期刊
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
卷 183, 期 -, 页码 -出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.ijheatmasstransfer.2021.122207
关键词
Honeycomb-like superhydrophobic surface; Jumping-droplet condensation; Flooding condensation transition; Substrate thermal conductivity; Droplet departure frequency; Constriction resistance
资金
- National Natural Science Foundation of China (NSFC) [51776184]
- 100 Talents Program of Zhejiang University
This study investigates the characteristics and influencing factors of condensation heat transfer on honeycomb-like superhydrophobic surfaces. The results indicate that the thermal conductivity of the substrate plays a significant role in the heat transfer performance and droplet dynamics during condensation.
The efficiency of dropwise condensation heat transfer has been improved significantly by the development of superhydrophobic surfaces, which are usually fabricated by coating a thin superhydrophobic layer on different kinds of substrates (e.g., different metals/alloys). However, the effects of the thermal conductivity of the substrate on condensation heat transfer over such superhydrophobic surfaces remain unclear. In this paper, we investigated experimentally the condensation heat transfer and droplet dynamics on honeycomb-like superhydrophobic (HCLS) surfaces with hierarchical microporous structures, fabricated by an electrochemical method on four metallic substrates with different thermal conductivities, i.e., copper, brass H96, brass H65 and stainless steel SS316. We observed spontaneous droplet jumping on all these HCLS surfaces at a relatively low degree of subcooling. We also demonstrated the interplay between the substrate thermal conductivity and condensation heat transfer performance during the flooding condensation transition (FCT) by numerical simulations. In the jumping-droplet condensation and flooding condensation regimes, the condensation heat flux and heat transfer coefficient were found to be almost unchanged for different substrates. However, the substrate with a higher thermal conductivity leads to a higher condensation heat transfer coefficient as well as a higher droplet departure frequency at moderate degrees of subcooling, indicating the synergistic effect between the substrate thermal conductivity and droplet dynamics during FCT. The substrate thermal conductivity-mediated droplet dynamics enables a way for further enhancing condensation heat transfer on the HCLS surfaces. (c) 2021 Elsevier Ltd. All rights reserved.
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