Correlation for the Viscosity of Sulfur Hexafluoride (SF6) from the Triple Point to 1000 K and Pressures to 50 MPa

A wide-ranging correlation for the viscosity surface of sulfur hexafluoride (SF6) has been developed that incorporates generalized friction theory (GFT). The approach requires, as the core thermodynamic model, a reference-quality equation of state (EoS). Here the EoS of Guder and Wagner has been selected for that purpose. All available experimental data, to the extent of our knowledge, were considered in the development of the model. The correlation performs best in the low-pressure (less than 0.33 MPa) region from 300 K to 700 K where the estimated uncertainty (considered to be combined expanded uncertainty with a coverage factor of two) is 0.3%. In the region from 300 K to 425 K for pressures less than 20 MPa, the estimated uncertainty is less than 1%. Where there were data available for validation at temperatures from 230 K to 575 K for pressures up to 50 MPa, the estimated uncertainty is 2%. The correlation extrapolates in a physically reasonable manner and may be used at pressures to 100 MPa and temperatures from the triple point to 1000 K. (C) 2012 by the U.S. Secretary of Commerce on behalf of the United States. All rights reserved. [http://dx.doi.org/10.1063/1.3702441]