Influence of Spectral Particle Properties on Radiative Heat Transfer in Combusting Systems

Thermal radiation accounts for the majority of the heat transfer in solid fuel fired combustion systems due to contributions from particle laden combustion gases. Hence, gas and particle radiative properties play an important role on radiative heat exchange. One of the challenges in radiative property calculations is the spectral dependency, as spectral resolution of those properties is directly reflected on the computational cost of the global model. This is why some simple approximations are usually preferred, especially for particles. In fact, spectral dependency of particle properties is often neglected in the majority of relevant literature by using a gray approach, in which representative wavelength and/or complex index of refraction values are deployed for different particle types. Nevertheless, recent studies indicate that accurate representation of spectral particle radiation may become as important as that of spectral gas radiation for the accurate calculation of radiative heat transfer in combusting systems even at low particle loads. In this presentation, spectral nature of particle radiation is re-explored within the frame of these new findings and its influence on radiative heat transfer predictions, as well as on the share of particle radiation, is discussed.