THE ROLE OF SLIDING BUBBLES IN BOILING ON TUBE BUNDLES
The case is examined for the existence of sliding bubbles in boiling outside tube bundles and their reported influence on the heat transfer. The dryness fraction or quality is used as the basis for examination because at zero quality the contribution from sliding bubble effects is minimal while at higher quality it may be predominant.
Boiling of R113 on a 90-tube bundle is examined and it is shown that a heat transfer model based on boiling or convection occurring, rather than the addition of the two, is more representative of the data. The boiling part is caused by nucleate boiling and the effects of sliding bubbles on the sides of the tubes. In the case of boiling on a single tube in bubbly flow it is shown experimentally that sliding bubbles enhance the heat transfer at the sides. Work on the local mechanism is reviewed and it is concluded that disruption of the liquid boundary layer is more important than evaporation of the mi его layer under the sliding bubble.