Ab initio Calculated Results Require New Formulations for Properties in the Limit of Zero Density – The Viscosity of Methane (CH4)

Published: October 27, 2017

Author(s)

Arno R. Laesecke, Chris D. Muzny

Abstract

A wide ranging formulation for the viscosity of methane in the limit of zero density is presented. Using ab initio calculated data of Hellmann et al. from 80 K to 1500 K, the functional form was developed by guided symbolic regression with the constraints of correct extrapolation to T  0 and in the high temperature limit. The formulation was adjusted to the experimental data of May et al. from 2007 so that these are represented within their estimated expanded uncertainty of 0.096 % (k = 2) in their temperature range from 210.756 K to 391.551 K. Based on comparisons with original data and recalibrated viscosity ratio measurements, the uncertainty of the new correlation is estimated to be 0.2 % to 700 K, 0.4 % to 1100 K, 1 % to 1500 K, and physically correct at higher temperatures. At temperatures below 210 K the new correlation agrees with experimental data within 0.2 % down to 150 K. Hellmann et al. estimated the uncertainty of their calculated data at 1 % to 80 K. The new formulation extrapolates in a physically correct way to T -> 0.
Citation: International Journal of Thermophysics
Pub Type: Journals

Keywords

Correlation, limit of zero density, methane, molecular interactions, reference standards, symbolic regression, viscosity.
Created October 27, 2017, Updated October 30, 2017