Concerning the methods of thermocouple embedding in experimental studies of cooling the high-temperature bodies in subcooled and saturated liquids
A.R. Zabirov1, I.A. Molotova2, I.A. Belyaev1, V.A. Ryazantsev2, V.V. Yagov2
1Joint Institute for High Temperatures of RAS, Moscow, Russia
2Moscow Power Engineering Institute, Moscow, Russia
Keywords: boiling, experiment, thermocouple, micronucleate boiling, Leidenfrost effect
Abstract
The paper analyzes the methods of temperature measurements of cooling the high-temperature bodies in liquids. Experimental studies on cylindrical samples with different embedding of thermocouples have been carried out in three liquids. It is shown that even in the case of cooling in saturated liquids, external thermocouples, whose electrodes play the role of cooling fins, distort the measured temperatures significantly. Using external thermocouples, it is impossible to record correctly the rate of hot body cooling in liquid and the temperature of transition of cooling to an intensive regime. Using only a central thermocouple is permissible at low Bio numbers. However, even in this case, with intensive cooling, the difference between the temperatures of the center and the surface can reach several tens of degrees. With a decrease in the thermal conductivity of a sample and an increase in its linear dimensions, the temperature gradient increases (especially at intense cooling), and the correct physical interpretation of the process becomes impossible.
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