Dropwise condensation heat transfer enhancement on surfaces micro/nano structured by a two-step electrodeposition process

Abstract

Condensation is an important regime of heat transfer which has wide applications in different industries such as power plants, heating, ventilating and air conditioning, and refrigeration. Condensation occurs in two different modes including filmwise (FWC) and dropwise (DWC) condensation. DWC occurring on hydrophobic and superhydrophobic surfaces has a much higher heat transfer capacity than FWC. Therefore, wide investigations have been done to produce DWC in recent years. Superhydrophobic surfaces have micro/nano structures with low surface energy. In this study, a two-step electrodeposition process is used to produce micro/nano structures on copper specimens. The surface energy of specimens is reduced by a self-assembled monolayer using ethanol and 1-octadecanethiol solution. The results show that there is an optimum condition for electrodeposition parameters. For example, a surface prepared by 2000 s step time has 5 times greater heat transfer than FWC while a surface with 4000 s step time has nearly the same heat transfer as FWC. The surfaces of the fabricated specimens are examined using XRD and SEM analyses. The SEM analyses of the surfaces show that there are some micro-structures on the surfaces and the surface porosities are reduced by increasing the second step electrodeposition time.

Keywords

dropwise condensation / heat transfer / electrodeposition / micro/nano structure / porosity

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