Purpose

This study aims to analyze entropy generation and magnetohydrodynamic (MHD) natural convection of hybrid nanofluid in a square cavity, with a heated elliptical block placed at the center, in presence of a periodic-variable magnetic field.

Design/methodology/approach

In this paper, simulations were performed with a FORTRAN home code. The numerical methodology used to solve Navier–Stokes, energy and entropy generation equations with corresponding boundary conditions, is essentially based on the finite volume method and full multigrid acceleration.

Findings

The cavity is filled with Ag–Tio₂/Water hybrid nanofluid. The main objective of this investigation is to predict the effects of body’s size (6 cases), type of applied magnetic field (variable or uniform), the non-dimensional period number of the variable magnetic field (VMF) (0.2 ≤ Λ ≤ 0.8), the inclination angle of the VMF (0 ≤ χ ≤ 90), Rayleigh number (5 × 103 ≤ Ra ≥ 105) and Hartmann number (5 ≤ Ha ≥ 100) on thermal performance, heat transfer rate, entropy generation and flow patterns.

Originality/value

To the authors’ best knowledge, this paper is the first numerical investigation deals with the entropy generation and natural convection of hybrid nanofluid in a two-dimensional cavity, with specific thermal boundary conditions, containing an elliptical block under periodic-variable magnetic field. Different combinations between flow-governing parameters were made to find optimal thermal performance.

中文翻译：

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变磁场下含椭圆障碍的方腔混合纳米流体自然对流热性能分析

目的

本研究旨在分析混合纳米流体在方形腔中的熵产生和磁流体力学 (MHD) 自然对流，其中加热椭圆块位于中心，存在周期性变化的磁场。

设计/方法/方法

在本文中，使用 FORTRAN 家庭代码进行模拟。用于求解具有相应边界条件的 Navier-Stokes、能量和熵生成方程的数值方法基本上基于有限体积法和全多重网格加速。

发现

腔体填充有Ag-Tio ₂ /水混合纳米流体。本研究的主要目的是预测身体大小（6 例）、外加磁场类型（可变或均匀）、可变磁场的无量纲周期数 (VMF) (0.2 ≤ Λ ≤ 0.8) 的影响)、VMF 的倾角 (0 ≤ χ ≤ 90)、瑞利数 (5 × 103 ≤ Ra ≥ 105) 和哈特曼数 (5 ≤ Ha ≥ 100) 对热性能、传热率、熵生成和流动模式的影响.

原创性/价值

据作者所知，本文是第一个数值研究涉及二维腔中混合纳米流体的熵产生和自然对流，具有特定的热边界条件，包含在周期变量磁场下的椭圆块。对流动控制参数进行了不同的组合，以找到最佳的热性能。