Theoretical Studies on Transient Pool Boiling Based on Microlayer/Macrolayer Model : Mechanism of Transition from Nonboiling Regime to Film Boiling

Abstract

An analytical model for transient pool boiling heat transfer was developed in this study. The boiling curves of transient boiling were obtained based on the microlayer/macrolayer models proposed by us and the mechanism of transition from nonboiling regime to film boiling, i.e., direct transition was theoretically examined. Since the nucleate boiling heat flux is mainly due to the evaporation of the microlayer and the initial thickness of the microlayer decreases rapidly with increasing superheat, the duration of nucleate boiling is markedly decreased as the incipient boiling superheat is increased. It is found that the direct transition is closely connected to the rapid dryout of the microlayer which occupies almost the whole surface at high wall superheat.