Uniform magnetic field (UMF) effect on the heat transfer of a porous half-annulus enclosure filled by Cu-water nanofluid considering heat generation

Background: In this work, the effect of a uniform magnetic field (UMF) on the natural convection heat transfer of Cu-water nanofluid in a porous half-annulus cavity is studied by finite element method, considering heat generation. The effects of four parameters (magnetic field angle (γ), Hartmann number (Ha), nanoparticles volume fraction (φ) and Rayleigh number (Ra)) on the local and average Nusselt numbers of outer wall have been investigated. Methods: Numerical Finite Element Method (FEM) based on FlexPDE commercial code was used to solve the described problems and the validation was also performed by Finite Difference Method (FDM) in previous studies. Results: It was found that by applying external magnetic field with a certain angle with respect to the geometry, the maximum local heat Nusselt number could shift to one side of outer wall and the shift is dependent on the angle of the imposed magnetic field. Conclusion: Our results also confirm that increasing the Hartmann number decreases the Nusselt number due to Lorentz force resulting from the presence of stronger magnetic field which slows down the fluid motion and in turn leads to a decreased heat transfer.