基于热线法的低温导热系数测量研究

发布时间：2018-03-26 14:28

  本文选题：导热系数　切入点：热线法　出处：《南京航空航天大学》2015年硕士论文

【摘要】：绝热材料的导热系数随材料的结构、成分、温度和湿度等变化很大,在一些文献提供的物性表中基本查不到低温下的导热系数,而低温下绝热材料的导热系数又是人们关注的重点,因此研究如何快速有效地测量绝热材料低温下的导热系数对于航空、航天、低温贮存及运输、低温技术的发展具有重要意义。本课题是工信部高技术船舶科研计划《新型液化天然气船液货围护系统预先研究》项目的一部分,目的是获取聚酰亚胺泡沫塑料在液氮温区内,导热系数随温度变化的关系,为新型液化天然气液货舱围护结构的绝热材料选型提供依据。本文重点研究了平行热线法测量低温环境下绝热材料的导热系数。理论上根据热线法建立了热量传递的瞬态数学模型、对数学模型进行了数值模拟;试验上,根据平行热线法原理,搭建了导热系数测量试验台。理论上分析了铂电阻传感器代替热电偶测量温度带来的误差,与实际测量结果进行了对比,分析了引起误差的原因及误差大小。分析了铂电阻平整布置于硬质材料之中形成的空气薄层给导热系数测量带来的误差,及减小此误差所采取的办法。实际测量了聚酰亚胺(软、硬)在-160℃~25℃温度下的导热系数,得到了测试材料的导热系数随温度变化的数据。利用该测量平台得到聚氨酯泡沫以及聚酰亚胺(软、硬)在常温下的导热系数,与经国家玻璃纤维产品质量监督检验中心测得的鉴定值对比,其相对误差最大不超过5%。证明本课题采用的导热系数测量方法及数学模型有效,因此低温环境下测量的导热系数能应用于实际。
[Abstract]:The thermal conductivity of adiabatic materials varies greatly with the structure, composition, temperature and humidity of the materials. However, the thermal conductivity of adiabatic materials at low temperature is the focus of attention. Therefore, how to measure the thermal conductivity of adiabatic materials at low temperature quickly and effectively for aerospace, aerospace, cryogenic storage and transportation is studied. The development of cryogenic technology is of great significance. This project is part of the project of "advance research on liquid and cargo envelope system of new type liquefied natural gas ship" in the high-tech ship scientific research project of the Ministry of Industry and Information Technology, the purpose of which is to obtain polyimide foam plastics in the liquid nitrogen temperature region. The relationship between thermal conductivity and temperature, This paper focuses on the measurement of thermal conductivity of insulating materials in low temperature environment by parallel hot wire method. In theory, heat transfer is established according to hot wire method. A transient mathematical model, The mathematical model is numerically simulated, and in the experiment, according to the principle of parallel hot wire method, the thermal conductivity measurement test-bed is built. The error caused by platinum resistance sensor instead of thermocouple in measuring temperature is analyzed theoretically. Compared with the actual measurement results, the causes and magnitude of the errors are analyzed, and the errors of the measurement of thermal conductivity caused by the thin layer of air formed by the platinum-resistance leveling arrangement in the hard materials are analyzed. The thermal conductivity of polyimide (soft and hard) at -160 鈩，

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