Single- and Two-Phase Thermal Transport in Microchannels With Embedded Staggered Herringbone Mixers

Improving mixing is an effective means to enhance singleand two-phase heat transfer in microchannels. However, it is challenging to induce since the flow in microchannels is laminar in the most working conditions. We report that heat transfer rate and critical heat flux (CHF) on 1-methoxyheptafluoropropane (HFE-7000) can be significantly enhanced by patterning embedded micromixers on the bottom walls in a parallel silicon microchannel array, which consists of five parallel channels (height, width, length: 250 μm × 220 μm × 10 mm). Compared with a plain-wall microchannel array at a mass flux range of 1018 to 2206 kg/m2· s and a heat flux range of 10 to 198 W/cm2, singlephase heat transfer rate, two-phase heat transfer rate, and CHF are enhanced up to 221%, 160%, and 61% using microscale staggered herringbone mixers in microchannels, respectively. These mixers consist of 7 or 3.5 Hz with 12 staggered herringbone grooves (50 μm in depth and width) with 90° between two asymmetric arms in each cycle. Its asymmetry is defined in accordance with the off center position of the apex of the herringbone groove. Finally, experimental results suggest that the locations and coverage of the micromixers have significant impacts on both single and two-phase heat transfer in microchannels.