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首页> 外文期刊>Experimental Thermal and Fluid Science: International Journal of Experimental Heat Transfer, Thermodynamics, and Fluid Mechanics >Thermohydraulic investigation of turbulent flow through a round tube equipped with twisted tapes consisting of centre wings and alternate-axes
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Thermohydraulic investigation of turbulent flow through a round tube equipped with twisted tapes consisting of centre wings and alternate-axes

机译：通过圆管的湍流的热工水力研究，圆管装有由中心翼和交替轴组成的扭曲带

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摘要

The effects of the twisted tapes consisting of centre wings and alternate-axes (WT-A) on thermohydraulic properties in a round tube, were investigated. The effects of other three types of twisted tapes including: (1) the twisted tape with wings alone (WT), (2) the twisted tape with alternate axes alone (T-A), and (3) the typical twisted tape (TT), were also studied for comparison. All twisted tapes used were twisted at constant twist length (y) of 57. mm, corresponding to a constant twist ratio (y/. W) of 3.0. The wings were generated along the centre line of the tape with three different angles of attack, (?= 43°, 53° and 74°). Test runs were conducted using water as a testing fluid with Reynolds number range between 5200 and 22,000. Under the similar condition, the heat transfer rate in the tube fitted with the WT-A was consistently higher than those in the tube equipped the WT, T-A and plain tube. It is also found that the heat transfer rate increased with increasing angle of attack. Over the range studied, the use of WT-A at ?= 74° was found to be the most effective for heat transfer enhancement, giving thermal performance factor of up to 1.4. Mean values of Nusselt number (Nu), friction factor (f), thermal performance factor (?) provided by the WT-A (at ?= 74°) were respectively, 17.7%, 30.6% and 7.8% higher than those in the tube with WT (at ?= 74°), 20.8%, 53% and 4.9% higher than those in the tube with T-A, and 62%, 123% and 24% higher than those in the tube with TT. The superior performance of the WT-A over those of the other tapes could be attributed to the combined effects of the following actions: (1) a common swirling flow by the twisted tape (2) a vortex generated by the wing (3) a strong collision of the recombined streams behind each alternate point. For a better understanding on flow phenomena, flow-visualization by smoke wire technique is also presented. In addition, the experimental correlations of Nusselt number, friction factor and thermal performance factor were also developed.
机译：研究了由中心翼和交替轴（WT-A）组成的扭曲带对圆管中热工液压性能的影响。其他三种类型的扭曲带的效果包括：（1）仅带翼的扭曲带（WT），（2）仅具有交替轴的扭曲带（TA），以及（3）典型的扭曲带（TT），还进行了比较研究。使用的所有扭曲带均以57. mm的恒定扭曲长度（y）扭曲，对应于3.0的恒定扭曲比（y /。W）。翼是沿着带子的中心线以三个不同的迎角（α＝ 43°，53°和74°）产生的。使用水作为雷诺数范围在5200和22,000之间的测试液进行测试。在类似条件下，装有WT-A的管子的传热率始终高于装有WT，T-A和普通管子的管子。还发现传热速率随迎角的​​增加而增加。在所研究的范围内，发现在θ= 74°处使用WT-A是最有效的传热增强方法，其热性能系数高达1.4。 WT-A提供的努塞尔特数（Nu），摩擦因数（f）和热性能因数（η）的平均值分别为（α= 74°），分别比WT-A高17.7％，30.6％和7.8％。 WT管（在α= 74°时）比TA管高20.8％，53％和4.9％，比TT管高62％，123％和24％。 WT-A优于其他胶带的性能归因于以下作用的综合作用：（1）扭曲胶带产生的常见旋流（2）机翼（3）产生的涡流a每个替代点后面的重组流强烈碰撞。为了更好地了解流动现象，还提出了通过烟丝技术进行流动可视化的方法。此外，还建立了努塞尔数，摩擦系数和热性能系数的实验相关性。

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