A numerical study of mixed convection flow and heat transfer inside a square cavity with inlet and outlet ports is performed. Given a fixed position of the inlet port, the location of the outlet port is varied along the four walls of the cavity in order to determine the best configuration of the system corresponding to maximum heat transfer rate and minimum pressure drop. The presence of nanoparticles in the base fluid are simulated using theoretical models. It is observed that the average Nusselt number is an increasing function of Reynolds number, Richardson number and nanoparticle volume fraction. The pressure drop coefficient is also increased in the presence of nanoparticles. Moreover the performance of the nanoparticle utilization on the enhancement of heat transfer at higher Richardson numbers is less than that at lower Richardson numbers. (C) 2014 Elsevier B.V. All rights reserved.