THEORETICAL MODEL FOR BUBBLE FREQUENCY IN NUCLEATE POOL BOILING INCLUDING SURFACE EFFECTS.

One of the important boiling parameters is the frequency of bubble departure. A theoretical model is formulated herein to predict the bubble frequency as a function of the nucleation cavity radius as well as the surface superheat and liquid subcooling. In this model, the time variations of the surface temperature throughout the bubble cycle are incorporated. Parametric study of the predictive equations shows that the frequency of bubble departure decreases with the decrease of surface superheat and the increase of liquid subcooling, a trend which agrees with the published data. It is also shown that smaller nucleation cavities are able to emit vapor bubbles with higher frequencies than those corresponding to the larger cavities. Experimental results obtained by boiling water and iso-propyl alcohol on a single copper surface having two different surface finishes showed good agreement with the theoretical model.