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Wetting behavior-dependent heat transfer performance during dropwise condensation on engineered hydrophobic surfaces.

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Title: Wetting behavior-dependent heat transfer performance during dropwise condensation on engineered hydrophobic surfaces.
Authors: Lo, Chi-Chun1 (AUTHOR), Chen, Li-Jen1,2 (AUTHOR) ljchen@ntu.edu.tw
Source: International Journal of Heat & Mass Transfer. Aug2026, Vol. 264, pN.PAG-N.PAG. 1p.
Subjects: Wetting, Heat transfer, Hydrophobic surfaces, Surface roughness, Film condensation
Abstract: Global water scarcity has intensified the demand for efficient technologies to harvest atmospheric moisture. Dropwise condensation (DWC) stands out for its superior heat transfer performance due to the rapid removal of discrete droplets. However, the efficiency of DWC is governed by the wetting behavior of condensed droplets, which remains a topic of active investigation. Fourteen hydrophobic surfaces with single-micro-scale and dual-scale (micro-nano-scale) roughness were fabricated. The condensed droplets on these surfaces exhibit four wetting states: Wenzel state, Cassie state, partial Cassie (Wenzel-Cassie mixed) state, and Wenzel state with irregular three-phase contact lines. The results demonstrate that stable Cassie DWC can occur on single-micro-scale roughness surfaces, not just on dual-scale roughness surfaces. On single-micro-scale roughness surfaces exhibiting Cassie DWC , high droplet mobility, and an average departure diameter of 741.5 µm, a 33.0% enhancement in both condensate mass collection rate and heat transfer performance is observed relative to the flat substrate. In contrast, Wenzel DWC surfaces show the most significant reductions in both metrics, with degradation of up to 15.9%. Although dual-scale roughness surfaces also exhibit Cassie DWC , condensation mechanisms and limited surface durability reduce condensate collection, resulting in approximately half the condensate mass collection rate compared with single-micro-scale Cassie DWC surfaces. Overall, the lower fabrication cost, simpler processing, and improved durability of single-micro-scale roughness Cassie DWC surfaces present a promising and practical alternative for scalable applications such as power generation, desalination, and thermal management. • The droplet's wetting behavior effect on condensation heat transfer is discussed. • Single-micro-scale surfaces show a + 33% in heat transfer compared to flat substrates. • Single-micro-scale surfaces balance the heat transfer and water collection efficiency. • Dual-scale surfaces can stably maintain the Cassie dropwise condensation. • Coalescence-induced jumping is only observed on dual-scale surfaces. [ABSTRACT FROM AUTHOR]
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Database: Engineering Source
Description
Abstract:Global water scarcity has intensified the demand for efficient technologies to harvest atmospheric moisture. Dropwise condensation (DWC) stands out for its superior heat transfer performance due to the rapid removal of discrete droplets. However, the efficiency of DWC is governed by the wetting behavior of condensed droplets, which remains a topic of active investigation. Fourteen hydrophobic surfaces with single-micro-scale and dual-scale (micro-nano-scale) roughness were fabricated. The condensed droplets on these surfaces exhibit four wetting states: Wenzel state, Cassie state, partial Cassie (Wenzel-Cassie mixed) state, and Wenzel state with irregular three-phase contact lines. The results demonstrate that stable Cassie DWC can occur on single-micro-scale roughness surfaces, not just on dual-scale roughness surfaces. On single-micro-scale roughness surfaces exhibiting Cassie DWC , high droplet mobility, and an average departure diameter of 741.5 µm, a 33.0% enhancement in both condensate mass collection rate and heat transfer performance is observed relative to the flat substrate. In contrast, Wenzel DWC surfaces show the most significant reductions in both metrics, with degradation of up to 15.9%. Although dual-scale roughness surfaces also exhibit Cassie DWC , condensation mechanisms and limited surface durability reduce condensate collection, resulting in approximately half the condensate mass collection rate compared with single-micro-scale Cassie DWC surfaces. Overall, the lower fabrication cost, simpler processing, and improved durability of single-micro-scale roughness Cassie DWC surfaces present a promising and practical alternative for scalable applications such as power generation, desalination, and thermal management. • The droplet's wetting behavior effect on condensation heat transfer is discussed. • Single-micro-scale surfaces show a + 33% in heat transfer compared to flat substrates. • Single-micro-scale surfaces balance the heat transfer and water collection efficiency. • Dual-scale surfaces can stably maintain the Cassie dropwise condensation. • Coalescence-induced jumping is only observed on dual-scale surfaces. [ABSTRACT FROM AUTHOR]
ISSN:00179310
DOI:10.1016/j.ijheatmasstransfer.2026.128764