Impingement Heat Transfer by Jet Issuing from Cross-Shaped Nozzle.

Abstract

Heat transfer characteristics and flow patterns were measured over the plate for various separation distances between the nozzle exit and target plate when the air issuing from a sharpedged cross-shaped nozzle impinges on the plate. The local heat transfer coefficients in the radial direction for different circumferential positions were calculated using the wall temperatures measured by means of thermocouples, and the flow patterns were observed using a oil-titanium IV oxide method. The isotherms of the infrared images were also measured using an infrared radiometer with a two-dimensional array of InSb sensors. The geometric axes were switched due to the self-induced velocity of a vortex filament ; the convex corners became flat and the concave corners generated outward ejection. The distribution of the iso-heat-transfer-coefficient contours corresponds well to the flow pattern and the isotherm contours. These contours extended diagonally and demonstrated the Andrew's cross pattern for the short separations, subsequently becoming the octagonal patten, and then becoming circular at large separations. The correspondence of the heat transfer characteristic to the flow behaviors, and the heat transfer mechanism were also described.