Optimization design for sustainable condensation via polymer-deposited nanoengineered surface

Controlling droplet transport behaviors on micro/nanoscale-modified surfaces is a key challenge for condensation enhancement. Improving its efficiency can greatly benefit water harvesting, the organic Rankine cycle, and nuclear power plant safety systems. However, many proposed surface modification methods require intricate steps or costly devices that may hamper the scalability of practical applications. Also, the thermal performance of modified surfaces under non-condensable gas conditions requires further investigation. Here, we propose a two-step facile surface fabrication method. Polytetrafluoroethylene is deposited on chemically decorated silver-coated surfaces to create a multi-scale, multi-material hydrophobic surface. Surface flooding is avoided at high subcooling and under various non-condensable gas concentrations. A heat transfer coefficient increment of 177.3 % at the subcooling of 35 K is achieved by maintaining stable dropwise condensation. The enhancement mechanism is attributed to improving the surface porosity. The hybrid coating layer has a smaller pore width, leading to larger Laplace pressure. As a result, condensing droplets can maintain Cassie state with a decrease of critical sliding radius and an increase of sliding frequency. Furthermore, the optimization design of the macroscale groove array for efficient droplet sliding is achieved by theoretically analyzing droplets’ suction and bridging dynamic behaviors. The proposed surface modification method can benefit a broad range of condensation heat transfer and water-harvesting applications.

© 2024 Elsevier Ltd. All rights reserved.