Purpose

This study aims to numerically analyse the impact of an inclined magnetic field and Joule heating on the conjugate heat transfer because of the mixed convection of an Al₂O₃–water nanofluid in a thick wall enclosure.

Design/methodology/approach

A horizontal temperature gradient together with the shear-driven Flow creates the mixed convection inside the enclosure. The nonhomogeneous model, in which the nanoparticles have a slip velocity because of thermophoresis and Brownian diffusion, is adopted in the present study. The thermal performance is evaluated by determining the entropy generation, which includes the contribution because of magnetic field. A control volume method over a staggered grid arrangement is adopted to compute the governing equations.

Findings

The Lorentz force created by the applied magnetic field has an adverse effect on the flow and thermal field, and consequently, the heat transfer and entropy generation attenuate because of the presence of magnetic force. The Joule heating enhances the fluid temperature but attenuates the heat transfer. The impact of the magnetic field diminishes as the angle of inclination of the magnetic field is increased, and it manifests as the volume fraction of nanoparticles is increased. Addition of nanoparticles enhances both the heat transfer and entropy generation compared to the clear fluid with enhancement in entropy generation higher than the rate by which the heat transfer augments. The average Bejan number and mixing-cup temperature are evaluated to analyse the thermodynamic characteristics of the nanofluid.

Originality/value

This literature survey suggests that the impact of an inclined magnetic field and Joule heating on conjugate heat transfer based on a two-phase model has not been addressed before. The impact of the relative slip velocity of nanoparticles diminishes as the magnetic field becomes stronger.

中文翻译：

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焦耳加热下倾斜磁场存在下纳米流体共轭混合对流和熵产生的非均匀模型

目的

这项研究的目的是对由于厚壁围壁中Al ₂ O _3-水纳米流体的混合对流而产生的倾斜磁场和焦耳热对共轭传热的影响进行数值分析。

设计/方法/方法

水平温度梯度与剪切驱动的流动一起在外壳内部产生混合对流。在本研究中采用非均匀模型，其中纳米颗粒由于热泳和布朗扩散而具有滑移速度。通过确定熵的产生来评估热性能，熵的产生包括磁场的影响。采用交错网格上的控制体积方法来计算控制方程。

发现

由施加的磁场产生的洛伦兹力对流场和热场产生不利影响，因此，由于存在磁力，传热和熵产生减弱。焦耳加热会提高流体温度，但会减弱热传递。磁场的影响随着磁场倾斜角的增加而减小，并且随着纳米粒子的体积分数的增加而表现出来。与透明流体相比，纳米颗粒的添加增强了热传递和熵的产生，其熵产生的增强高于热传递的增加的速率。评估平均Bejan数和混合杯温度，以分析纳米流体的热力学特性。

创意/价值

这项文献调查表明，基于两相模型的倾斜磁场和焦耳热对共轭传热的影响尚未得到解决。随着磁场变强，纳米粒子的相对滑动速度的影响减小。