Fundamentals of Thermal Radiation

After a brief overview of the fundamentals of the three modes of heat transfer, this chapter delves into the details of radiation—thermal radiation, in particular. Thermal radiation is identified as part of the full electromagnetic spectrum, and its special characteristics are discussed through the laws of blackbody radiation, namely the Stefan-Boltzmann law, Wien's displacement law, and Planck's law. The fundamentals of the directional nature of radiation are elucidated by introducing solid angles and radiation intensity (and its visible light counterpart luminance), and their relationship to radiative heat flux and energy conservation. Next, radiative properties that affect absorption, emission, reflection, and scattering are introduced, and their interrelationships, as stipulated by Kirchhoff's laws and energy conservation, are discussed briefly. The chapter concludes with a brief discussion of the Radiative Transfer Equation—the governing equation that describes radiative energy balance.