The effect of magnetic field on nanofluids heat transfer through a uniformly heated horizontal tube

In this study, the effects of magnetic field on forced convection heat transfer of Fe3O4 water nanofluid with laminar flow regime in a horizontal pipe under constant heat flux conditions were studied, experimentally. The convective heat transfer of magnetic fluid flow inside the heated pipe with uniform magnetic field was measured. Fe3O4 nanoparticles with diameters less than 100 nm dispersed in water with various volume concentrations are used as the test fluid. The effect of the external magnetic field (Ha = 33.4 x 10(-4) to 136.6 x 10(-4)) and nanoparticle concentrations (phi = 0, 0.1, 0.5, 1%) on heat transfer characteristics were investigated. Results showed that by the presence of a magnetic field, increase in nanoparticle concentration caused reduction of convection heat transfer coefficient. In this condition, heat transfer decreased up to 25%. Where, in the absence of an external magnetic field, adding magnetic nanoparticles increased convection heat transfer more than 60%. It was observed that the Nusselt number decreased by increasing the Hartmann number at a specified concentration of magnetic nanofluids, that reduction about 25% in heat transfer rate could be found. (C) 2016 Elsevier B.V. All rights reserved.