极端微间隙(x-µgap)基于热点热管理与制冷剂流动沸腾

Mohamed H. Nasr, C. Green, P. Kottke, Xuchen Zhang, Thomas E. Sarvey, Y. Joshi, M. Bakir, A. Fedorov
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引用次数: 3

摘要

由于无法散热,特别是在所谓的局部“热点”的高功率密度下,下一代微处理器的性能正在迅速达到极限。微间隙散热器中的对流沸腾换热具有耗散超高热通量的潜力。本文报道了三种用于热点热管理的专用微间隙冷却器的传热性能实验研究结果。在本研究中,采用硅微机械批量加工的矩形微隙,并采用薄膜电阻式测温仪,以评估其消散数kW/cm2极端热流的能力,同时将壁温保持在电子可靠性规定的极限内。在5 μm和10 μm高度的微隙中进行了带和不带针脚鳍的对流沸腾实验。测试部分使用电阻加热器从底部加热,并加盖玻璃,以便直观观察两相流状态。以R134a作为冷却剂,获得了微间隙压降和壁温测量结果,并将其映射为流动状态,在最高压力高达1.5 MPa时,热流高达5 kW/cm2,质量通量高达7,000 kg/m2s,出口蒸汽质量接近统一。这些实验参数构成了微隙高度(据我们所知最小)、质量通量和热通量方面的极值。新的流动形式,包括蒸汽羽流、液体段塞和超薄波状液体膜,被观察到作为增加热通量和微间隙几何形状的函数。基于与压降和热阻测量相关的流动可视化,已经假设了两相传热的主要机制。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Extreme-microgap (x-µgap) based hotspot thermal management with refrigerant flow boiling
Performance of the next generation microprocessors is rapidly reaching its limits due to inability to remove heat, especially at high power density from so-called local “hotspots”. Convective boiling heat transfer in microgap heat sinks has the potential to dissipate ultra-high heat fluxes. We report results of an experimental investigation of heat transfer performance of three dedicated microgap coolers for hotspot thermal management. In this study, a rectangular microgap, batch micromachined in silicon and instrumented with thin-film resistive thermometry, is employed to assess its capability of dissipating extreme heat fluxes of multiple kW/cm2 while keeping the wall temperature within the limits dictated by electronics reliability. Convective boiling in microgap with heights of 5 μm and 10 μm was tested with and without pin fins in the microgap. The test section was heated from the bottom using resistive heaters and capped with glass to enable visual observation of two-phase flow regimes. Microgap pressure drop and wall temperature measurements, mapped into flow regimes, were obtained with R134a as the coolant, for heat fluxes up to 5 kW/cm2, mass fluxes up to 7,000 kg/m2s, at maximum pressures up to 1.5 MPa and outlet vapor qualities approaching unity. These experimental parameters constitute extreme values in terms of microgap height (smallest reported to our knowledge), mass fluxes, and heat fluxes. New flow regimes, including vapor plumes, liquid slugs, and ultra-thin wavy liquid film, were observed as a function of increasing heat flux and microgap geometry. Dominant mechanism(s) of two-phase heat transfer responsible for each regime have been postulated based on flow visualization correlated with pressure drop and thermal resistance measurements.
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