Formation of air bubbles at orifices submerged beneath liquids

Abstract

The results of two investigations ore reported. Air bubbles were formed at orifices submerged beneath each of fourteen liquids. The surface tension of the liquids varied from 17.8 to 72.4 dynes/cm., and the viscosities ranged from 0.436 to 713 centipoise. In the first investigation, air bubbles were formed a t orifices at various angles of inclination. Orifice diameters ranging from 0.159 to 0.396 cm. were employed. The air-flow rate was varied from 0.1 to 100 CC.(at standard conditions)/sec. The results were obtained with two different apparatuses by three independent investigators.In the second investigation, the effect of the velocity of a liquid flowing post a horizontal, submerged orifice on the formation of air bubbles was determined. Liquid velocities ranging from 0.34 to 2.5 cm/sec., which spanned the region of laminar flow, were employed. Orifice diameters ranged from 0.15875 to 0.3175 cm., air-flow rates from 0.5 to 100 cc/sec. (at standard conditions).It was found that the bubble formation observed in each of these investigations could be correlated with the physical variobles of the system by the application of Newton's second law of motion to the bubble a t the instant just prior to its release from the orifice.Several chemical processes depend upon contacting a liquid as a continuous phase with a gas as a dispersed phase. The bubbling of a gas in some manner through a liquid is common to these processes. Geddes ( 3 ) attempted to calculate the plate efficiency of distillation columns from the size and number of bubbles contacting the liquid on the distillation trays. This article initiated research on the mechanics of bubble formation. Studies have been made by many investigators of the formation of gas bubbles at horizontal orifices and capillary tubes. However, the early workers neglected the effect of the volume of the chamber upstream from the orifice or capillary tube. Hughes et al. (6) have demonstrated the importance of the chamber volume. At large chamber volumes, the bubbles form at essentially constant pressure, which is usually the region of interest in industrial applications. All investigators observed two regions of formation, constantvolume and constant-frequency. In the constant-volume region, the volume of the bubble is nearly constant and almost independent of the flow rate of the gas. As the flow rate of the gas was increased, the frequency tended to approach a constant. In the constant-frequency region, the volume of the bubbles was proportional to the gasflow rate.Davidson and Amick ( 2 ) have described the different regions of bubble formation for horizontal orifices. The formation observed by the authors was essentialIy the same as that described by Davidson and Amick ( 2 ) . When the orifice was in the horizontal position, the shape of the bubbles was spherical at low flow rates, and at higher flow rates the bubble became elongated in the direction perpendicular to the orifice. At other angles, the bubbles were spherical at low flow rates and gradually assumed a hemispherica...

A non-spherical model for bubble formation with liquid cross-flow

“…The bubble center moves normal to the liquid #ow direction by the expansion process, as well as parallel to the liquid #ow due to the drag force. This motion is accounted for in some existing theoretical models by the inclination of the bubble neck or axis (Sullivan et al, 1964;Kim et al, 1994) and the virtual inclination of the nozzle (Kawase & Ulbrecht, 1981). The inclination of bubble axis has been observed in the experiments of Tsuge et al (1981) and Ghosh and Ulbrecht (1989).…”

“…The inclination of bubble axis has been observed in the experiments of Tsuge et al (1981) and Ghosh and Ulbrecht (1989). In our current model, the concept of inclination of bubble axis proposed by Sullivan et al (1964) is adopted. In the case of our non-spherical model, we assume that the bubble central axis tilts at an angle , which is determined by the liquid velocity, gas #ow rate and bubble volume.…”

“…In the case of our non-spherical model, we assume that the bubble central axis tilts at an angle , which is determined by the liquid velocity, gas #ow rate and bubble volume. Following the analysis of Sullivan et al (1964), the center of the bubble moves away in the horizontal direction with a velocity ; J , the uniform velocity of the cross-#owing liquid. Therefore, the bubble is displaced by a distance of (; J < @ /Q) at any instant.…”

“…Stich and Barr (1979) studied the e!ect of liquid cross-#ow on bubble formation at submerged ori"ces experimentally, and proposed an empirical correlation for "nal bubble radius in terms of gas #ow rate and liquid cross-#ow velocity. Sullivan, Hardy and Holland (1964) developed a semi-empirical model based on expansion, vertical displacement and horizontal displacement of a spherical bubble, the volume of which was correlated to experimental values of Reynolds and Froude numbers. Rigby, Evans and Jameson (1995) studied the mechanisms for gas dispersion from an ori"ce situated in the region of non-separated #ow on the surface of a cylinder immersed in liquid cross-#ow and proposed a model for #ow rate of induced gas.…”

A Novel, Inexpensive, and Rugged Probe for Measuring Gas Bubbles in Liquid Metals: Part I. Mathematical Modeling and Laboratory Experiments

“…[8][9][10][11][12][13][14][15] Consequently, the pressure fluctuations within the gas supply line are a complicated function of geometry, gas flow rate, and the physical properties of the two fluids. Schneider and Evans describe the pressure fluctuations that should occur in the limit of very low gas flow rate.…”