| In this thesis, a transient hot wire system capable to measure the thermal conductivity of fluids is designed and used to characterized different ferrofluids. For measurement purposes an electrical insulation is provided to the platinum wire, in order to obtain appropriate values of thermal conductivities of electrical conductive fluid. The influence of some important parameters on the thermal conductivity is studied. Two MnxZn 1-xFe2O4 (a water-based and a hydrocarbon-based) ferrofluids are compared in order to analyze their thermal conductivity. For the produced water-based ferrofluid, a chemical co-precipitation method and a double layer surfactant technique are employed in the production of the ferrofluids. The effect of the particle diameter, base fluid, volumetric concentration "&phis;" and chemical composition in the effective thermal conductivity of the ferrofluids are tested. The coating effect of the wire in the outcome of the transient hot wire system is analyzed by solving numerically the heat equation for the line source case. An enhancement is found in the effective thermal conductivity of all the nanofluids analyzed. |
