Rolling Ball Viscometer Calibration with Gas Over Whole Interest Range of Pressure and Temperature Improves Accuracy of Gas Viscosity Measurement

Abstract

A practical method for measuring gas viscosity uses gas to calibrate the rolling ball viscometer over the whole interest range of pressure and temperature. It reduces the turbulent effect of gas flow around the ball. The viscometer calibration at only atmospheric pressure yields poor results, because it cannot accommodate the turbulent effect at higher pressures. We used nitrogen to calibrate the viscometer for the pressure up to 8,000 psia and temperature up to 260 °F. Optimal tube inclination angle and also ball/tube diameter ratio ensure the laminar flow around the ball and improve the accuracy of the results. Viscosity measurements of ultrapure CO2 confirmed this technique.

Reference Correlation for the Viscosity of Carbon Dioxide

“…53 by the new correlation. Lines are drawn to help the reader to discern the variations of the deviations with pressure and temperature.…”

“…However, the data were neither reported in the publication nor were they provided upon request of the present authors. Davani et al 53 reported measurements with a rolling-sphere viscometer at nine temperatures from 309.82 K to 388.71 K and at five pressures from 27.6 MPa to 55.2 MPa. Vogel 23 recalculated the results of Vogel and Barkow of 1986 54 and those of Hendl et al of 1993 55 by referencing them to the highly accurate viscosity value of helium at room temperature by Cencek et al 28 Locke et al 56 contributed five data points for gaseous CO 2 at 303.2 K and pressures from 0.5 MPa to 4.5 MPa that were measured with a newly developed vibrating-wire viscometer.…”

“…in 2012. 53 A commercial rolling-sphere viscometer was used in this study at nine temperatures from 309.8 K to 388.7 K with pressures from 27.6 MPa to 55.2 MPa. The CO 2 sample had a purity of 99.9999 %.…”

“…14 Percent deviations of the experimental data by Davani et al . 53 from the new correlation are shown vs. pressure in Fig. 18.…”

“…Ranges of increasingly random scattering expand from 3.5 % at 377.6 K and 3.8 % at 366.5 K to 4.7 % at 329.8 K and eventually 6.5 % at 309.8 K. Because of this imprecision, the data of Davani et al . 53 were not used in the development of the new correlation.…”