Viscosity and velocity slip coefficients for gas mixtures: Measurements with a spinning rotor gauge

Abstract

A selection of experimental measurements for He-Ar, He-N2, and He-Ne binary gas mixtures which were made with a spinning rotor gauge (SRG) 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 and the velocity slip coefficient from the experimentally obtained data for each of the gas mixtures. The measured viscosities are in excellent agreement with existing literature values. Slip coefficients for binary gas mixtures have not previously been reported. An important issue here is whether the velocity slip coefficients for binary gas mixtures can be predicted accurately using separately measured tangential momentum accommodation coefficients. The calculation of slip coefficients from theory requires a knowledge of the accommodation coefficients of each constituent of the mixture. The dependence of these coefficients on the gas composition is not known and the simplest assumption is to regard them as being independent of the composition. The slip coefficients computed in conjunction with this work use this simple assumption in a theoretical expression for the slips. These computations led to reasonable agreement of the theoretical results with our data for the He-Ne mixture. Agreement in the cases of the He-Ar and He-N2 mixtures, however, was less than satisfactory.

Molecular Momentum Transport at Fluid-Solid Interfaces in MEMS/NEMS: A Review

“…[ 134 ], Bentz et al . [ 135 , 136 ] and Jousten [ 137 ] have used the spinning rotor gauge method to test many monatomic and polyatomic gases as well as mixed gases on the steel surface. The method was modified by Bentz et al .…”

Formation of Ammonia Clusters in a Free Molecular Jet of Binary Mixtures

“…Moreover, as implies in the calculations, the velocity slip maximises near a mole fraction of 50% (for 1:1 mixtures). In other works [39,40] the transport coefficients such as the viscosity, thermal conductivity for gaseous mixtures were measured. The dependence of these coefficients on the mixture composition was measured as a function of the mole fraction.…”

Measurements of viscosity, velocity slip coefficients, and tangential momentum accommodation coefficients using a modified spinning rotor gauge

“…[10][11][12][13][14] The technique primarily consists of using a SRG to measure the frictional drag induced by a gaseous medium on a freely spinning, magnetically levitated spherical rotor. The rotor is accelerated electrically to a desired rotational speed by a motor head.…”

“…In previous articles, we discussed the use of the SRG for measurement of these quantities for noble gases ͑He, Ar, and Kr͒, 10 for polyatomic gases ͑N 2 and CH 4 ͒, 11 and for binary gas mixtures ͑He-Ar, He-N 2 , and He-Ne͒. 12 In all of these previous experiments, a SRG was employed in which the axis of the sphere rotation was perpendicular to the axis of the cylindrical tube inside which the sphere rotates ͑in the MKS Instruments, Inc. gauge, the sphere rotation axis is vertical and the tube axis is horizontal͒. 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.…”