The mixed convection in a lid-driven cavity containing a hot elliptical centric cylinder was studied by using of Water-Aluminum oxide (Al2O3) nanofluid. The problem was simulated at different Richardson numbers (0.1, 1, 10, 100), different volume fractions (0, 0.1%, and 0.2%), different angles (0 degrees, 15 degrees, and 45 degrees), and temperature difference of 50 degrees C. The obtained results show that by Increase in Richardson number in a constant volume fraction and cavity angle decreases the Nusselt number, because increased Richardson number reduces the nanofluid velocity and increases the shear force. Also, increased in Richardson number reduces the decreasing trend of Nusselt number, because at the Richardson numbers of 0.1-10, the main heat transfer mechanism is forced convection; Also, increase in the temperature difference between the cold walls and the cylinder at a constant Richardson number, volume fraction and cavity angle increase the Nusselt number and heat transfer in such a way that the increasing trend of the Nusselt number depends on volume fraction, fluid velocity, and cavity angle. (C) 2017 Elsevier Ltd. All rights reserved.