Unformatted text preview: Chapter 12 Radiation Heat Transfer 1273 The temperature, pressure, and composition of combustion gases flowing inside long tubes are given. The rate of heat transfer from combustion gases to tube wall is to be determined. Assumptions All the gases in the mixture are ideal gases. Analysis The volumetric analysis of a gas mixture gives the mole fractions y i of the components, which are equivalent to pressure fractions for an ideal gas mixture. Therefore, the partial pressures of CO 2 and H 2 O are atm 10 . atm) 1 ( 10 . atm 10 . atm) 1 ( 10 . 2 2 H CO = = = = = = P y P P y P O w c T s = 600 K 20 cm Combustion gases, 1 atm T g = 1200 K The mean beam length for this geometry is, from Table 124, L = 3.6 V / A s = 1.8 D = 1.8(0.20 m) = 0.36 m where D is the distance between the plates. Then, atm ft .118 atm m 036 . m) atm)(0.36 10 . ( ⋅ = ⋅ = = = L P L P w c The emissivities of CO 2 and H 2 O corresponding to these values at the gas temperature of T g = 1200 K and 1atm are, from Fig. 1236, 1atm are, from Fig....
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 Fall '10
 Dr.DanielArenas
 Thermodynamics, Mass, Heat, Radiation, ε c

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