures and along the saturation line provide easy reference as well as the validation of computer codes.
A vibrating-wire viscometer of very high precision was used to measure the viscosity of methane and of two natural gases. The experimental data were, in general, taken at temperatures of 260, 280, 300, and 320 K and at pressures up to 20 MPa, and additionally in the case of methane at temperatures of 340 and 360 K and at pressures up to 29 MPa. The estimated uncertainty is ±0.3 and ±0.5% for methane and the natural gases, respectively. The new experimental data for methane were used together with zero-density or low-density viscosity values from this study and from the literature to develop a viscosity equation for natural gas composed of two contributions. The mixing rule of Wilke [J. Chem. Phys. 18: 517 1950] was applied for the zero-density viscosity part which is based on zero-density correlations for twelve components (methane, nitrogen, carbon dioxide, ethane, propane, n-and isobutane, n-and isopentane, n-hexane, n-heptane, and n-octane) and agrees with the values derived from experiment within ±0.3%. The density dependence of the residual viscosity part was correlated with methane data only, neglecting any temperature dependence, whereas the composition dependence is characterized by a pseudo-critical viscosity value. For methane the agreement between the correlated and experimental data is within ±0.5%. The values predicted with the correlation and the experimental data agree within ±1% for both the high calorific, H, natural gas and the low calorific, L, natural gas.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.