Capillarity and bubble formation in one component liquid-vapor systems

Abstract

An experimental technique is described whereby a wide variety of interfacial phenomena is observed. The system investigated is the one component carbon tetrachloride liquid-vapor system. The principal part of the apparatus is a vertical capillary which opens squarely at the top into a liquid reservoir. A vapor phase is created in the capillary so that it supports the liquid phase above it. Movie photography techniques are used to document the interfacial behavior in the capillary and also document the nature of bubble formation and detachment at the capillary mouth. Studies on very rapidly moving interfaces reveal that deformation of a bubble can be caused by inertial forces acting on it from the liquid phase above. Bubble deformation also occurs when rapidly growing bubbles reattach to the previously detached rising bubble. Movies of the action inside the capillary reveals phase fragmentation occurs in the nature of alternating but short-lived slugs of liquid and vapor. Phase fragmentation also occurs when vapor phase growth begins at a vapor nucleate entrapped in the liquid phase of the capillary. Experimental methods are employed to retard the interfacial movement so that its motion is not readily perceivable to the naked eye. Movie documentation reveals that the retarded interface responds to inherent fluctuations of the system. Fluctuations of a much higher frequency are also noted. Experiments are conducted whereby the retarded interface is slowly disturbed by increasing the heat input to the heat bath around the capillary. Studies of bubble detachment reveals that the bubble undergoes a necking action at the capillary mouth prior to detachment. For slowly forming bubbles, the surface force holding the neck to the capillary mouth can be equated to the buoyancy force acting on the detaching bubble.