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

摘要

Since the mean characteristic of nucleate boiling is bubble formation and collapse near the heating surface, in this study attempts have been made to investigate 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 introduced mechanisms, a series of bubble parameters was selected from the experimental data provided by the high-speed photography of a heated rod containing nucleate boiling regime on its surface. According to the present results, the portion of the mechanisms such as latent heat transfer, super heated layer mixing 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 turbulence induced by the bubble formation and collapse and quenching have the main performance in transferring heat from the heating surface to the bulk flow. The shared percentage of these two mechanisms is estimated between 23~58.5% and 20.5~40% respectively.