# Contribution à l'étude du changement de phase liquide-vapeur dans des capillaires micrométriques en vue des applications aux étanchéités statiques

Abstract : This investigation is aimed at the understanding of the liquid-vapor phase change in the micrometric paths (leak) formed in the contact region between two rough metallic surfaces (flanges) and a static gasket. The main objective is to evaluate the consequences of the phase change on the value of the flow rate. The leakage geometry is assimilated to a capillary tube of circular section and micron size diameter. The inlet and outlet pressures correspond respectively to liquid and vapor phase conditions. Phase change shall occur when the local pressure along the capillary falls below the saturation pressure because no heat is provided to the fluid across the capillary wall. Conservation and interfacial equations are written in non dimensional form in order to identify, by a phenomenological analysis, the preponderant mechanisms of boiling of R134a in confined spaces. It is shown that phase change occurs by heterogeneous nucleation and that the growth of the resulting vapor bubble is controlled by thermal phenomena. An experimental facility allowing the visualization of phase change in glass capillary tubes of circular cross section with diameters ranging from 20 to 100 $\mu m$ was fabricated. The visualization was performed using either a high speed camera or a webcam. From these visualizations, the consequences of phase change on the flow rate can be estimated. Experiments are conducted using a strict protocol guaranteeing that the equilibrium conditions are reached. According to chronological variations in the downstream pressure, no phase change occurs in the capillary : liquid is superheated till the outlet.
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https://tel.archives-ouvertes.fr/tel-00008547
Contributor : Pascal Jolly <>
Submitted on : Monday, February 21, 2005 - 3:31:46 PM
Last modification on : Thursday, October 29, 2020 - 2:06:02 PM
Long-term archiving on: : Friday, April 2, 2010 - 9:56:04 PM

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• HAL Id : tel-00008547, version 1

### Citation

Pascal Jolly. Contribution à l'étude du changement de phase liquide-vapeur dans des capillaires micrométriques en vue des applications aux étanchéités statiques. Mécanique [physics.med-ph]. Université de Poitiers, 2004. Français. ⟨tel-00008547⟩

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