Augmented boiling heat transfer on a copper nanoporous surface and the stability of nano-porosity in a hydrothermal environment
By Biao Tang and Rui Zhou and Longsheng Lu and Guofu Zhou
Published in International Journal of Heat and Mass Transfer
2015
Abstract
A novel in-situ surface alloying and dealloying (SA&D) approach is proposed for the fabrication of copper nanoporous surface (CNPS). The bubble dynamics and nucleate boiling heat transfer performance of the \CNPS\ were investigated by high-speed visualization. The bi-continuous porous structures on \CNPS\ facilitate the onset of boiling and significantly enhance the nucleate boiling heat transfer. Bubbles with smaller departure diameter and higher departure frequency on the \CNPS\ were observed compared to those on plain surface, which can be attributed to the differences in wettability and morphology. The chemical and morphological stability of as-dealloyed nanoporous copper (NPC) under saturated boiling environment were systematically studied. The \EDS\ results for different boiling times indicate \NPC\ of excellent chemical stability. The porosity evolution with time of the \NPC\ was recorded by \SEM\ images, and a continuous coarsening process controlled by surface diffusion was confirmed by quantitative analysis of the porosity feature size. A simple equation was given to describe the feature-size dependent stability performance of \NPC\ under the hydrothermal environment.