A MATHEMATICAL MODEL FOR RADIATION HEAT TRANSFER DURING COMBUSTION OF PULVERIZED COAL IN AN ABSORBING, EMITTING, AND ANISOTROPICALLY SCATTERING MEDIUM

The presence of large coal and ash particles in a pulverized coal-fired furnace makes the problem of radiation heat transfer exceedingly difficult to solve. A viable approach to this problem is the four-flux radiation heat transfer model which has been proposed and developed in this dissertation. This model takes into account the anisotropic and multiple scattering of thermal radiation by the solid particles present in a pulverized coal furnace. This is achieved by representing the anisotropically scattered radiation intensity in terms of uneven forward, backward, and sidewise scattering components f, b and s, respectively. The magnitude of these components depends on particle size and particle refractive index.; The proposed four-flux model has been coded in FORTRAN-IV language to produce subroutine QRAD. QRAD uses the finite-difference numerical method to reduce the four-flux model into a tri-diagonal matrix which is solved using the TDMA.; The computational results demonstrate that when tested on a non-scattering atmosphere, the radiative flux predictions by the proposed four-flux model compare fairly well with the results of the zone-method and Truelove's discrete ordinate S4 model. A sensitivity study performed in this dissertation shows that scattering has a strong influence on the magnitude of the radiative fluxes. The effect of anisotropy in scattering becomes more dominant as the scattering coefficient increases. This dissertation also includes analytically obtained values for absorption efficiency, scattering efficiency, and anisotropy factor for coal and ash particles.