Bubble Formation and Detachment Under the Influence of Electric Fields and the Role of Gravity

Boiling is an attractive solution to cooling problems in aerospace engineering because of the high heat transfer coefficients associated with phase change processes. Bubble detachment from an orifice shows some resemblance to bubble departure in boiling. The buoyancy force is responsible for bubble removal from the surface in terrestrial conditions. In space, with the gravity level being orders of magnitude smaller than on earth, bubbles formed during boiling can remain attached to the surface. As a result, the amount of heat removed from the heated surface can decrease, and it is difficult to predict reliably and accurately. The impact of electric fields is investigated with the aim to control bubble behavior and help bubble removal from the surface on which they form in reduced gravity. The behavior of single gas bubbles injected through an orifice into an electrically insulating liquid is studied in reduced gravity under the influence of static electric fields and the results of the experiments are compared with data obtained using a simplified model. The bubble life cycle was 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 suggest that these parameters significantly affect bubble behavior, shape, volume and dimensions at detachment.