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Influence of geometrical parameters on turbulent flow and heat transfer characteristics in outward helically corrugated tubes

机译：几何参数对向外螺旋波纹管湍流和传热特性的影响

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摘要

Concerning a novel outward helically corrugated tube manufactured through hydraulic forming under 290 MPa, a numerical study was conducted to investigate the mechanism of turbulent flow dynamics and heat transfer enhancement based on the Reynolds stress model (RSM) using the FLUENT software. A validation of the Reyholds stress model for turbulent flow over a wavy surface was performed, and the results were then compared with the results from a large eddy simulation (LES) model and with experimental measurements. The helically corrugated tubes with different corrugation height-to-diameter ratios and pitch to-diameter ratios are then evaluated to explore their influence on turbulent flow and heat transfer. It was found that the intensity of swirl flow was enhanced with an increase in the corrugation height, and it increased with a decrease in the corrugation pitch, the intensification of the swirl flow strengthens the heat transfer and resistance characteristics. The intensity of rotational flow was enhanced with an increase in the corrugation height, and increased with an increase in the corrugation pitch; the enhanced rotational flow causes an inhibition effect on heat transfer and resistance. Moreover, the maximum values of the local Nusselt number and the friction factor along the walls were observed at the reattachment point, and their minimum values appeared at the core of the swirl flow. It is therefore reasonable to keep the corrugation height-to-diameter ratios be less than 0.1, and the pitch-to-diameter ratios be less than 2 to ensure that the growth rate of the heat transfer is greater than the growth rate of the flow resistance. (C) 2017 Elsevier Ltd. All rights reserved.
机译：对于通过在290 MPa下水力成型制造的新型向外螺旋波纹管，进行了数值研究，以基于Fynent软件的雷诺应力模型（RSM）研究湍流动力学和传热增强的机理。对波浪表面湍流的Reyholds应力模型进行了验证，然后将结果与大型涡流仿真（LES）模型的结果和实验测量结果进行了比较。然后评估具有不同波纹高度直径比和螺距直径比的螺旋波纹管，以探讨它们对湍流和传热的影响。已经发现，随着波纹高度的增加，涡流的强度增加，而随着波纹间距的减小，涡流的强度增加，涡流的强度增强了传热和阻力特性。旋转流的强度随着波纹高度的增加而增加，并且随着波纹间距的增加而增加；增强的旋转流对传热和阻力产生抑制作用。此外，在重新连接点观察到了局部Nusselt数和沿壁的摩擦系数的最大值，而它们的最小值出现在旋流的核心。因此，合理的是，将波纹的高度与直径之比保持在0.1以下，而将螺距与直径之比保持在2以下，以确保传热的增长率大于流的增长率。抵抗性。 （C）2017 Elsevier Ltd.保留所有权利。

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