Role of entropy generation on thermal management during natural convection in tilted porous square cavities

The strategic application of entropy generation concept for optimization of the natural convection process has been studied in the present work. The wall, AB is isothermally heated and walls, BC and DA are cooled in presence of adiabatic wall CD. The numerical results are presented in terms of isotherms (θ), streamlines (ψ) and entropy generation maps for heat transfer (Sθ) and fluid flow (Sψ) for various modified Prandtl numbers (Prm=0.015 and 1000), modified Darcy numbers (Dam=10-5--10-2) and modified Rayleigh numbers (Ram=103 and 106). The maximum value of the entropy generation due to heat transfer (Sθ, max) is observed at hot and cold junction points (A and B), due to high temperature gradient, irrespective of Dam, Prm and inclination angles (ϕ). The active regions of Sθ occur at top portion of the walls, BC and DA at high Dam(Dam=10-2) and high Prm(Prm=1000). The maximum value of entropy generation due to fluid flow (Sψ, max) is found at various locations on the walls of the cavity whereas significant Sψ is also observed in the interior regions due to the friction between counter rotating circulation cells. The heat transfer rate along the wall AB (NuAB) and the total entropy generation (Stotal) are found to be constant for the conduction dominant regime (10-5≤Dam≤10-3) whereas non linear increasing trends are observed for convection dominant regime (10-3≤Dam≤10-2). The inclination angle ranges, 30° ≤ ϕ ≤ 50° and 25° ≤ ϕ ≤ 75° are optimal tilt angles for Prm=0.015 and 1000, respectively based on minimum entropy generation and reasonable heat transfer rate at high Dam(Dam=10-2) with Ram=106.