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A numerical investigation of laminar flow of a water/alumina nanofluid

机译：水/氧化铝纳米流体层流的数值研究

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The present paper reports the results of a numerical investigation of a tubular developing laminar flow of a water/alumina nanofluid under constant heat flux conditions. The nanofluid is modelled as a water/alumina nanoparticles mixture. Brownian and thermophoretic diffusion effects have been considered through the energy and nanoparticle concentration field equations. Though these modes of diffusion have been suggested extensively in the literature, their effect on momentum and energy transport has not yet been numerically analyzed. In addition, the model includes temperature and concentration effects over the transport properties of the nanofluid. A new CFD solver has been developed for the solution of the present set of governing equations. Model solutions have been sought for conditions corresponding to two experimental investigations carried out elsewhere. Base fluid (water) solutions have been used to asses the accuracy of the numerical model, the results being reasonably comparable to the experimental ones and adequately correlated by the Churchill and Ozoe correlation. Nanofluid solutions have been obtained for nanoparticles volumetric concentrations of up to 6%. A concentration boundary layer has been observed to develop along the wall of the pipe, a region which is progressively depleted of nanoparticles by the action of thermophoretic diffusion. A slight heat transfer enhancement has been found especially at the higher nanoparticle concentrations, with the maximum enhancement being of the order of 5%. The dimensionless numerical results, based on cross section (local) properties, fall within 25% with respect to the experimental ones. The Churchill and Ozoe correlation seems to adequately correlate numerical results for the range of Graetz numbers of the present investigation and for the lower range of nanoparticles concentration. Heat flux effects seem to play a potential role in nanofluid heat transfer at the tube wall though their significance has not been consistently investigated under the present investigation.
机译：本文报道了在恒定热通量条件下水/氧化铝纳米流体的管状显影层流的数值研究结果。将纳米流体建模为水/氧化铝纳米颗粒混合物。通过能量和纳米粒子浓度场方程已经考虑了布朗和热泳扩散效应。尽管这些扩散方式在文献中已被广泛提出，但尚未对它们对动量和能量传输的影响进行数值分析。此外，该模型还包括温度和浓度对纳米流体传输特性的影响。已经开发出一种新的CFD求解器来求解当前控制方程组。已寻求针对与其他地方进行的两次实验研究相对应的条件的模型解决方案。基础流体（水）解决方案已用于评估数值模型的准确性，其结果与实验结果相当，并且通过Churchill和Ozoe相关性充分关联。已经获得了纳米流体体积浓度高达6％的纳米流体溶液。已经观察到浓度边界层沿着管壁发展，该区域通过热泳扩散作用逐渐被纳米颗粒耗尽。已经发现，特别是在较高的纳米颗粒浓度下，传热略有增强，最大传热增强约为5％。基于横截面（局部）特性的无量纲数值结果相对于实验结果为25％以内。对于当前研究的Graetz数范围和较低的纳米粒子浓度范围，Churchill和Ozoe相关性似乎可以使数值结果充分相关。热通量效应似乎在管壁纳米流体传热中起着潜在作用，尽管在本研究中尚未对它们的重要性进行一致的研究。

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