Heat transfer characteristics based on microlayer structure in nucleate pool boiling for water and ethanol

The objective of the study is to elucidate the contribution of the microlayer evaporation on heat transfer in nucleate pool boiling of an isolated bubble region for water and ethanol on the basis of microlayer thickness measurement. The distribution of microlayer thickness formed under a growing bubble was measured by laser extinction method using a specially devised system with a thin optical fiber fabricated in a thin tube and gas blowing in former report. In this study, the dominant factors that determine the microlayer characteristics, such as thickness distribution, duration and area on the heat transfer surface were expressed by non-dimensional form based on the similarity of bubble growth rate. Furthermore, a numerical simulation was performed based on modeling of the boiling system. The heat transfer characteristics in nucleate boiling were investigated and the contribution of evaporation from the microlayer during nucleate boiling of isolated bubble region is demonstrated using the relations among dominant factors.