Extraordinary boiling enhancement through micro-chimney effects in gradient porous micromeshes for high-power applications

Abstract

Boiling enhancement from engineering surfaces is of fundamental importance for efficiency enhancement of energy systems and effective thermal management of high-power electronics. The present study develops highly cost-effective and ultrascalable copper porous micromeshes with gradient porosity to further maximize the boiling performance holistically. A unique micro-chimney effect in the gradient meshes, enabling ever-faster bubble departure at small diameters, is revealed to prevail throughout the entire nucleate boiling. This robust surface structure presents an outstanding critical heat flux up to 2719 kW/m2 simultaneously with ultrahigh heat transfer coefficient of 261 kW/m2K, which is superior to the maxima achieved in most relevant literatures. The analysis of facilitated bubble dynamics and comparison with an analytical model demonstrate that the micro-chimney effect due to simple porosity modulation is another significant mechanism to further enhance boiling capacity. Finally, as an example of potential areas, the nucleate boiling of gradient micromeshes exhibits great advantage of cell performance enhancement in concentrated ratio and electrical efficiency of concentrated photovoltaics. This study promises a high-performance surface modification for more efficient phase-change devices, such as flow boiling microchannels, boiling water reactors, and other high-power thermal systems.