Thermal conductivity of low melting point metals in the liquid state

S. Stankus1, I. Savchenko1 and A. Agazhanov2

1Kutateladze Institute of Thermophysics, Siberian Branch of the Russian Academy of Sciences, Russia
2Novosibirsk State University, Russia

Keywords: laser flash method, high temperature
property: thermal conductivity, thermal diffusivity
material: liquid metals

Despite significant number of investigations already carried out, thermal conductivity of liquid substances and materials is still one of the least studied properties. At present there are no data on thermal conductivity of melts that can be considered as standard ones. Results of measurements overstep the limits of total errors and rather frequently have different signs of temperature coefficients. New laser flash technique for the measurement of heat transfer coefficients of liquid metals is presented. Thermal conductivity and thermal diffusivity coefficients of indium, tin, lead, and bismuth have been determined using the laser flash method over the temperature range from melting point to 1400 K. Measurements were performed using set-up LFA–427 of NETZSCH company in argon protective atmosphere and cells were produced from stainless steel and molybdenum. Thickness of the liquid layer changed from 1.5 to 2.5 mm. Thermal diffusivity of steel and molybdenum was measured in extra experiments on the samples to find the material that is identical to one of the cells. Two-dimensional nonstationary equation of thermal conductivity describing propagation of the heat impulse in the cell was solved numerically. Processing of experimental data included calculation of time dependence of upper surface temperature of the cell normalized on maximum and its comparison with experimental thermogram. At the calculation of the thermogram, properties of the measuring cell material as well as density and heat capacity of the studied liquid were considered as known. Adjustment parameters were thermal diffusivity (or thermal conductivity) of liquid and total hemispherical emissivity of the boundaries of the cell. The criterion of adjustment completion was minimum value of the mean square deviation of the calculated and experimental thermograms. The experimental uncertainty of the heat transfer coefficients measurements is estimated to be within 3–5 %. We gratefully acknowledge the financial support for this research from the Russian Foundation for Basic Research (Grant No. 10-08-00802) and Russian Agency of Education.

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