Evaporation of Water Confined in a Cylindrical Pore

It was previously demonstrated in experiment that the vaporization enthalpy of water significantly decreased when it was confined in a nanopore. As a result, the evaporation rates can be significantly enhanced by covering the surface of water with a porous carbon fiber mat. To improve the design of porous materials for future applications such as water purification, we utilize molecular dynamics simulation to investigate the molecular mechanism of water vaporization enthalpy reduction under nanoconfinement. A water cylinder is placed inside a cylindrical tube with a contact angle determined by the interaction strength between the water molecules and the tube wall. Simulation results indicate that as the contact angle gets smaller (i.e., the lumen of the tube becomes more wettable), the evaporation flux of water also becomes smaller. At a given contact angle, as the tube diameter is reduced, the evaporation flux per cross-sectional area is slightly enhanced. Our results indicate that to further enhance evaporation of water confined in a nanopore, a possible strategy is to make the pore lumen less wettable and to use smaller pores.