低温保护热板法测量绝热材料导热系数研究-人机与环境工程专业论文.docxVIP

南京航空航天大学硕士学位论文 南京航空航天大学硕士学位论文 低温保护热板法测量绝热材料导热系数研究 低温保护热板法测量绝热材料导热系数研究 摘 要 绝热材料导热系数测量的准确性将直接影响绝热材料在使用过程中的合理性，经济性和安 全性。导热系数测定仪大多数基于瞬态法和稳态法这两种方法研制，测量范围大多在常温和中 温区域。随着低温技术的发展，需要绝热材料从常温到低温下的一系列导热系数，因此研究设 计一种测量中低温导热系数测定仪是必要的也是有意义的。本文介绍了导热系数测试的方法和 原理，以国标为指导设计出一种可以测量低温环境下绝热材料导热系数的保护热板法测试系统， 通过测量标定过的聚氨酯泡沫材料的导热系数验证测试系统的精度，通过测试给出硬质聚酰亚 胺泡沫从常温到低温下的导热系数曲线和最大相对误差。论文主要的工作有： 1.概述导热系数测试的基本原理，详细介绍平板法，保护热板法测量导热系数的模型和公 式，分析目前导热系数测试仪的基本现状和存在的不足。 2.参照国标 GB/T10294-2008，搭建保护热板法实验台；设计制作加热单元、温度测控系统； 设计数据采集系统；设计环境控制系统；编写测控交互界面，实现数据采集，记录和监视。 3.通过数值计算优化选择热板厚度，边缘绝热层厚度；通过编程计算不同制冷温度下液氮 的蒸发量；通过对试验台建模进行数值模拟，计算总结出防护热板法测试中的规律，通过实验 验证该规律。 4.测量聚酰亚胺泡沫从常温到低温的导热系数，生成导热系数曲线，分析误差因素，给出 实验台最大相对误差。 关键词：导热系数，绝热材料，保护热板法，低温，测试 I PAGE PAGE IV III III ABSTRACT The rationality, economy and safety in the use of insulation material is affected by the accuracy of measuring thermal conductivity of the insulation material. Coefficient of thermal conductivity measuring instruments are most based on the steady and transient method. The temperature is mostly in the region of room temperature and high temperature. With the development of low-temperature technology, theres an intensive demand for measuring thermal conductivity of the insulation material in the low-temperature. The method and principle in the measuring thermal conductivity coefficient are introduced in this paper, and a guarded hot plate apparatus which can measure the thermal conductivity of the insulation material in low-temperature according to the national standard was designed. The apparatuss accuracy was verified by measuring the thermal conductivity of a calibrated polyurethane foam. The apparatus measured the thermal conductivity of the polyimide foam from room temperature to low temperature and the maximum relative error is calculated. The main work of this paper is as follows: The basic principle of the measuring thermal conductivity test are briefly introduced. The model and calculation method of hot plate method and guarded hot plate method are des