Electric field effect on bubble detachment in reduced gravity environment
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 an electric field 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. The objective of the present 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. (C) 2006 Elsevier Inc. All rights reserved.