Measuring heat conductivity factors of liquids and liquid media at various temperatures

Аuthors

Boboshina S. B., Poberegsky S. A., Cherepanov V. V.^*, Lihushina E. V.

Moscow Aviation Institute (National Research University), 4, Volokolamskoe shosse, Moscow, А-80, GSP-3, 125993, Russia

*e-mail: vvcherepanov@yandex.ru

Abstract

Theoretical description of liquids behavior occupying an intermediate position between solids and gases faces serious difficulties. In associated liquids atom form complexes, i.e. associations, and methods for such liquids description are based on experimental studies. Thermal-physical properties of liquids depend drastically on pressure and temperature. Thus, studying temperature dependencies of liquids characteristics is of high relevance.

The article presents the results of experimental studies of a number of organic liquids thermal conductivity in dependence on temperature. The heat conductivity factor was being determined with the short-time measurements at the stage of irregular thermal mode. Compensational circuit with measuring sensor-probes equipped with resistive elements connected to the bridge legs was employed. A periodic sequence of measuring rectangular pulses was being fed to the probes. Variable signal compensation and the bridge circuit balancing were being realized the during the pause between the pulses when almost complete disappearance of the of the originated temperature field disturbance was taking place. The heat conductivity factor measurements were performed for liquid dimethylformamide and cyclohexanone at the temperatures of 200ºC — 1000ºC, and for carbon tetrachloride at temperatures of 0ºC — 75ºC. Ice with salt, or snow and salt mixture were being applied for the measuring facility elements cooling. Measurement error was no more than 2%. The heat conductivity factort of all liquids decreases linearly with temperature increase. Approximations of experimental dependences were obtained by the least squares method. The association degree of the studied liquids was computed with the Predvoditelev-Vargaftik formula. The article presents also the results of paraffin heat conductivity factor studies in the vicinity of melting-solidification point. These data are fundamental and may present interest fo the specialists dealing with heat exchange and phase transitions.

The obtained results can be used in various fields of mechanical engineering, energetics, transport, pharmaceuticals, as well as in the aerospace field. They may come in handy while design and operation of various types of heat exchange plants, as components of refrigerants used in cooling circuits, as well as when the problems of thermal compensation are of great importance in conditions of a sufficiently large variation of temperature and a wide temperature range during the operation of modern equipment.

Keywords:

heat conductivity; measurement; heated thread method; organic liquids; compensation scheme, associated liquids

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