Densities, Dielectric Permittivities, and Dew Points for (Argon + Carbon Dioxide) Mixtures Determined with a Microwave Re-entrant Cavity Resonator

Abstract

A microwave re-entrant cavity resonator was used for the determination of dew points, dielectric permittivities, and molar densities of two gravimetrically prepared (argon + carbon dioxide) mixtures, with carbon dioxide mole fractions of 0.9495 and 0.7509. Isochoric dew-point measurements of a (0.0505 argon + 0.9495 carbon dioxide) mixture were carried out over the temperature range from (257 to 291) K at pressures between (2.4 and 6.0) MPa. The measured dew-point pressures were consistent with the predictions of the recently developed multiparameter equation of state optimized for combustion gases (EOS-CG) within 0.35 %. Measurements of each mixture’s dielectric permittivity in the single-phase gas region over the temperature range from (273.2 to 313.3) K at pressures up to 6.5 MPa were used to determine the mixture molar densities at the same conditions. The method used to determine mixture molar densities from microwave-cavity measurements is based on an inversion of the polarizability mixing rule developed by Harvey and Prausnitz. The microwave-determined mixture densities had relative deviations from values measured for the same mixture with a two-sinker magnetic-suspension densimeter of 0.3 % or less. The new mixture density data agree within 0.37 % of predictions made using the EOS-CG and help identify literature data sets that should receive lower weighting in future model development.

Accurate High‐Pressure Measurements of Carbon Monoxide's Electrical Properties

“…However,f or polar,n on-conducting fluids such as CO, e'' is negligible below about 2GHz (see also Ref. [13]). Changes in the position of the boundary conductors, which determine the vacuum resonant frequency,v ary with the re-entrant cavity temperature T and pressure p as discussed, for example, by May et al [38] This variation can be represented by [Eq.…”

“…The experimental system used for the measurements in CO is the same as the one described previously by Ts ankova et al [13,14] for phase boundary,d ielectric permittivity and mixture density determinations of carbon dioxide-rich gas mixtures. The apparatus was originally constructed and built by the National Engineering Laboratory (NEL, East Kilbride, UK) [32] for determinations of the heating value of natural gas, based in part on dielectric permittivity measurements.…”

“…Therefore, robust experimental devices for accurate measurements over wide temperature and pressure ranges that are particularly suitable forr apid measurements in aggressive and hard-tohandle fluids are of great importance.M icrowaver e-entrant cavities [11,12] have shownt heir applicability where such experimentsa re required. Moreover,T sankova et al [13] have recently shown how dielectric permittivity measurements for high-pressure mixturesc an be used to determine mixture molar densities with relative combined expanded uncertainties (k = 2) 0.3 %, if the molar polarizabilities of the pure component fluids are adequately known. This approacho fferss ignificant opportunities for density determinationso fi ndustrially-impor-Accurate measurements of carbon monoxide's electrical properties were carriedo ut at high pressure for the first time enabling stringent comparisons with theoretical values calculated ab initio.…”

“…The experiments reported in the current paper were carried out by meansofamicrowaver e-entrant cavity resonator,w hich was recently presented by Ts ankovae tal. [13,14] for dew point as well as for dielectric permittivity andm ixture density determinations of carbon dioxide-rich fluid mixtures.I nt he present work, we report the first measurements of CO's dielectric permittivity at high pressures up to 8MPa. The experiments were conducted along four isotherms T = (255.10, 273.17, 293.25 and 313.28) K. Moreover,w ef itted the new dielectric permittivities to ac orrelation based on ad ielectric virial expansion for polar fluids, allowing the second dielectric virial coefficient, the electric dipole moment and the molecularp olarizability of the CO's molecule to be calculated.…”

Experimental density and an improved Helmholtz-energy-explicit mixture model for (CO2 + CO)

“…However, two major deficiencies were identified: first, some binary systems present large regions without data; second, there are significant discrepancies between different data sources. Despite some recent improvements in the data situation, including Tsankova et al [21,22] and Løvseth et al [23] on (CO2 + Ar), Petropoulo et al [24] on (CO2 + CH4), and Tsankova et al [25], Westman et al [26] and Souza et al [27] on (CO2 + CO), these deficiencies remain.…”