Consideration of Combined Thermal Radiative, Conductive and Convective in Solar Channels with and without Porous Media

Thermal radiation is analytically investigated in a saturated porous material subjected to Darcy- Brinkman’s law and also in a non porous flow channel.
The bottom wall is insulated and the top one is a glass plane under solar radiation, so that a portion of the radiation is reflected to the environment from
the glass cover and the rest of the radiation is absorbed by the glass and the porous medium below it. The purpose of this device is to heat the working
fluid of a heat engine in an electric power generating system. The problem is formulated as a combined radiative, conductive and convective problem in case
of non-local thermal equilibrium in which radiative heat transfer in the porous medium is treated as a heat generation. Analytical equation has been
employed for calculation of top heat loss coefficient. The fluid temperature variations are evaluated in direction of parallel to the flow, as well as the heat
transfer between the fluid and the porous medium. Results indicate that local temperature changes in the flow direction is a function of the Stanton
number, solid phase Biot number as well as porosity of the porous material. Furthermore, high thermal conductivity in the transverse direction and high
operating temperature are the advantage of using the porous medium in comparison with the non-porous flow channel.