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accurate measurement of thermophysical properties


Apparatuses for the accurate measurement of density and speed of sound of gases and liquids as well as for the measurement of viscosity of gases are operated at the chair of Thermodynamics. The apparatuses are complex measuring devices, and they are self-constructed. In most cases the measurement principle employed has been developed within the group. → Summary of Measurement Capabilities


Combined Measurement of Density and Viscosity of Fluids and Fluid Mixtures

Within a current DFG-project, (η, ρ, p, T, x)-data of three nitrogen + carbon dioxide mixtures and of three methane + ethane mixtures shall be measured within a temperature range from (253 to 473) K at pressures up to 20 MPa. Viscosity (expanded uncertainty, k = 2: 0.5%) and density (expanded uncertainty, k = 2: 0.1%) measurements will be carried out simultaneously using a viscometer-densimeter. For the same temperature range viscosity shall also be measured with a viscometer for low gas-densities (up to 2.0 MPa) with an expanded uncertainty of 0.3% (k = 2).


Speed of Sound- and Density Measurement of Fluids and Fluid Mixtures

Initially the speed of sound apparatus was used independently. So far, data for several alcohols (Methanol, Ethanol, 1-Propanol, 1-Butanol, Cyclopentane, 2-Propanol, 2-Butanol, Isobutanol, 1,2-Propanediol, 1,3-Propanediol, Ethane-1,2-diol) were measured over the temperature range from (–20 to 80) °C at pressures up to 30 MPa. Moreover, sound speed was measured in Benzene and Heavy Water (D2O). Thereby the expanded (k = 2) uncertainty in speed of sound was estimated to be between (0.011 and 0.036)%. The speed of sound apparatus and the single-sinker densimeter were modified recently so that the speed of sound and the density of fluids and fliud mixtures can be measured simultaneously. Density measurements can be carried out over the temperature range form (–25 to 200) °C. Overall, measurements can be conducted at pressures up to 20 MPa.


Accurate Measurement of the Density of Liquid Mixtures at Cryogenic Temperatures

Within the scope of the EMRP-project “Metrology for LNG“ combined with a research project of the European Gas Research Group (Groupe Europeen de Recherches Gaziers, GERG) an accurate densimeter for cryogenic liquid mixtures was set up. With this special device measurements can be carried out in a temperature range from (–180 to 30) °C at pressures up to 12 MPa. Currently density measurements on liquefied natural gas (LNG) continue within the EMRP-project “Metrology for LNG II“. Moreover, selected binary systems are investigated to improve equations of state for fluid mixtures.


Measurement of the Dielectric Permittivity of binary Gas Mixtures for the Determination of Dew Points
(as of February 1, 2019 at Chemnitz University of Technology, Professor Richter)

Dew points of pure gases or gas mixtures can be determined comparatively accurate as the dielectric properties change when approaching and crossing the phase boundary. Thereby, the phase transition from gas to liquid and the corresponding dielectric permittivity are accurately measured by analyzing the resonance frequency of a microwave re-entrant cavity. Measurements can be carried out with a special apparatus over a temperature range from (–50 to 100) °C at pressures up to 120 bar.


Emmy Noether Research Group (as of February 1, 2019 at Chemnitz University of Technology, Professor Richter)

The DFG funded Emmy Noether group develops new experimental techniques for the accurate measurement of dew-point densities of fluid mixtures. This includes the quantification of sorption effects, thus, significantly reducing uncertainties. Using the experimental results, a new theory will be forged, which will combine, for the first time, the well-established fields of thermodynamic property measurement and surface phenomena. Furthermore, the measured data will be used to establish multiparameter fundamental equations of state, whereby new ideas regarding the fitting strategy will be examined.


Expertise from Previous Projects

Two-Sinker Densimeter

Single-sinker Densimeter

pρT-Measurements with the Two-Sinker Densimeter

pρT-Measurements with the Single-Sinker Densimeter

Magnetic Suspension Balances