Time Variation of Nucleate Boiling Heat Transfer of Water under Reduced Pressure

Abstract

When water is heated in a beaker from room temperature, the temperature of the water goes up gradually and reaches the boiling point, where it becomes independent of time. The coefficient of heat transfer, however, varies with time, and after a certain lapse of time, it reaches a stationary state. This paper gives the results of experiment made under reduced pressures on the transient boiling phenomena taking place between the moment when the temperature reaches the boiling point and that when the coefficient of heat transfer becomes stationary. The experiments have been carried out with distilled water over the pressures ranging 0.2∼1.03 ata. Here is shown that the time variation of boiling heat transfer is very regular, which is caused by desorption of gas absorbed during the exposure of the heating surface to the atmosphere and that the rate of time variation of heat transfer becomes lower with pressure.