Influence of Fly Ash Composition on Non-gray Particle Radiation
Complex index of refraction is one of the principle causes, from which spectral nature of particle properties is originated. Hence its accurate representation is of considerable importance for radiative heat transfer predictions.
Chemical composition has a strong influence on the optical properties of particles and particle radiative properties are expected to change with its composition. Nevertheless, dependency of particle properties on chemical composition is often neglected in the majority of relevant literature as it is common to use a gray approach deploying representative optical properties for coal or ash particles.
In one of their recent work, Ates et al. (2018) addressed this issue and investigated the influence of spectral nature of complex index of refraction and its composition dependency on non-gray particle radiation for pulverized coal-fired furnaces, bubbling fluidized bed combustors and circulating fluidized bed combustors. Their investigation has shown that spectral particle radiation is of significant importance for accurate calculation of radiative heat transfer in combusting systems and it is originated from the spectral nature of the complex index of refraction rather than spectral nature of the incident radiation. Comparisons presented in their work also reveal that chemical composition has a significant effect on particle absorption properties as well as heat flux/source term predictions within the combustors. Based on these comparisons, they have presented one spectral and one gray complex index of refraction models for the evaluation of ash particle properties.
C. Ates, N. Selçuk, G. Kulah, Influence of fly ash composition on non-gray particle radiation in combusting systems, Journal of Quantitative Spectroscopy and Radiative Transfer, Volume 215, Pages 25-40, 2018. (https://doi.org/10.1016/j.jqsrt.2018.05.004)