Heat Transfer and Pressure Drop Analysis of a Confined Nanofluid Jet Flow Under a Non-uniform Magnetic Field

The current study investigates a multi-walled carbon nanotube (MWCNT)-water nanofluid jet flow inside a horizontal channel in forced convection mode under a non-uniform magnetic field created by six electrically conductive wires arranged in a staggered pattern outside the channel's lower and upper walls. The physical phenomena are mathematically formulated by combining the Navier-Stokes and Maxwell equations and then solved numerically using the finite volume method. The effects of the magnetic field intensity (Ha), the jet opening ratio (R), and the Reynolds number (Reh) on the flow and heat transfer characteristics are analyzed. The results indicate that stagnation and acceleration zones form near the magnetic sources, becoming more significant at high Hartmann numbers and low Reynolds numbers. The size of the vortices at the channel inlet, which tend to become asymmetric at low R and high Reh, progressively decreases until they disappear as the magnetic field strength increases. The heat transfer improves as Ha and Reh increase while R decreases. A correlation between the critical Reynolds number, from which the narrowing at the channel inlet is thermally more advantageous than the fully open channel, and Ha and R is proposed. The highest deviation from the numerical results does not exceed 5%. Finally, an intense magnetic field with a low opening ratio is recommended to ensure a high heat transfer gain for a low-pressure loss. An optimal situation arises for the studied physical system when R = 1/6 and Ha = 50.