Molecular Dynamics Study of Phase Transition Heat Transfer in Water Nanofilm on Nanorough Surfaces

The thermal management of micro- and nano-electromechanical systems is closely related to maintaining optimal system performance and reliability. Heat dissipation through the phase transition of the working medium has emerged as an effective approach to these problems. In this study, the phase transition of liquid nanofilms over copper surfaces with various heat fluxes, nanoroughness, and wetting conditions is studied by means of molecular dynamics simulations. The results indicate that the phase transition mode of the water nanofilm is normal evaporation at low heat flux and explosive boiling at high heat flux. Two different nanorough surfaces with the same surface area have almost an identical effect on the water nanofilm phase transition. Explosive boiling occurs earlier on hydrophobic surfaces, which is consistent to the macroscopic phenomenon. The heat flux at which explosive boiling occurs on nanorough surface increases for hydrophobic and neutral surfaces compared with smooth surfaces and remains constant for hydrophilic surfaces. The onset of explosive boiling on nanorough surfaces is later than that on smooth surfaces. These findings on the mechanism of heat and mass transfer at the micro- and nanoscale are conducive to efficient utilization and energy conservation.