Thermodynamics HW Solutions 956

Thermodynamics HW Solutions 956 - 15 . ( = = = g s c T T L...

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Chapter 12 Radiation Heat Transfer 12-69 A mixture of CO 2 and N 2 gases at 1200 K and a total pressure of 1 atm are contained in a spherical furnace. The net rate of radiation heat transfer between the gas mixture and furnace walls is to be determined. Assumptions All the gases in the mixture are ideal gases. T g = 1200 K T s = 600 K 2 m Analysis The mean beam length is, from Table 12-4 L = 0.65 D = 0.65(2 m) = 1.3 m The mole fraction is equal to pressure fraction. Then, atm ft .64 0 atm m 195 . 0 m) atm)(1.3 15 . 0 ( = = = L P c The emissivity of CO 2 corresponding to this value at the gas temperature of T g = 1200 K and 1 atm is, from Fig. 12-36, 14 . 0 atm 1 , = ε c For a source temperature of T s = 600 K, the absorptivity of the gas is again determined using the emissivity charts as follows: atm ft .32 0 atm m 0975 . 0 K 1200 K 600 m) atm)(1.3
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Unformatted text preview: 15 . ( = = = g s c T T L P The emissivity of CO 2 corresponding to this value at a temperature of T s = 600 K and 1atm are, from Fig. 12-36, 092 . atm 1 , = c The absorptivity of CO 2 is determined from 144 . ) 092 . ( K 600 K 1200 ) 1 ( 65 . atm 1 , 65 . = = = c s g c c T T C The surface area of the sphere is 2 2 2 m 57 . 12 m) 2 ( = = = D A s Then the net rate of radiation heat transfer from the gas mixture to the walls of the furnace becomes W 10 1.936 5 = = = ] ) K 600 ( 144 . ) K 1200 ( 14 . )[ K W/m 10 67 . 5 )( m 57 . 12 ( ) ( 4 4 4 2 8 2 4 4 net s g g g s T T A Q & 12-53...
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