Numerical study of mixed convection flows in a lid-driven enclosure filled with nanofluid using variable properties

This paper focuses on the study of mixed convection heat transfer characteristics in a lid-driven enclosure filled with nanofluids using variable thermal conductivity and variable viscosity. The fluid in the enclosure is a water-based nanofluid containing Al2O3 nanoparticles. The top and bottom horizontal walls are insulated, while the vertical walls are kept at different constant temperatures with the top surface moving at a constant speed. The study has been carried out for the Richardson numbers of 0.01-100, the solid volume fraction of 0-0.06 and the Grashof number of 10(4). Various results for the streamlines and isotherms as well as the local and average Nusselt numbers are presented. The variable viscosity and thermal conductivity of both the Brinkman and the Maxwell-Garnett model were compared. Significant differences are found between the magnitudes of heat transfer enhancement in the enclosure for two employed models. (C) 2012 Elsevier B.V. Open access under CC BY-NC-ND license.