Evaluation of Heat Transfer Shear of Different Mechanisms in Subcooled Nucleate Boiling

Since the mean characteristic of nucleate boiling is bubble formation andcollapse near the heating surface, in this study attempts have been made toinvestigate heat transfer effects due to the bubbles ebullition and collapse cycle.All possible heat transfer mechanisms are studied qualitatively and quantitatively.For quantitative calculation of the heat transfer portion by each of the introducedmechanisms, a series of bubble parameters was selected from the experimentaldata provided by the high-speed photography of a heated rod containingnucleate boiling regime on its surface. According to the present results, theportion of the mechanisms such as latent heat transfer, super heated layermixing and single-phase heat transfer are between 6~15%, 12~17%, and 3~5%,respectively. The results also show that the two mechanisms of the turbulenceinduced by the bubble formation and collapse and quenching have the mainperformance in transferring heat from the heating surface to the bulk flow. Theshared percentage of these two mechanisms is estimated between 23~58.5%and 20.5~40% respectively.