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Composition du jury :

Direction and supervision : Directed by Laurence FOURNAISON, Research Director at INRAE, co-directed by Didier DALMAZZONE,Professor at ENSTA IP Paris, and supervised by Anthony DELAHAYE and Pascal CLAIN.

Summary: Refrigeration, which is used in many sectors (food industry, chemicals, medical, transport or housing), accounts for 20% of national electricity consumption. The use of CO2 hydrate slurries as secundary fluids makes it possible to reduce the environmental impact of refrigeration systems. These fluids have a high energy density thanks to their high latent heat of phase change (500 kJ.kg-1hydrates), and their phase change temperature can be adjusted over a wide range (273 - 298 K). Hydrates are ice-like crystals composed of water and containing guest molecules. Understanding and controlling the crystallization kinetics of hydrates remains a major scientific challenge. The first limitation is linked to the slow crystallization kinetics of CO2 hydrates, and the second to the rapid tendency of hydrates to agglomerate during flow. This thesis uses different methods to characterize formation kinetics. Based on a material and heat balance approach during crystallization, key parameters were highlighted to improve transfers. An original device was designed to measure heat transfer during crystallization. A parametric study of the effect of the amount of CO2 in the system, the nature of the stirring mobile and the stirring speed was carried out to identify the best means of intensification. Finally, specific measurements of CO2 mass transfer from the vapour phase to the liquid phase were used to determine the kLaobtained according to the intensification parameters selected.