Estimate the total, hemispherical emissivity for polished stainless steel at 800 K using Equation 12.43 along with information provided in Figure 12.17. Assume that the hemispherical emissivity is equal to the normal emissivity. Perform the integration using a band calculation, by splitting the integralin to five bands, each of which contains 20% of the blackbody emission at 800 K. For each band, assume the average emissivity is that associated with the median wavelength within the band λ_m, for which half of the blackbody radiation within the band is above λ_m  (and half is below λ_m). For example, the first band runs from λ = 0 to λ₁, such that F_{(0 → λ1)} = 0.2, and the median wavelength for the first band is chosen such that F_{(0 → λm)} = 0.1. Also determine the surface emissive power.

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Spectral, normal emissivity, En 1.0 0.8 0.6 0.4 0.2 0.1 0.2 Silicon carbide, 1000 K 0.4 0.6 1 2800 K Tungsten 1600 K 2 4 6 Wavelength, λ(um) 10 Aluminum oxide, 1400 K Stainless steel, 1200 K heavily oxidized ||||| Stainless steel, 800 K polished 20 40 60 100