Thermodynamics HW Solutions 885

Thermodynamics HW Solutions 885 - Chapter 11 Fundamentals...

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Chapter 11 Fundamentals of Thermal Radiation 11-48E A spherical ball emits radiation at a certain rate. The average emissivity of the ball is to be determined at the given temperature. Ball T =950 R D = 5 in Analysis The surface area of the ball is AD == = ππ 22 12 05454 (5/ ) . ft ft 2 Then the average emissivity of the ball at this temperature is determined to be 0.158 = × = = ⎯→ = 4 4 2 -8 2 4 4 R) 950 )( R Btu/h.ft 10 )(0.1714 ft (0.5454 Btu/h 120 T A E T A E σ εσ ε 11-49 The variation of transmissivity of a glass is given. The average transmissivity of the pane at two temperatures and the amount of solar radiation transmitted through the pane are to be determined. Analysis For T= 5800 K: λμ μ λ 11 03 0035 1 T =⎯
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