Investigation of heat transfer in porous media or packed beds with stagnant filling fluid without any external fluid flow and external convection is the purpose of the present work. The evaluation is based on two aspects: (i) the conduction heat transfer in solid and gas phases; and (ii) the radiation heat transfer between particles in the voids. Because of small amount of absorption and scattering coefficients of gases, effect of these parameters on radiation and overall effective thermal conductivity is not considered. Geometry and structural properties of packed bed in this study is a rectangular bed with infinite cylinders located regularly and has point contact which each other and gas trapped in the void between four contacted cylinders. In order to achieve a better understanding of heat transfer, an effective thermal conductivity is introduced and effect of different parameters such as temperature gradient, pressure, emissivity, solid and gas thermal conductivity, and size of the particles has been analyzed. Three kind of gas, nitrogen, hydrogen and air, use as a stagnant fluid phase. According to thermal conductivity of these gases, effective thermal conductivity of bed in the presence of hydrogen, which has the highest thermal conductivity between these gases, is more than the other two gases; and then nitrogen cause higher effective thermal conductivity. Gradient of temperature in the voids make the gas to move and circulate in the voids that cause the lower heat transfer in the direction of heat transfer. Between these three gases, hydrogen has the highest thermal conductivity that thermal gradient puts a greater impact on this gas that cause more circulation and less heat transfer. Temperature gradient of bed has a direct effect on the effective thermal conductivity when the temperature of hot side of the bed decrease, the effective thermal conductivity and radiation thermal conductivity also decrease. In other hand the effect of pressure is small and negligible, except for using hydrogen as stagnant fluid and in the case of pressure is more than 10 bar, which increase of pressure cause the more effective thermal conductivity. But when the pressure is less than 10 bar the effective thermal conductivity has a very small change. Pressure of bed don’t change the radiation thermal conductivity at all because the pressure do not influence the radiation characteristic of materials. Thermal conductivity of solid phases (cylinders) has a significant role on heat transfer and effective thermal conductivity; but when solid thermal conductivity exceeds certain limits (higher than 100 W/m.k, effect of this parameter decreases sharply and after this limit effect of solid thermal conductivity is negligible. The most important and decisive parameter that cause low effective thermal conductivity and mild temperature distribution in bed, is diameter or quantity of cylinders. When the dimentions of bed is fixed, increasing the quantity of cylinders or decreasing the diameter of cylinders cause the lower effective thermal conductivity and radiation thermal conductivity because of shrinking the voids. At the end, packed bed of spheres use to calculate the effective thermal conductivity of bed. In the case of using the spheres instead of cylinders, gas can move between spheres and don’t trap between particles that cause more effective thermal cunductivity. Keywords : Packed Bed, Effective Thermal Conductivity, Thermal Radiation, Variable Thermal Conductivity, Stagnant Fluid