Superhydrophilic Composite Structure of Copper Microcavities and Nanocones for Enhancing Boiling Heat Transfer

Abstract

AbstractA type of high‐efficiency boiling heat transfer (BHT) interfaces based on superhydrophilic copper microcavity and nanocone (CMN) composite structure are reported. In principle, these microcavities are efficient nucleation sites, facilitating decreasing surface superheat required for onset of nucleation boiling (ONB) and enhancing heat transfer coefficient (HTC); discrete nanotips facilitate the departure of boiling bubbles at smaller scale; shallow microcavities with depth of a few micrometers can avoid excess interface thermal resistance; and the superwetting effect of structure itself helps improve critical heat flux (CHF). Through exploring morphology, wettability, boiling mass and heat transfer properties of CMN structures varied with growth time, an optimal interface is obtained with 142% enhancement in the maximum HTC, 64% enhancement in CHF, and 33% decrease in the ONB superheat as compared to the flat copper surface. Meanwhile, combined experiments and theoretical analyses also clarify why the in situ growth of CMN structures on the copper surface can effectively enhance BHT and why the BHT enhancement effects become worse as the growth time of CMN structure increases. This work not only widens the application scope of superwetting surfaces but offers new insight how to rationally design superhydrophilic micro‐ and nanostructures so as to achieve more efficient BHT.