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.
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).
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.
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. Utilizing this apparatus, density measurements on various LNG-like mixtures and binary mixtures were performed within several projects. The recorded (ρ, p, T, x)-data can be used to validate existing equations of states and/or for the development of new models.
English description will follow.
For the gravimetric determination of adsorption kinetics and equilibria, three different measuring devices based on magnetic suspension balances are available. The first device is designed for kinetic adsorption measurements of gases such as CO2, O2, CH4, or H2 at temperatures up to 150 °C and pressures up to 6 MPa. In order to determine the adsorption of low adsorbing gases like H2, this device is equipped with a highly-sensitive 1 µg balance. The second device (10 µg balance) is optimized for adsorption measurements in the low-pressure range from (0.1 to 200) kPa at temperatures up to 80 °C. With this device, adsorption measurements of the gas phase of a VLE equilibrium of fluids as methanol, toluene, or water can also be performed. These fluids can be filled in an inert gas atmosphere using an existing glove box. The third device (10 µg balance) is originally designed for thermogravimetric measurements at temperatures up to 1200 °C and pressures up to 2 MPa, but is also adapted for adsorption measurements at elevated temperatures. The temperature range of the adsorption measurements is limited due to possible reactions taking place and therefore depends on the measuring system to be investigated.
English description will follow.