Heat transfer in annular enclosure filled with nanofluid

In this paper, we present a numerical study of natural convection heat transfer in annular enclosure packed with nanofluid. The inner diameter is equiped with two symetrical fins, and subjected to volumetric heat generation while the outer cylinder is kept adiabatic. The finite volume method is used to solve the governing equations , such as the continuity , mass and energy equations by the use of the Fluent 6.3.26 software.The effect of the size of the nanoparticles on the rate of heat transfer is carried out and investigated. The study has been conducted considering two nanofluids of based water with Al2O3 and TiO2 nanoparticles for a solid volume fraction (0≤ ϕ ≤ 0.09) and nanoparticles diameter of (5nm ,20nm and 80nm) at Rayleigh number Ra=12000. Results have shown that adding nanoparticles in the base fluid have produced an increasing of the rate of heat transfer. The nanofluid water/Al2O3 gives better heat transfer enhancement at small particles diameter than the nanofluid Water/TiO2.