Numerical Study of Forced, Mixed and Natural Convection of Nanofluids Inside a Ventilated Cavity Containing Different Shapes of Cold Block

In the present investigation, the finite volume analysis is used for solving forced, mixed and natural convection of the nanofluid inside a ventilated cavity with a central cold block. The effect of mixed convection is reached by cooling on the inlet port of the vented cavity and uniformly heating on its bottom wall. Water-based nanofluids with Cu, Al2O3, and TiO2 nanoparticles at different sizes (25 nm <= d(p) <= 145 nm) are chosen for investigation. Dimensionless forms of continuity, Navier-Stokes and energy equations with the specified boundary condition have been solved numerically over a wide range of Richardson number (0.1 <= Ri <= 100) and nanoparticle volume fraction (0 <= phi <= 0.05). The Grashof number is kept constant at (Gr = 10(4)), so that the Reynolds number takes different values (Re = 10, 31.62, 100, and 316.22). The Corcione models have been used to calculate nanofluid effective viscosity and thermal conductivity. The effects of two different geometric forms of the cold obstacle (square and triangular) on fluid flow and heat transfer rate are also investigated. The results reveal for some cases, that by the reduction of the Richardson number and size of solid particles, the heat transfer is enhanced. It is also noticed that there is an optimal nanoparticles concentration which the maximum mean Nusselt numbers occurs.