An Improved nongray-wall emissivity-absorptivity model for the Full-Spectrum Correlated K-distribution method

Abstract

In practical combustion chambers, the emissivity of wall materials in general varies spectrally and inappropriate treatments may lead to significant errors in modeling radiative heat transfer. To reduce the error of the Full-Spectrum Correlated K-distribution (FSCK) method in practical problems involving nongray walls, a nongray-wall model is proposed by reordering the wall emissivity and absorptivity separately, in which the Planck function at the wall temperature and an effective mean temperature is used as the weight function of wall emissivity and absorptivity, respectively. As a result, this new model preserves the wall emission and considers the spectral radiative property of the wall. Radiative heat transfer calculations in 1D and 3D configurations bounded by nongray walls are simulated to evaluate the accuracy of this new model. The results show that this new model is in general more accurate than the recently developed nongray-wall model (Liu et al., Int. J. Heat Mass Transf. 2021), especially in cases where the wall-to-wall radiative heat transfer plays an important role. It is also showed that this new model is less sensitive to the choice of the effective mean temperature and the medium blackbody emission-averaged temperature is recommended.