The goal of this numerical study, is to investigate the hydromagnetic mixed convection heat transfer flow inside a ventilated cavity, crossed by hybrid nanofluid. This latter is made of Ag and MgO nanoparticles (50:50 vol %) dispersed in water as base fluid. The enclosure is under the influence of a uniform and constant magnetic field, applied in a horizontal direction. In this work, the cavity is of right angled trapezoid shape, and is assumed to be of infinite length in the third direction imparting a two-dimensional character to the flow. The cavity is subjected to a laminar and steady jet of fresh hybrid nanofluid entering the enclosure through an opening placed on the lower corner of the bottom wall which is adiabatic, just like the vertical right wall. The fluid is evacuated through an opening representing the upper base of the cavity. The left wall is inclined, and is maintained at a constant and uniform hot temperature. It is assumed that the nanofluid is Newtonian, incompressible and substantially behaves as a single phase fluid. Moreover, the Boussinesq approximation is valid for buoyancy force. New correlations to predict the viscosity and thermal conductivity of Ag-MgO / water hybrid nanofluid are employed in the study. The dimensionless governing equations with the appropriate boundary conditions, are discretized by the finite volume method and solved numerically via the SIMPLER algorithm.

All the simulations were performed for the case of pure mixed convection (Ri = 1), and are presented on the one hand, through hydrodynamic and thermal fields in the cavity as well as the velocity profiles. On the other hand, a special focus is granted to the heat transfer rate, through the evaluation of the average Nusselt number at the hot inclined wall.

The study focuses on the determination of the conditions that provide the best thermal performance of the cavity. We investigate the effect of some parameters including the influence of the hybrid nanofluid jet intensity (Reynolds number), the magnetic field strength (Hartmann number) and nanoparticles volume fraction. The results indicate that the hybrid nanofluid flow is strongly affected by the increase in the intensity of the magnetic field. Globally, the augmentation of Reynolds and Hartmann numbers enhance the heat transfer rate. We also note that, the increase in nanoparticles concentrations promotes the heat transfer. However, the contribution of nanoparticles on the improvement of heat transfer has a significant impact at low values of the Reynolds number.