Unformatted text preview: 0.245 . 1555 . 0896 . = − + = α Δ − α + α = α w c g The emissivity of the inner surfaces of the tubes is 0.9. Then the net rate of radiation heat transfer from the combustion gases to the walls of the tube becomes W 10,745 = − ⋅ × + = α − ε σ + ε = − ] ) K 378 ( 245 . ) K 790 ( 194 . )[ K W/m 10 67 . 5 )( m 827 . 2 ( 2 1 9 . ) ( 2 1 4 4 4 2 8 2 4 4 rad s g g g s s T T A Q & ( b ) The heat of vaporization of water at 1 atm is 2257 kJ/kg (Table A9). Then rate of evaporation of water becomes kg/s 0.0773 = × + = + = ⎯→ ⎯ = + J/kg 10 7 . 333 W ) 745 , 10 050 , 15 ( 3 rad conv evap evap rad conv fg fg h Q Q m h m Q Q & & & & & & 12104 …. . 12106 Design and Essay Problems KJ 1285...
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 Fall '10
 Dr.DanielArenas
 Thermodynamics, Mass, Heat, Radiation, Heat Transfer, ε c

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