Thermo-hydraulic characteristics of magnetic nanofluid in opposing and assisting minichannel under the influence of external magnetic field

Abstract

The present numerical study investigates the effect of external magnetic field on a magnetic nanofluid flow in an inclined channel. A uniform magnetic field is used to generate vortex in the channel for heat transfer enhancement. Fe3O4–water nanofluid of 2 vol. % is flowing in an inclined two-dimensional channel with a heated bottom wall. Numerical simulations are carried out for different inclination angles varying from −90° < θ < 90° at low Reynolds numbers, in the presence of external magnetic field of intensities varying from 0–2000 G. The heat sink has dimensions of 40 × 4 mm2, with a magnet pair placed at 15 mm from the origin. Different thermo-hydraulic properties, like Nusselt number, friction factor, pressure drop and thermal enhancement factor (TEF), are calculated for all the cases. There is an average increase in the Nusselt number by 4.95% and 19.27% when a magnetic field of 1500 and 2000 G is applied, respectively. This heat transfer enhancement comes with a penalty of 32.95% and 89.23% increase in the friction factor for the respective magnetic fields. Magnetic field decreases the pressure drop by reducing the contact area for positive inclinations, while increases pressure drop by increasing turbulence for negative inclinations. TEF for the flow increases by 9.53% and 12.50% when the magnetic field of 1500 and 2000 G is applied, respectively. The TEF value is observed to be greater than one for very large ranges of inclinations when magnetic fields are applied, as compared to the flow without magnetic field.