Heat Transfer and Pressure Drop During Laminar Annular Flow Condensation in Micro-Channels
Heat Transfer and Pressure Drop During Laminar Annular Flow Condensation in Micro-Channels
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DOI：
10.1080/08916152.2012.737261
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发表时间：
2013-03
影响因子：
3.5
通讯作者：
H. S. Wang;J. Rose
中科院分区：
文献类型：
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作者：
H. S. Wang;J. Rose
微通道内凝结换热的实验研究与关联式之间存在着很大的分歧。主要问题是蒸汽侧阻力通常明显小于冷却剂侧的阻力，因此仅测量总阻力的方法以及通过减去阻力获得的蒸汽侧传热系数容易产生很大的不确定性。一些最近的相关性，主要是基于R134a的数据，在比较R134a和相同条件下的预测时，是相当一致的。当相关性用于具有广泛不同性质的流体时，发现了广泛的差异，这一事实表明，一些或所有的相关性没有捕获所有的基本机制。当将相关性应用于R134a时，发现了非常相似的预测，这表明不同研究中使用的数据集基本一致。类似的评论适用于压降。环形层流冷凝流的特殊情况允许完全理论解，而不依赖于经验输入。对于这种冷凝模式和特定的流体，可以计算通道几何形状、流动参数和管壁温度、局部传热系数和局部压力梯度以及局部质量和空隙率。文章概述了该理论，并讨论了最近的发展。与传热和压力梯度的关联式进行了比较。对于传热系数，环形流理论的结果与应用于R134a时的关联式惊人地吻合。对于氨，理论结果介于从相关性获得的广泛分布的值之间。环空层流模型给出的压力梯度结果一般低于关联式给出的结果。
There is wide disagreement between experimental investigations and correlations for heat transfer during condensation in micro-channels. The major problem is the fact that the vapor-side resistance is usually appreciably smaller than that on the coolant side so that methods where only the overall resistance is measured, and the vapor-side heat transfer coefficient obtained by subtraction of resistances, are prone to large uncertainty. A few more recent correlations, based mainly on data for R134a, are in fair agreement when predictions for R134a and for the same conditions are compared. The fact that wide discrepancies are found when the correlations are used for fluids with widely different properties indicates that some or all of the correlations do not capture all of the essential mechanisms. That closely similar predictions are found when the correlations are applied to R134a indicates that the datasets used in the different studies were in essential agreement. Similar comments apply for pressure drop. The special case of annular laminar condensate flow permits wholly theoretical solution without recourse to empirical input. For this mode of condensation and for specified fluid, channel geometry, flow parameters and tube wall temperatures, local heat transfer-coefficient, and local pressure gradient can be calculated as well as local quality and void fraction. The theory is outlined in the article, and recent developments are discussed. Comparisons with the correlations for heat transfer and pressure gradient are given. For the heat transfer coefficient, the results of the annular flow theory are in surprisingly good agreement with the correlations when applied to R134a. For ammonia, the theoretical results lie between the widely spread values obtained from the correlations. Results for pressure gradient given by the annular laminar flow model are generally lower than those given by the correlations.