Purpose

This study aims to investigate entropy generation through natural convection and examine heat transfer properties within a partially heated and cooled enclosure influenced by an angled magnetic field. The enclosure, subjected to consistent heat production or absorption, contains a porous medium saturated with a hybrid nanofluid blend of Cu-Fe₃O₄ and MoS₂-Fe₃O₄.

Design/methodology/approach

The temperature and velocity equations are converted to a dimensionless form using suitable non-dimensional quantities, adhering to the imposed constraints. To solve these transformed dimensionless equations, the finite-difference method, based on the MAC (Marker and Cell) technique, is used. Comprehensive numerical simulations address various control parameters, including nanoparticle volume fraction, Rayleigh number, heat source or sink, Darcy number, Hartmann number and slit position. The results are illustrated through streamlines, isotherms, average Nusselt numbers and entropy generation plots, offering a clear visualization of the impact of these parameters across different scenarios.

Findings

Results obtained show that the Cu-Fe₃O₄ hybrid nanofluid exhibits higher entropy generation than the MoS₂-Fe₃O₄ hybrid nanofluid when comparing them at a Rayleigh number of 10⁶ and a Darcy number of 10^–1. The MoS₂ hybrid nanofluid demonstrates a low permeability, as evidenced by an average Darcy number of 10^–3, in comparison to the Cu hybrid nanofluid. The isothermal contours for a Rayleigh number of 10⁴are positioned parallel to the vertical walls. Additionally, the quantity of each isotherm contour adjacent to the hot wall is being monitored. The Cu and MoS₂ nanoparticles exhibit the highest average entropy generation at a Rayleigh number of 10⁵ and a Darcy number of 10^–1, respectively. When a uniform heat sink is present, the temperature gradient in the central part of the cavity decreases. In contrast, the absence of a heat source or sink leads to a more intense temperature distribution within the cavity. This differs significantly from the scenario where a uniform heat sink regulates the temperature.

Originality/value

The originality of this study is to examine the generation of entropy in natural convection within a partially heated and cooled enclosure that contains hybrid nanofluids. Partially heated corners are essential for optimizing heat transfer in a wide range of industrial applications. This enhancement is achieved by increasing the surface area, which improves convective heat transfer. These diverse applications encompass fields such as chemical engineering, mechanical engineering, surface research, energy production and heat recovery processes. Researchers have been working on improving the precision of heated and cold corners using various methods, such as numerical, experimental and analytical approaches. These efforts aim to enhance the broad utility of these corners further.

中文翻译：

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使用 Cu-Fe3O4 和 MoS2-Fe3O4 纳米流体在部分加热的方形外壳中浮力驱动的水磁流和传热的比较分析

 目的

本研究旨在研究自然对流产生的熵，并检查受倾斜磁场影响的部分加热和冷却外壳内的传热特性。外壳经受持续的热量产生或吸收，包含一种多孔介质，饱和了 Cu-Fe₃O₄ 和 MoS_{2-Fe 3}O₄ 的混合纳米流体混合物。

设计/方法/方法

温度和速度方程使用合适的无量纲量转换为无量纲形式，并遵守施加的约束。为了求解这些变换的无量纲方程，使用了基于 MAC（标记和单元）技术的有限差分方法。全面的数值模拟涉及各种控制参数，包括纳米颗粒体积分数、瑞利数、热源或散热器、达西数、哈特曼数和狭缝位置。结果通过流线、等温线、平均努塞尔数和熵生成图来说明，清楚地展示了这些参数在不同场景中的影响。

 发现

获得的结果表明，当将 Cu-Fe₃O₄ 杂化纳米流体的瑞利数为 10⁶ 和达西数为 ^10-1 进行比较时，Cu-Fe 3 O 4 杂化纳米流体比 MoS_{2-Fe 3}O₄ 杂化纳米流体表现出更高的熵生成。与 Cu 杂化纳米流体相比，MoS₂ 杂化纳米流体表现出低磁导率，平均达西数为 ^10-3 证明了这一点。瑞利数为 10⁴的等温等值线平行于垂直壁放置。此外，还监测了与热壁相邻的每个等温线等值线的数量。Cu 和 MoS₂ 纳米粒子在瑞利数为 10⁵ 和达西数分别为 ^10-1 时表现出最高的平均熵产生。当存在均匀的散热器时，腔体中心部分的温度梯度减小。相比之下，没有热源或散热器会导致型腔内的温度分布更加强烈。这与均匀散热器调节温度的情况有很大不同。

 原创性/价值

这项研究的独创性是检查在包含混合纳米流体的部分加热和冷却外壳内自然对流中熵的产生。部分加热的边角对于优化各种工业应用中的传热至关重要。这种增强是通过增加表面积来实现的，从而改善了对流传热。这些不同的应用包括化学工程、机械工程、表面研究、能源生产和热回收工艺等领域。研究人员一直致力于使用各种方法（例如数值、实验和分析方法）提高加热角和冷角的精度。这些努力旨在进一步提高这些角落的广泛用途。