Pool boiling experimental investigation on in-situ hierarchical Cu(OH)2 nanograss

Abstract

This study fabricated the in-situ Cu(OH)2 hierarchical nanograss surface (HNS) via immersion method for simultaneous enhancement of the critical heat flux (CHF) and heat transfer coefficient (HTC) in diverse experimental conditions. Nanograss stripes were patterned, and then in-situ grown on the copper substrate through the chemical modification. The effect of the Cu(OH)2 HNS on the pool boiling heat transfer performance was systematically examined. Furthermore, the optimized HNS which can exhibit the highest CHF and HTC was identified based on comparative experiments. It is found that the numerous nanoscale cavities existing in the HNS can act as the active nucleation sites for facilitating the boiling process. Experimental results reveal that the HNS can reduce the independent bubble departure diameter, increase the bubble departure frequency and significantly delay the bubble mergence due to much improved capillary pumping and replenishment of cooling liquid. According to the experiments, the CHF on the optimized HNS sample, were improved by 97.8% compared with the smooth surface and the HTC is enhanced to 2.4 W/cm2K, which is equivalent to an augmentation of 25.7% compared to that on smooth surface. Meanwhile, the HNS can improve the heat transfer uniformity and stability with temporal temperature variations less than 1 K at CHF, which is pivotal to the efficient thermal management of miniaturized devices.