Fractal Characteristics And Fractal Characterization Of Thermal Properties Of Particulate Materials

In the thesis, the fragmentation and accumulation of materials and the characteristics of particle accumulation are studied. The fractal models of the fragmentation process of materials and the effective thermal conductivity of particulate materials are established, a computer simulation program of particle accumulation is also set up. According to the model and program, the characteristics and thermal properties of particulate materials are analyzed with the fractal theory.First of all, according to the principle of fractal geometry, a fractal model of the fragmentation process of materials is established, and the fractal characteristics of the fragmentation process of materials are revealed. On the basis of this, the factors that affect the fractal dimension of particle-size distribution and the particle-size distribution are analyzed. Based on the comparison between the fractal particle-size distribution and some commonly used empirical formulae and practical particle-size distribution, it is concluded that the fractal is the essential characteristics of particle-size distribution of materials. The model is proved to be valid and could be put into practical application both theoretically and practically.Secondly, the accumulation process of particles is predigested, and the random process of particle accumulation is analyzed in detail with the method of vector analysis. Then a computer simulation program of particle accumulation is set up. With this, an operational easily software that simulates particle accumulation is programmed in Fortran language, and the visualization of the simulation result is realized by Matlab software.In the end, it is proved that the particle accumulation has fractal characteristics with the computer simulation result. The effects of accumulation area on the porosity and box dimension of particulate materials are analyzed, and then the relation between the porosity and box dimension of particulate materials is analyzed. A fractal model is established to calculate the effective thermal conductivity of particulate materials. Then the factors affecting the effective thermal conductivity are analyzed. Based on the comparison between the model prediction and the actual measurement, it is proved that the model could be used to estimate the effective thermal conductivity of the actual particulate materials.