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首页> 外文期刊>Journal of Heat Transfer >Formation of Nano-Adsorption Layer and Its Effects on Nanofluid Spray Heat Transfer Performance
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Formation of Nano-Adsorption Layer and Its Effects on Nanofluid Spray Heat Transfer Performance

机译：纳米吸附层的形成及其对纳米流体喷雾传热性能的影响

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For spray cooling using nanofluid as the working fluid, a nano-adsorption layer is formed on the heated surface and affects the heat transfer performance of the cooling system. This study performs an experimental investigation into the formation of this nano-adsorption layer and its subsequent effects on the spray heat transfer performance of a cooling system using Al_2O_3-water nanofluid as the working fluid. The experiments consider four different nanoparticle volume fractions (i.e., 0 vol. %, 0.001 vol. %, 0.025 vol. %, and 0.05 vol. %) and two different surface roughnesses (i.e., 0.1 μm and 1.0 μm). The experimental results show that the 0.001 vol. % nanofluid yields the optimal heat transfer performance since most of the nanoparticles rebound from the heated surface directly on impact or are washed away by subsequently arriving droplets. The surface compositions of the spray-cooled specimens are examined using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). The results reveal that for all of the nanofluids, a nano-adsorption layer is formed on the surface of the spray-cooled test pieces. Moreover, the layer thickness increases with an increasing nanoparticle concentration. A greater nano-adsorption layer thickness not only results in a higher thermal resistance but also reduces the effect of the surface roughness in enhancing the heat transfer performance. In addition, the nano-adsorption layer absorbs the nanofluid droplets under the effects of capillary forces, and therefore reduces the contact angle, which induces a hydrophilic surface property.
机译：对于使用纳米流体作为工作流体的喷雾冷却，在被加热的表面上会形成纳米吸附层，并影响冷却系统的传热性能。本研究对这种纳米吸附层的形成及其对使用Al_2O_3-水纳米流体作为工作流体的冷却系统的喷雾传热性能的后续影响进行了实验研究。实验考虑了四个不同的纳米粒子体积分数（即0体积％，0.001体积％，0.025体积％和0.05体积％）和两个不同的表面粗糙度（即0.1μm和1.0μm）。实验结果表明，0.001体积％。 ％纳米流体产生最佳的传热性能，因为大多数纳米颗粒在撞击时直接从受热表面反弹，或者被随后到达的液滴冲走。使用扫描电子显微镜（SEM）和能量色散X射线光谱仪（EDS）检查喷雾冷却样品的表面成分。结果表明，对于所有的纳米流体，在喷雾冷却的测试件的表面上形成了纳米吸附层。而且，层厚度随着纳米颗粒浓度的增加而增加。较大的纳米吸附层厚度不仅导致较高的耐热性，而且降低了表面粗糙度在增强传热性能中的作用。另外，纳米吸附层在毛细作用力的作用下吸收纳米流体液滴，因此减小了接触角，从而引起了亲水性表面性质。

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