Porous media have considerable importance in improvement of heat transfer and storage. This research includes an experimental and theoretical study of natural convection heat transfer between two concentric cylinders filled with a porous medium, under condition of applying uniform heat flux on the inner cylinder and constant outer surface temperature for the outer cylinder. Two types of filling material were used as porous medium , iron and glass beads , the study shows that the heat dissipated ability in the inner cylinder is function of Rayligh number , and the Nusselt number increase is directly proportional with the increase in Rayligh number .
Fluent program was used to show the heat dissipation and the flow lines inside the gap between the two cylinders , the experimental results show that the nature of the heat distribution depends greatly on Rayligh number , and the use of highly heat conductive materials as porous medium will completely cancel the convection as a mean of heat transfer.
Key wards: Heat transfer, Natural convection, Porous medium, and two concentric cylinders.