Experimental investigations were performaed on the flat plate cooling effectiveness through infrared thermography technique. Surface temperature distribution on the flat plate was measured by means of infrared thermography. The experimental facility and infrared thermography method are described in detail. Tests were conducted under different blowing rations which range from 0.3 to 2.0. The result, presented in terms of cooling efficiency distribution along the plate surface shows the influence of blowing ration on heat transfer. The maximum cooling efficiency achieved in the immediate region with a blowing ration of 0.3, then decreases significantly along the streamwise direction. Cooling efficiency increase slightly at the high blowing ration in far downstream area because of the jet adhere to the plat again. Along the spanwise direction, the jet concentrated in the center of the hole at low blowing ration, while spread evenly at high blowing ration. The jet can take different forms, depengding on the blowing ration, the jet can remain attached, detach and reattach or lift-off comletely. Therefore, cooling efficiency does not change with blowing ration monotonously.
