Experimental Setup for Measuring the Thermal Conductivity of Pressurized Solutions

Knowledge about the thermal conductivity is expedient whenever heat transport is involved in a process. As pressure plays an important role in a multitude of treatments or reactions, conductivity measurements have also been carried out under pressure for various substances (e. g. lubricants, plant oils and several foods). Experimental data are needed as this property cannot be derived from equations of state. Nevertheless, data about thermal conductivity of pressurized fluid mixtures are scarce. Hence, an apparatus appropriate for measuring thermal conductivities of dense and supercritical solutions under pressure was set up in this work. The applied principle of measurement is based on transient heat transfer. A line heat source was used as the probe and the maximum slope evaluation method without the need for calibration was applied. The thermal conductivity of polydimethylsiloxane (Mw = 11000 g/mol) has been found to increase under helium pressure and the results were in good agreement with comparison values obtained by a hot-wire method. Consequently, first measurements on polydimethylsiloxane saturated with gaseous carbon dioxide were carried out at 25 °C. In this case, the conductivity decreased in the investigated pressure range up to 5 MPa.