UNSTEADY NON-DARCIAN FORCED-CONVECTION ANALYSIS IN AN ANNULUS PARTIALLY FILLED WITH A POROUS MATERIAL

Numerical solutions are presented for the problem of transient, develo ping, forced-convection flow in concentric annuli partially filled wit h porous substates. The porous substrate is attached either to the inn er cylinder (case I), or to the outer cylinder (case O). In both cases , the boundary in contact with the porous substrate is exposed to a su dden change in its temperature while the other boundary is kept adiaba tic. Including the macroscopic inertial term, the Brinkman-Forchheimer -extended Darcy model is used to model the flow inside the porous doma in. The effects of different parameters regarding the geometry, the so lid matrix and the fluid on the hydrodynamic and thermal behavior are investigated. It is shown that porous substrates may improve Nusselt n umber by 1200 percent keeping other flow and geometrical parameters fi xed. Also, it is Sound that there is an optimum thickness for the poro us substrate beyond which there is no significant improvement in Nusse lt number In the present work, the dimensionless hydrodynamic entrance length Z(en) varies within the range 2-45 and it has significant effe ct on the fully developed Nusselt number at steady-state conditions. A s a result, the macroscopic inertial term in the porous domain momentu m equation should not be neglected.