Ferrohydrodynamic mixed convection in Fe3O4-water/EG or Ni3Fe-water/EG ferrofluid in a porous square vented enclosure

In this study, we look at the effects of various parameters on mixed convection in ferrofluid within a square porous medium with a heated bottom wall subjected to a non-uniform magnetic field and compare the heat transfer performance of water/EG-based magnetite (Fe3O4) and awaruite (Ni3Fe) ferrofluids. The Darcy-Brinkman-Forchheimer model is used for modelling ferrofluid flow through the porous medium, and the non-uniform magnetic field is generated using three current-carrying wires located below the heated wall. The finite difference method is used to solve the system of nonlinear governing equations, and graphical results for streamlines, isotherms and local Nusselt number are generated via MATLAB. We find that increasing the natural convection, forced convection and magneto convection, all significantly enhance the heat transfer from the bottom wall and also increase the local Nusselt number on the hot wall. A local minimum and maximum Nusselt number are identified on the heated wall at positions x = 0.68 and x = 0.84 respectively when forced convection is more prominent. An increase in the nanoparticle volume fraction, Darcy number or the magnetocaloric effect also enhances the heat transfer in system and the local Nusselt number. In particular, when the magnetocaloric effect and permeability of the porous material are large, natural convection is dominated by forced convection and magnetoconvection. It is also seen that the overall heat transfer performance is better for the Ni3Fe ferrofluid than the Fe3O4 ferrofluid. This study has potential applications in fields such as thermal engineering, particularly in the design of cooling systems for electronic devices or nuclear reactors.