RADIATIVE HEAT TRANSFER CALCULATION FOR PULVERIZED COAL COMBUSTION APPLICATION OF LORENZ-MIE THEORY
A new method has been developed for improving radiative transfer calculations in particle-laden flows such as pulverized coal clouds. This method takes into account the scattering characteristics of single particles derived from Lorenz-Mie theory.
The improved calculation method realized for this study is a so-called flux method, used for solving the equation of radiative transfer. This equation expresses the variation of monochromatic radiation intensity along a path through an absorbing, emitting and scattering medium. For a medium such as a particle-laden flow, the coefficients appearing in this equation can be expressed in terms of the particles scattering characteristics and are calculated through the Lorenz-Mie theory. Then the coefficients show asymptotic behaviour; scattering and absorption efficiencies are approximately equal; scattering is strongly anisotropic, forward scattering being preponderant.
When applied to a 100 kW pulverized coal combustor the improved two-flux method leads to an accurate description of radiative transfer and exhibits clearly the influence of this transfer on coal particles history.