Study On The Heat Transfer Properties Of Woven Insulation Material's Pores And Structures

Insulation material is a kind of materials or composites is provided with conspicuous anti-resistance and lower thermal conductivity. It was seen as constituted of fibers and apertures, analyzed from materials function, thermal insulation materials are widely used as a functional material of myriad porous. So the aperture should be an important values norm of thermal insulation materials, also a key problem in studying the heat transfer properties. As a result of its puffed and myriad porous characters, there absolutely exist a channel which a quantity of energy can pass from and 3-D pore structures which lay between fibers. The distribution characters of pores and holes have a close correlation with its properties, such as heat transfer,permeability and so on. Studying the pore structures of insulation materials not only enriches the heat transfer theory, but also furnishes a strong foundation for bringing energy saving into effect,realizing thermal insulation materials'optimal designing and process improvement. Consequently, studying the heat transfer properties of thermal insulation materials has a terrible concernful meaning.In this paper, the average aperture value of interyarn,porosity and fractal dimension of thermal insulation materials to its heat transfer properties on static condition and dynamic were studied. The paper including several aspects as below: first, the apertures norms of thermal insulation materials, which including the average fluent aperture,pore size distribution,the minimum aperture,the maximum aperture,the average aperture value of interyarn and so on, were measured by means of aperture meter manufactured by the PMI Company of America; The porosity of thermal insulation materials was measured by media saturation method; the fractal dimension, which tokens the complexity of thermal insulation materials, was calculated by picture-handling technology. Second, dynamic heat transmitting properties of thermal insulation materials and warmth retention testing methods have been developed. Through regression analysis, the regular of the heat transfer properties changes along with the average aperture value of interyarn,porosity and fractal dimension come into being. Third, the testing characteristic difference of dynamic heat transfer equipment and warmth retention instrument were made a comparative analysis, in order to validate the correctness and applicability of the equipment.After analyzing, some deductions were attained. First, the distribution of pores is asymmetric in fabric, and there are a lot of differences in pore size. while the major law is terribly analogical: the distribution of pore size has a wide range from small to big with the asymmetry of peak value towards left; the bigger aperture has a smaller proportion, but its contribution is bigger in fact; the smaller aperture has a heavier proportion and distributes in a lesser area. Second, the dynamic testing indexes, heating rate errand,thermal conductivity and thermal insulation, take on linear correlation with the average value aperture of interyarn respectively; The average value aperture of interyarn and temperature regime answering time takes on parabola relationship, as well as thermal insulation and porosity or fractal dimension; on static condition, the average value aperture of interyarn has a linear relationship with CLO value and thermal insulation, as well as porosity and CLO value. However, the average value aperture of interyarn displays parabola relationship with thermal conductivity, as well as fractal dimension and CLO. Thirdly, the dynamic heat transfer testing equipment is answer for designing requirement, and feasible in theory and actual. It has advantage compare to the warmth retention instrument. Although there have not comparability between the dynamic heat transfer testing and the warmth retention testing, there have assessment index in common. Analyzing these two kinds of testing method, it will be good to comprehend the effect of pore structure to the heat transfer properties all around.Finally, this discourse illustrates the prospects of the developing direction of this topic.