Taming thermodynamic chaos and entropy generation study in MHD Al₂O₃-water nanofluid flow through corrugated porous media using Brinkman-Forchheimer model

This study investigates the magnetohydrodynamic (MHD) natural convection and entropy generation of an Al₂O₃−water nanofluid within a porous wavy annulus, with a heated inner cylinder. This research addresses a critical gap in the literature by analyzing the synergistic effects of a magnetic field, nanoparticle concentration, and complex porous media on both heat transfer and thermodynamic irreversibility using the Brinkman-Forchheimer extended Darcy model, with governing equations solved numerically via the Finite Element Method in COMSOL Multiphysics, validated through rigorous mesh refinement. The analysis focuses on the interplay of streamlines, isotherms, and local/average Nusselt number against the physical parameter. Key results demonstrate that surface corrugation of the inner cylinder N disrupts thermal boundary layers, boosting the average Nusselt number by 20%, while nanoparticle addition enhances it by 25%. Conversely, the Hartmann number Ha suppresses convection, reducing the average Nusselt number by 50%. A novel entropy generation analysis reveals a fundamental transition in irreversibility dominance where thermal effects dominate and contribute 80% at low Ra, while the magnetic and viscous irreversibility prevail and account for 60% at high Raand Ha. The Bejan number decreases by 12% as porosity ε increases, indicating that higher porosity favors friction-dominated irreversibility over thermal effects. This study significantly benefits the design and optimization of compact heat exchangers and thermal management systems for MHD power generators, where managing high heat fluxes under magnetic influence is paramount.