Simultaneous measurement of density and viscosity of n-pentane from 298 to 383 K and up to 100 MPa using a vibrating-wire instrument

Abstract

Experimental results of density and viscosity of n-pentane are reported at temperatures from 303 to 383 K and pressures up to 100 MPa. The two properties were measured simultaneously using one single vibrating-wire sensor, which is composed of a sinker suspended from a thin metallic wire, both of which are immersed in the sample fluid. The oscillation characteristics of the wire are obtained by means of an electromagnetic coupling. The response of the wire is related to the density of the fluid mainly through the buoyancy force acting upon the sinker, whereas the viscosity of the fluid affects the damping of the oscillations. The technique is based on a rigorous theoretical framework and thus, once all of the sensor parameters are known, either by independent means or from a single reference experiment, no extensive calibration procedures are required for measurements at high pressure or at temperatures away from ambient conditions. The present results of density exhibit a precision of ±0.04% and an estimated accuracy of ±0.2%. The viscosity measurements exhibit a precision of ±0.5% and are judged accurate within ±2.5%. Tests of the instrument with gaseous nitrogen are reported in order to assess the performance of the technique when measuring in a fluid of low viscosity.