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

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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