Theory and Design of an Absolute Viscometer for Low Temperature-High Pressure Applications

Abstract

A capillary tube absolute viscometer which is capable of measuring viscosity of a gas from above ambient to very low temperatures, with pressures up to 500 atm, has been designed and constructed. The viscometer has the unique feature of being applicable to low temperatures with the entire flow system maintained at the same temperature. The necessary equation for calculating viscosity measured on this viscometer has been derived. The proximity to and deviation from steady state operation for the viscometer have been clarified analytically. The analysis shows that the deviations from steady state are particularly important at low pressure.