Research Into Building Ceramics' Thermal Properties During Drying Based On Fractals Theory

The investigation of thermal properties is a very important part in researching the drying process. The issue is on the base of analyzing building bodies'microstructure. But as building bodies, the internal structure of porous media is so complicated and irregular that the quantitative analysis is hard to be gained by Euclidean geometry. Then the advantage of fractal geometry is reflected. Firstly, after researching some box-counting algorithms which have been published, this thesis put forward an improved arithmetic and computes the fractal dimension of SEM pictures of building bodies. It's found that building bodies'dimension is close to the Sierpinski carpet's.Secondly, when length is the measure scale, the thermal conductivity's mathematical expression has been derived by thermal resistance method on the simplified hypothetical model. It's found that the thermal conductivity is correlative to the measure scale and the thermal conductivities of solid and the gas-liquid mixture in building bodies. The scale is to have a more obvious impact on it. After looking into experimental results relate to different temperature and moisture elimination rate, 20μm is an appropriate measure scale.The building bodies'effective thermal conductivity, effective specific heat and effective thermal diffusivity have been computed at different temperature and different moisture elimination rate when the measure scale is 20μm. The effective thermal conductivity shows a linear relationship with temperature and a quadratic relationship with moisture elimination rate. A linear relationship between the effective specific heat and temperature and moisture elimination rate, and a quadratic relationship between the effective thermal diffusivity and temperature and moisture elimination rate are found. As the temperature increases, the effective thermal conductivity, the effective specific heat and the effective thermal diffusivity increase. Contrary, as the moisture elimination rate decreases, they reduce.