添加物对氧化硅气凝胶隔热性能影响的实验研究及瞬态平面热源法导热系数测试精度分析

The heat transfer mechanism within aerogel nano-porous thermal insulation materials is very complicated because the heat transfer modes within these material contain heat conduction via solid and gaseous and thermal radiation, and the existence of size effect at nanoscale within these modes. Therefore, there are many difficulties and uncertainties on predicting the thermal insulation performance theoretically. Both the theoretical assumptions of transient plane source (TPS) and the uncertainty of input/output parameters have impact on the measuring accuracy. But the influence can't be analyzed directly. The research subjects of this project are silica aerogel material and thermal conductivity measurement method. The objectives of this project are (1) to experimental investigate the influences of material components including porosity, fibers content, opacifier types (SiC, ZrO2 and TiO2), content and size and temperature and gas pressure on the thermal insulation performance of the composite; (2) to numerical study the uncertainty of TPS method introduced by theoretical assumptions when measuring thermal conductivity of anisotropic material, thin slab material and specific capacity and combined with uncertainty introduced by input/output parameters to obtain the accuracy of TPS method when measuring different kind of materials; (3) to numerical study the contribution of thermal radiation when using TPS method to measure the thermal conductivity of semitransparent medium. The research not only provides abundant experimental data for thermal insulating mechanism analysis and performance optimization, but also offers uncertainty analysis basis and experimental guidance when using TPS method. Therefore, this research has academic significance and application value of engineering.

气凝胶纳米多孔隔热材料内部传热机理复杂，包含固相导热、气相导热和辐射传热，且均存在纳米尺度效应，理论分析预测材料隔热性能具有很多难点和不确定性。瞬态平面热源法理论模型假设及测试输入输出参数测试误差均会影响测量的精度，但难以通过直接分析获得。本项目以氧化硅气凝胶材料及导热系数测试方法为研究对象，通过实验测试研究材料组分（包括孔隙率，纤维含量，遮光剂种类、含量和大小）和环境条件对复合材料隔热性能的影响；采用数值模拟分析瞬态平面热源法理论假设对各向异性材料、薄板材料导热系数和比热测量精度的影响，结合输入输出参数的测量误差获得该方法测试不同类型材料的精度；应用数值模拟探索瞬态平面热源法测试半透明介质导热系数时辐射传热的作用。本项目研究可为气凝胶材料的隔热机理分析和性能优化设计提供实验数据支撑，为应用瞬态平面热源法测试提供精度分析依据和实验指导，研究具有重要的科学意义和工程应用价值。

气凝胶纳米多孔隔热材料内部传热机理复杂，且不同传热模式均存在纳米尺度效应，理论和数值分析预测材料隔热性能具有很多难点和不确定性，因此其隔热性能研究更加依赖实验测试。瞬态平面热源法测量材料导热系数的理论模型假设会影响测量的精度，但难以通过直接分析获得，影响测量结果的可靠性。本项目以氧化硅气凝胶复合材料隔热性能测试及瞬态平面热源法导热系数测试精度分析为研究目标，实验研究了研究材料组分、微观结构、温度、气压条件对复合材料隔热性能的影响规律，建立了复合材料等效导热系数工程预测模型，测试了材料光谱辐射特性，获得辐射传热对材料等效导热系数的贡献大小及规律；采用数值模拟方法析了瞬态平面热源法测试各向异性材料时探头厚度、半径以及被测材料各向异性比对测量精度的影响规律，以及测试半透明隔热材料时内部实际辐射传热与测量理论的不一致引起的测量误差，并揭示了温度和材料消光系数对测量精度的影响规律，数值分析法还被成功用来分析瞬态热线和瞬态热带法测试半透明介质高温导热系数时辐射传热对测量精度的影响以及修正瞬态平面热源法测试理论假设、校准曲线、测试界面热阻在测量不同类型材料时引入的测量误差及变化规律。本项目研究可为气凝胶材料的隔热机理分析和性能优化设计提供实验数据支撑，为应用瞬态平面热源法测试提供精度分析依据和实验指导，研究具有重要的科学意义和工程应用价值。