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Experimental study of heat transfer and phase change condensation in a developing, two-dimensional wall jet flow field with an isothermal boundary condition.

机译：在等温边界条件下发展的二维壁面射流场中传热和相变冷凝的实验研究。

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摘要

Benchmark data were obtained in a developing wall jet flow field as a means to validate computational models utilized for automotive defroster/demister flow design. A non-impinging, two-dimensional wall jet flow was utilized due to the relatively simplicity of the flow geometry and the similarity of the boundary conditions to the actual defroster flow field.; Isothermal, non-isothermal, non-condensing and non-isothermal, condensing flow regimes were measured and compared to results obtained from a two-dimensional computational model. The experimental, mean velocity profiles at streamwise locations greater than 7.62 slot widths downstream agreed with results in the literature to within 1% [Launder and Rodi, 1981]. The computational models tended to over-predict velocity and temperature gradients at the wall surface and over-predicted growth of the inner shear region by as much as 60% while under-predicting the jet-spreading rate. The model predictions of the mean velocity and the streamwise-normal stress agree within 10% and 20% respectively throughout the developing region investigated here. A new technique was developed to measure small aliquots of water utilizing headspace gas chromatography with a flame ionization detector. This measurement technique provided measurements of water from 0 to 3 mg with an accuracy of ±0.038 mg at a 95% confidence level for the regression model. This technique is more robust and exceeds the capability of gravimetric equipment that is readily available. The development of this technique was essential to provide an accurate measure of condensate in the required range and to meet other requirements, such as specimen isolation, of the experimental program.; A novel optical technique was developed to measure transient, local condensate thickness on reflective surfaces. Surface reflectance measurements to 8–12 μm wavelengths (infrared) were correlated with H2O condensate thickness present on the surface. This technique proved to be highly sensitive with a dynamic range from 0 to 5 μm. Measurement accuracy depends on the target utilized. Accuracy of ±0.17 μm at a 95% confidence level was attained for ensemble surface calibrations (multiple target average). It appears that a single calibrated target would provide greater measurement accuracy. This technique was utilized to provide measurements of transient condensation development in the wall jet flow and estimates of the local, instantaneous mass transfer coefficient were calculated. Results indicated that the technique is an extremely sensitive condensate thickness indicator but that uncertainty in the mass transfer coefficient can be of the same order of magnitude or larger than the measurement due to the potential error in determining the concentration difference in the flow field.
机译：在发展中的壁面射流场中获得基准数据，作为验证用于汽车除霜器/除雾器流量设计的计算模型的手段。由于流动的几何形状相对简单，并且边界条件与实际除霜器流场的相似性，因此采用了无障碍的二维壁面射流。测量了等温，非等温，非冷凝和非等温，冷凝流动状态，并将其与从二维计算模型获得的结果进行了比较。在下游大于7.62缝隙宽度的流向位置处的实验性平均速度分布与文献中的结果一致，在1％以内[Launder and Rodi，1981]。该计算模型倾向于高估壁面的速度和温度梯度，高估内部剪切区域的增长多达60％，而低估了射流的扩散速度。在本文研究的整个发育区域中，平均速度和流向法向应力的模型预测分别在10％和20％之内。开发了一种新技术，可通过带有火焰电离检测器的顶空气相色谱法测量水的小等分试样。对于回归模型，此测量技术可在95％置信水平下对0至3 mg的水进行测量，精度为±0.038 mg。该技术更强大，并且超过了现有的重量分析设备。该技术的发展对于在所需范围内提供准确的冷凝水测量并满足其他要求（例如实验程序的样品分离）至关重要。开发了一种新颖的光学技术来测量反射表面上的瞬态局部凝结水厚度。在8–12μm波长（红外）下的表面反射率测量值与表面上存在的H 2 O冷凝物厚度相关。事实证明，这项技术非常敏感，动态范围为0至5μm。测量精度取决于所使用的目标。整体表面校准（多个目标平均值）的准确度为95％置信度下±0.17μm。似乎单个校准目标将提供更高的测量精度。该技术用于提供壁面射流中瞬态冷凝发展的测量值，并计算局部瞬时传质系数的估计值。结果表明，该技术是一种非常灵敏的冷凝物厚度指示剂，但由于确定流场中浓度差的潜在误差，传质系数的不确定性可能与测量结果相同或更大。

著录项

  • 作者

    Hoke, Paul Bryan.;

  • 作者单位

    Michigan State University.;

  • 授予单位 Michigan State University.;
  • 学科 Engineering Mechanical.
  • 学位 Ph.D.
  • 年度 2001
  • 页码 211 p.
  • 总页数 211
  • 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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