Heat transfer including particle and gas radiation in subsonic MHD diffuser - II

Abstract

Heat transfer in subsonic MHD diffusers, by convection and by gas and slag particle radiation, is analyzed by simultaneously solving the radiation transport equation and the quasi-three-dimensional gasdynamic equations. The efficiency factors for extinction and scattering by particles are calculated from the Mie theory. For a reference diffuser geometry, the heat transfer by convection is found to be 25 MW, and the radiative heat transfer varies from 44 MW to 79 MW, depending on the rate of ash carryover into the channel. Results reveal that the heat transfer is sensitive to the ash carryover into the channel, slag particles spectrum, electrical conductivity of ash, gas composition, and wall emissivity. It is observed that, because of multiple scattering, the particles shield the short wavelength radiation emitted by potassium atoms. The impacts of heat transfer enhancement by gas radiation in the channel and by gas-plus-particles radiation in the diffuser on MHD system design are assessed. It is suggested that, from the system design point of view, the diffuser be regarded as a part of the radiant boiler. No significant effect of radiation enhancement on the ability to decompose NO/sub x/ is anticipated.