NON-GREY GAS RADIATIVE-TRANSFER ANALYSES USING STATISTICAL NARROW-BAND MODEL

Nongrey gas radiation analyses were conducted using the statistical na rrow-band model and four implementation methods: the exact or the corr elated formulation, the noncorrelated expression, grey-band approximat ion based on global absorption coefficient, and a new approximate meth od. The new method is also a grey-band approximation but utilizes the local absorption coefficient. Using results of the correlated formulat ion as benchmark solution, accuracy of the three approximate narrow-ba nd implementation methods was investigated for several one-dimensional non-grey gas radiation problems in parallel plate enclosure containin g radiating gases of both uniform and non-uniform temperatures and/or concentrations. Radiative source term and wall heat flux predicted by the noncorrelated expression and the new method are in very close agre ement with each other and in fair to good agreement to benchmark solut ions. Radiative source term calculated from the grey-band approximatio n based on global absorption coefficient is in serious error. CPU time saving of two orders of magnitude can be achieved by using the three approximate implementation methods, relative to the correlated formula tion. The new method provides slightly better accuracy than the noncor related approach with additional advantages that an arbitrary solution method can be employed and less CPU-time is required. (C) 1998 Nation al Research Council of Canada. Published by Elsevier Science Ltd. All rights reserved.