An investigation of heat transfer in heat exchange devices with spirally-coiled twisted-ducts using nanofluid
An investigation of heat transfer in heat exchange devices with spirally-coiled twisted-ducts using nanofluid
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DOI：
10.1016/j.applthermaleng.2018.07.112
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发表时间：
2018-10
影响因子：
6.4
通讯作者：
M. Khoshvaght-Aliabadi;S. Khaligh;Z. Tavassoli
中科院分区：
文献类型：
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作者：
M. Khoshvaght-Aliabadi;S. Khaligh;Z. Tavassoli
介绍了一种新的弯曲风管设计——螺旋盘绕扭曲风管，并对其进行了实验和数值分析。水和铜/水纳米流体的质量浓度分别为0.5%和1%。结果表明，螺旋盘绕扭曲管道的热流体输运特性受扭转节距（tp）和盘绕节距（cp）的强烈影响。研究范围为：tp= 0.05、0.1、0.15 m, cp= 0.015、0.025、0.035 m。结果表明，螺旋盘绕的螺旋管在扭转节距和盘绕节距最小的情况下（tp= 0.05,cp= 0.015），努塞尔数和摩擦系数增大最大。这项工作的一个关键结果是，在较高的格雷茨数下，扭转节距的影响更为明显，而在较低的格雷茨数下，线圈节距的影响更为明显。同样，通过部署结合Nusselt数增强和相应摩擦系数增强的性能指标，对螺旋缠绕扭曲管的整体热液性能进行评估。其中，螺旋缠绕扭曲管道attp= 0.05 m和cp= 0.025 m在最大Graetz数下的性能指标最高，为1.39。此外，铜纳米粒子悬浮在水中对换热有明显的强化作用，压降也有一定的增大，且随着纳米粒子浓度的增加，强化作用增强。当采用1.0%纳米流体时，性能指标提高到1.88,attp= 0.05 m, cp= 0.025 m。最后，利用得到的结果，建立了两种关系式来模拟格列茨数14 ~ 58范围内螺旋缠绕扭曲管道内的努塞尔数和摩擦因数。
A new design of curved ducts namely spirally-coiled twisted-duct is introduced and analyzed both experimentally and numerically. Water and Cu/water nanofluid at two concentrations of 0.5% and 1% by mass are considered as working fluid. The results show that the dependence of thermo-fluidic transport characteristics on the geometry of spirally-coiled twisted-duct is strongly influenced by twist-pitch (tp) and coil-pitch (cp). The studied ranges aretp= 0.05, 0.1, and 0.15 m andcp= 0.015, 0.025, and 0.035 m. The maximum augmentations of Nusselt number and friction factor are recorded for the spirally-coiled twisted-ducts with the lowest twist-pitch and coil-pitch (i.e.tp= 0.05 andcp= 0.015). One of the key outcomes of this work is that the effect of twist-pitch is more pronounced at higher Graetz numbers, while at lower Graetz numbers the effect of coil-pitch is more noticeable. Likewise, with the deployment of a performance index combining the enhancement in Nusselt number and corresponding augmentation in friction factor, the overall hydrothermal performance of spirally-coiled twisted-ducts is assessed. Among the studied cases, the spirally-coiled twisted-duct attp= 0.05 m andcp= 0.025 m possesses the highest performance index of 1.39 at the maximum Graetz number. Also, a noticeable heat transfer enhancement due to suspension of copper nanoparticles in water is obtained with a certain augmentation in the pressure drop, and the enhancement is intensified with increasing the concentration of nanoparticles. The performance index enhances up to 1.88 when the 1.0% nanofluid is used in the spirally-coiled twisted-duct attp= 0.05 m andcp= 0.025 m. Finally, using the obtained results, two correlations are established to model Nusselt number and friction factor inside the spirally-coiled twisted-ducts for the Graetz number range of 14–58.