The Principle And Application Of Test Of Warm Performance Of High Buoyancy Fibrous Porous Materials

High bulky fibrous porous materials are an important accessory, universally used for padding in warm products, such as cold protective clothing, bedding, cushion and so on. High bulky fibrous porous materials are composed by the fibers arrayed randomly inside. The flexible and low strength give the ductile property to the materials. Recently, the bulky fibrous porous materials widely used at home and abroad, such as natural fiber products, chemical fiber products, and natural fiber/chemical fiber blended products. The heat transfer channel is very complicated in the bulky fibrous porous materials due to the fibers arrayed randomly. This is very different from heat transfer mechanism of normal fabric. Till now there is no special testing method designated to the bulky fibrous porous materials in the aspect of heat transfer.This paper discussed how to improve the accuracy of heat transfer property of bulky fibrous porous materials. The main contents and results are as follows:1. The heat transfer mathematical model is established based on the porous heat transfer theory. By the simulation, the temperature field and testing error of double plate sensor are built. It gives the basement of theory and experiment.2. The improvement of hardware of double plate sensor is to add an aid to the warm testing system, including thermal insulation device and thickness control device. The thickness control device can test thermal property of sample at different thickness.3. Based on the simulation method, the relation between testing error of double plate sensor and effective thermal conductivity, permeability, thickness, porosity is investigated. The results show that when the thickness is higher than 1 cm, and permeability is lower than 10-7m2, the testing error of thermal conductivity is decreased with the increase of effective thermal conductivity; when the thickness is lower than 1cm, the testing error of thermal conductivity is only related with thickness, and increased with the increase of thickness; when the permeability is lower than 10-4m2 and higher than 10-7m2, the testing error of thermal conductivity is increased with the increase of permeability; when the permeability is no bigger than 10-7m2, the testing error of thermal conductivity is not affected by the internal convection.4. Based on the simulation method, the relation between thickness, permeability, porosity, effective thermal conductivity and heat flux is established. The improved calculation formula is built with the curve fitting method. It is proved the accuracy of improved calculation formula of thermal conductivity using multilayer materials experiment, and testing the internal temperature field of bulky fibrous porous materials comparing with the simulated temperature field.5. For investigating origin of divergence of warm performance of bulky fibrous porous materials, it is simulated the relation between heat flux and physical parameters as well as construction parameters. The results show the downward trend of heat flux with porosity is increased with the thermal conductivity, which is to say it is not obvious when the thermal conductivity of fiber is small; the rising trend of heat flux with diameter of fiber is opposite to the porosity. When the porosity is decreased to 0.8, the diameter has no affection to the heat flux. The thermal equivalence time is increased with the decrease of porosity, and increased with the increase of thickness; when the thickness increase to some value, the thickness is no affection to the heat flux; when the thermal conductivity of fiber is near to 0.3W/m·℃, the heat flux at the same thickness is in proportion to the initial thickness, which is to say the bigger the initial thickness, the worse of the warm performance when the wadding is compressed. The convection inside the bulky fibrous porous materials is small, and the conduction is a big part inside the bulky fibrous porous materials; the environment temperature is no affection to the thermal equivalence time.6. It is tested the compression, moisture absorption, wicking and thermal performance of high bulky fibrous porous materials made with different animal fibers, and found the thermal conductivity of wadding made by rabbit hair fiber is better; the elasticity recovery of wadding made with camel hair fiber is better; the permeability of wadding made with yakwool fiber and camel hair fiber are better; the method of blending of linear animal fibers with flower shape duck fibers can descend the thermal conductivity of wadding; the warm performance of linear animal wadding is better than the wadding made with linear fiber blended with duck fiber.7. By the combination of auxiliary testing instruction used in this paper with the improved calculation formula of thermal conductivity, we got the thermal conductivity of bladder flocculent materials made with different fibers. We tested the insulation values of different clothing system through the thermal manikin. The weight of bulky wadding at different temperature is got. By research, it is found adding some kapok fibers to the down wadding can enhance its thermal insulation performance and lower its weight.