Radiative heat transfer rate between two gray bodies can be calculated by the equation stated below.
The two separate terms fa and fe can be combined and given the symbol f. The heat flow between two gray bodies can now be determined by the following equation:
The symbol (f) is a dimensionless factor sometimes called the radiation configuration factor, which takes into account the emissivity of both bodies and their relative geometry. The radiation configuration factor is usually found in a text book for the given situation. Once the configuration factor is obtained, the overall net heat flux can be determined. Radiant heat flux should only be included in a problem when it is greater than 20% of the problem.
Calculate the radiant heat between the floor (15 ft x 15 ft) of a furnace and the roof, if the two are located 10 ft apart. The floor and roof temperatures are 2000F and 600F, respectively. Assume that the floor and the roof have black surfaces.