Thermal radiative coefficients of cylindrically and spherically shaped soot particles and soot agglomerates

Abstract

Simple and computer attractive models for calculating radiation properties are still needed. This paper gives correlations for the Planck and Rosseland means of the extinction and scattering coefficients for both cylindrically and spherically shaped soot particles. The means are valid for temperatures between 400 and 2400 K and particle radii between 0.001 and 0.5 mum. The errors of these means are less than 1%. The Planck mean asymmetry ( g) factors for cylindrically and spherically shaped soot particles are also given in order to be able to calculate their effective ( transport) properties. The RDG-PFA (Rayleigh-Debye-Gans polydisperse fractal aggregates) theory has been used for creating the correlations of the effective Planck and Rosseland means of the extinction and scattering coefficients of the soot agglomerates. The means of the agglomerates are valid for temperatures between 400 and 2400 K and primary particle diameters between 0.01 and 0.07 mum. The extinction coefficient of the agglomerated soot lies between that of spherical and cylindrical soot particles. A 3D test case, using the discrete ordinates method of order 8 (DOM S8), shows that the scattering of the agglomerates is of very little importance, as it comes to the temperatures and wall heat fluxes.