Natural Convection and Entropy Generation in a Porous Enclosure Filled with Non-Newtonian Nanofluid

In the present work, the analysis of natural convection and entropy generation in a square porous cavity, having either a flat or a wavy vertical wall, filled with a non-Newtonian nanofluid is reported. The effect of Rayleigh number (10(5)-10(6)), non-Newtonian power-law index (0.6-1.4), Darcy number (0.0001-0.01), Hartmann number (0-90), and volume fraction of CuO nanoparticles (0-0.12) on heat transfer characteristics has been thoroughly examined. It is found that the average surface Nusselt number for an undulated wall is less than that of a plane wall. Nu for all the cases increases with Ra and Da and decreases with Ha. The mixing of the nanoparticles with both Newtonian and non-Newtonian fluids enhances the heat transfer only for Da of 0.01 and Ha less than 30 for all Ra. When Da is low at 0.0001, the addition of nanoparticles to a fluid enhances the heat transfer for all the cases except Ra of 10(6) at n less than 1. The entropy generation is significant near the vertical wall because of the higher temperature and velocity gradient. The magnitude of S-HT is found to be very less as compared with S-FF and S-H.S-HT, S-FF, and S-H increase with an increase in Da for all cases; however, for a Ha of 60 or 90, there exists an optimum for S-FF for a Da ranging from 0.0005 to 0.001. Finally, the correlation for the average surface Nu as a function of the pertinent input parameters has been proposed for both Newtonian and non-Newtonian fluids, which can be referred in the academics and the industrial world.