Abstract
To study the enhancement and degradation mechanism of impinging two-phase heat transfer, air/water two-phase jet was applied on the cooling of copper surface of 30 mm in diameter. The larger heat transfer and stagnation pressure fluctuation were observed with the nozzle of larger diameter. The large nozzle could provide the more significant enhancement of heat transfer and pressure fluctuation with an addition of air. It was considered that the enhancement of heat transfer was due to the stimulation of thermal boundary layer with an addition of air. Furthermore for the actual application, the two-phase jet was generated with the auto air-bleeding nozzle of 8 mm in the outlet inner diameter. Air could be automatically supplied into the nozzle inside with the low pressure generated with the converging water flow. Significant enhancement of heat transfer could be also provided with the air-bleeding nozzle. The distance between nozzle and surface did not affect the enhancement behavior of heat transfer. Air inhalation volume depend on air intake angle. Therefore, to see the absorbing behavior, the observation was done with the high speed camera.
