Abstract: With hypothesis that radiation is incoherent, based on Planek's definition of radiative entropy, radiative entropy transfer equation and local radiative entropy generation in semitransparent graded index medium are derived. A calculation method based on discrete-ordinates approach is used to solve radiative entropy transfer equation in semitransparent graded index medium. A one-dimensional slab system filled with semitransparent graded index medium is taken as an example to verify the radiative entropy transfer equation and the calculation method. Numerical results of dimensionless radiative entropy generation of the slab system agree well with entire thermodynamics analysis.

Key words: radiative entropy transfer equation, radiative entropy generation, discrete-ordinates method, semitransparent medium, graded index