Effect of Triangular Roughness Elements on Pressure Drop and Laminar-Turbulent Transition in Microchannels and Minichannels
Effect of Triangular Roughness Elements on Pressure Drop and Laminar-Turbulent Transition in Microchannels and Minichannels
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DOI：
10.1115/icnmm2006-96062
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发表时间：
2006
期刊：
影响因子：
--
通讯作者：
Timothy P. Brackbill;S. Kandlikar
中科院分区：
文献类型：
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作者：
Timothy P. Brackbill;S. Kandlikar
粗糙度元素以不同的方式影响内部流动。其中一个影响是在雷诺数比预测的Re=2300更低的情况下从层流过渡到湍流。RIT在该领域的初步工作是由Schmitt和Kandlikar（2005）以及Kandlikar等人（2005）完成的，本研究是这些工作的延伸。本研究中使用的通道是矩形的，在具有机械粗糙度元素的墙壁之间具有不同的间距。粗糙度单元呈锯齿状结构，在405µm和815µm两个节距下，粗糙度单元高度分别为107和117µm。基于压缩流面积的水力直径和雷诺数分别为424µm ~ 2016µm和210µm ~ 2400µm。沿着88.9 mm的流长在16个位置进行压力测量，以确定局部压力梯度。得到了摩擦因子和向湍流过渡的结果，并与Schmitt和Kandlikar（2005）报告的数据进行了比较。粗糙度因素使层流区较早过渡到湍流区，利用基于收缩流面积的水力直径可以准确预测层流区的摩擦因数。
Roughness elements affect internal flows in different ways. One effect is a transition from laminar to turbulent flow at a lower Reynolds number than the predicted Re=2300. Initial work at RIT in the subject area was performed by Schmitt and Kandlikar (2005) and Kandlikar et al. (2005), and this study is an extension of these efforts. The channel used in this study is rectangular, with varying separation between walls that have machined roughness elements. The roughness elements are saw-tooth in structure, with element heights of 107 and 117 µm for two pitches of 405 µm and 815 µm respectively. The resulting hydraulic diameters and Reynolds numbers based on the constricted flow area range from 424 µm to 2016 µm and 210 to 2400 respectively. Pressure measurements are taken at sixteen locations along the flow length of 88.9 mm to determine the local pressure gradients. The results for friction factors and transition to turbulent flow are obtained and compared with the data reported by Schmitt and Kandlikar (2005). The roughness elements cause an early transition to turbulent flow, and the friction factors in the laminar region are predicted accurately using the hydraulic diameter based on the constricted flow area.