瞬态热线法热物性测试技术的数值模拟研究

发布时间：2018-05-16 04:41

  本文选题：瞬态热线法 + 数值模拟　； 参考：《华北电力大学(北京)》2016年硕士论文

【摘要】：瞬态热线法是一种常用的热物性测量方法,现已被推广应用于粉体、液体、复合材料、含湿多孔介质、高温下非透明和半透明固体等材料的导热系数测量。鉴于瞬态热线法的非稳态测量的特点,误差估计一直是该类测试技术的难题。针对该类技术,利用数值模拟进行导热系数测量误差的分析更不多见。本文通过数值模拟对瞬态热线法导热系数的测量误差进行分析研究,分析各种因素对瞬态热线法导热系数测量误差的影响规律。论文在论述瞬态热线法测量的原理、模型和分类的基础上,对其建立数学模型,并采用Fluent进行数值模拟,得到温度场分布及监测点温度值,根据理论公式得出导热系数的模拟值,将模拟值与设定值进行比较得到导热系数的测量误差。根据瞬态热线法的原理及假设,选取了不同的试样尺寸、热线半径和热线热容进行模拟,得到导热系数的相对误差随不同参数变化的规律。研究结果表明,数值模拟得到的温度场分布与理论分析相吻合。在其它参数一定时,测量误差随着试样尺寸的减小而增大,随着热线半径的增大而增大,随着热线热容的增加而增大,且瞬态热线法更适合测量导热系数小的材料。当试样的尺寸w×b≥6.5 mm×16.5mm时,利用瞬态热线法测得1.5W/(m·K)λ2.0 W/(m·K)的材料,导热系数与设定的导热系数之间的相对误差可以保证在0.5%以内；当热线半径为r0=0.001mm时,导热系数的测量误差的增长量很小,增长量仅为0.029%,基本不随热线热容的变化而变化；当热线半径小于0.006mm时,如果被测试样的导热系数γ=0.1W／(m-K),相对误差的增长量很小,几乎不变,基本可以忽略。因此利用瞬态热线法测量材料的导热系数时,为提高测量精度应选用大尺寸的试样、较小半径和小热容的热线。本文所做工作可为瞬态热线法热物性测试技术的误差估计提供基本的理论依据和参考。
[Abstract]:Transient hot wire method is a commonly used method for measuring thermal properties. It has been widely used in the measurement of thermal conductivity of powders, liquids, composite materials, wet porous media, and non-transparent and translucent solids at high temperature. In view of the characteristics of transient hot-wire method, error estimation is always a difficult problem in this kind of measurement technology. For this kind of technology, the error analysis of thermal conductivity measurement by numerical simulation is less common. In this paper, the measurement error of thermal conductivity of transient hot wire method is analyzed by numerical simulation, and the influence of various factors on the measurement error of thermal conductivity of transient hot wire method is analyzed. On the basis of describing the principle, model and classification of transient hot-wire method, the mathematical model is established, and the temperature field distribution and temperature value of monitoring point are obtained by numerical simulation with Fluent. According to the theoretical formula, the simulation value of thermal conductivity is obtained, and the measurement error of thermal conductivity is obtained by comparing the simulated value with the set value. According to the principle and hypothesis of transient hot wire method, different specimen size, hot wire radius and hot wire heat capacity are selected to simulate, and the relative error of thermal conductivity varies with different parameters. The results show that the temperature distribution obtained by numerical simulation is in agreement with the theoretical analysis. When other parameters are fixed, the measurement error increases with the decrease of sample size, with the increase of hot-wire radius, and with the increase of hot-wire heat capacity, and the transient hot-wire method is more suitable for measuring materials with small thermal conductivity. When the sample size w 脳 b 鈮，

本文编号：1895521