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Show 8 Jordan Loftus SeD. Texaco Inc - August 24. 1989 gray gas or a three gray gas model. When firing oil, user may elect to specify a soot extinction coefficient, Ks, based on experience: Eq. 1. where Ks equal zero, it reverts to the one clear - two gray gas model and { } indicates a function of the enclosed variable. This model is well suited to refinery heaters where the flame fill only a small volume of the radiant chamber and where highly luminous flames are avoided to prevent smoke in stack. For large sooty flames Godridge 12 reported: complex refractive index mean soot concentration mean particle diameter density of soot (ultimate) soot extinction coefficient n c d p Ks 2.29 - 1.49i 3.09E-6 1b / cf 0.05 microns 124.8 pcf 0.0184 rec. ft. The real gas emissivity of the flue gas (stream 8 of Table 1) is computed from a parametric fit of the graphs for carbon dioxide and water plus corrections given in Hottel and Sarofim's chapter 6. The two gray gas extinction coefficients, Kg,l and Kg ,2 are computed at two beam lengths and 2750 degrees Rankine. The temperature dependent coefficients of the gas weighing factors, ag,n {T g }, are then calculated from 20 real ·gas emissivities at f1ve temperatures, 1750 ~ Tg ~ 3750 degrees Rankine and four beam lengths LI12, L16, LI2 where L equals 30 Feet. The flue gas absorptivity is calculated using the same extinction coefficients: Eq. 2. The temperature dependent coefficients of the surface weighing factors, as n (T ,T s )' are calculated from 20 real gas emissivitie~ at five temperatures, 1000 ~ Ts ~ 3000 degrees Rankine and same four beam lengths. B. Equivalent Sink Plane Emissivity The fraction of incident radiant! absorbed by m traverses across a row(s) of black tubes is related to ratio R of the outside tube diameter to the center to center space spacing: ! - 1 - [ ( 1- R2 )0.5 - R acos R 1m Eq. 3. 12. Godridge, A.H. & Hammond, G.E. "Emissivity of s Very Large Residual Oil Flame", 12th Sym. (Int) on Combustion (1968) 1219. |
