An experimental study on the flow and heat transfer characteristics of longitudinal vortices induced by an inclined impinging jet into a crossflow (Measurements of heat transfer coefficients using thermochromic liquid crystal)

Heat transfer measurements were carried out for a turbulent inclined impinging jet issued into a crossflow. The inclined jet is characterized by the two angles; a pitch angle raised from a horizontal jet-installed wall and a skew angle measured in horizontal plane from the crossflow direction. The present study was designed to see if longitudinal vortices can be induced by the inclined impinging jet itself and it is effective to enhance heat transfer from a target wall. The surface temperatures of the target wall were measured using thermochromic liquid crystal sheets, the color images of which were taken with a CCD video camera. Neural network method was applied to transform accurately and effectively the color images into wall temperature distributions. It is demonstrated that heat transfer enhancement is attained over a wider spanwise region as the velocity ratio of the jet to the crossflow is increased, and that a peak Nusselt number appears around the same spanwise location off the jet nozzle regardless of the velocity ratio.