Double-diffusive natural convective in a porous square enclosure filled with nanofluid

In this work, effects of double-diffusive natural convection of Al2O3-water nanofluid on flow field and heat transfer in a porous square cavity are investigated. Homogeneous and two-component non-homogeneous of Buongiorno's model that includes the effects of Brownian motion and thermophoresis are utilized, while the Darcy model is used for the porous medium. The governing equations are discretized using the finite difference and control volume method. Properties of nanofluid have been assumed functions of temperature and volume fraction of nanoparticles. Since constant Rayleigh number could not be used, simulations have been performed for various physical conditions such as temperature difference between the hot and cold walls from 1 to 20 °C, bulk volume fraction of nanoparticles from 0 to 0.04, and porosity between 0.1 and 0.5. Both models suggest that by increasing the bulk volume fraction of nanoparticles heat transfer is reduced, but non-homogeneous model predicts a greater reduction compared to the homogeneous model. Also non-homogeneous model predicts reduced heat transfer with increased porosity.