| OCR Text |
Show is absorption coefficient and subscript b is blackbody. The boundary spectral radiative intensity at a diffuse and gray wall is : 7v(5w,-_) = £ w v/b w w(5j4-( 1"£ w JJJ/z-_.Vv(.w,QW, for h-Q'X), (3) where ew is wall surface emissivity, h is unit normal vector at a wall surface and subscript w is wall. The radiative properties of combustion gases are calculated from the exponential wide-band model, in both nongray gas model and gray gas model. First, the w-th band-averaged transmittance rn is calculated from the exponential wide-band model as : r.-^-r*-. (4) n n.n where TH is the optical depth at the band head, and A^ is the band absorption divided by the exponential decay width. The band-averaged absorption coefficient Kn is : m T - /_v Kn=-rL> (5) where the local mean pathlength /_ is : /m=3.6^. (6) In this equation, A and Vare a local area and volume of medium (or a control volume). The total emissivity e is given as : £ = I ^ A F „ , (7) n where en is the band emissivity, and the black body fraction AFn is expressed as : f B{v,T)dv f B(v,T)dv A ^ „ = ^ = ^ - - i • (8) ^B(v,T)dv °T |
