MIXED-CONVECTION FLOW IN A LID-DRIVEN SQUARE CAVITY FILLED WITH A NANOFLUID WITH VARIABLE PROPERTIES: EFFECT OF THE NANOPARTICLE DIAMETER AND OF THE POSITION OF A HOT OBSTACLE

In this article, a mixed-convection flow in a cavity filled with an Al2O3/water nanofluid and having an inside hot obstacle and variable properties is studied numerically using the finite volume method. The thermal conductivity and effective viscosity of the nanofluid were determined using the new variable properties models proposed by Xu and Jang, respectively. The bottom, top, and the left walls of the cavity are adiabatic, while the right wall is maintained at a cold temperature (T-c) A hot rectangular obstacle is located at the bottom of the square cavity. The upper adiabatic lid is moving in its positive direction. To numerically solve the governing equations, the finite volume method along with a displaced grid system is used, and the equations are transformed into a code using FORTRAN. In this study the influence of some important parameters such as the diameter of a nanoparticle, Richardson number, and the position of the hot obstacle on the hydrodynamic and thermal characteristics are discussed. The results indicate that a decrease in the nano particle diameter at a constant Ri enhances heat transfer. On the other hand, the heat transfer rate increased as Ri was decreased for a particular diameter and position of the hot obstacle.