International Journal of Microscale and Nanoscale Thermal. . . . ISSN: 1949-4955 Volume 2, Number 3 © 2011 Nova Science Publishers, Inc. MIXED CONVECTION FLOW OF A NANOFLUID IN A SQUARE LID-DRIVEN CAVITY WITH A LOCALIZED HEAT SOURCE AT THE BOTTOM W ALL M. A. Mansour 1 , Ali J. Chamkha 2 , and Sameh E. Ahmed 3 1 Department of Mathematics, Faculty of Sciences, Assuit University, Assuit, Egypt 2 Manufacturing Engineering Department, The Public Authority for Applied Education and Training, Shuweikh 70654, Kuwait 3 Department of Mathematics, Faculty of Sciences, South Valley University, Qena, Egypt ABSTRACT A numerical analysis is performed to examine laminar mixed convection cooling of a constant heat flux at the bottom wall of a square enclosure filled with water-base nanofluid containing various volume fractions of Cu, Ag, Al 2 O 3 and TiO 2 . The finite difference method is employed to solve the dimensionless governing equations of the problem. The influences of the governing parameters, namely, Reynolds number, location and geometry of the heat source, the type of nanofluid and solid volume fraction of nanoparticles on the cooling performance are studied. The present results are validated by favorable comparisons with previously published results. The results of the problem are presented in graphical and tabular forms and discussed. Keywords: Mixed convection, nanofluid, heat source, finite difference method. NOMENCLATURE length of the heat source ( ) specific heat, distance between the left wall and center of the heat source ( ) Grashof number gravitational acceleration,  Email: achamkha@yahoo.com B L b / p C 1 1   K kg J D L d / Gr ) / ( 2 3 f f v T L g   g 2  ms