INFLUENCE OF APPLYING MAGNETIC FIELD ON THERMAL AND HYDRAULIC CHARACTERISTICS OF FE3O4/WATER MAGNETIC NANOFLUID MOVING IN A TWISTED DUCT

This study introduces an investigation of the effect of combining passive and active techniques on enhancing heat transfer by using a ferrofluid passing through a twisted duct subjected to an external magnetic field. The effect of changing the number of magnets, magnetic flux density, nanoparticle volume fraction, and twist ratio on the heat transfer enhancement is studied. The optimum magnetic field configuration was achieved by adjusting the rate of increase of magnetic flux density to 80% between each two successive magnets. Results show that the proposed hybrid technique is promising in providing significant heat transfer enhancement compared to the traditional techniques, but the pressure drop values become relatively higher due to the increased friction levels. The twist ratio value that achieves the optimum thermo-hydraulic performance is found to be 3.7. The limit of mag- netic flux density, which, if exceeded, causes the thermo-hydraulic performance to decline, is 800 Gauss. It is found that applying a magnetic field with 1,000 Gauss flux density with a nanoparticle volume concentration of 5% and a twist ratio of 3.7 at Reynolds number of 8,400, enhances the Nusselt number by 25.78% compared to the case using water without twisting in the absence of a magnetic field.