Composite porous surfaces of microcavities for enhancing boiling heat transfer

Abstract

Enhancing boiling heat transfer by surface modification has the potential to increase the efficiency of energy systems and to address thermal management bottlenecks in electronics. In order to realize simultaneous enhancement of critical heat flux (CHF) as well as heat transfer coefficient (HTC) for boiling heat transfer processes, we developed a porous surface covered by microcavities (MCPS), which was fabricated by the three-step method of a powder sintering technique followed by chemical modification methods. The pool boiling heat transfer properties of MCPSs were systematically investigated in atmospheric pressure conditions, together with the bubble dynamics characteristics. The results showed that compared to plain Cu surfaces (PCSs), a 2.2 times higher CHF, a 2.5 times higher HTC as well as 85% lower onset of nucleate boiling (ONB) were demonstrated on the MCPSs. Owe to the formation of numerous microcavities and capillary-induced liquid rewetting, compared with PCPSs, the MCPS could increase the nucleation density, reduce bubble departure diameter and increase departure frequency. Finally, the wicking velocity of different surfaces obtained from the capillary wickability tests showed that there was a good linear relationship between the wicking velocity and CHF. The results showed that the liquid supply with capillary wickability could prevent the expansion of dry spots and maintain a higher CHF. This study provides a high-performance surface modification, which leads to significant industrial application prospects for high-power microelectronics cooling.