Transient temperature field in the chamber for measurement of surface tension of supercooled liquids

Abstract eng:
We present results of mathematical modeling of the transient temperature field in a new chamber developed to measure surface tension of supercooled liquids, and results of auxiliary measurements. The chamber is designed to enable a very fast (within 0.1 s) formation of a homogeneous temperature field (within 0.02 K) after a temperature jump of 60 K. The interior of the chamber of dimensions 20x16x32 mm is filled with dry nitrogen surrounding the measuring capillary and thermometers (very fine thermocouples and RTD’s). The temperature jump is generated by switching the flow direction of the nitrogen serving as a heat transmitting fluid. To reduce the thermal boundary layer near the bottom and ceiling walls, they are made permeable and some gas is sucked out. The flow in the chamber is laminar. We compute the temperature field analytically and numerically, using the commercial software Fluent. The analytical solution results in a series of goniometric and confluent hyperbolic functions. The Fluent code has been adapted to accept special boundary conditions for the velocity and temperature fields at the permeable walls. The results indicate that the design objectives of the experimental device were met.

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