Intermittent spray cooling on rationally-designed hierarchical surfaces for enhanced evaporative heat transfer performance

Abstract

We propose the high-performance evaporative spray cooling strategy by combining the hierarchical flake formation and the intermittent spraying. A simple, scalable, and cost-effective method was introduced to fabricate hierarchical flakes with multi-scale wicks where the size of the pores varies along the direction normal to the wick plane, which provides substantially improved wicking capability for capillary pumping. In addition, the intermittent spray methods allowed for more efficient evaporative cooling by enabling the reduction in spraying volume. Through the thermal management experiments, the hierarchical flake heat exchanger could provide up to -32.1% reduced amount of sprayed water and - 1.8 times higher energy efficiency compared to the untreated aluminum heat exchanger during intermittent spraying. Using the quantitative analysis on the single-droplet evaporation and water retention ability, we systematically demonstrate the effects of the combination of hierarchical flake and intermittent spray scheme on the efficient thermal management. We believe that our outcomes of this work show the potential of the spray cooling method for the heat exchangers and present the scalable evaporative surfaces applicable to various evaporative cooling applications.