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<p>This study investigates the thermal behavior of Rayleigh–Bénard flow and entropy generation in a trapezoidal enclosure containing two immiscible fluids: air and TiO<sub>2</sub>–water nanofluid, under the influence of a periodic magnetic field with different heating patterns. The governing equations were solved numerically using the finite element method, with code validation performed against established experimental and numerical results. The investigation encompassed parametric variations of Rayleigh number (10<sup>3</sup> ≤ Ra ≤ 10<sup>6</sup>), Hartmann number (0 ≤ Ha ≤ 80), magnetic field period (0.1 ≤ <i>λ</i> ≤ 0.9), and nanoparticle volume fraction (0 ≤ <i>ϕ</i> ≤ 0.05) under uniform, parabolic, and sinusoidal heating conditions. Results demonstrate that increasing Ra from 10<sup>3</sup> to 10<sup>6</sup> enhances heat transfer significantly, with uniform heating showing the highest sensitivity (443.9% increase in <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\({\text{Nu}}_{\rm{av}}\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mtext>Nu</mtext> <mi mathvariant="normal">av</mi> </msub> </math></EquationSource> </InlineEquation>). The magnetic field exhibits a suppressive effect, reducing <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\({\text{Nu}}_{\rm{av}}\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mtext>Nu</mtext> <mi mathvariant="normal">av</mi> </msub> </math></EquationSource> </InlineEquation> by 67.8% as Ha increases from 0 to 80 under uniform heating. Entropy generation peaks at 3000 units in the nanofluid layer at Ra = 10<sup>6</sup>, with uniform heating generating the highest irreversibilities. The sinusoidal heating pattern consistently demonstrates superior thermodynamic performance, maintaining stable heat transfer characteristics and minimal entropy generation across varying operational parameters, suggesting its potential for practical thermal management applications.</p>

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Entropy generation in Magneto–Rayleigh–Bénard convective heat transfer of a TiO2-water nanofluid and air bilayer system with magnetic oscillations and non-uniform heating

  • 期刊论文

  • 发表日期：

    2025年9月6日

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  • Ahmed M. Hassan,
  • Hakim S. Sultan Aljibori,
  • Nasser H. Hamza,
  • Abdul Amir H. Kadhum,
  • Rafel H. Hameed,
  • Ameer K. Salho

摘要

This study investigates the thermal behavior of Rayleigh–Bénard flow and entropy generation in a trapezoidal enclosure containing two immiscible fluids: air and TiO2–water nanofluid, under the influence of a periodic magnetic field with different heating patterns. The governing equations were solved numerically using the finite element method, with code validation performed against established experimental and numerical results. The investigation encompassed parametric variations of Rayleigh number (103 ≤ Ra ≤ 106), Hartmann number (0 ≤ Ha ≤ 80), magnetic field period (0.1 ≤ λ ≤ 0.9), and nanoparticle volume fraction (0 ≤ ϕ ≤ 0.05) under uniform, parabolic, and sinusoidal heating conditions. Results demonstrate that increasing Ra from 103 to 106 enhances heat transfer significantly, with uniform heating showing the highest sensitivity (443.9% increase in \({\text{Nu}}_{\rm{av}}\) Nu av ). The magnetic field exhibits a suppressive effect, reducing \({\text{Nu}}_{\rm{av}}\) Nu av by 67.8% as Ha increases from 0 to 80 under uniform heating. Entropy generation peaks at 3000 units in the nanofluid layer at Ra = 106, with uniform heating generating the highest irreversibilities. The sinusoidal heating pattern consistently demonstrates superior thermodynamic performance, maintaining stable heat transfer characteristics and minimal entropy generation across varying operational parameters, suggesting its potential for practical thermal management applications.