Study of nucleate boiling in microgravity conditions, aplicated to the ArineV cryogenics tanks

Ce rapport de thèse porte sur une étude expérimentale et théorique de l'ébullition en microgravité. Les expériences furent réalisées en condition de gravité terrestre, en vol parabolique et en fusée-sonde. Les expériences en vol parabolique ont montré l'influence de divers paramètres sur le transfert thermique et ont mis en évidence les mécanismes contrôlant le transfert thermique. De l'écriture des équations gouvernant ces mécanismes et de l'identification des échelles caractéristiques, une corrélation permettant d'estimer le transfert de chaleur lors de l'ébullition en microgravité pour une large gamme de fluide est bâtie. L'expérience en fusée-sonde a permis d'étudier l'influence des gaz incondensables et notamment de la convection Marangoni sur le comportement de l'ébullition et sur le transfert thermique.Between the different propulsion phases, the Ariane V rocket passes through microgravity periods and solar radiation can induce boiling in its cryogenics tanks. Experiments were performed during 6 parabolic flights and in a sounding rocket to study pool boiling in microgravity. In the parabolic flight experiments, the influence of pressure, subcooling and surface roughness was studied. It is showed that subcooling has a weak effect on microgravity boiling heat transfer, and that roughness is an important factor also in microgravity. Detailed results on the behavior of bubbles and on the superheated liquid layer show that the heat transfer mechanisms can be divided in two groups : the primary mechanisms which directly take energy from the wall and the secondary mechanisms which transport the energy stored in the fluid by the primary mechanisms, from the vicinity of the wall to the bulk liquid. The secondary mechanisms appear not to limit primary mechanism heat transfer which explains the weak influence of gravity on heat transfer. From the study of equations governing primary mechanisms and the definition of new scales, a correlation is built to predict heat transfer in microgravity for a wide variety of fluids. In the sounding rocket experiment, the influence of non-condensable gases was studied. The existence of two regimes of boiling heat transfer with non-condensable gas is established. The temperature in the primary bubble is directly measured and the influences of both Marangoni convection and non-condensable gas on both heat transfer and bubble growth are also considered