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Two-phase flow morphology and local wall temperatures in high-aspect-ratio manifold microchannels
International Journal of Heat and Mass Transfer ( IF 5.2 ) Pub Date : 2020-06-01 , DOI: 10.1016/j.ijheatmasstransfer.2020.119551
Kevin P. Drummond , Justin A. Weibel , Suresh V. Garimella

Abstract Manifold microchannel heat sinks can dissipate high heat fluxes at moderate pressure drops, especially during two-phase operation. High-aspect-ratio microchannels afford a large enhancement in heat transfer area; however, the flow morphology in manifold microchannels during two-phase operation, as well as the resulting thermal performance, are not well understood. In this work, a single manifold microchannel representing a repeating unit in a heat sink is fabricated in silicon with a bonded glass viewing window. Samples of different channel lengths (750 μm and 1500 μm) and depths (125 μm, 250 μm, and 1000 μm) are considered; channel and fin widths are both maintained at 60 μm. Subcooled fluid (HFE-7100) is delivered to the channel at a constant flow rate such that the fluid velocity at the inlet is ~1.05 m/s in all cases. A high-speed camera is used to visualize the two-phase flow in the channel through the glass sidewall; an infrared camera measures the temperature distribution on the opposite channel sidewall. The flow visualizations reveal that vapor nucleation occurs at stagnation regions below the manifold near the inlet plenum and at both corners adjacent to the channel base. For deep channels (1000 μm), at sufficiently high heat fluxes, vapor completely covers the base of the channels and liquid does not re-wet the surface in this region. This newly identified vapor blanketing phenomenon causes a significant decrease in performance and an increase in the measured channel wall temperatures. This study reveals the critical role of the two-phase flow morphology in manifold microchannel heat sink design.

中文翻译:

高纵横比歧管微通道中的两相流形态和局部壁温

摘要 歧管微通道散热器可以在中等压降下耗散高热通量,尤其是在两相运行期间。高纵横比的微通道大大提高了传热面积;然而,在两相操作期间歧管微通道中的流动形态以及由此产生的热性能尚不清楚。在这项工作中,代表散热器中重复单元的单个歧管微通道是用硅制造的,带有粘合玻璃观察窗。考虑了不同通道长度(750 μm 和 1500 μm)和深度(125 μm、250 μm 和 1000 μm)的样品;通道和鳍片宽度均保持在 60 μm。过冷流体 (HFE-7100) 以恒定流速输送到通道,以便在所有情况下入口处的流体速度约为 1.05 m/s。高速摄像机用于可视化通道中通过玻璃侧壁的两相流;红外摄像机测量对面通道侧壁上的温度分布。流动可视化显示蒸汽成核发生在靠近入口增压室的歧管下方的停滞区域以及与通道底部相邻的两个角落处。对于深通道 (1000 μm),在足够高的热通量下,蒸汽完全覆盖通道底部,液体不会重新润湿该区域的表面。这种新发现的蒸汽覆盖现象会导致性能显着下降和测量的通道壁温度升高。这项研究揭示了两相流形态在歧管微通道散热器设计中的关键作用。
更新日期:2020-06-01
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