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首页> 外文期刊>International Journal of Heat and Mass Transfer >Flow regime maps for smooth horizontal tubes at a constant heat flux
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Flow regime maps for smooth horizontal tubes at a constant heat flux

机译：恒定热通量下光滑水平管的流态图

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The existing constant heat flux boundary condition flow regime maps are accurate for high Prandtl number fluids, however, they are inaccurate at lower Prandtl numbers and tube diameters and specifically for water as the working fluid. The purpose of this paper was to develop a flow regime map that can be used for both high and low Prandtl number fluids for a wide range of tube diameters. Furthermore, not only to develop a map for fully developed flow, but also for developing flow. An experimental set-up was designed, built and validated against results from literature. Two smooth circular test sections with inner diameters of 4 mm and 11.5 mm, respectively, and lengths of 5.5 m and 9.5 m, respectively, were used. Heat transfer measurements were taken at a range of Reynolds numbers from laminar to turbulent. Water was used as the test fluid and the Prandtl number was limited between 3 and 7. Experimental results from literature complemented the test matrix used for this study, especially with high Prandtl number data. Six flow regime maps were developed for a constant heat flux boundary condition and a square-edged inlet, and these flow regime maps are original for four reasons. Firstly, it contains contour lines that show the Nusselt number enhancements due to free convection effects. Secondly, it is valid for a wide range of tube diameters and Prandtl numbers. Thirdly, the flow regime maps were developed as a function of temperature difference (Grashof number) and heat flux (modified Grashof number). Finally, four of the six flow regime maps are not only valid for fully developed flow, but also developing flow.
机译：现有的恒定热通量边界条件流动状态图对于高Prandtl数的流体是准确的，但是，在较低Prandtl数和管直径的情况下（特别是对于作为工作流体的水）它们是不准确的。本文的目的是开发一种流态图，该图可用于宽范围的管径的高和低普朗特数流体。此外，不仅要为充分发展的流量绘制地图，而且还要为发展流量绘制地图。设计了一个实验装置，并根据文献结果进行了验证。使用两个光滑的圆形测试部分，其内径分别为4 mm和11.5 mm，长度分别为5.5 m和9.5 m。在层流到湍流的雷诺数范围内进行传热测量。使用水作为测试液，普朗特数限制在3到7之间。文献的实验结果补充了用于本研究的测试矩阵，尤其是具有高普朗特数的数据。针对恒定的热通量边界条件和方形进气口，开发了六个流态图，这些流态图是原始的，其原因有四个。首先，它包含等高线，这些等高线显示了由于自由对流效应而导致的Nusselt数增强。其次，它适用于各种管径和普朗特数。第三，根据温度差（格拉斯霍夫数）和热通量（修正的格拉斯霍夫数）绘制了流态图。最后，六个流态图中的四个不仅对完全展开的流有效，而且对展开的流也有效。

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