Thèse Experimental Study And Modelling Of Heat Transfer In Flow Boiling H/F - Doctorat.Gouv.Fr

Établissement : Institut National Polytechnique de Toulouse École doctorale : MEGEP - Mécanique, Energétique, Génie civil, Procédés Laboratoire de recherche : IMFT - Institut de Mécanique des Fluides de Toulouse Direction de la thèse : Julien SEBILLEAU ORCID 0000000276495287 Début de la thèse : 2027-09-01 Date limite de candidature : 2026-11-23T23:59:59 This thesis aims to better understand the heat transfer during flow boiling by performing experiments that allow to measure precisely bubble growth and the heat transfer associated. This results will be use to develop accurate models that enable better design and optimization of energy systems. In this purpose a collaboration with the University of Ljubljana which is specialized in laser texturing of surface and its application to boiling and Interfaces team at IMFT that studies flow boiling for more than 25 years will give the good environment to perform this study. Heat transfer in nucleate flow boiling is often predicted by correlations of the literature. These correlations are generally established under narrowly defined conditions involving pressure, heat flux, wall superheat, liquid composition, wall material, and surface topology. These empirical laws therefore remain valid only within the parameter space for which they were developed. This limitation arises from the large number of coupled physical phenomena governing boiling, including heat and mass transfer, bubble vaporisation, transient conduction after bubble departure, and convection between nucleation sites. Advanced heat-transfer models in nucleate boiling [1, 2, 3] account for these mechanisms but require detailed analysis at the scale of individual bubbles.
Boiling liquid-vapor flows are encountered in a wide range of industrial applications, including steam generation in nuclear power plants, electronic component cooling, thermal management systems as heat pump, and air conditioning. In the context of energy efficiency and resource conservation, optimizing the design of these systems has become increasingly important. It is therefore essential to improve our understanding of the local-scale physical mechanisms governing boiling in order to develop accurate models that enable better design and optimization of energy systems. Many studies on boiling are performed with refrigerants such as traditional hydrofluorocarbons (HFCs) with a very high Global Warming Potential. The objective of the thesis is to study experimentally the heat transfer on a heated wall in nucleate flow boiling, both at the scale of one isolated bubble and on several bubbles, by using water instead of classical refrigerants. The dynamics of isolated vapour bubbles nucleated from a wall in a shear flow, in configurations ranging from pool boiling to flow boiling in channels oriented horizontally or vertically (upward and downward). Recent work on air bubbles injected into channel flows has proposed a new detachment criterion [4], which will be extended here to vapor bubbles. In parallel, heat transfer at the bubble foot and around the bubble will be characterised to predict bubble growth rates. Bubbles will be generated from an artificial cavity on a metal foil heated by the Joule effect. Thanks to laser texturing techniques [5] developed at University of Ljubljana bubble nucleation was controlled on a specific location on the heated foil. The bubble growth will be characterised from side view high-speed shadowgraphy. The wall temperature field will be captured using high-speed infrared thermography, allowing the local heat flux to be reconstructed from an energy balance. These coupled measurements optics have already been used at IMFT [6, 7] and at Ljubljana University [8].
The dynamics of isolated vapour bubbles nucleated from a wall in a shear flow, in configurations ranging from pool boiling to flow boiling in channels oriented horizontally or vertically (upward and downward). Recent work on air bubbles injected into channel flows has proposed a new detachment criterion [4], which will be extended here to vapor bubbles. In parallel, heat transfer at the bubble foot and around the bubble will be characterised to predict bubble growth rates. Bubbles will be generated from an artificial cavity on a metal foil heated by the Joule effect. Thanks to laser texturing techniques [5] developed at University of Ljubljana bubble nucleation was controlled on a specific location on the heated foil. The bubble growth will be characterised from side view high-speed shadowgraphy. The wall temperature field will be captured using high-speed infrared thermography, allowing the local heat flux to be reconstructed from an energy balance. These coupled measurements optics have already been used at IMFT [6, 7] and at Ljubljana University [8].

The PhD candidate must have a strong education in fluid mechanics and energy transfer. An appetite for experiments and knowledge in image processing will be necessary to complete the task successfully.

The application should be made on: https://edd-projets.utoulouse.fr/

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