Simulation of natural convective heat transfer and entropy generation of nanoparticles around two spheres in horizontal arrangement

Abstract

Herein, laminar convective heat transfer from two horizontally arranged spheres has been evaluated by using numerical models inside water-based fluids incorporated with alumina (Al2O3), copper oxide (CuO), and copper (Cu) nanoparticles. The problem was simulated for different Rayleigh numbers ranging from 103 to 106 and various volume fractions including 2, 4, 6, and 8%. The evaluation process included the perspective of both first and second thermodynamic laws. In-house FORTRAN code was provided to solve the equations based upon the finite volume method as well as the Multigrid acceleration. According to the obtained results, the average Nusselt number enhanced by 57.4% for both the spheres and plates with increment of the Rayleigh number from 103 to 106 for the constant volume fraction of 2%. In addition, nanoparticle type played a significant role on the heat transfer rate and generated entropy. Moreover, introduction of the Al2O3 nanoparticles into the water-based fluid resulted in approaching to the highest Bejan number of 0.98. Furthermore, the ecological coefficient of performance of CuO nanoparticles decreased by increment of the volume fraction at all Rayleigh numbers. In the volume fraction of 2%, it raised from 2.89 to 7.8 by increasing of the Rayleigh number from 103 to 106.