Accession Number : AD0680394

Title :   AN IMPROVED DIFFERENTIAL APPROXIMATION FOR RADIATIVE TRANSFER WITH SPHERICAL SYMMETRY.

Descriptive Note : Scientific interim rept.,

Corporate Author : MARTIN MARIETTA CORP BALTIMORE MD RESEARCH INST FOR ADVANCED STUDIES

Personal Author(s) : Traugott,Stephen C.

Report Date : NOV 1968

Pagination or Media Count : 41

Abstract : An improved closure condition is used to construct a purely differential equation which, with associated boundary conditions, describes radiative transfer with spherical symmetry. The method is equivalent in degree of complexity to the P4 moment approximation, that is, a spherical harmonic expansion retaining four terms. The improved closing conditions are especially constructed to allow both isotropic radiation and unidirectional, beam-like radiation. The method is applied to the problem of radiative equilibrium of a grey gas between two concentric black spheres maintained at different temperatures. Both radiative heat flux and temperature distribution from the present model are compared to known exact results, and it is shown that trends are correctly predicted by the improved differential approximation in the crucial limit of transparent gas and small inner sphere compared to outer. This is in contrast to both the conventional P2 and P4 moment approximations, which predict qualitatively incorrect results in this limit. (Author)

Descriptors :   (*THERMAL RADIATION, SPHERES), DIFFERENTIAL EQUATIONS, APPROXIMATION(MATHEMATICS), TEMPERATURE, HEAT FLUX, CORRELATION TECHNIQUES

Subject Categories : Thermodynamics

Distribution Statement : APPROVED FOR PUBLIC RELEASE