Analysis of optical properties in particle curtains

Abstract

Optical properties in particle curtains are investigated by means of a Monte Carlo Ray-Tracing (MCRT) model. The MCRT model calculates absorptance, transmittance and reflectance of curtains formed by discrete particles under different conditions. The effect of particle diameter, curtain thickness and solids volume fraction is studied for particles made of two materials with different absorptivity: sand (αp = 0.34) and CARBO (αp = 0.87). The absorptance of curtains with sand particles and CARBO particles can increase up to 0.75 and 0.97, respectively, in opaque curtains with solids volume fractions close to zero, which requires very thick curtains. If the opacity of the curtain decreases due to a smaller thickness, a greater particle diameter or a smaller solids volume fraction, the curtain absorptance decreases. Besides the MCRT model, an analytical model is developed to predict the optical properties of particle curtains in a simpler way than the MCRT method. The MCRT is used to validate the analytical model. The maximum difference in the curtain absorptance calculated by the MCRT model and the absorptance calculated by the analytical model is 0.048 in the case of sand and 0.02 in the case of CARBO particles. These small differences make the analytical model a very useful tool to integrate the calculation of optical properties in complex models of particle systems.