在热流量恒定的情况下,Al2O3 纳米流体在带深凹痕的层流管中的传热增强效果和压降性能:实验方法

Q1 Chemical Engineering
Alireza Khashaei, Mohammad Ameri, Shahram Azizifar
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引用次数: 0

摘要

本研究探讨了 Al2O3 纳米流体在深凹陷管道中纵向和圆周方向的传热增强和压降。它探讨了改善这种新型管几何形状热性能的机制。在雷诺数为 500 到 2250、恒定热通量为 10,000 W/m2 和纳米流体浓度为 0.1 wt% 到 1 wt% 的层流条件下,使用普通管和深凹陷管进行了实验。研究结果表明,局部速度增强、漩涡产生以及流动旋转和混合是改善深凹陷管道热性能的三个主要机制。结果表明,在 Re = 2250 条件下,与光滑管道相比,含有 1 wt% 纳米流体的深凹陷管道的对流传热系数最多可提高 3.42 倍。在此雷诺数下,努塞尔特数达到最大值 41.80,而摩擦因数比仅增加了 1.82。此外,圆周分析还揭示了凹陷引起的涡流是如何增强热传递的。结果还表明,管道几何形状的改变改变了流态区,允许在 Re = 2000 附近的较低雷诺数下发生湍流,这一点可通过努塞尔特数和摩擦因数图确定。深凹管的改进惩罚较低,在 Re = 500 时摩擦因数最高,为 0.38,热增强较高,因此在研究区域的性能评估标准(PEC)高达 2.80。然而,深凹管不适合雷诺数低于 1000 的情况。对于更高的速度,强烈建议在传统热交换器中用深凹陷管取代简单管。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Heat transfer enhancement and pressure drop performance of Al2O3 nanofluid in a laminar flow tube with deep dimples under constant heat flux: An experimental approach

This study examines the heat transfer enhancement and pressure drop of Al2O3 nanofluid in deep dimpled tubes in both longitudinal and circumferential directions. It explores mechanisms that improve the thermal performance of this novel tube geometry. Experiments were conducted using plain and deep dimpled tubes under laminar flow with Reynolds numbers from 500 to 2250, a constant heat flux of 10,000 W/m2, and nanofluid concentrations from 0.1 wt% to 1 wt%. The findings indicate that local velocity enhancement, vortex generation, and flow rotation and mixing are the three main mechanisms that improve the thermal performance of deep dimpled tubes. The results demonstrate that a deep dimpled tube with 1 wt% nanofluid can increase the convective heat transfer coefficient by up to 3.42 times compared to a smooth tube at Re = 2250. At this Reynolds number, the Nusselt number reaches a maximum of 41.80, and the friction factor ratio increases by only 1.82. Additionally, circumferential analysis reveals how dimple-induced vortices enhance heat transfer. The results also indicate that the tube geometry modification changes the flow regime zones, allowing turbulent flow at lower Reynolds numbers near Re = 2000, as identified by Nusselt number and friction factor plots. The deep dimpled tube has a low improvement penalty, with the highest friction factor of 0.38 at Re = 500 and high thermal enhancement, resulting in a performance evaluation criterion (PEC) of up to 2.80 in the studied region. However, the deep dimpled tube is unsuitable for Reynolds numbers below 1000. For higher velocities, replacing simple tubes with deep dimpled tubes in traditional heat exchangers is highly recommended.

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来源期刊
International Journal of Thermofluids
International Journal of Thermofluids Engineering-Mechanical Engineering
CiteScore
10.10
自引率
0.00%
发文量
111
审稿时长
66 days
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