Comparisons of Radiative Heat Transfer Calculations in a Jet Diffusion Flame Using Spherical Harmonics and k-Distributions

Abstract

A new nongray radiation modeling library for combustion gases has been implemented in OpenFOAM. The spectral models for single species include gray, correlation tables and full spectrum k-distributions (FSK) assembled from a narrow-band database. Mixing models for k-distributions include the multiplication and uncorrelated mixture models. Radiative transfer equation solvers for the library include spherical harmonics such as P 1 , P 3 , SP 3 and SP 5 as well as the optically thin approximation. The performance of the different solution methods is compared for accuracy and speed as a tool for future model strategy selection.

Eulerian–Eulerian multi-fluid methods for pulverized coal flames with nongray radiation

“…CH 4 , although included in the database, is not considered because its absorption bands do not overlap with the emission bands of other species. Inclusion of CH 4 is likely to cause a false prediction of absorption [18]. After calculating the k-distribution of a narrowband from mixing the k-distribution of each individual gas component, a constant narrowband solid phase absorption coefficient is added.…”

“…Traditional treatments employ bulk emissivity and a simple radiative transfer equation (RTE) solver for absorption [17]. A recent comprehensive comparison of different spectral models and RTE solvers revealed that spectral models that can account for nongray gas spectral variations are more important than RTE solvers in gaseous flames with not-so-small optical thickness [18]. The k-distribution methods, which can achieve line-by-line spectral accuracy with much less computational costs, were found to be superior in gaseous flames [16,18].…”

Spectral Photon Monte Carlo With Energy Splitting Across Phases for Gas–Particle Mixtures

“…The nongray effects for the solid phases, however, are not as significant, except near the centerline where each of the solid phases' absorption exceeds the emission (rÁ q < 0). The FSK/P1 approach has been shown to be highly accurate in terms of approximating the spectral dependence [39,40]. Therefore, most of the FSK/P1 errors for computing rÁ q are believed to be a result of the RTE solver (P 1 ), in particular, for optically thin regions.…”

A full-spectrum k-distribution look-up table for radiative transfer in nonhomogeneous gaseous media

“…Cai and Modest [12] regenerated the narrowband database using the newest HITEMP 2010 [13]. However, the mixing process for gas mixtures is computationally expensive, and creation of a single FSK for a twogas mixture still requires between 0.0549 s to 0.469 s, depending on the mixing model [14]. Clearly, if one million FSKs are needed per time step/iteration this becomes computationally prohibitive.…”

“…Clearly, if one million FSKs are needed per time step/iteration this becomes computationally prohibitive. This has prompted the development of simple correlation formulas for individual species at atmospheric pressure [15][16][17][18][19][20], from which kdistributions can be efficiently obtained; however, their accuracy are rarely satisfactory and sometimes may lead to serious errors [14]. Recently, Pearson et al [21,22] use absorption cross-sections instead of absorption coefficients) for CO 2 , H 2 O and CO over the full spectrum as a tool used in the SLW method, providing an alternative to solve the radiative property of nongray gas with excellent accuracy.…”