Enhanced flow boiling in microchannels integrated with supercapillary pinfin fences

Abstract

In conventional microchannels, the flow boiling performances are strongly affected by the highly transitional two-phase flow regimes. In this study, a novel capillary structure made from micro-pinfin fence has been explored and fabricated in microchannels to rectify the usually chaotic and unstable two-phase flows during boiling processes. A highly stable and efficient single annular two-phase flow regime is demonstrated experimentally and visually on two distinguished fluids: DI-water with high surface tension and completely wetting fluid of HFE-7100. More importantly, sustainable thin film evaporation has been established and resulted in the formation of a highly desirable V-shaped HTC curve, i.e., achieving high HTC at high working heat fluxes. This study aims at systematically characterizing flow boiling on this new microchannel configuration as well as the resulted superior stabilities of flow boiling. The experimental results show that the effective heat transfer rates are up to 92 kW/m2 K at G = 389 kg/m² s on water and 42 kW/m2 K at G = 231 kg/m² s on the HFE7100, respectively. Compared to performance in smooth microchannels, the enhancement of HTC is up to 300%. Without using inlet restrictors, CHFs are enhanced up to 830 W/cm2 and 216 W/cm2, corresponding to enhancements of 437% and 86% on water and HFE-7100, respectively.