Revised equivalent temperature formula.
To save having to repeat computations of radiances of several thermal sources with different temperatures that are radiating simultaneously or, alternatively, to compute the total radiance of a single source composed of several patches with different areas and temperatures, a concept of area-weighted temperature has been defined and used [U.S. Army Electronics Command Rep. 7043 (U.S. Army Electronics Command, Fort Monmouth, N.J., 1975); Opt. Eng. 15, 525-530 (1976)]. This equivalent temperature was said to be substituted in Planck function to obtain the total spectral radiance. Theoretical and computational examinations of the concept of area-averaged temperature reveal the need for its revision. To keep the advantage of a short-cut computation of the total radiance in the above-mentioned cases, a revised formula for the equivalent temperature is suggested.
Sar-Ei
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