A Continuously Weighed Pycnometer for Measuring Fluid Properties

Abstract

This paper documents the construction details and experimental procedures for the continuously weighed pycnometer used in our laboratory to measure fluid properties such as densities, saturation pressures, phase boundaries, and isothermal compressibilities. This apparatus consists of a cell suspended from an electronic balance at all times and a variable volume bellows cell which is used to adjust the confined sample density within an isothermal enclosure. The principal advantages of this apparatus are rapid measurement and relatively high accuracy. Some experimental results are presented to illustrate capability. The accessible experimental ranges are 100−450 K up to 200 MPa; measurement accuracy is 0.1% or better.

Sensorless Self-Excited Vibrational Viscometer with Two Hopf Bifurcations Based on a Piezoelectric Device

“…However, the measurement of the damping ratio γ corresponds to that of the kinematic viscosity ρ × η because the damping ratio γ is a function of the kinematic viscosity ρ × η under the condition that the response frequency of the vibrational viscometer is approximately constant as in the present experiments: Figure 8 (for detail, see Appendix A). Accurate estimation of density ρ is much easier because static measurement methods can be used as a pycnometer based on Archimedes' principle [34]. For these reasons, the proposed measurement method based on the bi-instability can be regarded as a measurement for viscosity.…”

Review on Natural Gas Thermopysical Property Measurement Techniques

“…A typical pycnometer consists of a weight measurement system, constant temperature bath, temperature control system and data acquisition system, a volume bellows cell for changing pressure and density without transferring mass, and a high vacuum system [19]. The major component of this method is a constant volume pycnometer suspended from a digital balance.…”

CHAPTER 2. Experimental Techniques 1: Direct Methods

“…The pycnometer is contained within a thermostat and is connected to a filling and pressure system by a fine, flexible capillary tube. Such systems have been developed at Cornell University by Machado and Streett 52 and at Texas A&M University, as described by Lau et al 53 The volume of the pycnometer was determined by calibration with well-characterized fluids, and the mass of sample was determined directly by comparing the weight of the vessel filled with sample and when evacuated. The systems at Cornell and Texas A&M operated over temperature and pressure ranges of (298 K to 489 K, 104 MPa) and (100 K to 450 K, 200 MPa), respectively.…”