In order to raise the heat transfer coefficient of industrial turbine oil, CuO/turbine oil naonofluid suspension is prepared at volume concentrations of less than 1 vol%. An experimental apparatus was designed and constructed to measure the heat transfer coefficient of conventional turbine oil and the nanofluid suspension. The results, clearly, showed that the amount of heat transfer coefficient was higher than the pure oil one under Peclet numbers of less than 300000. The ratio of mean heat transfer coefficient of the nanofluid suspension to that of the pure oil was larger than 1 for all volume concentration and Peclet numbers of this experiment and had the maximum of 1.40. It should be noted that this enhancement has the cost of increasing the pumping power due to the enhancement of the viscosity. Two possible mechanisms of the thermal conductivity enhancement and the increment of thermal development length are discussed.

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