Development of an Apparatus for Measuring Thermal Conductivity of Liquids with a Transient Short-Hot-Wire Method.

本研究的目的是基于一种新的瞬态短热线法，研制一种实用的测量液体导热系数和扩散系数的仪器。研究期间的主要成果如下：1。短句来源根据短热线热源周围不同液体在大参数范围内的二维非定常热传导的高精度数值解，得到了该方法赖以建立的热线平均温度演变的基本关系式。为了确定长宽比（长/直径）、涂层材料及其厚度对测量精度的影响，对几种已知热物理性质的样品液体进行了测量。结果表明，该方法可以在2%和5%的误差范围内确定热导率和热扩散率。利用溅射装置，在不同的真空压力、载气流量和氧浓度条件下，研究并确定了在线材上制备纯Al_2O_3绝缘防腐涂层的最佳条件。通过在高温下测量熔融碳酸盐作为导电和腐蚀液体，考察了涂层探针的电绝缘性、耐热性、防腐性能和耐久性。结果表明：(a)线径与膜厚的比值对绝缘层的耐久性有较大影响；(b)可制得导线直径约100 μ m的良好绝缘膜；(c)薄膜微裂纹导致铂丝腐蚀反应。使用具有良好绝缘膜的探针，可以在上述精度范围内测量熔融碳酸盐的导热系数和热扩散系数，并且具有良好的重现性。对测量序列程序进行了修改和改进。为实际测量制定了一个简单的程序。少

The aim of present study is to develop a practical apparatus for measuring the thermal conductivity and diffusivity of liquids based on a new transient short-hot-wire method. The main results during the research period are as follows :1. From high accurate numerical solutions of two dimensional unsteady heat-conduction for wide range of parameters corresponding to various liquids around a short-hot-wire heat source, the basic correlations for the wire mean temperature evolutions on which the present method is based were obtained.2. To confirm the effects of aspect ratio (length/diameter), coating material and its thickness on the measurement accuracy, several sample liquids with known thermophysical properties were measured. The results reveal that the present method can determine both the thermal conductivity and thermal diffusivity within the error of 2 and 5%, respectively.3. By using a sputtering apparatus under various conditions of vacuum pressure, carrier gas flow rate and oxyge … More n concentration, the optimum conditions to make an insulating and anticorrosive coating film of pure Al_2O_3 on the wire were investigated and determined.4. The qualities of the coated probe were investigated such as electrical insulating, heat-resisting, anticorrosive characteristics and durability, by measuring a molten carbonate as an electro-conductive and corrosive liquid at high temperature. The results reveal that (a) the durability of insulating layr is greatly affected with the ratio of wire diameter to film thickness ; (b) it is possible to make a good insulating film for the wire diameter about 100 mum ; and (c) micro-crack of the film results in corrosive reaction of platinum wire.5. With a probe having a good insulating film, the thermal conductivity and thermal diffusivity for molten carbonate could be measured within the above accuracy and with good reproducibility.6. A measurement sequence program was modified and improved. A simple procedure was developed for a practical measurement. Less