Singh, V; Kabi, P; Mandal, P; Zhang, J; Bahal, S; Tiwari, MK; (2023) NANOHIERARCHICAL METAL-ORGANIC FRAMEWORKS FOR ENHANCED DEW HARVESTING EFFICIENCY. In: Proceedings of the 17th International Heat Transfer Conference, IHTC-17. IHTC: Cape Town, South Africa.

Text IHTC-17-paper.pdf - Accepted Version Access restricted to UCL open access staff Download (1MB)

Abstract

Dropwise condensation is extremely important in a wide range of energy applications such as powerplant heat exchangers, water harvesting, thermal desalination, self-cleaning surfaces, and heating and air conditioning. At the same time, developing a coating that promotes dropwise condensation with mechanochemical robustness is a challenge. Here, we designed a nanohierarchical coating with three levels of nanoscale roughness. This was achieved by growing metal-organic frameworks (MOF) on nanoporous alumina obtained via environmentally friendly anodization. Zirconium based MOF is selected due to their exceptional chemical resistance and high shear stability to protect sensitive, alumina substrate. MOF is grown using covalently attached self-assembly of organic linker to form conformal 3D network of interconnected nanoparticles which demonstrated strong mechanochemical robustness. Post-synthetic functionalization with long-chain alkyl silane altered the wettability from hydrophilic to superhydrophobic. The surfaces demonstrated excellent mechanochemical robustness tested under a series of tape peeling, mechanical abrasion and chemical immersion tests and are suitable for power plant condensers. Finally, the advantage of using a nanohierarchical design, specifically in dew harvesting, is established by studying the water condensation rates of similarly textured surfaces, in presence and in absence of MOFs over long durations (8 hours). Preliminary results show that the MOF on alumina is indeed effective in increasing condensation flux when compared to similarly textured surfaces and does not fail even after 70 hours of continuous dew harvesting.

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