Jader Riso Barbosa Jr.

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Electrical properties of fluid mixtures are needed in the design of systems in which the process streams or working fluids come into direct contact with electrically live parts. This is the case, for instance, of hermetic refrigeration compressors, in which the refrigerant-lubricating oil mixture inside the crankcase wets the electric motor continuously. Electrical properties of fluid mixtures are also important in the design of phase fraction detectors, like impedance and capacitance void fraction sensors for two-phase flow in pipes. The purpose of this dissertation is to develop an experimental apparatus and an experimental procedure to measure electrical properties (dissipation factor and rel- ative permittivity) of mixtures involving volatile substances (liquefied gases and refrigerants) and oils under different pressure and temperature conditions. The experimental apparatus was designed and built following the recommendations of the german and american standards for measurements of electrical properties of fluids. The procedure was verified against data for pure substances available in the open literature. Experimental results were generated for mixtures of polyol ester (POE) ISO 10 lubricating oil and refrigerants 134a and 1234yf for tem- peratures and solubilities ranging from 25 to 55ºC and 0 to 100%. Empirical correlations were used to predict the relative permittivity of the mixtures, with RMS deviations with respect to the experimental data lower than 1%.

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