Nanobubble nucleation in pool boiling systems via non-equilibrium molecular dynamics simulations*

Pool boiling is a complex and out of equilibrium process and key phenomena take place at different scales. Molecular interactions are particularly important as they strongly affect the resulting nano-bubble nucleation as a result of the combined effect of wettability, wall superheat and surface roughness. The interplay of these parameters is here investigated at the nanometre scale through non-equilibrium molecular dynamics simulations for a Lennard-Jones system. A rectangular cavity is considered as nucleation spot and its width-to-depth ratio is taken as a measure of the defect size effects. Heat is uniformly provided from the bottom through a tethered solid wall. Nucleation times are directly extracted from the MD data and fitted to a classical nucleation theory-based model, resulting in a good agreement. The systematic analysis of the effect of all the aforementioned parameters is summarized in a phase diagram and interesting insights into the boiling process are achieved by analysing the heat flux and temperature fields inside the nucleation spot. The conducted analysis shows a promising way to link the molecular scale to higher-scale models in a more general multiscale framework.