| The investigations on the three-dimensional mathematical model and its numerical method of heat transfer in utility boiler furnaces are made in this thesis. The special characteristics which the radiation transfer equation owned bring some difficulties in its solution. At first, many approximation methods of radiation transfer are reviewed in the thesis. According to the process of radiation heat transfer in furnaces, some simplifications are made and discrete ordinate method is presented.In coal-fired furnaces the neglect of the scattering effect in flue gas media will cause large error. It also cause the error of temperature in furnace and heat flux in wall. So it is considered and the perfect model of combust rate distribution, the parameters of radiation physics characteristics and the suitable iteration solution are selected and carried out.In order to verify the model and the corresponding program, simulation on the boiler furnaces which have large volume and complex shape are carried out, the distribution of physics variable obtained and the characteristics of heat transfer in combustion are analyzed in detail.Both experiments and calculations can draw a conclusion that the ratio of height to width of furnace can reflect the discipline of geometrical dimensions of furnaces. The furnaces thermal calculation which considered it can get a good agreement with measured data. By comparison with the results of numerical and thermal calculations, it is found that they are identical qualitatively. Finally, the causes about the influence of furnaces shape on heat transfer are also analyzed. |
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