A new reference correlation for the viscosity of methanol

A new reference-quality correlation for the viscosity of methanol is presented that is valid over the entire fluid region, including vapor, liquid, and metastable phases. To describe the zero-density viscosity with kinetic theory for polar gases, a new expression for the collision integral of the Stockmayer potential is introduced. The initial density dependence is based on the Rainwater-Friend theory. A new correlation for the third viscosity virial coefficient is developed from experimental data and applied to methanol. The high-density contribution to the viscosity is based on the Chapman-Enskog theory and includes a new expression for the hard-sphere diameter that is a function of both temperature and density. The resulting correlation is applicable for temperatures from the triple point to 630 K at pressures up to 8 GPa. The estimated uncertainty of the resulting correlation (with a coverage factor of 2) varies from 0.6% in the dilute-gas phase between room temperature and 630 K, to less than 2% for the liquid phase at pressures up to 30 MPa at temperatures between 273 and 343 K, 3% for pressures from 30 to 100 MPa, 5% for the liquid from 100 to 500 MPa, and 10% between 500 MPa and 4 GPa. At very high pressures, from 4 to 8 GPa, the correlation has an estimated uncertainty of 30% and can be used to indicate qualitative behavior. (c) 2006 American Institute of Physics.