Purpose

The nanofluid natural convection heat transfer in a hollow complex enclosure, which is named as Shamse knot shape, is studied numerically. This paper aims to present how the Rayleigh number, nanoparticle volume fraction, Hartmann number and hollow side length affect the fluid flow and heat transfer characteristics.

Design/methodology/approach

The continuity, momentum and energy equations have been solved using lattice Boltzmann method (LBM). Numerical simulation has been obtained for a wide range of Rayleigh number (10³ ≤ Ra ≤ 10⁶), nanoparticle volume fraction (0 ≤ ϕ 0.05) and Hartmann number (0 ≤ Ha ≤ 60) to analyze the fluid flow pattern and heat transfer characteristics. Moreover, the effect of hollow side length (D) on flow field and thermal performance is studied.

Findings

The results showed that the magnetic field has a negative effect on the thermal performance and the average Nusselt number decreases by increasing the Hartmann number. Because of the high conduction heat transfer coefficient of nanoparticles, the average Nusselt number increases by rising the nanoparticle volume fraction. The effect of adding nanoparticles on heat transfer is more effective at low nanoparticle volume fraction (0 ≤ ϕ ≤ 0.01). It was also found that at Ra = 10⁶, when the hollow side length increases to 3, the flow pattern becomes different due to the small gap. The averaged Nu is an increasing function of D at low Ra and an opposite trend occurs at high Rayleigh number.

Originality/value

For the first time, the effects of magnetic field, Rayleigh number, nanoparticle volume fraction and hollow side length on natural convection heat transfer of hybrid nanofluid (Ag-TiO₂/water) is investigated in a complicated cavity.

中文翻译：

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Ag-TiO2 /水杂纳米流体在Shamse结形腔中的磁流体动力学研究

目的

数值研究了空心复合罩中的纳米流体自然对流换热，称为“沙姆斯结”形状。本文旨在介绍瑞利数，纳米颗粒体积分数，哈特曼数和空心边长如何影响流体流动和传热特性。

设计/方法/方法

连续性，动量和能量方程式已使用格子Boltzmann方法（LBM）求解。数值模拟已经获得了广泛的瑞利数（10 ³  ≤太阳神≤10 ⁶），纳米颗粒的体积分数（0≤ φ 0.05）和哈特曼数（0≤哈≤60）来分析流体流动模式和传热特征。此外，研究了空心边长（D）对流场和热性能的影响。

发现

结果表明，磁场对热性能有负面影响，平均哈塞尔数通过增加哈特曼数而降低。由于纳米颗粒的高导热系数，平均努塞尔数通过增加纳米颗粒的体积分数而增加。传热增加纳米粒子的效果是在低纳米颗粒体积分数（0≤更有效φ ≤0.01）。还发现在Ra＝ 10 ⁶时，当中空侧边长度增加到3时，由于小的间隙，流型变得不同。在低Ra下，平均Nu是D的增加函数，而在高瑞利数下出现相反的趋势。

创意/价值

首次研究了复杂腔体中磁场，瑞利数，纳米颗粒体积分数和空心边长对混合纳米流体（Ag-TiO ₂ /水）自然对流传热的影响。