Thermodynamics HW Solutions 955

Thermodynamics HW Solutions 955 - T s = 450 K and 1atm are,...

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Chapter 12 Radiation Heat Transfer 12-68 A mixture of H 2 O and N 2 gases at 600 K and a total pressure of 1 atm are contained in a cylindrical container. The rate of radiation heat transfer between the gas and the container walls is to be determined. Assumptions All the gases in the mixture are ideal gases. Analysis The mean beam length is, from Table 12-4 8 m 8 m T g = 600 K T s = 450 K L = 0.60 D = 0.60(8 m) = 4.8 m Then, atm ft .36 2 atm m 72 . 0 m) atm)(4.8 15 . 0 ( = = = L P w The emissivity of H 2 O corresponding to this value at the gas temperature of T g = 600 K and 1 atm is, from Fig. 12-36, 36 . 0 atm 1 = ε w For a source temperature of T s = 450 K, the absorptivity of the gas is again determined using the emissivity charts as follows: atm ft 1.77 atm m 54 . 0 K 600 K 450 m) atm)(4.8 15 . 0 ( = = = g s w T T L P The emissivity of H 2 O corresponding to this value at a temperature of
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Unformatted text preview: T s = 450 K and 1atm are, from Fig. 12-36, 34 . atm 1 , = w The absorptivity of H 2 O is determined from 39 . ) 34 . ( K 450 K 600 ) 1 ( 45 . atm 1 , 65 . = = = w s g w w T T C The surface area of the cylindrical surface is 2 2 2 m 6 . 301 4 m) 8 ( 2 m) 8 ( m) 8 ( 4 2 = + = + = D DH A s Then the net rate of radiation heat transfer from the gas mixture to the walls of the furnace becomes W 10 5.244 5 = = = ] ) K 450 ( 39 . ) K 600 ( 36 . )[ K W/m 10 67 . 5 )( m 6 . 301 ( ) ( 4 4 4 2 8 2 4 4 net s g g g s T T A Q & 12-52...
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