Analysis of Radiative Energy Transfers: Black‐body Radiation

In conducting various engineering calculations, it is often necessary to determine the energy fluxes exchanged between surfaces, as well as the temperatures which would be reached by these surfaces at steady state. These calculations are considerably facilitated by introducing the concept of a black body, which makes it possible to link the radiating behavior of any surface to that of a reference surface called “black surface” or “black body”. The chapter presents the physical laws expressing the radiation of the reference surfaces (black surfaces). It also develops methods for analyzing radiative energy transfers between real bodies. The Planck and Stefan-Boltzmann laws can be used to obtain the monochromatic flux density and total flux density, respectively, that are radiated by a black body. The chapter further compares the flux densities emitted in the infrared, by different radiating sources: an industrial fuel furnace, an induction furnace and the Sun.