MHD-Driven natural convection and heat transfer enhancement in hybrid nanofluid-filled sinusoidal porous enclosure

Natural convection in nanofluids is an important process of thermal transport enhancement in the absence of external energy sources, and it makes it extremely preferred in terms of advanced thermal management. In the current research a detailed numerical research is conducted to study the steady magnetohydrodynamic $$\:\:\left(MHD\right)\:$$ two phase natural convection and thermal transport in a cold sinusoidal porous container that has a rigidly placed hot circular object in the middle. A nanofluid of hybrid $$\:F{e}_{3}{O}_{4}\:-MWCNT$$ /water is saturated in the enclosure. Governing equations of continuity, momentum and energy are formulated in term of dimensionless form and then solved using the Galerkin Finite Element Method ( $$\:GFEM$$ ). The $$\:COMSOL$$ Multiphysics is used to conduct numerical simulations, and the effects of the main controlling parameters, such as the $$\:Ra$$ ( $$\:{10}^{4}-{10}^{6}$$ ), $$\:Da$$ ( $$\:{10}^{-6}-{10}^{-2}$$ ), $$\:Ha$$ ( $$\:0-100$$ ) as well as the difference in the diameter of the circular obstacle, are analyzed based on the analyses of streamlines, isotherms, and the distributions of the local and average Nusselt numbers. The findings indicate that increment in the Rayleigh number and nanoparticle concentration significantly improves convective heat transfer which ends up resulting in high average Nusselt numbers. In addition, an inverse relationship was observed between the Hartmann number and the average Nusselt number, with increasing $$\:Ha$$ from 0 to 100 reducing $$\:{Nu}_{avg\:}$$ by approximately $$\:21.30\%\:$$ because the intensified Lorentz force suppresses fluid circulation and weakens convective heat transfer. Geometric changes in the inner circular obstacle also provide a significant increase in thermal transport with the $$\:{Nu}_{avg\:}$$ growing by about $$\:19.6\%$$ to $$\:58.2\%.$$ The presented results are informative on the interplaying effects of magnetic fields, porous media, and hybrid nanofluids, and, therefore, they offer meaningful information when designing effective thermal systems.