An Experiment of Nucleate Boiling under Reduced Pressure

Abstract

There have been more than one publications issued on the heat transfer of nucleate boiling under a pressure lower than atmospheric pressure, but little is yet known about the mechanism of boiling. The experiments given in the present work have been carried out with distilled water with the ranges of heat flux and pressure covering 9000∼30000 kcal/m²h and 0.4∼1.033 kg/cm² abs. respectively. It has been verified that the diameter of a bubble just leaving the heating surface decreases and the frequency of bubble formation increases with pressure and that the generation of bubbles becomes irregular under reduced pressure. The physical meaning of pressure factor in the correlating equation of nucleate boiling heat transfer that had been derived by one of the authors, has not been clarified yet. The data of the present experiment have led the authors to find that the pressure factor is only modifiable to the rate of growth of bubbles.