Experimental study of internal forced convection of ferrofluid flow in non-magnetizable/magnetizable porous media

In this work, the thermal and hydrodynamic performance of ferromagnetic fluid, which flows through a copper tube in thermal entrance region, has been studied. The flow in the tube is laminar and subjected to constant heat flux. A part of the tube contains a porous medium with paramagnetic properties and porosity of 0.46. Ferrofluid is composed of Fe3o4 and water with (CH3)4NOH as a surfactant that is prepared in three different volume fractions. The effects of constant and oscillating magnetic fields on convective heat transfer coefficient were examined for various Reynolds numbers, frequencies and volume fractions. The results show that the maximum enhancements of average heat transfer coefficient of Ferrofluid in a magnetizable porous medium under constant and oscillating magnetic fields are 9% and 38.66%, respectively in comparison with that of water in no magnetic field condition. This enhancement is reduced to 6.39% and 36.13% for a non magnetizable porous medium. The results indicate that variable magnetic field enhances convective heat transfer coefficient and this enhancement is greater in the magnetizable porous medium.