ABSTRACT
This chapter discusses several models and formulations for radiative transfer through translucent materials, windows, and coatings. The reflection, transmission, and absorption of solar and environmental radiation through single- and multi-layered windows are very important for determining heating and cooling loads of buildings, designing flat-plate solar collectors, and many different optical devices. When a window or transmitting layer is very thin, so that its thickness is comparable to the radiation wavelength, there can be interference between incident and reflected waves. For thin films or coatings on substrates exposed to radiation with very narrow spectral spans, such as a laser beam, the partially coherent theory becomes important in predicting the reflectance and absorptance of the films. Thin films produce wave interference effects between incident and reflected waves in the film, thus influencing their reflection and transmission characteristics. The chapter considers the ray-tracing method and then the net-radiation method to predict transmission through windows.
