Purpose

This study aims to investigate the buoyancy-induced heat and mass transfer phenomena in a backward-facing-step (BFS) channel subjected to applied magnetic field using different types of nanofluid.

Design/methodology/approach

Conservation equations of mass, momentum, energy and concentration are used through velocity-vorticity form of Navier–Stokes equations and solved using Galerkin’s weighted residual finite element method. The density variation is handled by Boussinesq approximation caused by thermo-solutal buoyancy forces evolved at the channel bottom wall having high heat and concentration. Simulations were carried out for the variation of Hartmann number (0 to 100), buoyancy ratio (−10 to +10), three types of water-based nanofluid i.e. Fe₃O₄, Cu, Al₂O₃ at χ = 6%, Re = 200 and Ri = 0.1.

Findings

The mutual interaction of magnetic force, inertial force and nature of thermal-solutal buoyancy forces play a significant role in the heat and mass transport phenomena. Results show that the size of the recirculation zone increases at N = 1 for aiding thermo-solutal buoyancy force, whereas the applied magnetic field dampened the fluid-convection process. With an increase in buoyancy ratio, Al₂O₃ nanoparticle shows a maximum 54% and 67% increase in convective heat and mass transfer, respectively at Ha = 20 followed by Fe₃O₄ and Cu. However, with increase in Ha the Nuavg and Shavg diminish by maximum 62.33% and 74.56%, respectively, for Fe₃O₄ nanoparticles at N = 5 followed by Al₂O₃ and Cu.

Originality/value

This research study numerically examines the sensitivity of Fe₃O₄, Cu and Al₂O₃ nanoparticles in a magnetic field for buoyancy-induced mixed convective heat and mass transfer phenomena in a BFS channel, which was not analyzed earlier.

中文翻译：

---

Fe3O4/Cu/Al2O3-水纳米流体在磁场作用下通过后向台阶通道的双扩散混合对流的数值研究

目的

本研究旨在研究使用不同类型的纳米流体在施加磁场的后向台阶 (BFS) 通道中浮力引起的传热和传质现象。

设计/方法/方法

通过 Navier-Stokes 方程的速度-涡量形式使用质量、动量、能量和浓度的守恒方程，并使用 Galerkin 加权剩余有限元法求解。密度变化由 Boussinesq 近似处理，该近似是由在具有高热量和浓度的通道底壁处产生的热溶浮力引起的。模拟了哈特曼数（0到100）、浮力比（-10到+10）、三种水基纳米流体即Fe ₃ O ₄、Cu、Al ₂ O ₃在χ = 6%时的变化, Re = 200 和Ri = 0.1。

发现

磁力、惯性力的相互作用以及热溶浮力的性质在热量和质量传输现象中起着重要作用。结果表明，再循环区的尺寸在 N = 1 时增加，以帮助热溶浮力，而施加的磁场抑制了流体对流过程。随着浮力比的增加，Al ₂ O ₃纳米颗粒在对流热和传质方面分别显示出最大 54% 和 67% 的增加，在 Ha = 20 时，其次是 Fe ₃ O ₄和 Cu。然而，随着 Ha 的增加，N = 5 的 Fe ₃ O ₄纳米颗粒的 Nuavg 和 Shavg 分别最大减少 62.33% 和 74.56%，其次是 Al₂ O ₃和铜。

原创性/价值

本研究以数值方式检验了磁场中 Fe ₃ O ₄、Cu 和 Al ₂ O _{3纳米颗粒对 BFS 通道中浮力引起的混合对流传热和传质现象的敏感性，这是之前没有分析过的。}