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首页> 外文期刊>Journal of Heat Transfer >Comparison of Natural Convection Around a Circular Cylinder With Different Geometries of Cylinders Inside a Square Enclosure Filled With Ag-Nanofluid Superposed Porous-Nanofluid Layers
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Comparison of Natural Convection Around a Circular Cylinder With Different Geometries of Cylinders Inside a Square Enclosure Filled With Ag-Nanofluid Superposed Porous-Nanofluid Layers

机译：填充银纳米流体叠置多孔纳米流体层的方形外壳内具有不同几何形状的圆柱体的圆柱周围自然对流的比较

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Numerical simulations are carried out for fluid flow and natural convection heat transfer induced by a temperature difference between a hot inner cylinder with different geometries (i.e., circular; triangular; elliptic; rectangular; and rhombic) and a cold outer square enclosure filled with nanofluid superposed porous-nanofluid layers. The Darcy–Brinkman model is applied for the saturated porous layer with nanofluid. Moreover, the transport equations (mass, momentum, and energy) are solved numerically using the Galerkin weighted residual method by dividing the domain into two sets of equations for every layer with incorporating a nonuniform mesh size. The considered domains in this investigation are closely examined over a wide range of Rayleigh number (10 ~( 3 ) ≤ Ra ≤ 10 ~( 6 ) ), Darcy number (10 ~( −5 ) ≤ Da ≤ 10 ~( −1 ) ), the thickness of porous layer (0% ≤ X _( p ) ≤ 100%), thermal conductivity ratio (1 ≤ R _( k ) ≤ 20), and nanoparticle volume fraction (0 ≤ φ ≤ 0.1), respectively. The nanofluid is considered to be composed of Ag-nanoparticle and water as a base fluid. The results showed that the obtained total surfaces-averaged Nusselt numbers of the enclosure, in all cases, at the same operating conditions, the rate of heat transfer from the outer enclosure which the triangular cylinder is located inside is better. Also, as the thickness of the porous layer is increased from 20% to 80%, the free convection performance will decrease significantly (to about 50%) due to the hydrodynamic properties of the porous material.
机译：对具有不同几何形状（即，圆形，三角形，椭圆形，矩形和菱形）的热内圆柱体与填充有纳米流体的冷正方形外罩之间的温差引起的流体流动和自然对流传热进行了数值模拟多孔纳米流体层。 Darcy–Brinkman模型适用于具有纳米流体的饱和多孔层。此外，使用Galerkin加权残差法，通过将每层划分为两组方程组并结合了不均匀的网格尺寸，从而使用Galerkin加权残差法对输运方程（质量，动量和能量）进行数值求解。在广泛的瑞利数（10〜（3）≤Ra≤10〜（6）），达西数（10〜（-5）≤Da≤10〜（-1）的广泛范围内，仔细研究了所考虑的域），多孔层的厚度（0％≤X _（p）≤100％），导热系数（1≤R _（k）≤20）和纳米颗粒的体积分数（0≤φ≤0.1）。纳米流体被认为由银纳米颗粒和作为基础流体的水组成。结果表明，在所有情况下，在相同操作条件下，所获得的外壳的总表面平均Nusselt数，三角形圆柱体位于内部的外壳的传热速率更好。另外，随着多孔层的厚度从20％增加到80％，由于多孔材料的流体动力学特性，自由对流性能将显着降低（降低到约50％）。

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