In situ investigation of liquid films in pulsating heat pipe

[Display omitted] •3D shape of the liquid film inside PHP is reconstructed from experimental data.•Existence of a liquid ridge adjacent to the film contact line is shown.•Both film shape and thickness are explained theoretically.•Film profile theory agrees with the experiment.•Theory for the meniscu...

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Bibliographic Details
Published in:Applied thermal engineering 2017-11, Vol.126, p.1023-1028
Main Authors: Fourgeaud, Laura, Nikolayev, Vadim S., Ercolani, Eric, Duplat, Jérôme, Gully, Philippe
Format: Article
Language:English
Subjects:
Drying
Heat
Heat pipes
High aspect ratio
Interferometry
Liquid films
Optical grid deflection technique
Optics
Oscillation
Physics
Pipes
Pulsating heat pipe
Studies
Taylor bubbles
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Summary:[Display omitted] •3D shape of the liquid film inside PHP is reconstructed from experimental data.•Existence of a liquid ridge adjacent to the film contact line is shown.•Both film shape and thickness are explained theoretically.•Film profile theory agrees with the experiment.•Theory for the meniscus oscillation dynamics is proposed and compared to experiment. To understand functioning of the pulsating (or oscillating) heat pipe (PHP), a liquid film deposited by an oscillating meniscus is studied experimentally inside the simplest, single branch PHP, which is a straight capillary sealed from one end. The PHP capillary is of rectangular section of high aspect ratio. The evaporator is transparent so that the films can be studied by two complementary optical methods: grid deflection method and interferometry. We were able to measure the dynamic film profile during the self induced meniscus oscillations. It has been shown that the PHP films have the same origin as those of the Taylor bubbles; their thickness right after deposition is well described by the classical formulas. The film shape in PHPs differs from the classical wedge-shaped film observed in capillary heat pipes because both of the larger thickness and of the receding triple liquid-vapor-solid contact line. The film slope is very weak, with a growing in time ridge adjacent to the contact line. It is shown that this ridge is the dewetting ridge. Its dynamics is defined mainly by the capillary effects. Such results can be generalized to the conventional multi-branch PHP.
ISSN:1359-4311
1873-5606
DOI:10.1016/j.applthermaleng.2017.01.064