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...
The formation of air bubbles at constant pressure at submerged orifices was investigated for several liquids. The frequency of formation of the bubbles was determined by the use of a stroboscope, and the rate of gas flow was measured with conventional rotameters. Several orifices having diameters ranging from 0.0794 to 0.397 em. were employed, and the gas flow rate was varied from about 0.1 cc. (at standard conditions)/sec. to about 150 cc./sec. It was found that the formation of bubbles could be correlated with the physical variables of the system by the application of Newton's second law of motion to the bubble at the instant just prior to its release from the orifice.Gas, as a dispersed phase, plays a significant role in numerous physical and chemical processes. This is reflected by the attention given in the literature to the formation of gas bubbles at capillary tubes, orifices, and other devices submerged beneath liquid surfaces (1, 2, 4, 5, 6). I n the experiments described herein the bubbles were formed a t approximately constant pressure within the gas chamber (Figure 1) by passing air through orifices each of which was submerged in several liquids in turn. Correlat>ion of the physical variables involved was achieved through the application of Newton's second law of motion.It his been established that a t very low rates of air flow the kiae of the bubble is nearly independent of the flow rate and is determined primarily by the orifice diameter, the surface tension, and the liquid density. A t higher or intermediate rates of gas flow the size of the bubble becomes dependent upon the rate of gas flow through the orifice, as shown by Davidson et al. (1). A t very high rates of gas flow Leibson et al. (6) demonstrated that the apparent jet of air issuing from the orifice is actuaIly a series of closely spaced, irregular bubbles which undergo further separation upon rising through the liquid.The influence of the volume of the gas chamber (Figure 2) and other physical dimensions of the apparatus on the formation of bubbles has been pointed out by Hughes et al. (4), who also observed that the effect of the chamber volume was not considered in the treatment of many of the data in the literature. Davidson et al. (1) demonstrated that as long as the volume of the gas chamber was less than a critical size it did not affect the formation of bubbles. For a given orifice diameter and gas flow rate the volume of the bubbles formed increased as the chamber volume was increased until approximately constant pressure within the gas chamber was approached. Most of the experiments reported in the literature were carried out with both capillary tubes and relatively small gas-chamber volumes; however in some instances Davidson (1) and Leibson (6) did use chamber volumes large enough to insure the formation a t constant pressure within the gas chamber.Since the majority of the bubble type of contactors employed in industrial applications operate at constant gaschamber pressure and since such data are scarce, this investigati...
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