Characteristics of the thermal radiation of nonisothermal regions

In thermophysical studies based on optical pyrometry with a noncontact determination of characteristic temperature, an instability of the radiator temperature can produce appreciable error. Additional difficulties arise for a nonuniform temperature distribution over the radiating surface. The current investigation was aimed at studying the salient features of the radiation characteristics of nonisothermal surfaces, determining the significant criteria of temperature nonuniformities for the simplest configurations of a radiating region with the most typical temperature profiles, correlating the characteristic and surface-average thermodynamic temperatures, and obtaining the effective temperature which defines the radiant energy transfer and characterizes the radiative heat transfer rate. Analytical equations are derived which describe a distortion of heat radiation characteristics for gray diffuse and black surfaces, bounded by straight lines or circumferences, with linear and parabolic temperature profiles. 5 refs., 2 figs., 1 tab