Numerical study of mixed convection heat transfer in a lid-driven cavity filled with a nanofluid

This paper reports a numerical study of mixed convection in a square enclosure, filled with a mixture of water and different types of nanoparticles. The upper and the bottom walls of the cavity are thermally insulated, while the remaining walls are mobile and differentially heated. In order to solve the general coupled equations, a computer code based on the finite volume method is used and it has been validated after a comparison between the present results and those of the literature. To make clear the effects of the governing parameters on the fluid flow and heat transfer inside the square, a wide range of the Richardson number, taken as 0.01 to 100, and the nanoparticles volume fraction, taken from 0 to 10%, is investigated. The phenomenon is analyzed through streamlines and isotherm plots with a special attention to the Nusselt number. The obtained results show that the mean Nusselt number is an increasing function of the decrease Richardson number, and increases with increasing values of the nanoparticles volume fraction, and far from the natural convection mode, higher heat transfer is noted with Ag-water nanofluid. At the end, useful correlations predicting heat transfer rate as a function of the solid volume fraction are proposed for each value of the Richardson number, which predict the numerical results within ±0.02%.