A large body of nonluminous gas at a temperature of 1100°C has emission bands between 2.5 and 3.5 ?m and between 5 and 8 ?m. At 1100°C, the effective emittance in the first band is 0.8 and in the second 0.6. Determine the emissive power of this gas in W/m2.
GIVEN
• A large body of nonluminous gas
• Gas temperature (T) = 1100°C = 1373 K
• Emission bands: 2.5 ?m < ?1 < 3.5 ?m 5 ?m < ?2 < 8 ?m
• Effective emittances: ?1 = 0.8; ?2 = 0.6
FIND
• The emissive power (E) in W/m2
SKETCH
PROPERTIES AND CONSTANTS
the Stephan-Boltzmann constant (?) = 5.67 × 10–8 W/(m2 K4)
The total emittance is
where
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