Chapter 11 Fundamentals of Thermal Radiation 11-35A small surface is subjected to uniform incident radiation. The rates of radiation emission through two specified bands are to be determined. A = 1 cm245°AssumptionsThe intensity of incident radiation is constant. Analysis(a) The rate at which radiation is incident on a surface per unit surface area in the direction (θ,φ) is given as φθθθφddIdAQddGiisincos),(==&The total rate of radiation emission through the band between 0°and 45°can be expressed as 2sincos),(204501πφθθθiiIddIG==∫∫==since the incident radiation is constant (Ii= constant), and 2/)0sin45(sinsincos2sincos2245020450πθπφ=−==∫=dddApproximating a small area as a differential area, the rate of radiation energy emitted from an area of 1 cm2in the specified band becomes W3.46=×⋅×===−)m101)(srW/m102.2(5.05.0242411,dAIdAGQii
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