Due to the lack of energy sources, augmentation of heat transfer in heat exchangers is an important subject. Also increasing the heat transfer in systems that are related to the energy reduces the environment pollution. Different ways were suggested for enhancing the heat transfer in heat exchangers, among them convective heat transfer in systems including porous inserts attracts many researchers due to the wide applications of these systems in engineering processes and equipment like geothermal energy recovery, air heaters, drying processes, electronics cooling, solid matrix heat exchangers, etc. by using porous media, the space and material needed for heat exchanger would be reduced. In the present work, laminar fully developed flow and convective heat transfer between two parallel plates of a conduit were simulated. Effects of five parameters such as three geometrical and two inherent parameters of porous media were studied. The parameters were thickness of porous media, distances of porous media layers to the wall, number of layers of porous media, permeability of the porous media and ratio of effective porous media conductivity to pure fluid conductivity. Simulation was done using FLUENT software. Besides, constant temperature boundary condition was used at the walls. In modeling of the energy traort, the local thermal equilibrium is assumed. Comparing the results of the present study to the analytical solutions, a reasonable agreement was observed. At first, a simple channel was modeled and compared with analytical solution and reasonable agreement was observed. After that channels with porous media were simulated and It was found that the previously mentioned parameters had significant influence on fluid flow and heat transfer in certain conditions. The results thoroughly document the dependence of the Nusselt number and pressure loss on several parameters of the problem. All results are non-dimensionalized. To study the heat transfer and pressure drop due to the porous media, two non-dimensional numbers were used namely Nusselt number and pressure drop coefficient. Two different effective porous media conductivity to pure fluid conductivity ratio, 1 and 10 were considered in simulation and at each ratio, different ternds for Nusselt number were reported. This issue can be reasoned by this fact that at each conductivity ratio of unity, hydrodynamics of problem is important while at conductivity ratio of 10, hydrodynamics and thermal considerations would affect the Nusselt number. In order to consider the effects of porous media on heat transfer and pressure drop simultaneously, a non-dimensional number was introduced namely performance evaluation criteria, PEC. The results show that when the thermal conductivity and Darcy number of porous media are high, adjoining two layers of porous media to the walls would result in the best performance and it would be better by increasing the thickness of porous media. This is a practical case as woven screen materials show similar conditions. Also it was observed that for thin layers with high permeability of porous media, increasing the number of layers would reduce the heat transfer while for thick layers with low permeability of porous media, increasing the number of layers would increase both heat transfer and pressure drop. Keywords: Heat transfer, Porous media, Convective heat transfer, Performance evaluation criteria, Fully developed fluid flow.
