ABSTRACT
In Chapter 5, we presented a detailed analysis and solution procedure for radiation exchange analysis within enclosures made up of black or gray diffuse boundary 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 made 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, re¢ned computations are not meaningful if only very approximate property data are available. Also, the many režections and re-režections in an enclosure tend to average out radiative nonuniformities, for example, emitted plus režected radiation leaving a directionally emitting surface may be fairly diffuse if it is chiežy composed of režected energy from radiation incident from many directions.
