Development of a New Apparatus for Measuring Thermal Conductivities of Fluid Mixtures and Biological Fluids

该项目的目的是开发一种用于测量气体和液体热导率的新仪器。该装置的原理是基于等温球体稳态自然对流的传热特性，设计了一个简单的装置，用一个珠状热敏电阻作为加热球体。（1）通过引入热敏电阻的有效直径和三个装置常数，可以准确地估计热敏电阻与理想球体的形状差异、热敏电阻内部不均匀发热引起的温度分布不均匀以及引线的热损失等各种影响。(2)对于液体和气体，样品容器的内径必须分别大于热敏电阻直径的约30倍和40倍。(3)当其它物理性质已知时，对空气、水、乙醇、甲醇和制冷剂R113的测量误差估计在2%以内。(4)通过对水-乙醇、水-甲醇和R113-油三种二元液体混合物导热系数的测量，表明该装置对流体混合物导热系数特性的基础研究是有效的。

This project was performed to develop a new apparatus for measuring thermal conductivities of gases and liquids. The principle of the apparatus is based on the theoretically established heat-transfer-characteristics for steady free convection from an isothermal sphere.A very simple apparatus was devised with a bead thermistor as the heated sphere. From the tests with the apparatus, following results were obtained:(1) Various effects caused by the difference in shape between the thermistor and an ideal sphere, nonuniform temperature distribution due to heterogeneous heat generation in the thermistor and heat loss from lead wires can be accurately estimated by introducing an effective diameter of the thermistor and three apparatus constants.(2) Inner diameter of sample vessel must be larger than about 30 and 40 times of thermistor diameter for liquids and gases, respectively.(3) Inaccuracy of the present method is estimated to be within 2% from the measurements for air, water, ethanol, methanol and refrigerant R113, when the other physical properties are known.(4) The measurements of thermal conductivities of binery liquid mixtures of waterethanol, water-methanol and R113-oil show that this apparatus is effective to the basic study for characteristics of thermal conductivities of fluid mixtures.The measurement for biological fluids has been undertaken.