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Fundamental studies of thermal transport and liquid-vapor phase change using microscale diagnostic techniques.

机译:使用微型诊断技术进行热传输和液汽相变的基础研究。

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摘要

Fundamental studies of thermal transport and fluid flow in single-phase and two-phase systems are conducted using microscale diagnostic techniques. An infrared micro-particle image velocimetry technique is extended to the study of fluid flows in a low signal-to-noise ratio environment. Measurements of flow distribution in a microchannel heat sink are conducted with this technique. It was concluded that careful manifold design is critical for ensuring that uniform flow is supplied to the parallel microchannels.;The effects of surface roughness on nucleate pool boiling and flow boiling are studied. For pool boiling, a range of surface roughness from Ra = 0.038 mum to 10.0 mum are investigated. In water, the 10.0 mum surface results in approximately twice the heat transfer coefficients obtained with the 0.038 mum surface, at a fixed heat flux. The influence of surface roughness on the heat transfer coefficient is correlated as h ∼ (Ra) 0.1 for water and h ∼ (Ra) 0.2 for FC-77. Due to the differences in the surface-roughness exponent, no single nucleate pool boiling correlation in the literature offers satisfactory predictions for the entire range of experimental conditions under consideration.;Modifications to an existing pool boiling correlation for improved accuracy over a greater range of surface roughness were explored. An experimental database of almost 3000 data points was constructed from studies in the literature and the present work. A modified correlation was developed that includes the difference in behavior of nucleate boiling due to surface roughness effects in moderately wetting fluids such as water than for highly wetting fluids. The correlation was found to lead to improved predictions across the experimental database.;For flow boiling, the range of surface roughness under investigation is between 1.4 mum and 6.7 mum. At higher heat fluxes, 25 to 35% higher heat transfer coefficients are measured on the 6.7 mum roughness surface compared to the 1.4 mum surface. The ability of flow boiling correlations to accurately predict the heat transfer coefficients over a wide range of surface roughness was explored.;Laser-induced fluorescence thermography was demonstrated for studying the temperature field around a growing vapor bubble during nucleate flow boiling. The capabilities of the technique were explored and with further refinements, the technique shows promise in yielding important insights into the nucleate boiling heat transfer phenomenon.
机译:使用微型诊断技术对单相和两相系统中的热传输和流体流动进行了基础研究。红外微粒图像测速技术已扩展到研究低信噪比环境中的流体流动。用这种技术对微通道散热器中的流量分布进行测量。结论是,仔细的歧管设计对于确保向平行的微通道提供均匀的流量至关重要。;研究了表面粗糙度对核池沸腾和流动沸腾的影响。对于池沸腾,研究了从Ra = 0.038微米到10.0微米的表面粗糙度范围。在水中,在固定的热通量下,10.0毫米的表面产生的导热系数大约是0.038毫米表面的两倍。表面粗糙度对传热系数的影响,对于水,h〜(Ra)0.1,对于FC-77,h〜(Ra)0.2。由于表面粗糙度指数的差异,文献中没有单个核池沸腾相关性可以为所考虑的整个实验条件提供令人满意的预测。;对现有池沸腾相关性的修改可在更大范围的表面上提高准确性探索粗糙度。通过文献研究和目前的工作,建立了将近3000个数据点的实验数据库。已开发出一种改进的相关性,其中包括在中等润湿性流体(例如水)中由于表面粗糙度影响而引起的核沸腾行为与高度润湿性流体相比的差异。相关性被发现可以改善整个实验数据库的预测。对于流动沸腾,所研究的表面粗糙度范围在1.4微米至6.7微米之间。在较高的热通量下,在6.7微米的粗糙度表面上测得的传热系数比1.4微米的表面高25%至35%。探究了流沸腾相关性在宽范围的表面粗糙度上准确预测传热系数的能力。证明了激光诱导荧光热成像技术可用于研究成核流沸腾过程中不断增长的蒸汽泡周围的温度场。对该技术的功能进行了探索,并进行了进一步的改进,该技术显示出对产生核沸腾传热现象的重要见解的希望。

著录项

  • 作者

    Jones, Benjamin J.;

  • 作者单位

    Purdue University.;

  • 授予单位 Purdue University.;
  • 学科 Engineering Mechanical.
  • 学位 Ph.D.
  • 年度 2010
  • 页码 321 p.
  • 总页数 321
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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