Dynamics of water condensation on a switchable surface originated from molecular orientations.

Abstract

In heat transfer systems, how water condenses on the surface is critical to the energy efficiency of the system. With fixed surface wettability, hydrophilic surfaces enhance the nucleation rate but result in filmwise condensation due to pinning effect, which impedes the heat transfer between water vapor and surface during droplet growth. A hydrophilic surface with high drop mobility is realized with static tailored wettability surfaces, while tunable surfaces have potential in more comprehensive manipulation in condensation with different scale in time and scale. However, the mechanism has rarely been investigated and elucidated. In this paper, we investigate water condensation on a tunable surface originated from surface tension distribution control. The surface tension distribution under applied electric field is modeled and tested. We demonstrate that the surface tension manipulated by liquid crystal orientation alters the nucleation site density. Also, the periodic surface tension distribution aligns condensed water drops and decelerates the radius growth of droplets. The mechanism of active water condensation manipulation can be further applied to other tunable surfaces for various applications such as atmospheric water generator, heat transfer systems, and desalination systems.