Flow of perfluorohexane in the entry region of a uniformly heated horizontal cylindrical duct was studied in a regime of weakly turbulent mixed convection. Heat transfer coefficients were measured at five cross sections along the heated length and various values of flow rate and heat flux were imposed. A different thermofluid-dynamic behavior was observed between the upper and lower sides of the pipe. Correlations of the Nusselt number for developed and developing flow were proposed, showing agreement with the experimental data within the 10% deviation band.

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