Bubble Dynamics in Sub-cooled Nucleate Boiling

Generation, growth and departure dynamics of bubbles are the important physics associated with the study of nucleate boiling. Contrary to the saturated liquid condition, the growth and departure processes under sub-cooled condition have been found to reveal varying dynamical and thermal responses. The phenomenon is dominated by the phase-change occurring as a result of condensation at the interface near the sub-cooled liquid, evaporation at the superheated liquid layer and the microlayer evaporation. The microlayer is a thin liquid layer underneath the growing bubble which is formed as a result of viscous stresses acting at the liquid attached to the wall. The bubble, influenced by the combined effect of various phase-change processes may depart, oscillate or remain attached to the substrate depending on the degree of subcooling of liquid. The present work demonstrates such phenomena exhibited by a single nucleating bubble through numerical simulations using the solutions of complete Navier-Stokes and energy equations. The numerical technique incorporates the combined level-set and volume of fluid (CLSVOF) approach for interface capturing and a microlayer-model to determine the phase-change contribution associated with the microlayer.