A radiation model for the numerical simulation of coal-fired furnaces using body-fitted grids

A model for predicting radiative heat transfer in coal-fired furnaces is presented. The radiative transfer equation is modelled by the discrete ordinates method for body-fitted coordinates using the SQ-approximation. The gas absorption coefficient is determined by a weighted-sum-of-grey-gases model, the radiative properties of coal and ash particles are derived from the specific area and a mean efficiency factor of the particle cloud. The scattering phase function is modelled by the Delta-Eddington approximation. The entire radiation model is adopted for vector and parallel computers guaranteeing numerical efficiency. It is tested at an idealized squared combustion chamber with black walls filled by an emitting, absorbing medium with constant absorption coefficient. The computations are carried out on several curvilinear non-orthogonal grids using different boundary conditions. On all grids the computed radiative source terms and wall heat fluxes are in very good agreement with the analytic solution. Furthermore, the model is validated at a coal-fired test facility. Apart from the near burner region the computed temperature distribution only slightly deviates from the measured values.