In the present investigation, the behavior of laminar convective flow and heat transfer in a three‐dimensional horizontal square duct using different water‐based nanofluids (Fe3O4/water, and carbon nanotubes/water) is numerically investigated. The channel is subjected to a periodic partial or full magnetic field. The outer surface is subjected to a constant heat flux density. The problem is numerically solved via the finite volume method with a second‐order precision. The numerical simulations covered a range of the Reynolds number 50 ≤ Re ≤ 400, Hartmann number 0 ≤ Ha ≤ 50, and concentration of nanoparticles 0 ≤ ϕ ≤ 0.02 for different modes of the magnetic field application and direction. Examination of the hydrodynamic and thermal behavior shows significant heat transfer performances obtained when applying transversal and partial periodic magnetic fields simultaneously. More precisely, it is found that the favorable protocol improved the heat transfer rate by 85% in the duct flowing by the Ferrofluid at Ha = 50. Furthermore, findings illustrate that the overall heat transfer rate presented in terms of the mean Nusselt number and the highest compromise (heat transfer augmentation‐pressure losses diminution) are obtained in the case of Fe3O4 nanoparticles for all taken values of Reynolds and Hartmann numbers, whatever the manner and direction of the applied magnetic field.

Heat transfer and entropy generation of laminar flow of a ferrofluid in different cross-section channel subjected to partial and full magnetic field are investigated in this study. A constant heat flux condition was applied on the external surface. The conservation equations (mass, momentum, and energy) are solved numerically via the finite volume method with a second-order precision. The effects of fully or partially applying a magnetic field with different directions and intensities on thermodynamic features, heat transfer, and entropy generation have been investigated. Analyses were carried out in four different cross-section channels, namely triangular, rectangular, circular, and elliptical. Results indicate that the circular cross-section channel provides higher heat transfer rates and lower entropy generation than non-circular cross-section channels.