ABSTRACT
In Chapter 5, we have presented a detailed analysis and solution procedure for radiation exchange within enclosures with black or gray diffuse surfaces. One additional restriction was that the radiative properties were independent of temperature. However, as discussed in Chapter 3, most materials deviate from the idealizations of being black, gray, diffuse, or having temperature-independent radiative properties. The assumption of idealized surfaces is sometimes justied to simplify the computations. This is often reasonable because the radiative properties may not be known to high accuracy, especially their detailed dependence on wavelength and direction; hence, rened computations are not meaningful if only very approximate property data are available. Also, multiple reections and rereections in an enclosure tend to average out radiative nonuniformities; for example, emitted plus reected radiation leaving a directionally emitting surface may be fairly diffuse if it is chiey composed of reected energy from radiation incident from many directions.
