Radiative transfer in dispersed media: Considering the effect of host medium absorption on particle scattering

For many practical radiative transfer problems in dispersed media, the host medium surrounding the particles is absorbing rather than lossless, therefore it may lead to inaccurate results when the effect of host medium absorption on particle scattering is neglected. This paper presents a systematical investigation on the radiative transfer problems for three different cases of refractive indexes for spherical particles embedded in an absorbing medium. The single-scattering properties of the particles are calculated using the recently developed public-domain Lorenz-Mie program for the case of an absorbing host medium. The directional-hemispherical reflectance and transmittance for a plane-parallel layer of spherical particles are obtained by using the Monte Carlo method. The effects of host medium absorption, particle size parameter and size distribution on the radiative transfer characteristics are discussed. The results show that neglecting the effect of host medium absorption on particle scattering will underestimate the directional-hemispherical reflectance and transmittance to some extent. Meanwhile, the errors caused by using the conventional Lorenz-Mie theory increase obviously with increase of host medium absorption index and particle size parameter. For the case of monodisperse particles embedded in an absorbing thin layer (i.e., with layer thickness of 0.05 mm and host medium absorption index of 0.01), the relative error of hemispherical reflectances increases approximate linearly from 5.9% to 59.4% with the particle size parameter increases from 1.0 to 40. (C) 2019 Elsevier Ltd. All rights reserved.