Initial Stage of Nucleate Boiling at Atomic Scale

We investigated the initial stage of nucleate boiling on ideally smooth surface with a molecular dynamics simulation technique. Lennard-Jones model liquid was confined in a rectangular simulation cell, contacting with a flat smooth heating wall. Extra kinetic energy was given to particles in vicinity of the wall. As the temperature of liquid on the wall increases, the liquid thermally expands, which causes the pressure decrease, leading to formation of bubble nuclei, or cavitation, of atomic scale. We found that the nucleation is affected by surface wettability (hydrophobic or hydrophilic) as well as the magnitude of heat flux. When the surface is hydrophobic and the heating area is small, a size oscillation of generated bubbles was observed, which is determined by the balance among the heating flux from the wall, thermal diffusion into the surrounding liquid, and latent heat consumption during the phase change.