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首页> 外文期刊>Heat Transfer Engineering >Natural Convection of AI_2O_3 Nanofluid Between Two Horizontal Cylinders Inside a Circular Enclosure
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Natural Convection of AI_2O_3 Nanofluid Between Two Horizontal Cylinders Inside a Circular Enclosure

机译：圆形外壳内两个水平圆柱之间的AI_2O_3纳米流体自然对流

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摘要

Natural convection heat transfer within horizontal annuli has many engineering applications such as heat exchangers like fire tube heaters. In this paper numerical methods were used for the computational analysis of heat transfer from the fire tube/hot tube to the gas tube/cold tube inside the water medium using alumina nanoparticles. Because of eccentricities of both hot and cold cylinders and different diameters, the geometry is asymmetric. The mathematical model is based on two-dimensional continuity, momentum, energy, and volume fraction equations, which are solved numerically. The simulation was done for different values of particle loading, 1%, 2%, and 5%, at Rayleigh numbers 10~3, 10~4, and 10~5. The results show that nanoparticles enhance the heat transfer by increasing the volume concentrations of particles. It was observed that the maximum and minimum augmentation of the average Nusselt number are about 30% and 14% at the Ra = 10~3 and Ra = 10~5, respectively. Although the average Nusselt number rises by increasing the Rayleigh number, the ratio of heat transfer using nanofluid to that by pure fluid decreases. Using 5% volume fraction of alumina nanoparticles at Rayleigh number of 10~3 increases the heat transfer to cold tube by about 23% compared to the pure water. The effect of nanolayer formation around particles was considered in a thermal conductivity model, which shows approximately 5% increase in the Nusselt number. To verify the solution results, comparisons with previously published work on the basis of special cases are performed.
机译：水平环形空间内的自然对流传热具有许多工程应用，例如热交换器（如火管加热器）。在本文中，数值方法被用于使用氧化铝纳米粒子对水介质中从火管/热管到气体管/冷管的热传递进行计算分析。由于冷，热缸的偏心和不同的直径，几何形状是不对称的。该数学模型基于二维连续性，动量，能量和体积分数方程，并对其进行了数值求解。在瑞利数为10〜3、10〜4和10〜5的情况下，针对粒子负载的不同值1％，2％和5％进行了仿真。结果表明，纳米颗粒通过增加颗粒的体积浓度来增强热传递。观察到在Ra = 10〜3和Ra = 10〜5时，平均Nusselt数的最大增加和最小增加分别约为30％和14％。尽管平均纳塞尔数通过增加瑞利数而增加，但使用纳米流体的传热率与通过纯流体的传热率却下降。与纯水相比，在瑞利数为10〜3的情况下使用5％的氧化铝纳米粒子体积分数可使向冷管的热传递增加约23％。在导热系数模型中考虑了粒子周围纳米层形成的影响，该结果显示努塞尔数增加了约5％。为了验证解决方案的结果，在特殊情况下与以前发表的作品进行了比较。

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  • 来源
    《Heat Transfer Engineering》 |2017年第4期|177-189|共13页
  • 作者

    Ebrahim Khalili; Ahmad Saboonchi; Mohsen Saghafian;

  • 作者单位

    Department of Mechanical Engineering, Isfahan University of Technology, Isfahan, Iran;

    Department of Mechanical Engineering, Isfahan University of Technology, Isfahan, Iran;

    Department of Mechanical Engineering, Isfahan University of Technology, Isfahan, Iran;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);
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  • 正文语种 eng
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