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In the present paper a numerical study of natural turbulent convection in a tall cavity filled with nanofluids. The cavity has a heat source embedded on its bottom wall, while the left, right, and top walls of the cavity are maintained at a relatively low temperature. The working fluid is a water based nanofluid having three nanoparticle types: aluminum, Cu, and CuO. The influence of pertinent parameters such as Rayleigh number, the type of nanofluid, and solid volume fraction of nanoparticles on the cooling performance is studied. Steady forms of 2-D Reynolds- аveraged-Navier-Stokes equations and conservation equations of mass and energy, coupled with the Boussinesq approximation, are solved by the control volume based discretisation method employing the SIMPLE algorithm for pressurevelocity coupling. Turbulence is modeled using the standard k-ε model. The Rayleigh number is varied from 2.491009 to 2.491011. The volume fractions of nanoparticles were varied in the interval 0 ≤ φ ≤ 6%. Stream lines, isotherms, velocity profiles, and temperature profiles are presented for various combinations of Rayleigh number, the type of nanofluid, and solid volume fraction of nanoparticles. The results are reported in the form of average Nusselt number on the heated wall. It is shown that for all values of Rayleigh number, the average heat transfer rate from the heat source increases almost linearly, and monotonically as the solid volume fraction increases. Finally, the average heat transfer rate takes on values that decrease according to the ordering Cu, CuO, and Al2O3. [ABSTRACT FROM AUTHOR]