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ISSN Online: 2377-424X

ISBN Print: 1-56032-797-9

International Heat Transfer Conference 11
August, 23-28, 1998, Kyongju, Korea

A Comprehensive Radiation Model for Numerical Simulations of Pulverised Coal Flames

Get access (open in a dialog) DOI: 10.1615/IHTC11.4290
pages 307-312

要約

Radiation is the most important mode of heat transfer in pulverised coal flames. More than 90 % of the heat extracted from flames in steam generators are due to radiation. Therefore, special emphasis should be put on the calculation of radiative heat transfer when designing combustion chambers.
Especially numerical simulation methods for combustion processes have to deal with the complex nature of radiative heat transfer in complex geometries and inhomogeneous media.
Radiation models are needed and are including the optical properties of gases, particles and walls and a radiation transport model. In this paper models are proposed for describing the optical properties of the gaseous components carbon dioxide and water vapour, optical properties of coal and ash particles and the radiation transport equation. The described radiation models are suited for computational fluid dynamics simulations. For modelling the gaseous radiation a new definition of the Weighted Sum of Grey Gas Model (WSGGM) is given which does not only consider the emission of radiation only but also the absorption. Particles are treated as grey radiators. The radiation characteristics of coal and ash particles are compared. For particles in coal flames an equation is found for calculating the optical properties from those of coal and ash particles. For modelling the radiation transport a new model is proposed. The new model combines the Discrete Transfer Method and the Discrete Ordinate Method.