Experimental study of the flow boiling heat transfer characteristics of teardrop-like micro-pin-finned chip surface in semi-open microchannel

Phase change flow boiling heat transfer in microchannel is a very efficient thermal management mode for high-power electronics/devices. However, it is still a challenge to achieve comprehensive enhancement of flow boiling heat transfer performance at low power consumption. Herein, we devised and manufactured a set of teardrop-like micro-pin-finned chip surfaces, demonstrating their exceptional enhancement in flow boiling heat transfer efficiency within semi-open microchannels with negligible pumping energy input. Benefiting from the effective expansion area, the pinning effect and the streamlined bionic structure of the micro-pin-fins, the staggered teardrop-like micro-pin-finned surface (S37) exhibits simultaneous enhancement of critical heat flux (CHF) and heat transfer coefficients (HTC). The CHF and HTC peaks reached 414.1 W/cm² and 42,153.3 W/m²·K, with maximum enhancement ratios of 52.8 % and 78.1 % relative to the smooth surface. A nearly linear improvement in the heat flux (from 93.1 to 414.1 W/cm², enhanced by 447.8 %) is observed within a minimal fluctuation in wall temperatures, not exceeding 10 °C. The semi-open microchannels provide ample space for boiling nucleation bubbles to move efficiently, enhancing heat transfer performance while maintaining a very low pressure drop (≤1.2 kPa) and without increasing power consumption. In situ observation and analysis of the boiling bubble dynamics indicated teardrop-like micro-pin-finned chip promotes the phase change heat exchange process by massive nucleation sites, and effective control of boiling bubbles by pinning effect. These findings not only provide guidance for the rational design of boiling heat transfer-enhanced surfaces and heat sinks, but also point the way to achieving efficient thermal management of power devices.