Purpose

The purpose of this study is to advance turbulent thermal convection inside the constant heat-flux round tube inserted by multiple perforated twisted tapes.

Design/methodology/approach

The novel design of this study is accomplished by inserting several twisted tapes and drilling some circular perforations near the tape edge (C1, C3, C5: solid tapes; C2, C4, C6: perforated tapes). The turbulence flow appearances and thermal convective features are examined for various Reynolds numbers (8,000–14,000) using the renormalization group (RNG) κ−ε turbulent model and Semi-Implicit Method for Pressure-Linked Equations (SIMPLE) algorithm.

Findings

The simulated outcomes reveal that inserting more perforated-twisted tapes into the heated round tube promotes turbulent thermal convection effectively. A swirling flow caused by the twisted tapes to produce the secondary flow jets between two reverse-spin tapes can combine with the main flow passing through the perforations at the outer edge to enhance the vortex flow. The primary factors are the quantity of twisted tapes and with/without perforations, as the perforation ratio remains at 2.5 in this numerical work. Weighing friction along the tube, C6 (four reverse-spin perforated-twisted tapes) brings the uppermost thermal-hydraulic performance of 1.23 under Re = 8,000.

Research limitations/implications

The constant thermo-hydraulic attributes of liquid water and the steady Newtonian fluid are research limitations for this simulated work.

Practical implications

The simulated outcomes will avail the inner-pipe design of a heat exchanger inserted by multiple perforated twisted tapes to enhance superior heat transfer.

Originality/value

These twisted tapes form tiny circular perforations along the tape edge to introduce the fluid flow through these bores and combine with the secondary flow induced between two reverse-spin tapes. This scheme enhances the swirling flow, turbulence intensity and fluid mixing to advance thermal convection since larger perforations cannot produce large jet velocity or the position of perforations is too far from the tape edge to generate a separated flow. Consequently, this work contributes a valuable cooling mechanism toward thermal engineering.

中文翻译：

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通过多个穿孔扭带安装的加热圆管的湍流的热水力性能

目的

本研究的目的是促进由多个穿孔扭带插入的恒定热通量圆管内的湍流热对流。

设计/方法论/途径

本研究的新颖设计是通过插入几条扭曲的胶带并在胶带边缘附近钻一些圆形穿孔来完成的（C1、C3、C5：实心胶带；C2、C4、C6：穿孔胶带）。使用重正化群 (RNG) 检查各种雷诺数 (8,000–14,000) 的湍流外观和热对流特征 κ-ε湍流模型和压力关联方程半隐式方法 (SIMPLE) 算法。

发现

模拟结果表明，在加热的圆管中插入更多的穿孔扭曲带可以有效地促进湍流热对流。由扭曲带引起的旋流在两个反向旋转带之间产生二次流射流，可以与穿过外缘穿孔的主流结合以增强涡流。主要因素是扭带的数量以及有/无穿孔，因为在本数值工作中穿孔比率保持在 2.5。权衡沿管的摩擦力，C6（四个反向旋转穿孔扭曲带）在 Re = 8,000 时带来最高的热工水力性能，为 1.23。

研究局限性/影响

液态水和稳定牛顿流体的恒定热水力属性是该模拟工作的研究限制。

实际影响

模拟结果将利用插入多个穿孔扭带的热交换器的内管设计来增强卓越的传热。

原创性/价值

这些扭曲的带子沿着带子边缘形成微小的圆形穿孔，以引导流体流过这些孔，并与两个反向旋转带子之间引起的二次流结合。该方案增强了旋流、湍流强度和流体混合，以促进热对流，因为较大的穿孔不能产生较大的射流速度或穿孔的位置距离胶带边缘太远而无法产生分离流。因此，这项工作为热工程提供了有价值的冷却机制。