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The Effects of Agitation on Convective Heat Transfer with Applications to Electronics Cooling.

机译：搅拌对对流换热的影响及其在电子冷却中的应用。

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摘要

With continuously increasing number of chips and smaller and smaller CPU sizes, heat fluxes that need to be dissipated from computers are on a rapid increase. CPU cooling being critical to the performance of electronic devices, this field demands considerable research focus. Researchers have been pushing existing computer cooling technologies to their limits and also developing new cooling techniques. Forced convection, spray jet cooling, boiling heat transfer are a few to name. Different technologies have their respective merits and limits in terms of their cooling capability, reliability, ease of manufacturing and durability. Forced convection using air has always been preferred due to its cost effectiveness and reliability. The traditional way of employing this technique has been by using a blower fan that cools the heat sink that dissipates heat from the chips. However, the current heat removal demands better performance than that can be provided by a blower fan alone. Agitation is a strong mixing mechanism that can disturb the near-wall flow, thin the thermal boundary layer and enhance the convective heat transfer. This thesis study carries a detailed study of agitation alone through a Large Scale Mock Up (LSMU) unit which is dynamically similar to a single channel of a heat sink. The LSMU has a translationally oscillating plate (agitator) inside the channel cavity. Time averaged heat transfer coefficients and time resolved velocity measurements have been made along different regions of the channel to characterize the convective cooling performance of the agitator. The ensemble-averaged mean velocity variations show periods of acceleration, deceleration and flow reversal during a cycle as a result of agitator movement. Turbulence is found to increase toward the end of the acceleration phase and persist through the deceleration phase. A parametric study has been done to explore the effects of agitator frequency (f), amplitude (A) and agitation velocity (2piAf) on heat transfer and flow mechanism. The heat transfer coefficient increases with the increase in frequency and amplitude. At a fixed agitation velocity, heat transfer coefficient is mainly governed by the agitation velocity irrespective of the value of amplitude or frequency.
机译：随着芯片数量的不断增加以及CPU尺寸越来越小，需要从计算机散发的热通量正在迅速增加。 CPU冷却对于电子设备的性能至关重要，该领域需要大量的研究重点。研究人员一直在将现有的计算机冷却技术推向极限，并且还在开发新的冷却技术。强制对流，喷射冷却，沸腾传热等仅举几例。不同的技术在冷却能力，可靠性，易于制造和耐用性方面各有优缺点。由于其成本效益和可靠性，一直首选使用空气进行强制对流。采用该技术的传统方式是使用鼓风机，该鼓风机冷却散热器以散发来自芯片的热量。但是，当前的散热要求比单独使用鼓风机提供的性能更好。搅动是一种强力的混合机制，可以扰乱近壁流动，使热边界层变薄并增强对流传热。本论文的研究通过大型模拟（LSMU）单元对搅拌进行了单独的详细研究，该单元动态类似于散热器的单个通道。 LSMU在通道腔内部具有平移振荡板（搅拌器）。沿通道的不同区域进行了时间平均传热系数和时间分辨速度测量，以表征搅拌器的对流冷却性能。集合平均速度变化显示由于搅拌器运动而在一个周期内的加速，减速和逆流周期。发现湍流在加速阶段结束时增加，并在减速阶段持续存在。已经进行了参数研究，以探索搅拌器频率（f），振幅（A）和搅拌速度（2piAf）对传热和流动机理的影响。传热系数随着频率和幅度的增加而增加。在固定的搅拌速度下，传热系数主要由搅拌速度控制，而与振幅或频率的值无关。

著录项

  • 作者

    Agrawal, Smita.;

  • 作者单位

    University of Minnesota.;

  • 授予单位 University of Minnesota.;
  • 学科 Engineering Mechanical.
  • 学位 Ph.D.
  • 年度 2014
  • 页码 177 p.
  • 总页数 177
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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