Temperature-compensated 3omega hot wire instrument for thermal conductivity and thermal diffusivity of liquids
The amplitude and phase of 3? hot wire signal can be exploited to simultaneously and independently determine the sample thermal conductivity k and thermal diffusivity a. A patented temperature-compensated dual-probe configuration cancels the large unbalance of the fundamental frequency in temperature-dependent processes. Thus k of vegetable oils for use in concentrated solar power plants was determined in the range from the ambient to 230 oC. High resolution k and a measurements were performed on nanofluids. Mean-field theory was used for modeling the effective k of ferrofluids, allowing for determination of interfacial thermal resistance between magnetite particles and base fluid. This in turn resulted in k estimation of the double molecular layer of surfactant (monocarboxylic acid) surrounding the particles, the role of which is to prevent particle sedimentation. Eventually, the equivalent axial thermal conductivity of a single monocarboxylic acid molecule was derived, which is consistent with the respective bulk value.
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Mihai Chirtoc (POC,Primary Presenter), University of Reims Champagne-Ardenne, email@example.com;