Heat Transfer Characteristic of a Duct Flow with Longitudinal Vortices Induced by an Inclined Impinging Jet. (1st Report, Measurement of Wall Heat Transfer Coefficients Using Thermochromic Liquid Crystal.)

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Heat transfer measurements were carried out for an inclined impinging jet into a crossflow. Surface temperatures of a heat transfer target wall were measured using thermochromic liquid crystal sheets. Neural network method was applied to conversion of the colors of the liquid crystal sheet images into the temperatures. The inclined jet is characterized by the following two angles ; one is a pitch angle measured up from the jet-installed wall and the other a skew angle measured from the crossflow direction. The flow configuration of this experimental apparatus was designed in the new idea that longitudinal vortices could be generated by the inclined impinging jet into the crossflow to enhance heat transfer from the target surface. It was demonstrated that heat transfer enhancement was attained over wider spanwise region when the ratio of the jet velocity to the crossflow velocity is increased, and that peak Nusselt numbers appeared around z/d=5 constantly regardless of the velocity ratio.