Thermal efficiency of a ferrofluid in a horizontal channel with non-uniform magnetic fields and curved heat sources:...

This study presents a comprehensive numerical investigation of the hydrothermal characteristics of water-Fe₃O₄ ferrofluid in a horizontal channel subjected to a non-uniform magnetic field and two curved wall-mounted heated obstacles. The channel is equipped with constant-temperature heat sources on the walls, a uniform inflow temperature, and a constant outflow pressure. The effects of three spatially varying magnetic field configurations on the flow dynamics and thermal behavior around the heated obstacle are analyzed using the finite element method (FEM). The findings reveal that increasing the magnetic field intensity significantly alters velocity streamlines and isotherms. Although greater magnetic field strength leads to only a marginal reduction in overall heat transfer (less than 1%), modifications to the shape of the heated obstacle markedly affect performance. Specifically, increasing the height of the protrusion enhances the core flow velocity and boosts the average Nusselt number by up to 31.3%. Conversely, elongating the heated region reduces wall-adjacent velocity and causes up to a 94.92% decrease in the average Nusselt number. These results highlight the critical role of obstacle geometry and magnetic field design in enhancing thermal performance in magnetically driven nanofluidic systems.