Buoyancy induced convection in magnetite nanofluid filled in enclosure with thick fin under magnetic field produced by a magnetic source

Abstract

Buoyancy-induced convection of the magnetite nanofluid-filled enclosure with a thick fin on the heated surface is investigated under the magnetic field generated by a magnetic source. Since the heat transfer characteristic is sensible to the thermo-physical properties of the fluid used, these properties are determined experimentally to reduce the error. Magnetite nanofluid of low particle concentration is prepared using two-step method experimentally. Thermal conductivity, dynamic viscosity, and density of the prepared fluid is measured and utilized in the numerical study. The buoyancy-induced convection is characterized in terms of Rayleigh number, the magnetic field strength, the fin material's thermal conductivity, and the magnetic source's position. The numerical investigation is performed for various dimensionless numbers, including Rayleigh number (103 ≤ Ra ≤ 105), Hartmann Number (0 ≤ Ha ≤ 75), and thermal conductivity ratio (10 ≤ Kr ≤ 1000). The thermal conductivity ratio is observed to affect the heat transfer rate significantly. With the increase in the thermal conductivity ratio, more heat is inducted inside the enclosure, causing a higher heat transfer rate. The magnetic field has an inverse relation with the convection current, whereas the Rayleigh number has positive relation. The position of the magnetic source significantly affects the heat transfer rate. The rate is found to be minimum when the source is below the center of the enclosure compared to when it is below one of the vertical surfaces.