Approximate Correction for Unsteady Pressure Differential in a Capillary-Tube Gas Viscosimeter

Equations are developed which satisfactorily describe the change in the pressure differential with time for a closed, constant-volume system which utilizes a coiled-capillary tube and a constant-rate pump to determine gas viscosities. Viscosities are computed at transient, unsteady, and apparent-steady-state conditions. As long as the flow rates are not too high and the pressure level is not too low, the computed viscosities appear to be reliable.