Heat transfer and entropy generation of natural convection on non-Newtonian nanofluids in a porous cavity

In this paper, heat transfer and entropy generation on laminar natural convection of non-Newtonian nanofluids in a porous square cavity have been analyzed by Finite Difference Lattice Boltzmann Method (FDLBM). The porous cavity is filled with water and nanoparticles of copper (Cu) while the mixture shows shear-thinning behavior. This study has been conducted for the certain pertinent parameters of Rayleigh number (Ra = 10(4)-10(5)), Darcy number (Da = 0.001, 0.01, and 0.1), and power-law index (n = 0.6-1), and the volume fraction has been studied from phi o = 0 to 0.04. Results indicate that heat transfer and different irreversibilities enhance as Rayleigh number increases. The enhancement of the volume fraction augments heat transfer and the entropy generations due to heat transfer and fluid friction. The drop of the Darcy number causes the heat transfer and different entropy generations to decline considerably. Interestingly, the behavior of heat transfer and the studied entropy generations against the alteration of the power-law index is different in various Darcy numbers. In addition, the Bejan number demonstrates that the proportion of the irreversibilities due to heat transfer and fluid friction changes with the variation of the scrutinized parameters. (C) 2016 Elsevier. B.V. All rights reserved.