Taylor bubbles (known also as slug flows or segmented flows) are characterized by elongated bullet-like shape vapor bubbles moving in a capillary tube. These capillaries are often employed in compact heat transfer devices to provide efficient cooling of electronics (heat pipes) and steam generation in nuclear reactors, for instance. While the bubble flows in the tube, a liquid film forms between the heated wall and the liquid-vapor interface. Its thickness can range from a few μm up to several tens of microns, representing a low resistance to the heat transfer from the wall towards the liquid-vapor interface thus allowing a large amount of heat exchange with the wall at evaporation or condensation. Taylor bubble flow is therefore a desired flow pattern inside capillaries aiming at high heat transfer capabilities. The physical understanding of Taylor bubble flows requires the comprehension of several physical phenomena such as dewetting dynamics, formation of thin liquid films, heat transfer and phase change. Experiments performed to measure the thickness of liquid film, its drying, wall temperature and heat flux are therefore vital to validate physical models developed for detailed numerical studies that can improve our understanding of these phenomena. Even though a wide range of studies are available in the current literature, precise measurements of the liquid film and the effects associated to the flow of two Taylor bubbles flowing near to each other are some examples of still lacking knowledge on this topic. In this context, a novel experimental installation is being developed to study Taylor bubbles rising in a capillary channel. In this particular setup, we aim at exploring the fundamental aspects of the film formation, the thickness profile along the bubble and its dynamics in specific conditions still not fully understood. The experimental results will be used to validate numerical simulations that will be performed in the framework a following PhD thesis as a continuation of this internship work.   

The selected candidate will:

·         Perform a literature review.

·         Execute experimental tests of Taylor bubble flow. 

·         Post-process the data using image treatment tools.

·         Interpret the results.  

·         Present and discuss the findings during meetings and write a final report.

The candidate is a student who has a good knowledge on fluid mechanics and optics. He/She is highly motivated to perform an experimental work with state-of-the-art optical instrumentation and wants to pursue a PhD after the internship by complementing the experiments with numerical simulations. Programming skills using Matlab and image treatment tools are required.