热线法热导率测定技术

一、前言热导率是确定陶瓷、耐火材料耐热冲击性能的重要参数,也是设计窑炉炉壁时选择材料的依据.热导率测定的方法有:稳定热流法的比较法和非稳定热流法的热线法等.自HAUPIN首先用热线法成功地测定出陶瓷的热导率之后,到七十年代,许多欧洲国家相继建议将热线法定为测定陶瓷、耐火材料的标     

含碳(或碳化硅)耐火材料热导率的测试

为了解决导电、高导热、易氧化的含碳(或碳化硅)耐火材料热导率难以测定的问题,在平行热线法的基础上通过对试样埋炭保护,在热线与试样之间作化学隔离和电绝缘处理,对仪器设备进行相应的改进等措施,建立了含碳(或碳化硅)耐火材料热导率测定方法,并对部分典型含碳耐火材料和含碳化硅耐火材料的热导率进行了实测。     

纳米流体热导率的测量

运用瞬态热线法测定了不同种类、不同体积份额配比的纳米流体的热导率,分析了纳米粒子属性、份额、尺度等因素对纳米流体热导率的影响.实验结果表明,在液体中添加纳米粒子显著增加了液体的热导率.通过对实验结果进行分析,提出了计算纳米流体热导率的关联式.     

平行热线热导率试验方法在耐火材料的应用和发展

阐述了热线法测试技术的发展过程,重点介绍了国家标准——平行热线法的测试原理及方法,并指出利用平行热线法测量耐火材料的热导率、热扩散系数及比热容这些热物性指标是切实可行的,从而拓宽了平行热线法的测试范围;还明确了热线法应用于耐火材料测试的优越性,并提出了该技术的发展方向。     

液相己二酸二乙酯热导率

己二酸二乙酯是有机合成重要的溶剂和中间体,也在日用化学工业和食品工业,如香料、增塑剂等方面应用广泛。近年来,含氧燃料如己二酸二乙酯可以改善油品性能和降低柴油机排放,被认为是良好的柴油添加剂和替代燃料。然而到目前为止,对己二酸二乙酯的热物性研究相对不足。利用钽丝作为热线的瞬态双热线系统对温度区间为283～383K、压力区间为0.1～30MPa的液相己二酸二乙酯热导率进行了实验研究,并将实验数据拟合为温度和压力的关联式。实验数据与热导率关联式计算结果的标准偏差和最大偏差分别为0.14%和0.43%,热导率的标准合成不确定度为±1.0%。     

碳酸二甲酯液相热导率

利用瞬态单热线法重新研制了一套可耐高压的热导率测量装置,热导率测量的不确定度为±2%。用推荐物质甲苯对该装置在286～350 K的温度范围内进行了检验,得到的结果与甲苯热导率推荐值的绝对平均偏差为0.48%。用该装置对温度区间为290～390 K、压力区间为0.1～30 MPa的碳酸二甲酯(DMC)的热导率进行了实验研究,并将实验数据拟合成关于温度和压力的热导率方程,实验数据与拟合方程计算值的最大偏差为-1.97%,绝对平均偏差为0.86%。     

耐火材料热导率的数值推演方法

为了解决目前通过GB/T 5990—2006测定耐火材料热导率时存在的成本高、周期长、试样制作困难等问题,基于微观结构特征和数值分析技术,提出了一种耐火材料热导率推演方法,并运用该方法推演了高铝砖的热导率。结果表明,数值推演结果与理论计算结果相吻合。推演方法实现了对耐火材料热导率的预测,解决了试验方法测定热导率存在的问题,克服了多孔材料气孔率与其热导率的理论计算公式适用范围有限且不精确的缺点,提供了对热导率推演和设计的高效方法。     

含锆高铝耐火纤维毡的导热性能研究

测定了含锆高铝耐火纤维毡在不同条件下的高温热导率 ,并分析了温度 容重 方向对热导率的影响。结果表明 :容重一定时 ,热导率随温度升高而升高 ;高温热导率随容重升高而减小 ;材料热导率的各向异性比较显著     

HFE7100和HFE7500的热物理性质

为了获得氢氟醚HFE7100、HFE7500的热物理性质参数,补充现有数据不足,为其作为电子元器件的冷却介质、工业清洗剂等工程应用提供技术支持,利用瞬态热线法测量了常压下HFE7100和HFE7500的热导率,并用表面光散射法测量了HFE7100和HFE7500的液相黏度和表面张力。HFE7100和HFE7500的热导率和液相黏度均关联成温度的多项式函数,HFE7100热导率和黏度的实验值和关联式的平均绝对偏差分别为0.37%和1.19%,HFE7500热导率和黏度的实验值和关联式的平均绝对偏差分别0.08%和1.10%。利用改进的van der Waals关联表面张力和温度的关系,HFE7100和HFE7500的表面张力的实验值和关联式的平均绝对偏差分别为0.03 mN·m^-1和0.02 mN·m^-1。获得的HFE7100和HFE7500的热导率、黏度和表面张力实验数据及方程,可为其工程应用提出数据支持。     

HFE7100和HFE7500的热物理性质

为了获得氢氟醚HFE7100、HFE7500的热物理性质参数,补充现有数据不足,为其作为电子元器件的冷却介质、工业清洗剂等工程应用提供技术支持,利用瞬态热线法测量了常压下HFE7100和HFE7500的热导率,并用表面光散射法测量了HFE7100和HFE7500的液相黏度和表面张力。HFE7100和HFE7500的热导率和液相黏度均关联成温度的多项式函数,HFE7100热导率和黏度的实验值和关联式的平均绝对偏差分别为0.37%和1.19%,HFE7500热导率和黏度的实验值和关联式的平均绝对偏差分别0.08%和1.10%。利用改进的van der Waals关联表面张力和温度的关系,HFE7100和HFE7500的表面张力的实验值和关联式的平均绝对偏差分别为0.03 m N·m-1和0.02 m N·m-1。获得的HFE7100和HFE7500的热导率、黏度和表面张力实验数据及方程,可为其工程应用提出数据支持。     

Thermal conductivity of polymers by hot-wire method

The hot-wire standard technique, mostly used for ceramic materials, was adapted to determine the thermal conductivity of nylon 6,6, polypropylene, poly(vinyl chloride), and poly(methyl methacrylate). The results obtained showed that the hot-wire standard technique can be used with accuracy and reproducibility to measure the thermal conductivity of polymers. In the second stage, to verify the effect of the use of a lignin (a “macromonomer”) in the thermal conductivity of phenolic resins, this technique was applied to phenol-formaldehyde and phenol–lignin–formaldehyde resins. © 1996 John Wiley & Sons, Inc.     

气相色谱法测定作业场所中的苯、甲苯、二甲苯

介绍的苯、甲苯、二甲苯热导池检测器气相色谱测定方法，具有灵敏主高、准确性好的特点。     

High-Temperature tests of heat-insulating refractory materials for thermal conductivity

Specialists of D. I. Mendeleev Russian University of Chemical Engineering have created an installation for determining the thermal conductivity of heat-insulating refractory materials in the range of 20–1000°C using a measuring cross. The data obtained for materials tested by the steady-flow method and the hot-wire method (ISO 8894-1:1987 (E)) differ by no more than 12%.     

Effect of Some Chemicals on Thermal Conductivity of Impregnated Laminated Veneer Lumbers Bonded with Poly(vinyl acetate) and Melamine–Formaldehyde Adhesives

Thermal conductivity is a very important parameter in determining heat transfer rate and is required for the development of drying models and for the industrial operations such as adhesive cure rate. The objective of this research was to investigate the effects of impregnation on the thermal conductivity of six-layered laminated veneer lumber (LVL) made of beech and pine. Boric acid, zinc chloride, and ammonium sulfate were used as impregnation chemicals and poly(vinyl acetate) (PVAc) and melamine-formaldehyde (MF) adhesives as bonding agent were used to produce LVLs. The veneers were impregnated by using the vacuum-pressure method. The thermal conductivity test was performed based on ASTM C 1113-99 hot-wire method. Results showed that the impregnation chemicals increase the thermal conductivity. As impregnation chemicals the highest values were obtained with boric acid and zinc chloride. In addition, the thermal conductivity of LVL made of beech was higher than that of LVL made of pine. The thermal conductivity of LVL bonded with PVAc was absolutely higher than LVL bonded with MF in both wood species.     

平行热线法测定耐火材料导热系数的理论基础及技术

在一无限大试样中有一无限细而长的线状热源，导出了试样导热系数的计算公式。该公式与ISO8894-2中的计算公式相吻合。实验表明，使用的热线的直径与材质以及热电偶的直径对测得的导热系数的准确性有一定影响，尤其是热线和热电偶的对称埋设对测量结果的准确性是十分重要的。     

氧化硅纳米流体的导热性能研究

采用瞬态热线法测量SiO2-水和SiO2-乙二醇两种纳米流体在不同体积分数和温度下的导热系数,分析研究纳米SiO2体积含量、温度及悬浮稳定性对纳米流体导热系数的影响。研究结果表明,纳米流体的导热系数显著高于基体液体的导热系数,且随着粒子体积分数的增大和温度的升高均有所提高;对于悬浮稳定性越好的纳米流体,它的导热系数增加量越大。     

A Study of Effective Thermal Conduction in Lightweight Foam Corundum Refractories

Thermal conduction of lightweight foam corundum refractories is studied by a hot-wire method. Empirical relations for the thermal conductivity as a function of temperature (20 – 1100°C) and porosity (79 – 93%) are derived. The thermal conductivity at higher temperature is less dependent on porosity because of the increased role of radiation in the heat conduction process.     

Investigation on two abnormal phenomena about thermal conductivity enhancement of BN/EG nanofluids

The thermal conductivity of boron nitride/ethylene glycol (BN/EG) nanofluids was investigated by transient hot-wire method and two abnormal phenomena was reported. One is the abnormal higher thermal conductivity enhancement for BN/EG nanofluids at very low-volume fraction of particles, and the other is the thermal conductivity enhancement of BN/EG nanofluids synthesized with large BN nanoparticles (140 nm) which is higher than that synthesized with small BN nanoparticles (70 nm). The chain-like loose aggregation of nanoparticles is responsible for the abnormal increment of thermal conductivity enhancement for the BN/EG nanofluids at very low particles volume fraction. And the difference in specific surface area and aspect ratio of BN nanoparticles may be the main reasons for the abnormal difference between thermal conductivity enhancements for BN/EG nanofluids prepared with 140- and 70-nm BN nanoparticles, respectively.     

双热流计法测定聚氨酯保温材料的导热系数

简要介绍了几种测定固体材料导热系数的方法,重点讨论了稳态双热流计法测定聚氨酯保温材料导热系数的方法原理、导热仪的结构、影响测试结果的因素,并对提高检测结果的准确性、减少误差提出了建议。