Buoyancy-induced convective flow and heat transfer over obstacles embedded inside a Cu-water nanofluid-saturated porous cavity

In this article, a comprehensive study of convective flow over the obstacles (i.e., heaters and freezer) inside the cavity filled with Cu-water nanofluid-saturated porous medium is made. The flow is induced due to heated vertical walls and a cooled top wall, as well as partial attachment of obstacles with the bottom wall. A non-Darcy model that includes Darcy and Brinkman terms has been adopted. The coupled governing equations are solved numerically by the finite element method using the penalty approach. The influence of different controlling parameters, Rayleigh number (Ra), nanoparticle volume fraction (phi), Darcy number (Da), Prandtl number (Pr), aspect ratio (A(r)), and porosity (epsilon) on the dynamics of flow and heat transfer rate have been addressed. The flow dynamics as well as heat transfer rate have been analyzed with help of streamfunction and temperature contours. Results show that the flow structure (i.e. streamlines) is controlled by nipple shape bicellular structure and the velocity profile includes the point of inflection. The variation of the Nusselt number as a function of the volume fraction of the nanoparticle is almost linear. In contrast to pure fluid, at 10% volume fraction of nanoparticle, the enhancement in heat transfer rate is found up to 30%.