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Ebullition nucléée sur des surfaces ultra-polies : Influence de la topographie et du revêtement sur le phénomène de nucléation

Abstract : An experimental study was conducted in order to understand the phenomenon of nucleation in boiling. This study was done on smooth surface or ultra-smooth surface made of aluminum, the working fluid is acetone. The analysis was realized as a function of the topography of the sample, roughness level, and as a function of nanocoating of the surface in order to modify the wettability. The study classed the sample in three categories, depending on the surface condition: the ultra-smooth surface, the ultra-smooth surface with defect and the rough surface. The good characteristics were obtained for the ultra-smooth sample with randomly distributed defects led to the fabrication of ultra-smooth sample with controlled artificial cavity. The results obtained with these latter samples present the best performances. A two-fold improvement over rough surfaces is observed, representing a substantial gain. Although it is the foundation of most theoretical models, the nucleus at the origin of the formation of a bubble has never been observed experimentally because its size exceeds the capacity of the traditional means of measurement. In this memory, an optical method - based on the resonance of plasmons on surfaces with a diffraction grating - is used to study this phenomenon. The experiments demonstrate the ability of this method to measure the temperature variation in the wall of the sample before boiling. Plasmon resonance measurements show that there is no change in the density of the fluid near the wall for overheating close to the boiling point. The nucleation is too fast to be measured. However, first nuclei of condensation were detected by this method, which is a very promising result.
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https://tel.archives-ouvertes.fr/tel-02061369
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Submitted on : Friday, March 8, 2019 - 9:37:06 AM
Last modification on : Wednesday, July 8, 2020 - 12:42:51 PM
Long-term archiving on: : Monday, June 10, 2019 - 10:49:43 AM

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  • HAL Id : tel-02061369, version 1

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Mostafa Al Masri. Ebullition nucléée sur des surfaces ultra-polies : Influence de la topographie et du revêtement sur le phénomène de nucléation. Thermique [physics.class-ph]. Université de Lyon, 2017. Français. ⟨NNT : 2017LYSEI057⟩. ⟨tel-02061369⟩

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