MD study of forced liquid film spreading and evaporation in a pore channel

• Effect of external force on evaporation thin film spreading is studied. • Evaporation occurring at both internal meniscus and external liquid film. • There is an optimal range for the liquid supply velocity. • Compound wettability design achieves optimal evaporation performance. Thin liquid film evaporation in porous media with external driving forces provides effective high-heat-flux cooling, but the mechanisms of liquid film spreading and phase transition remain unclear. Molecular Dynamics simulations reveal that under external force, the meniscus curvature radius decreases while the evaporation film extends significantly. External force enables simultaneous evaporation at both pore menisci and external liquid-film interfaces, whereas capillary-driven flow confines evaporation to pore menisci. There is an optimal range for the liquid supply velocity: both insufficient and excessive velocities hinder evaporation. Low velocity reduces evaporation rate and causes incomplete meniscus evaporation, while high velocity forms thick external films increasing thermal resistance. Optimal velocity ensures efficient liquid delivery and maximizes gas-liquid interface area. Wall wettability critically affects evaporation: hydrophobic walls limit film spreading with slow evaporation, hydrophilic walls stabilize evaporation zones, while superhydrophilic surfaces inhibit pore evaporation but enhance external spreading. A composite design (strongly hydrophilic inside/superhydrophilic outside pores) achieves optimal performance by extending synergistic evaporation and enhancing heat transfer based on the MD results.