The Analysis Of Radiative Transfer Characteristics Of Nonspherical Particle System

The radiation theory of non-spherical particle has wide applications across the field of weather\industrial manufacture\biology and so on. Particles in aerosol and hearth are the typical particle systems. In these systems, particles have different sharps. It will create errors if we simplify the particles as spheres. In this thesis, the factors which affect the radiation properties of non-sphere particle system are analyzed in detail. The main research work are as follows:1 The radiation properties of particles with different sharps and materials in non-absorbed medium are calculated by discrete dipole approximation(DDA) method and Mie theory. The result shows that particles have the best ability of absorption and scattering when their size parameters are during 0.1 to 10. By the increase of size parameter, the scattering factor becomes higher than absorptive factor and more scattering energy is confined to forward direction. The distribution of optical properties of particles with different materials(Al, Ag, W, pulverized coal) is very different. When the volume of different sharps of particles are the same, the absorption factor and scattering factor will become bigger by the increase of the cross-sectional area which is perpendicular to the incident light. On the other hand, particles will have more scattering energy when their sharps are more deviated from sphere.2 Simplifying the different sharps of particles in hearths to six sharps and calculating the radiation characteristics of the six sharps of particles. We assume that the particles in the hearth have no effect with each other and transform the radiation parameters of different particles into absorption\scattering coefficient and phase function of particle systems which have the same fraction. From the results we find that the sharp of particles with the size parameter from 0.1 to 10 has an important effect on the absorption and scattering coefficient especially for those particles with small size parameters.3 We regard the radiation heat transfer in a pulverized coal combustion as the object of study and establish the model of radiation heat transfer which is calculated by Mento Carlo method. The result shows that the size parameter of particles with the same volume fraction plays an important role in the heat transfer. When the size parameter is smaller than 6, the heat exchange flow will increase when the size parameter becomes bigger and it reaches to the peak around the size parameter of 6, then the heat exchange flow become stable when the size parameter is larger than 6. When the size parameter is less than 0.6, the heat exchange flow have a big difference between spheres and non-spherical particles especially for those particles which have edges and corners.