THE EFFECTS OF PARTICLE-SIZE DISTRIBUTION AND REFRACTIVE-INDEX ON FLY-ASH RADIATIVE PROPERTIES USING A SIMPLIFIED APPROACH

The radiative properties of a fly-ash polydispersion are calculated using a simplified approach based on Mie theory. The experimental data of fly-ash complex refractive index of Goodwin (Infrared optical constants of coal slags, Technical Report T-255, Stanford University, California) are employed in the calculation to take into account the wavelength-dependence of optical constants. The uncertainty in representing the particle size distribution is addressed explicitly. Due to this uncertainty, the uncertainty of the wavelength-integrated Planck mean absorption and scattering coefficients can be over 10%. The use of wavelength-independent optical constants for fly-ash yields unacceptable results of Planck mean coefficients.