微纳结构材料气凝胶的传热机理研究

Aerogel, as one kind of ultralight nano-porous materials is developing very rapidly in recent years. With good heat insulation properties, aerogel has a broad application prospect in the field of energy conservation and environmental protection. However, there is no existing numerical model can fully reveal the complex internal heat transfer mechanism in gas condensate so far, due to the heat transfer in the solid-phase conduction, radiation heat transfer, and other mutual coupling of heat transfer, etc. Based on the basic characteristics of the carbon aerogels, there are mainly three topics in this project. a). The radiative heat transfer characteristics of nanostructures and near-field effect, and the scale effect of nanoparticles thermal conductivity are analyzed. b). Solid phase and radiation thermal conductivity heat transfer models in the aerogel are developed. c). The effect of solid-phase conduction and radiation heat transfer on the properties of aerogel insulation are analyzed. Besides, a variety of heat transfer models on nanoparticles skeleton including solid conduction and radiation heat transfer are implemented. Furthermore, the associated link between microstructure and material properties of the aerogel is conducted. The research aims to find the energy transfer rules within the aerogel nanostructures, and reveal the microscopic mechanism of heat transfer. All parameters influencing on internal heat transfer will be conducted and optimized. The above studies purpose to provide a scientific basis for the thermal design of aerogel material.

气凝胶是近年发展十分迅速的超轻多孔纳米材料，具有良好的隔热性能，在节能环保领域有着广泛应用前景。但由于气凝内存在固相导热和辐射传热等多种相互耦合的传热方式，其内部传热机理极为复杂，现有数值模型还不能完全揭示这些机理。本项目拟根据氧化物气凝胶的基本特征，研究：气凝胶内纳米结构的辐射传热特性及近场效应，纳米颗粒导热的尺度效应；发展气凝胶内固相和辐射导热率的传热模型；分析固相导热以及辐射传热对气凝胶隔热性能的影响，建立纳米颗粒骨架的固体导热和辐射传热的多种传热模型，实现气凝胶内微观结构与宏观材料性质之间的关联。发现气凝胶内纳米结构中能量传输规律，揭示其微观传热机理，对影响气凝胶材料内部传热过程的诸参数进行优化，为气凝胶材料的隔热设计提供科学依据。

气凝胶是近年发展十分迅速的超轻多孔纳米材料，具有良好的隔热性能，在节能环保领域有十分广泛的应用。针对气凝胶内部多种耦合传热机理的复杂性，本项目从数值模拟和实验研究两个方面对气凝胶内耦合传热过程进行了系统性研究。主要工作和研究成果简介如下：（1）采用理论分析的方法，通过分析气凝胶内能量载子的输运规律，分别构建了基于声子导热的气凝胶纳米多孔材料的固相导热模型、基于分子导热的气凝胶纳米多孔材料的气相导热模型、以及气凝胶纳米多孔材料的辐射传热模型，并通过与前人的结果对比，验证了上述模型的正确性和有效性。（2）通过扫描电镜对微纳米结构的气凝胶进行微观形态表征，通过比表面积及孔隙度分析仪获得实验用气凝胶的比表面积、平均孔直径、颗粒间孔体积等多孔材料的宏观结构特征。搭建了气凝胶有效导热系数的实验测试平台，对不同结构气凝胶的有效导热系数进行了实验测量，分析了压力和温度等参数对气凝胶的有效导热系数的影响规律，为进一步对气凝胶内结构优化设计提供了技术支持。（3）构建了气凝胶内固相导热、气相导热和辐射传热的多种能量耦合传递模型，并在此基础上模拟了气凝胶内部多种传热模式耦合的传热过程，分析了环境温度、压力、密度、比表面积、颗粒直径等多种参数对气凝胶有效导热系数的影响规律。以上成果为发现气凝胶内纳米结构中能量传输规律，揭示其微观耦合传热机理，为气凝胶材料的隔热设计提供科学依据。.依托本项目，共发表SCI期刊论文6篇，国际会议论文4篇；联合培养在读研究生3名，其中1人获一等奖学金；项目负责人获得“陕西省青年托举人才”、“长安大学本科毕业论文优秀指导教师”等荣誉称号，并受邀参加葡萄牙里斯本举办的SDEWES2016大会、中国昆明举办的NEFES2017大会等国际学术会议4次。