Faculty of Mechanical Engineering, University of Tabriz, Tabriz, Iran
In this study the 2D laminar and steady water-based Al2O3 nanofluid flow over a cylinder with circular, horizontal and vertical elliptical cross section by constant surface temperature boundary condition has been studied. The main goal of this research is to investigate the effects of different natural and mixed convection heat transfer mechanisms on the convective heat transfer coefficient, and the entropy generation due to the thermal and frictional origination. Conservation equations of the mass, momentum and energy under the assumption of incompressible, Newtonian nanofluid, by using the homogeneous single phase method have been solved. The impact of considered parameters in this study (alteration in cross section, convective flow direction and volume fraction of nano particles) in enhancing the heat transfer rate is studied in association with the entropy generated value in each case. Based on the results, the vertical elliptical cross section, in comparison with others, shows the highest entropy generation value and the heat transfer coefficient in all considered mechanisms. Moreover, mixed convection heat transfer type 2, in which the force flow is perpendicular to the buoyant flow direction, has the highest entropy generation and heat transfer rate for all cross sections. In addition, in all cases in the presence of the nanoparticles, the heat transfer rate and entropy generation increases.