Experimental investigation on flow boiling in leaf-inspired open microchannels

Enhancing the flow boiling heat transfer performance in open microchannels remains a key research focus in advanced thermal management. In this study, leaf-inspired open microchannels equipped with microscale wire mesh and featuring nanoscale-modified heating surfaces were fabricated to examine how micro-nano composite structures affect flow boiling. Comparative visualization experiments were performed on rectangular and tapered smooth microchannels and their corresponding leaf-inspired microchannels to characterize flow pattern evolution during flow boiling. The effects of leaf-inspired micro-nano composite structures on heat transfer mechanisms and pressure drop characteristics were further investigated. The experimental results demonstrated that the leaf-inspired structures achieved significant heat transfer enhancement compared with conventional smooth microchannels at a mass flux of G = 525 kg/(m 2 ·s). The heat transfer coefficient (HTC) in the rectangular and tapered channel sections was increased by up to 149% and 225%, respectively. Notably, the enhanced liquid rewetting capability of the leaf-inspired structures effectively mitigated local dryout. At G = 700 kg/(m 2 ·s), the critical heat flux (CHF) of rectangular leaf-inspired open microchannels reached 4162.93 kW/m 2 , which was approximately 1.7 times that of conventional rectangular smooth channels (2432.26 kW/m 2 ). Mechanistic analysis suggests that the leaf-inspired structures may improve fluid transport pathways and enhance phase-change heat transfer, thereby contributing to improved flow boiling performance and delayed heat transfer deterioration.