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Study of Effective Thermal Conductivity of Plant Fiber Materials with Network Structure Based on Fractal Theory

Author: YuMiaoChun
Tutor: XieYongQun
School: Fujian Agriculture and Forestry University
Course: Wood Science and Technology
Keywords: Plant fiber Reticular formation Thermal conductivity Fractal model Inorganics
CLC: TS653.929
Type: Master's thesis
Year: 2011
Downloads: 97
Quote: 0
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Abstract

Excessive CO2 emissions that cause global warming, extreme weather constantly, reduce carbon emissions has become the focus of global concern, the development of biomass materials provide an important way to solve the energy crisis and building energy efficiency issues. Reticular plant fiber material is a liquid foaming principle prepared porous fiber skeleton of lightweight new materials, has a low density, high performance insulation and acoustic noise reduction performance in packaging, insulation and environmental protection many areas will have broad application prospects. This article by a variety of means of the thermal conductivity of the material of the mesh structure of plant fibers experimental and theoretical studies and analyzes of inorganic substances on the thermal conductivity of the material. First, different process parameters on the network structure of plant fiber material thermal conductivity, including different types of raw materials (Moso bamboo (Phyllostachys pubescens) pulp, pulp the Ci of bamboo (Neosinocalamus affinis), bamboo (Dendrocalamopsis Oldham) pulp) The slurry concentration (4%, 4.6%, 5%), a blowing agent used in an amount (30 ml, 50ml, 70 ml), the foaming time (4min, 6min 8min), the amount of adhesive (20ml, 30ml, 50ml) and other parameters. Foam molding raw materials after beating dehydration, process conditions by orthogonal table L18 (37) after drying different performance of the test sample, and then detect the thermal conductivity and mechanical properties of the samples comprehensive selection of the better technology program: slurry concentration of 4.6%, the adhesive dosage 30ml, type of feedstock chemical wood pulp 10%, 20% fir fluff pulp, 70% Tsz bamboo blowing agent 50ml foaming time 6min; the orthogonal experiment at the same time the variance The analysis results show that the material thermal conductivity, the type of raw materials and the impact of slurry concentration is extremely significant, foaming agent and foaming time significantly, adhesive dosage had no significant effect. The better technology program based on individual parameters for single-factor test, the results show that for different types of raw materials, the mesh structure of plant fiber material thermal conductivity variation: Mao bamboo gt; the Merciful bamboo gt; Green bamboo gt; chemical wood pulp gt; fir fluff pulp;, the mesh structure of the plant fiber material thermal conductivity decreases and then increases with increasing slurry concentration, slurry concentration of 4.6%, the mesh structure of plant fiber materials time with foaming minimum thermal conductivity; increase of the blowing agent, the network structure of the plant fiber material change in the overall thermal conductivity, but the trend decreases and then increases, the blowing agent 50ml minimum; increase, the mesh structure of the plant fiber material thermal conductivity first decreases and then increases, the foaming time as 6min minimum. Secondly, the introduction of the fractal theory, the irregular geometry of the mesh structure of plant fiber material microstructure research. Based on test Get reticular formation cross section of plant fiber material, the use of computer image analysis to calculate the fractal dimension of the section, followed by the establishment of a fractal structure of the material model and the simplified thermal model using equivalent thermal resistance calculated the thermal conductivity coefficient, fractal model of the thermal conductivity of the network structure of plant fiber material: (?) results show that the method of calculation of value is in good agreement with the measured values, and therefore the fractal model is more reasonable. Further quantitative analysis of thermal conductivity of the network structure of plant fiber material impact factors show that the thermal conductivity and porosity of the material of the mesh structure of plant fiber materials, related to the fractal dimension and the pure air, the thermal conductivity of the solid phase, the thermal conductivity with with the porosity increases with an approximately linear downward trend, decreases with the increase in the number of materials fractal dimension increases with increasing vapor thermal conductivity, and the curve between the two basic phase with the proportional function of the curve anastomosis, the thermal conductivity increases with the solid phase is increased, but when the solid phase increases the thermal conductivity, the influence of the thermal conductivity solid phase of the material thermal conductivity becomes small, consistent with the test results, the more proof plant fiber material of the mesh structure fractal model of the thermal conductivity of credibility. Finally, the preliminary study the impact on the plant fiber material properties of the mesh structure of the inorganic material, inorganic material of the mesh structure of plant fiber material the existing reinforcing effect can be improved flame retardant properties of the material, also found that the silica, sodium silicate, and boric acid modified better. Selected nine kinds of inorganic materials, research acidic inorganics and alkaline inorganic materials with different amount of impact on the network structure of plant fiber material thermal conductivity, results show that the addition of inorganic mesh structure of plant fiber material thermal conductivity did not change significantly, and only a slight increase, which also proves the validity of the fractal model of the thermal conductivity of the network structure of plant fiber material; specific point of view, and add a variety of inorganic materials thermal conductivity with the addition amount of trend varies . In short, the conclusions obtained in the experimental analysis of the thermal conductivity of the network structure of plant fiber material variation and influencing factors and fractal model analysis with each other should permit relationship.

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