Abstract: Experimental study was performed to measure the local heat transfer coefficient of a small vertical heater impinged with a single jet of N² gaswater mixture. Very high heat transfer coefficient was recorded at high jet velocity. It was found that heat flux as high as 2.8×10⁸ W/m² was disspated at room temperature from a heated surface, maintaining low temperature only at 58℃. A low heat flux so called negtivc temperature difference was measured. The effects of jet velocity and nozzle-to-plate spacing were investigated experimentally. This cooling method is proposed to be used in microelectronic devices.