Analysis of entropy generation during mixed convection in porous square cavities: Effect of thermal boundary conditions

Computational studies on entropy generation during laminar mixed convection in porous square enclosures have been carried out based on Darcy-Brinkman-Forchheimer model using the penalty finite element method. Finite element simulations are performed for the isothermally hot bottom wall, adiabatic top wall, and isothermally cold side walls (case 1) or linearly heated side walls (case 2) or linearly heated left wall with isothermally cold right wall (case 3) for a wide range of modified Darcy numbers (10-5 ≤ Dam ≤ 10-2), Grashof numbers (Gr = 103-105), and modified Prandtl numbers (Prm = 0.026 and 7.2). Further, the effects of Dam on the total entropy generation (Stotal), average Bejan number (Beav), and average Nusselt number are discussed. It is found that Re = 100 is preferred over Re = 1 based on larger heat transfer rate with minimum entropy generation for Prm = 0.026 and 7.2, 10-5 ≤ Dam ≤ 10-2 at Gr = 105 for all the cases.