New application method of the zonal model for simulations of pulverized coal-fired furnaces based on correction of total exchange areas

Abstract

New application method of the zonal model in numerical simulations of pulverized coal-fired furnaces, continual corrections of the total exchange areas (CCTEA), is presented. The method is based on the corrections of the surface–surface, surface–volume, and volume–volume total exchange areas according to the changes of the surface zone emissivities during the iterative calculation of the numerical simulation and summation rules of the total exchange areas, so that it provides zero radiative exchange in an isothermal system. The method was developed for the homogeneous and uniform flame radiative properties. The results obtained by the CCTEA method were compared with the results obtained by the previously developed repeated run of numerical simulation (RRNS) method, based on multiple succesive run of the numerical simulation. The differences of the result obtained by the methods were found for various conditions of numerical investigations: initial wall emissivity, total extinction coefficient, and thickness of the ash deposit layer. The gas-phase phase radiative properties were determined by the simple gray gas model and weighted sum of gray gases model. Investigation showed small differences of the results obtained by the methods and their sensitivity to conditions of numerical investigation. The CCTEA method is an improvement of the RRNS method as it provides almost the same results after the single run of the numerical simulation and reduces the computation time.