Single bubble nucleation in water-filled 59-nm nanochannel

Abstract

Bubble nucleation, by surface heating, is simulated in a water-filled 59 nm height silicon-dioxide nanochannel using computational fluid dynamics. Disjoining pressure of water is integrated in the continuum-level simulations to capture the molecular effects of nanoscale confinement. Input parameters of imposed heat flux and phase-transition coefficient are widely varied to perform a set of 50 simulations. Bubble nucleation occurs within a narrow temperature range of 124.7 ± 2.5 °C, and in excellent agreement with prior experimental finding. Onset of bubble nucleation occurs at the center of the channel rather than at the surface due to the presence of disjoining pressure, i.e., no three-phase contact line forms and a water film is present between the bubble and the surface. Post nucleation, three distinct paths of bubble collapse, steady-state, and continuous growth are observed, with the last case leading to formation of three-phase contact line. Such behavior is attributed to a critical thickness of the water film and associated disjoining pressure. The present work sheds light on the importance of disjoining pressure and its dominance in governing the bubble onset and growth behavior. Such fundamental understanding can potentially advance the development of future thermal management devices, such as heat pipes.