AVS 45th International Symposium
    Vacuum Technology Division Tuesday Sessions
       Session VT-TuA

Paper VT-TuA6
Viscosity and Slip Measurements with a Modified Spinning Rotor Gauge

Tuesday, November 3, 1998, 3:40 pm, Room 329

Session: Drag Pumping and Transition Flow Phenomena
Presenter: J.A. Bentz, University of Missouri, Columbia
Authors: J.A. Bentz, University of Missouri, Columbia
S.K. Loyalka, University of Missouri, Columbia
R.V. Tompson, University of Missouri, Columbia
Correspondent: Click to Email
The spinning rotor gauge (SRG) has become a practical method in determining the coefficients of viscosity, velocity slip, and tangential momentum accommodation for rarefied gases with a high degree of accuracy. In previous papers, we discussed the use of the SRG for measurement of these quantities for noble gases (He, Ar, and Kr), polyatomic gases (N@sub2@ and CH@sub4@), and binary gas mixtures (He-Ar, He-N@sub2@, and He-Ne). In all of our previous experiments, we considered the axis of sphere rotation parallel to the axis of the cylindrical tube inside which the sphere rotates (in the MKS gauge, the sphere rotation axis is normal to the tube axis). Based on these calculations, we suggested how the results could be used for measurements of viscosity, the velocity slip and the tangential momentum accommodation coefficients. However, the theory used for our calculations required a sphere spinning co-axially to the cylinder. We have modified our experimental apparatus to achieve this geometry. A selection of experimental measurements for He and Ar gases which have been made with a modified spinning rotor gauge are reported. All of the experiments were conducted in the slip regime. Theoretical results from a previous paper on the SRG are used to extract values of the viscosity, the velocity slip coefficient and tangential accommodation coefficient from the experimentally obtained data for both gases. These are compared with previous experimental results. The measured viscosities are in excellent agreement with existing literature values.