Thermodynamics HW Solutions 983

Thermodynamics HW Solutions 983 - = + + + = + + + = 1 12 ....

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Chapter 12 Radiation Heat Transfer 12-100 A thin aluminum sheet is placed between two very large parallel plates that are maintained at uniform temperatures. The net rate of radiation heat transfer between the plates and the temperature of the radiation shield are to be determined. Assumptions 1 Steady operating conditions exist 2 The surfaces are opaque, diffuse, and gray. 3 Convection heat transfer is not considered. Properties The emissivities of surfaces are given to be ε 1 = 0.8, 2 = 0.9, and 3 = 0.12. Analysis The net rate of radiation heat transfer with a thin aluminum shield per unit area of the plates is T 2 = 550 K ε 2 = 0.9 T 1 = 750 K ε 1 = 0.8 Radiation shield ε 3 = 0.12 2 W/m 748.9
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Unformatted text preview: = + + + = + + + = 1 12 . 1 12 . 1 1 9 . 1 8 . 1 ] ) K 550 ( ) K 750 )[( K W/m 10 67 . 5 ( 1 1 1 1 1 1 ) ( 4 4 4 2 8 2 , 3 1 , 3 2 1 4 2 4 1 shield one , 12 T T Q & The equilibrium temperature of the radiation shield is determined from K 671.3 = + = + = 3 4 3 4 4 2 8 2 3 1 4 3 4 1 13 1 12 . 1 8 . 1 ] ) K 750 )[( K W/m 10 67 . 5 ( W/m 9 . 748 1 1 1 ) ( T T T T Q & 12-80...
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