玻化微珠保温砂浆导热系数模型研究

发布时间：2018-01-21 18:17

本文关键词： 最小热阻力均匀化方法热阻网络等效导热系数玻化微珠保温砂浆有限元模拟　出处：《湖南大学》2014年硕士论文　论文类型：学位论文

【摘要】：玻化微珠保温砂浆具有优越的保温性能和较好的物理力学性能，因而在建筑节能领域的应用日趋广泛。工程应用上衡量玻化微珠保温砂浆的主要技术性能指标是导热系数。因此，本文针对玻化微珠保温砂浆导热系数开展研究，建立理论模型、进行理论计算，并进行了实验验证。首先，本研究运用均匀化方法建立了玻化微珠保温砂浆单元胞体，根据横向热阻的不同将单元胞体划分成两种热阻网络，，基于最小热阻力法则推导了两种热阻网络等效导热系数计算公式。通过计算发现单元体热阻网络的划分方式对等效导热系数的计算结果有很大的影响。然后，应用ANSYS有限元软件模拟了导热系数测量方法——防护热板法，得到了单元体精确导热系数值。用ANSYS有限元软件模拟玻化微珠保温砂浆二维单元胞体的热传导过程，从得到的二维单元温度云图和热流矢量图分析了两种热阻网络模型计算值与有限元模拟值偏差来源，并对热阻网络模型进行了改进，将改进后的热阻网络模型计算值与有限元模拟值及实验值对比，结果均显示改进后的热阻网络模型比原来的两种热阻网络模型计算精度更高。第三，用正交试验的方差分析，分析了除玻化微珠外其他组分掺量对玻化微珠保温砂浆导热系数的影响，得到了各因素对玻化微珠保温砂浆导热系数大小的影响顺序为发泡剂用量＞粉煤灰取代水泥量＞可再分散性乳胶粉用量的结论。最后，考虑到孔隙对导热系数影响较大，本研究针对加入引气剂或发泡剂的玻化微珠保温砂浆提出了一种以改进的热阻网络模型为基础的新模型。新模型忽略其他组分掺量的影响，增加孔隙率为一变量，将玻化微珠保温砂浆看成是由孔隙、玻化微珠、水泥基体组成的三元体系。经实验验证，当模型的孔隙率含量在10%以内时，采用新模型计算的导热系数误差可控制在5%以内。
[Abstract]:Vitrified microbead insulation mortar has excellent thermal insulation performance and better physical and mechanical properties. Therefore, it is widely used in the field of building energy conservation. The main technical performance index of glass microbead thermal insulation mortar is thermal conductivity in engineering application. In this paper, the thermal conductivity of vitrified microbead thermal insulation mortar is studied, the theoretical model is established, the theoretical calculation is carried out, and the experimental results are verified. Firstly, the cell body of vitrified microbead thermal insulation mortar is established by using homogenization method, and the cell body is divided into two kinds of thermal resistance networks according to the different transversal thermal resistance. Based on the principle of minimum thermal resistance, two formulas for calculating the equivalent thermal conductivity of thermal resistance network are derived. It is found that the partition of the thermal resistance network of the unit body has a great influence on the calculation results of the equivalent thermal conductivity. Then, ANSYS finite element software is used to simulate the thermal conductivity measurement method-the protective hot plate method. ANSYS finite element software was used to simulate the heat conduction process of the two-dimensional cell body of the vitrified microbead thermal insulation mortar. The source of the deviation between the calculated values of the two kinds of thermal resistance network model and the finite element simulation value is analyzed from the two-dimensional element temperature cloud diagram and the heat flux vector diagram, and the thermal resistance network model is improved. The calculated value of the improved thermal resistance network model is compared with the finite element simulation value and the experimental value. The results show that the improved thermal resistance network model is more accurate than the original two thermal resistance network models. Thirdly, with the analysis of variance of orthogonal test, the influence of the addition of other components on the thermal conductivity of the thermal insulation mortar is analyzed. It is concluded that the influence of various factors on the thermal conductivity of vitrified microbead insulation mortar is as follows: the amount of foaming agent > the amount of fly ash replacing cement > the amount of redispersible latex powder. Finally, considering that the porosity has a great influence on the thermal conductivity. In this paper, a new model based on the improved thermal resistance network model is proposed for the glass microbead insulation mortar with air entraining agent or foaming agent. The new model ignores the effect of other components. The increase of porosity is a variable, and the thermal insulation mortar is regarded as a ternary system composed of pores, vitrified beads and cement matrix. The experimental results show that the porosity content of the model is less than 10%. The error of thermal conductivity calculated by the new model can be controlled within 5%.
【学位授予单位】：湖南大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU578.1;TU551

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