Computational analysis of mixed convection water–Al2O3 nanofluid in a square cavity Effect of variable properties and moving wall location:

Abstract Mixed convection of a nanouid consisting of water and Al2O3 in a square cavity with using variable thermal conductivity and variable viscosity has been studied numerically. The left and right walls are maintained at different constant temperatures while upper and bottom insulated walls. Two different cases were considered based on moving wall position in the square cavity. In Case I the left vertical side (hot) moving upwards and In Case II the right vertical side (cold) moving downwards. The study has been carried out for the Richardson numbers of 0.01–100, the solid volume fraction of 0– 0.09 and the Grashof number of 104. The governing equations are solved numerically using the nitevolume approach. Results are presented in the form of streamlines, isotherms and average Nusselt number. It was found from the obtained results that, in general, the average Nusselt number of the hot wall increases with decreasing in Richardson number. Moreover the obtained results showed that the location of moving wall had most influence on increasing of average Nusselt number. Finally the results obtained using variable thermal conductivity and variable viscosity of Khnafer formulas were compared to the results obtained by the Maxwell-Garnett (MG) model and the Brinkman model. Signicant differences are found between the magnitudes of heat transfer enhancement in the enclosure for two employed models.