Exploring Kinetic-Limited Capillary Evaporation in Nanopores

微纳米孔蒸发由于其高的传质/换热通量，在电子制冷、膜蒸馏、太阳能蒸汽产生和材料合成等领域得到了广泛的应用。为了进一步提高这些与纳米孔蒸发相关的应用的性能，有必要了解从纳米孔蒸发的最终传输极限。这是一个长期的挑战，因为由于测量重要参数的困难，基于现有纳米孔膜的实验研究不能提供太多的见解。该项目将通过直接测量和研究单个纳米孔的蒸发量来解决这一巨大挑战。从这个项目中获得的新见解将加深我们对纳米尺度蒸发的理解，并为开发优化的蒸发结构提供启示。该项目包括针对不同学术水平学生的教育/外展活动。将为K-12学生开发卡通动画和动手实验室工具包。该项目将为K-12学生和本科生提供研究机会，特别是那些来自代表不足的群体的学生。本项目的研究目标是了解纳米孔的动力学限制蒸发，并实现蒸发纳米孔结构的最终性能。设计了一种新型的纳米孔-纳米通道混合蒸发测量装置，并系统地研究了纳米孔尺寸、表面性质和操作条件对动力学极限蒸发通量的影响。为了进一步了解有效蒸发面积和蒸发系数对动力学限制蒸发的单独贡献，还将研究原子薄纳米孔的蒸发。这些研究的实验结果将与MD模拟进行比较，以获得对观察到的依赖的完整理解。最后，将创建具有优化的孔径和孔隙率的基于纳米孔膜的双孔蒸发器，并将探索此类膜的最终蒸发性能。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

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.