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Electric Field Effect on Bubble Detachment in Reduced Gravity Environment

DOI: 10.1615/ICHMT.2004.IntThermSciSemin.710
pages 581-586

Estelle Iacona
Laboratoire EM2C du CNRS (UPR 288) et de l'Ecole Centrale Paris, Grande Voie des Vignes, 92295, Châtenay - Malabry, France

Cila Herman
Department of Mechanical Engineering, The Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, U.S.A.

Shinan Chang
Department of Mechanical Engineering, The Johns Hopkins University, 3400 N. Charles Street, Baltimore, Maryland, USA

Zan Liu
Department of Mechanical Engineering, The Johns Hopkins University, 3400 N. Charles Street, Baltimore, Maryland, USA

Résumé

The subject of the present study, the process of bubble detachment from an orifice in a plane surface, shows some resemblance to bubble departure in boiling. Because of the high heat transfer coefficients associated with phase change processes, boiling is utilized in many industrial operations and is an attractive solution to cooling problems in aerospace engineering. In terrestrial conditions, buoyancy is responsible for bubble removal from the surface. In space, the gravity level being orders of magnitude smaller than on earth, bubbles formed during boiling remain attached at the surface. As a result, the amount of heat removed from the heated surface can decrease considerably. The use of electric fields is proposed to control bubble behavior and help bubble removal from the surface on which they form. However, the direct study of bubbles formed during boiling is complex, since heat and mass transfer mechanisms are coupled to bubble dynamics. Our single gas bubble study will explore the possibility to better understand bubble behavior under these conditions. The objective of the study is to investigate the behavior of individual air bubbles injected through an orifice into an electrically insulating liquid under the influence of a static electric field. Bubble life cycles were visualized in terrestrial conditions and reduced gravity. Bubble departure, volume and dimensions at detachment were measured and analyzed for different parameters such as gravity level, electric field magnitude and electric field uniformity. Results show that these parameters significantly affect bubble behavior, shape, volume and dimensions at detachment.

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