A single-sinker magnetic suspension densimeter based on Archimedes buoyancy principle is described. Density measurements on high-purity nitrogen demonstrate the performance of the densimeter. Comprehensive (p, q, T) measurements at low densities on a gaseous mixture with mole fraction of (0.8977CH4 + 0.1023N2) were carried out on this densimeter at six temperatures from (170.586 to 270.054) K and at pressures ranging from (0.1333 to 1.5945) MPa. The overall uncertainty in density is estimated to be 0.1%. The uncertainty in temperature is estimated to be 5 mK and that in pressure is 250 Pa for (0 to 1.5) MPa and 390 Pa for (1.5 to 3) MPa, respectively. The experimental results of the (methane + nitrogen) mixture were compared with REFPROP 9.0, which used GERG-2008 and AGA8 equations of state to predict thermophysical properties of natural gas. The absolute relative deviations of density measurements are all within 0.1%. Meanwhile the experimental results were correlated using the virial equation of state (Virial EOS) with three different mixing rules. The calculated results using the virial EOS combined with VDW mixing rule show good agreement with the experimental data.
Compounds
#
Formula
Name
1
CH4
methane
2
N2
nitrogen
Datasets
The table above is generated from the ThermoML associated json file (link above).
POMD and RXND refer to PureOrMixture and Reaction Datasets. The compound numbers are included in properties, variables, and phases, if specificied;
the numbers refer to the table of compounds on the left.
Type
Compound-#
Property
Variable
Constraint
Phase
Method
#Points
POMD
1
2
Mass density, kg/m3 ; Gas
Temperature, K; Gas
Pressure, kPa; Gas
Mole fraction - 1; Gas
Gas
Buoyancy - hydrostatic balance with magnetic suspension - one sinker