Enhancement of heat transfer due to bubbles passing through a narrow vertical rertical rectangular channel. Theoretical analysis without evaporation on an interface.

Abstract

A theoretical analysis has been made to elucidate the mechanism of the enhancement of heat transfer due to bubbles passing through a narrow vertical channel. This analysis is introduced based on a change in heated surface temperature with a time during which the bubble passes through it. The characteristics of enhancement are given for a constant heat flux and a constant temperature, having a similar tendency to those obtained in the experiment. The heat transfer coefficients obtained are about 2 times as large as those predicted by the analysis. The difference between the results arises from the effect of the flow which is not taken into account in the analysis. In addition, the thickness of the liquid film, which plays an essential role in the enhancement of heat transfer due to the passing bubbles, is 71.7 μm within the experimental range of qw=1.3×104-2.8×105 w/m2, T0=0.1-1.0 sec, and lb=10, 20, and 30 mm.