Effect of Heated Length on the Critical Heat Flux of Subcooled Flow Boiling. Part l: Observation of Bubbles and Slug Length at Atmospheric Pressure

摘要

The effect of the heated length on the Critical Heat Hux (CHF) of subcooled flow boiling with water was experimentally investigated by means of a direct current heated plate made of stainless steel with various lengths. The motion of bubbles at near burnout was observed by a high-speed video camera under atmospheric pressure conditions. Consideration was made of the critical wavelength of the Helmholtz instability in several CHF mechanistic models. The slug length at CHF almost coincided with the critical wavelength. It is further confirmed that when the heated length is shorter than the critical wavelength, a large enhancement of the CHF is seen.