A Unified Relationship for Evaporation Kinetics

We experimentally realized and elucidated kinetically limited evaporation where the molecular gas dynamics close to the liquid-vapor interface dominate the overall transport. This process fundamentally dictates the performance of various evaporative systems and has received significant theoretical interest. However, experimental studies have been limited due to the difficulty of isolating the interfacial thermal resistance. Here, we overcame this challenge using an ultrathin nanoporous membrane in a pure vapor ambient. We showed that kinetically limited evaporation, when normalized properly, is solely determined by the pressure ratio between the ambient and the interface. We modeled the nonequilibrium gas kinetics and demonstrated good agreement between experiments and theory. Our work illustrates a unified fundamental relationship between the interfacial flux and the driving potential for evaporation in the dimensionless form. It also provides a general figure of merit for evaporative heat transfer as well as design guidelines for achieving efficient evaporation in applications such as water purification, steam generation, and thermal management.

Related Articles: Nature Communications 2019, Nano Letters 2017

Media Coverage: MIT News