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首页> 外文期刊>International Journal of Heat and Mass Transfer >Deterioration of heat transfer in turbulent channel flows due to nanoparticles
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Deterioration of heat transfer in turbulent channel flows due to nanoparticles

机译：由于纳米颗粒，湍流通道流中传热的劣化

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摘要

Custom-designed nanoparticles offer the possibility of influencing the thermo-physical properties of heat carriers, such as water and transformer oil. The present study aims to clarify to what extent such nanofluids may improve convective heat transfer under turbulent flow conditions. The applied assessment methodology is based on wall-resolving large eddy simulations and analytical considerations, exemplified by diamond-water nanofluids of different particle concentrations. It is observed that a change in heat transfer due to nanoparticles is affected by two competing mechanisms. On the one hand, the modified thermo-physical properties of the suspension obviously favor heat transfer. On the other hand, an addition of particles drastically dampens turbulence which causes the opposite effect. At fixed energy input by the pump, the second effect usually dominates, so that the performance of the nanofluid deteriorates compared to the carrier fluid without particles. In other words, increasing the turbulence intensity of the carrier fluid is more efficient to transfer a certain amount of thermal energy than using nanofluids. However, if a specific turbulence level shall not be exceeded in a technical system, nanoparticles can help to further improve convective heat transfer.
机译：定制的纳米粒子提供了影响热载体的热物理性质的可能性，例如水和变压器油。本研究旨在澄清这种纳米流体在多大程度上可以在湍流条件下改善对流热传递。应用的评估方法基于墙壁解决的大型涡流模拟和分析考虑，由不同颗粒浓度的金刚石水纳米流体举例说明。观察到，由于纳米颗粒引起的热传递变化受到两个竞争机制的影响。一方面，悬浮液的改性热物理性质明显有利于传热。另一方面，添加颗粒急剧抑制湍流，这导致相反的效果。在泵的固定能量下，第二效果通常占主导地位，使得纳米流体的性能与没有颗粒的载流体相比劣化。换句话说，增加载体流体的湍流强度比使用纳米流体来转移一定量的热能更有效。然而，如果在技术系统中不超过特定的湍流级别，纳米颗粒可以有助于进一步改善对流热传递。

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