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

本研究的目的是开发一种实用的测量液体导热系数和扩散率的装置，该装置基于一种新的暂态短热线法。研究期间的主要结果如下：1.从短热线热源周围各种液体对应的大范围参数的二维非稳态导热的高精度数值解出发，得到了本方法所基于的导线平均温度演变的基本关联式。为了确定长宽比(长径比)、涂层材料及其厚度对测量精度的影响，测量了几种已知热物理性质的样品液体。结果表明，该方法可以同时测定导热系数和热扩散率，误差分别在2%和5%以内。利用溅射装置在不同真空压力、载气流量和氧气…条件下进行溅射在较高的n浓度下，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。通过对熔融碳酸盐作为导电腐蚀性液体的高温测试，考察了涂层探头的电绝缘性能、耐热性、防腐性能和耐久性。结果表明：(A)绝缘层的耐久性受线材直径与膜厚之比的影响较大；(B)线材直径在100微米左右时可以得到良好的绝缘膜；(C)膜上的微裂纹导致了铂丝的腐蚀反应。利用具有良好绝缘膜的探头，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率，且具有良好的重复性。对测量序列程序进行了修改和改进。开发了一种用于实际测量的简单程序。较少

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