In the framework of a two-moment photo-hydrodynamic modelling of radiationtransport, we introduce a concept for the determination of effective radiationtransport coefficients based on the minimization of the local entropyproduction rate of radiation and matter. The method provides the nonequilibriumphoton distribution from which the effective absorption coefficients and thevariable Eddington factor (VEF) can be calculated. The photon distributiondepends on the frequency dependence of the absorption coefficient, in contrastto the distribution obtained by methods based on entropy maximization. Thecalculated mean absorption coefficients are not only correct in the limit ofoptically thick and thin media, but even provide a reasonable interpolation inthe cross-over regime between these limits, notably without introducing any fitparameter. The method is illustrated and discussed for grey matter and for asimple example of non-grey matter with a two-band absorption spectrum. Themethod is also briefly compared with the maximum entropy concept.
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