Purpose

This study/paper aims to deal with thermal convection and entropy production of a ferrofluid in an enclosure having an isothermally warmed solid body placed inside. It should be noted that this research deals with a development of passive cooling system for the electronic devices.

Design/methodology/approach

The domain of interest is a square chamber of size L including a rectangular solid block of sizes l₁ and l₂. Thermal convection of ferrofluid (water–Fe₃O₄ nanosuspension) is analyzed within this enclosure. The solid body is considered to be isothermal with temperature T_h and also its area is L²/9. The vertical borders are cold with temperature T_c and the horizontal boundaries are adiabatic. The flow driven by temperature gradient in the cavity is two-dimensional. The governing equations, formulated in dimensionless primitive variables with corresponding initial and boundary conditions, are worked out by using the finite volume technique with the semi-implicit method for pressure-linked equations algorithm on a uniformly staggered mesh. The influence of nanoparticles volume fraction, aspect ratio of the solid block and an irreversibility ratio on energy transport and flow patterns are examined for the Rayleigh number Ra = 10⁷.

Findings

The results show that the nanoparticles concentration augments the thermal transmission and the entropy production increases also, while the augmentation of temperature difference results in a diminution of entropy production. Finally, lower aspect ratio has the significant impact on heat transfer, isotherms, streamlines and entropy.

Originality/value

An efficient numerical technique has been developed to solve this problem. The originality of this work is to analyze convective energy transport and entropy generation in a chamber with internal block. To the best of the authors’ knowledge, the effects of irreversibility ratio are scrutinized for the first time. The results would benefit scientists and engineers to become familiar with the analysis of convective heat transfer and entropy production in enclosures with internal isothermal blocks, and the way to predict the heat transfer rate in advanced technical systems, in industrial sectors including transportation, power generation, chemical sectors, electronics, etc.

中文翻译：

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包含固体的外壳中铁磁流体的热对流和熵产生

目的

本研究/论文旨在处理外壳中铁磁流体的热对流和熵产生，外壳内部放置有等温加热的固体。应该指出的是，这项研究涉及电子设备被动冷却系统的开发。

设计/方法/方法

感兴趣的域是大小为L的方形腔室，包括大小为l ₁和l ₂的长方体块。在该外壳内分析了铁磁流体（水-Fe ₃ O ₄纳米悬浮液）的热对流。固体被认为是与温度 T _h等温的，并且它的面积是L ² /9。垂直边界是冷的，温度为 T _c并且水平边界是绝热的。腔内温度梯度驱动的流动是二维的。在均匀交错网格上，使用有限体积技术和半隐式压力关联方程算法，在具有相应初始和边界条件的无量纲原始变量中制定控制方程。对于瑞利数Ra = 10 ^{7 ，}检查纳米颗粒体积分数、固体块的纵横比和不可逆比对能量传输和流动模式的影响。

发现

结果表明，纳米颗粒浓度增加了热传递，熵产生也增加，而温差的增加导致熵产生的减少。最后，较低的纵横比对传热、等温线、流线和熵有显着影响。

原创性/价值

已经开发了一种有效的数值技术来解决这个问题。这项工作的独创性是分析具有内部块的腔室中的对流能量传输和熵产生。据作者所知，不可逆比的影响是第一次仔细审查。结果将使科学家和工程师熟悉对具有内部等温块的外壳中的对流传热和熵产生的分析，以及预测先进技术系统、工业部门（包括交通、发电、化工、电子等。