Performance Evaluation of the Flow in Micro Junctions: Head Change Versus Head Loss Coefficients
Performance Evaluation of the Flow in Micro Junctions: Head Change Versus Head Loss Coefficients
复制标题
微连接处流动的性能评估：水头变化与水头损失系数
DOI：
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发表时间：
2013
期刊：
影响因子：
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通讯作者：
H. Herwig
中科院分区：
文献类型：
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作者：
B. Schmandt;H. Herwig
由于流经管道系统中的导管部件而造成的损失可以用水头损失系数来表征。它们基本上解释了流场中的耗散，或者在更一般的意义上，解释了由于所考虑的管道部件而产生的熵。当仅涉及一个单一的质量流率时，基于熵的方法是直接的，并且可以将熵用作一般参考量。然而，如果质量流率是分裂或团结一样，在路口，出现了一些新的方面。在我们的研究中，这类管道组件的一般方法进行了讨论。与单一质量流率一样，通过确定熵产生率来解释损失。分支流的新方面是一个额外的参数，分流比，以及必须适当考虑的单个分支之间的能量转移的事实。事实证明，这种能量传递除了总压头的单独损失外，还改变了每个流动分支中的总压头。因此，当这种影响发生时，这些系数应该被命名为水头变化系数。作为一个例子，考虑通过T形接头的流动，确定两个分支的水头损失系数，并讨论其物理意义。
Losses due to the flow through conduit components in a pipe system can be characterised by head loss coefficients. They basically account for the dissipation in the flow field or, in a more general sense, for the entropy generation due to the conduit component under consideration. When only one single mass flow rate is involved, an entropy based approach is straight forward and ṁ can be used as a general reference quantity. If, however, the mass flow rate is split or united like in junctions, some new aspects appear.In our study the general approach for these kind of conduit components is discussed. Like for single mass flow rates losses are accounted for by determining the entropy generation rates. New aspects for the branched flows are an additional parameter, the splitting ratio, and the fact that there is an energy transfer between the single branches that has to be accounted for appropriately. It turns out that this energy transfer changes the total head in each flow brach in addition to a sole loss of total head. Therefore, the coefficients should be named head change coefficients when this effect occurs.As an example the flow through a T-shaped junction is considered, for which head loss coefficients are determined for both branches and discussed with respect to their physical meaning.Copyright © 2013 by ASME