Fractal Analysis Of Effective Thermal Conductivity Of Porous Fibrous Bifurcated Structure

Whether natural fiber or chemical fiber material has a porous structure,and a large number of fiber material exists in a universal and special fractal bifurcation structure.Such as the trunk and leaves of plants is a typical porous fibers with fractal bifurcation structure.Such structures are also commonly found in chemical fibers,such as woven garments,cotton spandex,fiberglass and fiber metal,etc.The difference between the branched fibers of chemical fibers and the natural fibers is that these branched fabrics are generally hidden inside the material structure The structure is more complicated.In recent years,with the progress of science and the multidisciplinary development,scientists from all over the world have been interested in the transmission characteristics of fractal bifurcation networks.There have been a lot of researches on the infiltration characteristics and flow characteristics of bifurcated networks.However,there are still many gaps in the research of heat transfer characteristics in bifurcated networks.Therefore,based on the existing research,this paper conducts a systematic study on the heat transfer phenomenon of the bifurcated fiber structure by means of the relevant knowledge of thermoelectric simulation theory and fractal theory,deduces its analytical expression of effective thermal conductivity,Revealing the heat transfer mechanism of porous fiber bifurcation structure and engineering applications are of great value.In the first chapter,this paper briefly introduces the research background and significance of the thermal conduction mechanism,fractal theory and bifurcation structure of porous media.In the second chapter,the criterion of porous media is mainly explained and the analytical model of fractal dimension D_Tof porous media is established to deeply understand the conduction mechanism of porous media.In the third chapter,the fiber heat conduction,thermoelectric simulation theory and the geometric structure of tree fractal bifurcation network are described in detail.This chapter is an important theoretical basis for the study of the effective thermal conductivity of bifurcate structure of porous fiber.As the tree fractal bifurcation network is divided into two kinds of symmetry and asymmetry,so in the fourth chapter,the first introduction of asymmetry factor,in fact,the symmetric tree fractal bifurcation network is asymmetric tree fractal bifurcation network?=1.A special case.Then,based on the theoretical knowledge in chapters two and three,the analytical expressions of the effective thermal conductivity and the structural parameters of the tree fractal bifurcation network are obtained.It is found that the effective heat of the bifurcation network Conductivity decreases with the increase of branch number m,branch length?proportion factor and branch number n,and when the area factor?(28)1,the effective thermal conductivity of the bifurcation structure is the maximum at this time;and when the effective thermal conductivity of the bifurcation structure Take the maximum rate,the diameter of the fractal dimensionD_d at this time by the asymmetry factor?to decide.Through the research of this paper,we can make the effective thermal conductivity of the bifurcated network structure reach a maximum through reasonable choice of the geometrical parameters of the porous fiber bifurcation structure,which not only contribute to the theoretical research of heat conduction of the porous fiber material,Its engineering fiber materials development and production has a good guide.