Theoretical model of microlayer formation for isolated boiling bubble

When a vapor bubble grows on a heated surface, a thin liquid layer (microlayer) forms at the base. Evaporation of the microlayer plays an important role in bubble growth during nucleate boiling, with a strong dependence on the initial thickness of the microlayer δ0. Thus, inaccurate prediction of the initial microlayer thickness leads to considerable error in the growth behavior of a single bubble, with accumulation generating physically unreasonable pictures for boiling heat transfer phenomena. The aim of this paper was to conduct a new experiment to aid the understanding of hydrodynamic phenomena during the formation of a microlayer underneath a boiling bubble, and to develop a sophisticated theoretical model for initial microlayer thickness that is in agreement with experiment. In conclusion, we studied the hydrodynamic formation of the microlayer beneath a vapor bubble growing on a heated surface in a stagnant pool. Classical models contain several idealizations (hemi-spherical bubble shape and neglecting surface tension effects), and significantly overestimate the initial microlayer thickness relative to experimental results. Precise observation of the growing bubble geometry during microlayer formation indicates that the bubble is oblate with a transition region between the microlayer and the macroscopic liquid, which reveals that surface tension plays a role in the process. This study also demonstrates the critical role played by the short-lived residual flow in microlayer formation.