Magnetohydrodynamic in partially heated square cavity with variable properties: Discrepancy in experimental and theoretical conductivity correlations

Natural convection nanofluid heat transfer enhancement in a partially heated cavity is considered under the effect of an external Lorentz force exerted through interaction of the nanoparticles and the applied constant magnetic field. The aluminum oxide (Al₂O₃ or alumina) nanofluid is considered to be with variable properties (i.e. thermal conductivity, viscosity and electric conductivity) and the cavity is partially heated from its left top corner. The effect of the inclination angle of the applied magnetic field is studied and analyzed. The Nusselt number is calculated at the heater to probe the heat transfer enhancement. Both effective thermal and electric conductivities have been investigated in their respective theoretical and experimental correlations. Numerical experiments are presented to show the discrepancy in heat transfer with the use of such correlations. A substantial difference in the heat transfer is noticed for the use of different correlations. An adverse effect is identified and analyzed with the increase of Hartmann number, the nanoparticle volume fraction, and the position of the heater within the cavity.