Double diffusive mixed convection in a Cu-Al2O3/water nanofluid filled backward facing step channel with inclined magnetic field and part heating load conditions

Abstract

The impact of inclined magnetic field on thermo-fluidic behaviour in a Cu-Al2O3/water nanofluid filled backward facing step channel, associated with thermo-solutal buoyancy induced mixed convection, has been numerically investigated. A novel part heating load boundary condition is applied at the bottom wall in order to model and analyse closer to the actual physics. The Navier-stokes equation in velocity-vorticity form along with energy and concentration equations are solved using Galerkin's FEM. The variation of buoyancy ratio (‒5≤N≤5), Hartmann number (0≤Ha≤50), inclination angle (0≤φ≤90) with two different part heating arrangements are analyzed systematically to understand the flow pattern and convective heat & mass transfer performance. Results show that at positive buoyancy ratio the solutal buoyancy force always supports the thermal buoyancy force augmenting the heat and mass transport phenomena. Increasing the inclination angle always give rise to the conductive mode of heat transfer compared to convective mode caused by the presence of stronger magnetic force. At N=5, change in Ha from 0 to 50 shows a maximum increment of 38% in Nuavg for φ= 0° wheras 5% reduction in Shavg is obtained for φ= 30°. Compared to case II, nearly 20 to 40% improvement in convective heat transfer is observed in case-I where heat sources are located closer to the channel step though hardly any change is observed in convective mass transfer between two different cases.