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An Improved Greenspan Acoustic Viscometer



J Wilhelm, Keith A. Gillis, J B. Mehl, Michael R. Moldover


We improved the Greenspan acoustic viscometer (double Helmholtz resonator) to measure the viscosity of gases at temperatures from 250 K to 400 K and at pressures up to 3.4 MPa. In anticipation of handling corrosive gases, all wetted parts of the apparatus are made entirely of metal. The improvements include a vibration damping suspension system and a centrally located connection between the resonator and the manifold that supplies gas to it. The symmetry of this location greatly reduces acoustic coupling between the resonator and the manifold. The viscometer was tested with argon, helium, xenon, nitrogen, and methane. Isothermal measurements were carried out at 298.15 K and 348.15 K and at pressures up to 3.2 MPa. Without calibration, the results differed from published viscosity data by -0.8 % to +0.3 % (0.43 % r.m.s.). These results are significantly better than previous results from Greenspan viscometers. The present data also yielded the speed of sound, which differed from literature data by +0.16 % to +0.20 % (0.18 % r.m.s.). Adding empirical effective-area and effective-volume corrections to the data analysis decreased the r.m.s. deviations to 0.13 % for the viscosity and to 0.006 % for the speed of sound. No unusual phenomena were encountered when the viscometer was tested with a helium-xenon mixture between 250 K and 375 K.
International Journal of Thermophysics
No. 5


acoustic resonator, argon, Greenspan viscometer, helium, helium-xenon mixture, methane, nitrogen, speed of sound, viscosity of gases


Wilhelm, J. , Gillis, K. , Mehl, J. and Moldover, M. (2000), An Improved Greenspan Acoustic Viscometer, International Journal of Thermophysics (Accessed April 19, 2024)
Created September 1, 2000, Updated February 17, 2017