Bubble Formation Model Research Articles

A model for steam bubble formation at a submerged nozzle in flowing subcooled water

A non-spherical model for bubble formation coupled with phase change at a submerged nozzle in a flowing subcooled liquid is presented. The interface element approach is applied to describe the dynamics of bubble formation. The bubble is assumed to be surrounded by a thin thermal boundary layer, in which the saturated steam condenses partially as the bubble grows. The effect of a parallel flowing liquid is taken into account by pressure analysis of surrounding liquid. The results computed from present model are compared with the experimental data in the literature as well as with the results computed from other models. The results are in good agreement and show a significant improvement over other models.

Bubble formation at a nozzle submerged in viscous liquids having yield stress

The effects of operating conditions on bubble volume formed from a nozzle submerged in some viscous media with yield stress were experimentally investigated. Pressure fluctuations in the gas chamber accompanied by bubble formation as well as bubble growth curves were measured. By analysis of the time course of pressure change in the gas chamber, the dependency of the gas flow rate into the gas chamber and the chamber volume on the polytropic coefficient of gas in the gas chamber was discussed. To simulate the bubble formation at a single nozzle in a viscous medium having yield stress, the non-spherical bubble formation model was proposed. The calculated bubble volumes agreed relatively well with the experimental ones.

A model for bubble formation and weeping at a submerged orifice

A theoretical model for bubble formation and weeping has been developed. Potential flow theory is used to describe bubble formation at the orifice. The influence of detached, rising bubbles on liquid pressure at the orifice is predicted by Oseen's modification to potential flow. Model predictions of bubble volumes, weeping flow rates and weep points agree well with experimental results.

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

A non-spherical model for bubble formation at an orifice with liquid cross-flow has been developed. The interface element approach is applied to describe the dynamics of bubble formation. The effect of liquid cross-flow on the bubble formation process is modelled by a combination of tilting of the bubble axis and liquid pressure analysis of each element on the bubble interface. Model predictions compare well with the experimental results available in the literature for different conditions of gas flow rate, orifice diameter and liquid cross-flow velocity. Simulated bubble shapes are highly non-spherical, especially at high liquid velocities, and bear a striking resemblance with the experimental high-speed video sequences.

Two-Phase Bubble Formation with Condensation at Nozzle Submerged in Immiscible Liquid.

To make uniformly sized liquid droplets in immiscible liquid, the condensable vapor bubbles uniformly generated from a nozzle were fed into cold continuous liquid phase. To estimate the size of the condensed dispersed droplets, a non-spherical bubble formation model with phase change is proposed. By using the present model, the two-phase bubble growth curves, the bubble shape change, and the molar number of uniformly dispersed droplets were simulated. The simulations correspond relatively well with experimental results.

Bubble formation in cocurrently upward flowing liquid

AbstractThe effects of liquid velocity, nozzle diameter, gas chamber volume and gas flow rate on volumes, shapes and growth curves of bubbles formed at a nozzle submerged in a cocurrently upward flowing liquid in a bubble column were experimentally investigated. The bubble volume decreases with increasing liquid flow velocity. The effect of liquid flow velocity on the volume of bubble increases with an increase in the gas flow rate. To simulate bubble formation at a nozzle submerged in cocurrently upward flowing liquid, a revised non‐spherical bubble formation model was proposed. Bubble volumes, bubble growth curves and shapes experimentally obtained in this study, as well as in previous experimental studies, are well predicted by the present model.

SO2 Bubble Formation at an Orifice Submerged in Water.

To estimate mass transfer rate during bubble formation at an orifice, a theoretical model is proposed for soluble gas bubble formation in liquid by modifying the non-spherical bubble formation model. The absorption rate from pure SO2 gas bubble to water is experimentally measured as well as bubble shape and growth rate. Mass transfer from the gas-liquid interface during bubble growth is described well by the penetration theory. Experimental bubble shape, bubble volume at its detachment from an orifice, growth rate and mass transfer rate are estimated well by the present model.

Behavior of Bubble Formation at Elevated Pressure.

In this study, bubble formation in high pressure systems is investigated. The volume and shape of bubbles formed at an orifice submerged in liquid under high pressure are experimentally measured. To elucidate the bubble formation mechanism and to estimate the bubble volume in high pressure systems, a non-spherical bubble formation model is used. When the volume and shape of the bubble are calculated by the model under highly pressurized conditions, surface tension should be considered as a function of system pressure. The volume and shape of bubble are estimated relatively well by the model, including the change in surface tension with the system pressure.

Bubble formation at orifice in viscoelastic liquids

AbstractTo evaluate the effect of viscoelasticity on bubble formation, four rheological parameters of viscoelastic liquids were defined and measured by a rheometer. The effects of operating conditions and concentration of polyacrylamide aqueous solutions (PAA) as viscoelastic liquids on bubble volume and the growth curve were experimentally measured. A high‐speed video camera showed that the shapes of a bubble growing in vis‐coelastic liquids are not spherical. In this study, a nonspherical bubble formation model was proposed to theoretically estimate the volume, shape and growth curve of bubbles formed from an orifice submerged in viscoelastic liquids which are assumed to follow Maxwell's viscoelastic model. This experimental results in relatively low concentrations of PAA, as well as previous researchers' results, agreed relatively well with the calculated ones by this model.

Bubble formation in flowing liquid under reduced gravity

A great deal of research has been done regarding bubble formation from submerged orifices in liquids under the force of gravity for the design of gas-liquid or gas-liquid-solid contacting equipment. On the other hand, little research has been done concerning bubble formation under reduced gravity conditions. For the basic design of the chemical process systems or life-support systems in space stations and on other planets, it is important to clarify the effects of various factors on the volume and shape of bubbles formed at submerged orifices or nozzles under reduced gravity conditions. In order to disperse adequately bubbles in liquids for mass transfer or chemical reaction processes at relatively low gas flow rates under reduced gravity, it is necessary to force bubbles to become detached from nozzles by external forces. In this study, the liquid flow was used as the external force on bubble formation. The aim of this study is to clarify the behavior of bubble formation in flowing liquids under reduced gravity conditions. We experimentally investigated the effects of gas flow rate, liquid flow velocity, and liquid flow direction (cocurrent, countercurrent or cross-current flow) on bubble formation for a period of 1.2 s under reduced gravity conditions that were produced in the 10 m drop tower at the Hokkaido National Industrial Research Institute at Sapporo in Hokkaido. In order to describe theoretically the bubble formation in flowing liquids under reduced gravity conditions, a revised non-spherical bubble formation model was proposed and the calculated results of the bubble volume were compared with the experimental ones.

Behavior of bubble formation in suspended solution for an elevated pressure system

The effects of various factors on the volumes of bubbles formed in suspended solutions under highly pressurized conditions, such as system pressure, orifice diameter, gas flow rate, gas chamber volume and solid particle concentration, were experimentally studied. A non-spherical bubble formation model considering the effects of solid particle concentration and the highly pressurized system is proposed in order to estimate bubble volumes.

Bubble formation at submerged nozzles for small gas flow rate under low gravity

To develop gas-liquid contacting processes in space stations, bubble formation at a nozzle submerged in liquid under low gravity was discussed. Effects of gas flow rate and surface tension on bubble formation were experimentally investigated over a 10 s period using the drop shaft of Japan Microgravity Center at Kamisunagawa in Japan. When the gas flow rate is comparatively small, a spherical bubble does not detach from the nozzle and continues to expand in quiescent liquids. To theoretically describe bubble formation under low gravity, the non-spherical bubble formation model was used. It is predicted by this model that bubble volume increases under constant flow conditions and a bubble does not detach from a nozzle when the gas flow rate is small in a quiescent liquid. These calculated results of bubble volume and shape agree well with the experimental ones.

The effect of gas-phase density on bubble formation at a single orifice in a two-dimensional gas-fluidized bed

In this study the effect of the gas-phase density on the process of bubble formation at a single orifice in a two-dimensional gas-fluidized bed has been studied experimentally and theoretically. Specifically, a detailed comparison between experimentally observed and theoretically calculated bubble growth curves has been made in the case where the density of the gas injected through the orifice (He and SF 6) differs significantly from the density of the primary fluidizing agent (air). The calculations have been carried out using an earlier developed, first principles hydrodynamic model of gas-fluidized beds which has been extended with a species conservation equation to calculate the composition of the fluidizing gas in the vicinity of the evolving bubbles. Besides, the present experimental and theoretical results were compared with predictions obtained from adapted versions of approximate bubble formation models previously reported in the literature. The advanced hydrodynamic model appears to predict the experimentally observed diameters satisfactorily. In addition, the model correctly predicts the effect of the gas-phase density on the experimentally observed bubble growth. This effect can be explained satisfactorily in terms of the dependence of the interphase momentum transfer coefficient on gas-phase density. Finally, calculations with a three-dimensional version of our hydrodynamic model have been carried out to account for the effect of the front and back wall of the pseudo two-dimensional gas-fluidized bed used in our experiments. Our preliminary computational results indicate that the magnitude of the wall effect strongly depends on the boundary condition enforced for the gas-solid dispersion at these walls. In the case that the no-slip boundary condition was enforced in the calculations for the solid phase, the wall effect was significant and a considerable deviation between computed and experimentally observed bubble growth curves was found. However, when a more realistic partial slip boundary condition for the solid phase was implemented the agreement between theory and experiment could be improved by altering the slip parameter in the partial slip boundary condition expression.

Observations on the Formation of Bubble Dispersion in Doped Tungsten

The effect of mechanical working on the morphological changes of the potassium-containing pores in doped tungsten has been investigated in the early stages of processing. The results are compared with the predictions of the bubble formation model proposed by Moon and Koo and the discrepancy between the theory and experimental facts is explained by the size-dependent deformability of the potassium pores. The results suggest that the small pores are less deformable than the larger ones. Therefore, the number of the bubbles in the rows of the recrystallized wire is less than the theoretically predicted value if the precursors of these bubble rows are very small pores of the ingot.

A theoretical model for the influence of gas properties and pressure on single-bubble formation at an orifice

A number of authors have on the basis of experiments determined that pressure and gas density can have and influence on bubble formation size. Usually this influence is attributed to the gas momentum force, generated by gas flowing into the bubble during its formaiton. In this article the theoretical bubble formation model of Tan and Harris has been (and slightly altered) in order to demonstrate (by comparing model calculations with literature experimental data) that gas properties and pressure can have a considerable influence on single-bubble formation even for conditions where the gas momentum force is still negligible. Finally, these results are also used to explain some observations that have been made in bubble columns.

Pressure fluctuations at individual grid holes of a gas-solid fluidized bed

For most work on bubble formation models in fluidized beds, a single orifice was used. This was not representative of commercial fluidized beds. Therefore, individual grid holes of a multi-orificed grid, in a large column (0.61 m diameter) with FCC catalyst were studied by placing pressure taps on top of individual holes. This is a simple and robust technique. Analysis of the pressure signals gave the average bubbling frequency and the probability distribution of bubbling frequency. The effects of superficial gas velocity, bed height-to-diameter ratio, and grid height were examined. An increase in superficial gas velocity caused an increase in the bubbling frequency. The probability distributions of the bubbling frequencies were log-normal.

Bubble formation under constant-flow conditions

Bubble volumes and shapes formed from a constant-flow nozzle submerged in liquids were measured experimentally. By modifying the previous works, a new constant gas flow condition was proposed. A nonspherical bubble formation model under constant-flow conditions was developed, and the calculated volumes and shapes of bubbles agreed with both the present experimental results and the previous works.

A model for bubble formation from an orifice with liquid cross-flow

Potential flow theory is used to derive a theoretical model for gas bubble formation at an orifice exposed to liquid cross-flow in the plane wall of a duct. Model simulations show good correspondence with experimental data for single-bubble formation, consistent with primary bubble growth being controlled by liquid inertia forces. These forces are quantified in terms of radial velocity and acceleration of the gas—liquid interface, and relative velocity between bubble and liquid. A simple “bubble pressure minimum” criterion yields reasonable prediction of bubble size.

Behavior of bubbles formed from a submerged orifice under high system pressure

The effects of various factors on the volumes and shapes of bubbles formed at a single orifice under highly pressurized conditions, such as system pressure, orifice diameter, gas flow rate and gas chamber volume, were studied. To clarify the bubble formation mechanism, the bubble shape during the bubble formation and bubble volume were measured. The experimental results were compared with the calculated ones by the revised non-spherical bubble formation model presented by the authors and they agreed qualitatively well.

Microcomputer-aided design analysis of evaporating liquid waste from the Melton Valley Storage Tanks (MVSTS)

A microcomputer software package, SFWS (Software for Water Sparging) Version 1.10, has been developed to analyze the sparging of water from the Melton Valley Storage Tanks (MVSTs) located at Oak Ridge National Laboratory (ORNL). SFWS is a menu-driven, user-friendly software package and does not require any previous experience with computer operating systems. The main menu is divided into four submenus consisting of: (a) evaporation of MVSTs, using thermodynamics analysis, (b) evaporation of MVSTs, using heat- and mass-transfer analyses, (c) comparison of the accuracy of this software against the experimental setup at ORNL, and (d) exit. The analysis is carried out based on the mathematical modeling of bubble formation, velocity of rise, and the Nusselt and Sherwood correlation obtained and used for heat- and mass-transfer analysis of gas/liquid two-phase flow (Perry & Green, 1984). The software is developed for the IBM or IBM compatible personal computer and is written in the GW-BASIC language.