Enhanced pool boiling heat transfer on a composite microstructured surface with mini-channels and micro-cavities under an electric field

Using electric field and structured surfaces to enhance boiling heat transfer has attracted widespread attention as an effective enhancement strategy. However, the current researches mainly focus on the boiling performance of uniformly distributed structured surfaces under an electric field. In this study, composite microstructured surfaces with mini-channels and micro-cavities were fabricated, and boiling performance was enhanced by applying an electric field. For the composite microstructured surface, the micro-pillars with micro-cavities at the tops are segmented by mini-channels, resulting in a non-uniform distribution of micro-pillars with micro-cavities. The boiling performance of composite microstructured surfaces using HFE-7100 as the working fluid was experimentally tested under different subcooling degrees with and without the electric field, and the enhancement mechanism was analyzed based on bubble behaviors. The results indicate that composite microstructured surfaces with mini-channels and micro-cavities can promote the separation of liquid-vapor paths, increase the bubble departure frequency, and enhance the disturbance of the flow field by utilizing the synergistic effect of electric field promoting the bubble departure at the micro-pillar tops and mini-channels hindering bubble coalescence, thereby significantly improving the heat transfer coefficient (HTC) while increasing the critical heat flux (CHF). At a subcooling degree of 35 K, the largest CHF and HTC obtained on the composite microstructured surface with electric field are 105.2 W/cm 2 and 1.82 W/(cm 2 ·K), respectively, which are 3.88 times and 4.79 times those of the smooth surface.