Two-Level Copper Oxide Nanostructured Surfaces for Condensation Heat Transfer

Condensation has been widely explored because of its importance in numerous applications including water desalination, water harvesting, and power generation. Previous studies have shown that the enhancement in condensation heat transfer can be achieved by the design of structured surfaces with desired surface chemistry. Especially, nanostructured surfaces have enhanced thermal transport performance by promoting dropwise condensation that shows lower thermal resistances than film condensation. Thus, the control of surface wettability has drawn significant interest by modulating surface morphology and surface chemistry. In this study, we explore microscopic-level droplet dynamics using various copper surfaces. Nanostructured copper surfaces are prepared by chemical immersion methods using alkaline solution, and further functionalized by using dodecanoic acid in order to provide hydrophobicity. Their wetting properties and condensation process are investigated using an optical microscope by capturing real-time phase change process. The results show that the surface morphology with the highest feature size ratio enables to achieve the highest droplet volume growth rate due to the hindering of pinning of droplets and droplet jumping events. The understanding of condensation behaviors using the copper oxide nanostructured surfaces can provide design rules for efficient surface structures for numerous condensation applications.