珠状热敏电阻在吸收剂量量热计中的应用

吸收剂量量热计要求其测温元件—珠状热敏电阻的标称值R_T和电阻温度系数α_T的年漂移量分别不大于0.02％和0.1％。本文叙述了为满足此要求而对热敏电阻进行“老化”、测量它的R_T、α_T装置、方法及测量结果。     

吸收剂量石墨量热计

为建立吸收剂量国家基准,研制了热损失补偿型石墨量热计。用串联的双热敏电阻作为定度加热器,外套与吸收体的热容之比等于其测温热敏电阻温度系数之比。介绍了该装置的主要构造、测量原理和方法,比较了理论计算和实际测量的温度-时间曲线,分析了系统误差。对于~(60)Co γ射线束,剂量率为0.8Gy/min时,单次测量的标准偏差为±0.6％;剂量率为0.17Gy/min时,单次测量的标准偏差为±1％。     

PZT和PT陶瓷的热释电效应与晶格参数的关系

测量了锆钛酸铅（ＰＺＴ）和钛酸铅（ＰＴ）陶瓷材料的热释电效应，利用Ｘ射线衍射测量了陶瓷材料在不同温度下晶格结构变化，研究了ＰＺＴ和ＰＴ陶瓷材料的热释电效应与晶格参数之间的相互关系，实验表明，陶瓷材料的热释电系数的大小与晶格参数随温度变化的情形有关，ｃ轴与ｃ／ａ比随温度变化大的材料，其热释电系数较高。     

PZT和PT陶瓷的热释电效应与晶格参数的关系

测量了锆钛酸铅（PZT和钛酸铅（PT）陶瓷材料的热释电效应，利用X射线衍射测量了陶瓷材料在不同温度下晶格结构变化，研究了PZT和PT陶瓷材料的热释电效应与晶格参数之间的相互关系，实验表明，陶瓷材料的热释电系数的大小与晶格参数随温度变化的情形有关，c轴与c／a比随温度变化大的材料，其热释电系数较高．     

脉冲加热测量材料热物性技术的综述与分析

使用脉冲热技术测量热物性参数的瞬态量热法克服了利用经典稳态法进行测量的许多缺陷,因而取得了很大的发展.本文介绍了利用脉冲加热技术进行热物性测量的基本原理,简单介绍了最近三十年国内外利用此技术进行热物性测量的原理和装置,以及利用扫描高速高温计进行热膨胀系数和热传导系数测量的方法和实验装置.最后介绍了该领域国内外的最新研究动态和发展方向.     

载冷剂低温热物性测试方法综述

航天器内的温度通过热控制系统中载冷剂的强制对流换热来调节。在研制和选择载冷剂时,根据载冷剂的性能要求,需要对流体工质在低温下的热物性参数进行测量。对现有的载冷剂物性测试方法进行了综述,总结了测量载冷剂密度、凝固点、沸点、黏度等参数的方法,并通过比较得出绝热量热法是低温下测量液体比热容的最佳方法,径向热流法适合于低温下测量液体工质的导热系数。     

用恒热流法测定多孔介质的热质迁移特性参数

设计了一种测定多孔介质热质迁移特性的实验装置。通过测定该装置中多孔介质的局部温含量和温度，结合恒热流下一维半无限大多孔介质热质迁移微分方程的解，得到了石英砂、玻璃珠等多孔介质的质扩散系数、热质扩散系数、名义热扩散系数、名义导热系数等热质迁移特性参数以及这些参数随湿含量、温度的变化。此外，还讨论了加热功率、初始湿含量等因素对测量的影响。     

Nd3+:Gd3Ga5O12晶体的热物理性能研究

提拉法生长了Nd^3＋：Gd3Ga5O12（Nd：GGG）单晶，用差示扫描量热法（DSC）和激光脉冲法分别测量了Nd：GGG激光晶体的比热和热扩散系数，计算得到晶体的导热系数，与用PPMS测量得到的导热系数相吻合．实验结果表明：Nd：GGG激光晶体具有较大的比热和导热系数，具有良好的热物理性能；Nd：GGG晶体的热扩散系数和导热系数随着温度的升高而减小；计算得到晶体的德拜温度为711K．     

热敏电阻液面探测器

一、基本原理及典型应用线路热敏电阻器是一种电阻值随温度变化而显著变化的半导体电阻器。这种元件在温度补偿和温度测量等方面的用途,已为人们所熟悉。当热敏电阻器用于上述场合时,一般要求通过热敏电阻器的电流很小,使之处于不发热的状态下进行工作。把热敏电阻器用作液面探测(指示、报警)器时,其基本条件是:通过热敏电阻器的电流必须充分发热,这样,由于热敏电阻器在空气中与在液体中的耗散系数差别很大,只要把热     

基于温度修正的新微量热计的设计与评定方法研究

提出了一种“温度修正”的有效效率获得方法,并就基于该方法的微量热计设计进行了说明。该方法采用“隔热段测温修正”的方法对热敏电阻座有效效率定标中隔热段的影响进行修正,避开了用散射参数修正的传统方法。由于散射参数测量引入的不确定度是功率基准不确定度的主要来源之一,这种方法从原理上消除了该不确定度引入。最后给出了隔热段温度变化曲线,实验证明方法可行。     

Thermal diffusivity of gadolinium in the temperature range of 287–1277 K

New experimental data on the thermal diffusivity of gadolinium in the temperature interval from 287 to 1277 K obtained by the laser flash method with an error of 3–4% are presented. Results are compared with the available literature data. Reference tables on the heat transfer coefficients of gadolinium for scientific and practical use are developed. Critical indices for the thermal diffusivity of gadolinium above the Curie point are determined. The limitations of the laser flash method during measurement in the region of phase transformations are briefly discussed.     

A new dynamic technique for the measurement of hemispherical total emittance

A new dynamic technique for the measurement of thermal conductivity under development at the IMGC requires accurate values of heat capacity and of hemispherical total emittance at high temperature. Until recently, these data were provided by subsecond pulse heating experiments performed on the same specimens in the same apparatus. The pulse heating technique is the most accurate method for the determination of heat capacity at high temperatures, but because of various experimental problems, the accuracy of hemispherical total emittance determinations is limited to 5%. A new method for a more accurate determination of hemispherical total emittance is proposed, which uses the same experimental data available from thermal conductivity experiments. An analysis of the temperature profiles measured during the free cooling indicates that regions with high-temperature gradients (toward the ends of the specimen) are the best regions for thermal conductivity measurements, while regions with low-temperature gradients (at the center of the specimen) are the best regions for hemispherical total emittance determinations. The new measurement method and some preliminary results are presented and discussed.Paper presented at the Second Workshop on Subsecond Thermophysics, September 20–21, 1990, Torino, Italy.     

Model calculations on heat flow in inhomogeneous thermal systems. 1 — Thermal conductivity and boundary resistance at low temperatures

A network modelling technique is applied to the analysis of inhomogeneous thermal systems at low temperatures. A calculation is presented of the temperature distribution and the heat flow in an experimental cell used for the measurement of thermal conductivity and thermal boundary conductance. In a sequel to this paper (part 2) a random number method will be used to analyse the behaviour of sinters in cryogenic heat exchangers.     

基于改进有序聚类法的立式加工中心进给系统温测点优化

为解决立式加工中心热误差补偿关键技术中温测点难选取的问题，提出了一种基于改进有序聚类法的机床进给系统温测点优化方法。首先，结合试验数据计算反映温测点温度变量与热误差相关性的互信息值，初步筛选机床各部件的温测点，消除测点间的耦合性；然后，根据筛选出的温测点，通过建立类直径矩阵和计算各类的最小误差函数，获得温度变量分类；最后，基于多元线性回归建立包含多个不同温测点的热误差模型，并对模型进行统计学综合分析，确定了最佳聚类数和最佳温测点。结果表明：在不同加工条件下采用改进有序聚类法建立的热误差模型的均方根误差和平均残差分别降至1.05 μm和1 μm以下，相较于采用传统有序聚类法和灰色关联度模糊聚类法建立的热误差模型，它具有更高的热误差预测精度和更好的鲁棒性。所提方法在中小型加工中心进给系统的温测点研究中具有广阔的应用前景。     

Contribution to the Transient Plane Source Method for Measuring Thermophysical Properties of Solids

The transient plane source method of measuring the thermal conductivity and thermal diffusivity uses a sensor in the shape of a thin disk, which simultaneously serves as the heat source and thermometer. This study describes improvements of the experimental apparatus, providing some details of the electrical bridge with the aim to obtain maximum reliability of the measurement results. The aim of the temperature function analysis is to find the optimal time of measurement. The relation between the data time window used for fitting, the uncertainty of the sensor temperature measurement, and the uncertainty of the results is presented and graphically illustrated using numerical simulation of the experiment. The theory was confirmed by the evaluation of real measurements on polymethylmetacrylate. The temperature function analysis revealed that a decrease of the temperature measurement uncertainty need not always lead to a fall in the total uncertainty of the results but to shorter experiments and smaller specimens.     

Analytical study for the estimation of thermal properties of processed meat based on hyperbolic heat conduction model

This study proposes an analytical method in conjunction with existing experimental temperature to estimate the unknown relaxation time and thermal diffusivity of processed meat based on the hyperbolic heat conduction model. This analytical method is a combination of the Laplace transform and least squares methods. The thermal contact resistance at the interface between adjacent samples at different temperatures is assumed to be negligible. The relaxation time is estimated from the temperature jump at a specific measurement location. The thermal diffusivity is determined from the definition of the dimensionless spatial coordinate and the resulting relaxation time. The results show that the relaxation time and thermal diffusivity obtained are in good agreement with the existing results. The obtained dimensionless temperature history at a specific measurement location is close to the experimental temperature data. This means that the Cattaneo–Vernottee (CV) model can be suitable for this study. The proposed analytical inverse method can be applied to determine a more accurate estimate of such problems. A comparison of the estimate obtained from CV and dual phase lag models is made.     

The Laser Flash Method with Repeated Pulses—Optimal Experimental Design Analysis

The paper deals with analytical aspects of the laser flash method with repeated pulses, which is a photothermal experimental method for measurement of the thermal diffusivity of solids. It concentrates on the data reduction—an estimation of the thermal diffusivity from the experimental data. Special attention is given to the technique of correction of the width and shape of the heat pulses. Results of sensitivity and optimal experimental design analysis are discussed in detail. It focuses on questions of the influence of setting the experimental parameters, heat pulse period and the number of applied heat pulses, to the sensitivity of the method as well as the optimum time of duration of an experiment.     

Dielectric-Constant Gas-Thermometry Measuring System for the Determination of the Boltzmann Constant at PTB

Dielectric-constant gas thermometry is being further developed at PTB to measure thermodynamic temperature and the Boltzmann constant k at the triple point of water. Due to the small electric susceptibility of gases, the targeted relative uncertainty of k of the order of 2 ppm can be achieved only if gas pressures up to 7 MPa and special 10 pF capacitors for the susceptibility measurements, including very large multi-ring toroidal cross capacitors, are used. This required development of a huge measuring system having a large heat capacity. Since the temperature measurement must be traceable to the triple point of water at a level of the order of 0.1 mK, a corresponding stability and homogeneity of the thermal conditions has to be realized. The design of the system and data characterizing its thermal parameters is described. The experimental results are compared with estimations based both on simple models and finite-element calculations.     

瞬态热线法导热系数测量实验数据处理方法的研究

为克服瞬态热线法导热系数测量中实验数据处理一般方法的弊端,将数值模拟引入实验数据处理过程,并通过比较理论计算曲线与实验曲线的符合程度来获得最终的实验结果。通过不同方法对实验数据处理结果的比较分析表明,所使用的方法可以更好地处理瞬态热线法导热系数测量数据,同时,与传统方法相比,采用较少的数据点即可得到正确的结果。研究结果不仅可以改进瞬态热线法导热系数实验数据的分析方法,而且对实验系统的设计与搭建也有借鉴意义。     

利用瞬态热线法测量固体导热系数

在利用瞬态热丝法测量固体与流体导热系数方法研究的基础上,对固体的导热系数进行了计算,提出了既有理论意义又包含了测量参数、既严格又简便的新表达式;分析与定量计算了模型误差、截断误差、热阻误差、热容忽视误差及测量系统的合成误差;并指出了减小误差的措施。在实验研究中,建立了试件测试台和自动化参数采集与数据处理的计算机测控系统。测量结果表明,所测得的3种固体材料的导热系数值与文献参照值相差约5％。具有一定的实用价值。