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 RD= 5 inAnalysisThe surface area of the ball is AD===ππ221205454(5/).ftft2Then the average emissivity of the ball at this temperature is determined to be 0.158=⋅×==⎯→⎯=442-8244R)950)(RBtu/h.ft10)(0.1714ft(0.5454Btu/h120TAETAEσεσε11-49 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. AnalysisForT=5800 K:λμμλ110300351T=⎯→
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