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Experimental study on heat transfer characteristics of microchannel systems using liquid crystal thermography.

机译：液晶热成像技术对微通道系统传热特性的实验研究。

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摘要

Microchannel heat transfer governs the performance of the microchannel heat sink, which is a recent technology aimed at managing the stringent thermal requirements of today's high-end electronics. The present thesis investigates the single-phase and flow boiling heat transfer characteristics in microchannel systems. A state-of-the-art test facility has been constructed for the experimental investigations. It is composed of a closed loop flow setup, a microscopic imaging system and an automated data acquisition system. A technique for using un-encapsulated thermochromic liquid crystals (TLC's) to measure the local heat transfer coefficient in microchannel geometries is developed. A unique localized calibration of the TLC material is employed to minimize the effects of lighting non-uniformity and variable coating thickness. Measurements are carried out in three different microtubes, and in two innovative parallel and radial microchannel heat sinks with 3.5 cm 2 footprint areas. The working fluids are distilled water, FC-72 and air.; Local single-phase heat transfer and frictional pressure drop measurements are presented for the laminar, transitional and turbulent flow regimes, in microtubes down to 0.25 mm. Local flow boiling heat transfer coefficient data are presented for a, quality up to 0.3, and for the conditions investigated, suggest a nucleation dominated region. Flow boiling oscillation characteristics in two parallel silicon microchannel heat sink configurations aimed at micro/nano-spacecraft thermal management are investigated. One is a standard heat sink with 45 parallel channels, whereas the second is similar, except with cross-linked paths at three locations. The oscillation amplitudes are relatively large and identical in frequency for the fluid pressure and temperature. Oscillation properties for the standard heat sink are correlated for different heat fluxes, while a first glimpse of the cross-linked heat sink performance under flow boiling instability conditions is presented. Optimization of a radial inflowing microchannel heat exchanger has been investigated numerically, after preliminary fabrication and experimentation trials. Unique to this optimization was consideration of channels with axially varying cross-sections. Three-dimensional conjugate analysis shows that when constrained by a fixed channel outlet area, increasing the channel inlet area will improve the thermal performance.; Overall, a method utilizing un-encapsulated TLC thermography for local heat transfer measurements in microgeometries has been developed, while investigating the flow and heat transfer characteristics in microchannel systems. The present work along with the advances in MEMS based manufacturing is expected to lead to the creation and development of a number of miniaturized technologies, from DNA analysis to power-plants-on-chips.
机译：微通道传热控制着微通道散热器的性能，这是一项旨在管理当今高端电子产品对热量的严格要求的最新技术。本文研究了微通道系统中的单相流沸腾传热特性。为了进行实验研究，已经建设了最先进的测试设施。它由一个闭环流量设置，一个显微成像系统和一个自动数据采集系统组成。开发了一种使用未封装的热致变色液晶（TLC）来测量微通道几何形状中的局部传热系数的技术。采用TLC材料的唯一局部校准，以最大程度地减少照明不均匀和可变涂层厚度的影响。测量是在三个不同的微管中进行的，并在两个创新的平行和径向微通道散热器中进行了测量，这些散热器的占地面积为3.5 cm 2。工作流体是蒸馏水，FC-72和空气。给出了层流，过渡和湍流状态的局部单相传热和摩擦压降测量结果，测量范围为0.25 mm以下的微管。给出了局部流动沸腾传热系数数据，质量高达0.3，对于所研究的条件，表明有一个成核占主导的区域。研究了针对微/纳米航天器热管理的两个平行硅微通道散热器配置中的流沸腾振荡特性。一个是具有45个并行通道的标准散热器，而第二个是相似的，除了在三个位置具有交联路径。对于流体压力和温度，振荡幅度相对较大并且在频率上相同。标准散热器的振荡特性与不同的热通量相​​关，同时给出了在沸腾不稳定性条件下交联散热器性能的第一印象。经过初步的制造和实验试验，对径向流入的微通道换热器的优化进行了数值研究。此优化的独特之处在于考虑了具有轴向变化横截面的通道。三维共轭分析表明，当受固定的通道出口面积限制时，增加通道进口面积将改善热性能。总体而言，在研究微通道系统中的流动和传热特性的同时，已开发出一种利用未封装的TLC热成像技术进行微几何形状中局部传热测量的方法。当前的工作以及基于MEMS的制造技术的进步有望导致从DNA分析到芯片上的功率装置的许多小型化技术的产生和发展。

著录项

  • 作者

    Muwanga, Roland Ssonko.;

  • 作者单位

    Concordia University (Canada).;

  • 授予单位 Concordia University (Canada).;
  • 学科 Engineering Mechanical.
  • 学位 Ph.D.
  • 年度 2007
  • 页码 346 p.
  • 总页数 346
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 机械、仪表工业;
  • 关键词

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