Exploring Kinetic-Limited Capillary Evaporation in Nanopores

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Evaporation from tiny nanopores, owing to its high mass/heat transfer fluxes, has found widespread applications in electronics cooling, membrane distillation, solar steam generation and materials synthesis. To further improve performance of these nanopore-evaporation-associated applications, it is essential to understand the ultimate transport limit of evaporation from nanopores. This has been a long-lasting challenge because experimental investigation based on existing nanoporous membranes cannot provide much insight due to difficulty in measuring important parameters. This project will solve this big challenge by directly measuring and studying evaporation from single nanopores. New insights gained from this project will deepen our understanding of evaporation at the nanoscale and shed light on developing optimized evaporative structures. This project includes education/outreach activities for students at various academic levels. Cartoon animations and hands-on lab kits will be developed for K-12 students. Research opportunities will be provided for K-12 students and undergraduates, especially those from underrepresented groups.The research objectives of this project are to understand the kinetic-limited evaporation from nanopores and to achieve the ultimate performance of evaporative nanoporous structures. A novel hybrid nanopore-nanochannel device design will be developed for evaporation measurements and the dependence of the kinetic-limited evaporation flux on nanopore dimension, surface properties, and operating conditions will be systematically investigated. To further understand the separate contributions of the effective evaporation area and the evaporation coefficient on kinetic-limited evaporation, evaporation from atomically thin nanopores will also be investigated. Experimental results of these studies will be compared with MD simulations to gain a complete understanding of the observed dependence. Finally, nanoporous membrane based bi-porous evaporator with optimized pore dimension and porosity will be created and the ultimate evaporation performance of such membranes will be explored.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.