Effect Of Bubble Size Research Articles

Comments on “Role of bubble size for the performance of continuous foam fractionation in stripping mode” by Hofmann et al.

Abstract A recent publication in this journal reported the effect of bubble size on foam fractionation performance. Whilst the bubble size is indeed an important parameter, bubble size measurement in the said article is likely affected by a well-known source of error, namely bubble distortion by the column wall which leads to an erroneous interpretation of the experimental phenomenon. Consequently, the authors resorted to empirical equations with little physical basis to correlate their experimental data, while established two-phase flow theories have been largely overlooked. This letter attempts to clarify such issues.

Dynamics of isolated confined air bubbles in liquid flows through circular microchannels: an experimental and numerical study

Experimental and numerical studies are performed to characterise the dynamics of isolated confined air bubbles in laminar fully developed liquid flows within channels of diameters d = 0.5 mm and d = 1 mm. Water and glycerol are used as the continuous liquid phase, and therefore, a large range of flow capillary numbers 10−4 < Ca < 10−1 and Reynolds numbers 10−3 < Re < 103 are covered. An extensive investigation is performed on the effect of bubble size and flow capillary number on different flow parameters, such as the shape and velocity of bubbles, thickness of the liquid film formed between the bubbles and the channel wall, and the development lengths in front and at the back of the bubbles. The micro-particle shadow velocimetry technique (μPSV) is employed in the experimental measurements allowing simultaneous quantification of important flow parameters using a single sequence of high-speed greyscale images recorded at each test condition. Bubble volume and flow rate of the continuous liquid phase are precisely determined in the post-processing stage using the μPSV images. These parameters are then used as initial and boundary conditions to set up CFD simulations reproducing the corresponding two-phase flow. Simulations based on the volume of fluid technique with the aim of capturing the interface dynamics are performed with both ANSYS Fluent v. 14.5, here augmented by implementing self-defined functions to improve the accuracy of the surface tension force estimation, and ESI OpenFOAM v. 2.1.1. The present approach not only results in valuable findings on the underlying physics involved in the problem of interest but also allows us to directly compare and validate results that are currently obtained by the experimental and computational methods. It is believed that similar methodology can be employed to rigorously investigate more complex two-phase flow regimes in micro-geometries.

An improved free surface electrospinning with micro-bubble solution system for massive production of nanofibers

An improved free surface electrospinning for high throughput of nanofibers by utilizing micro-bubble solution system has been successfully developed in the present paper. Compared with the conventional solution system based free surface electrospinning, more jets were observed to form on the edges of the stepped pyramid shaped spinneret simultaneously and nanofibers similar in quality (diameter, diameter distribution) were produced. In addition, the effect of bubble size on the diameters of nanofibers is experimentally studied, revealing that the smaller bubble size favors the smaller diameter. This novel solution system based free surface electrospinning will benefit to the development of free surface electrospinning.

Effect of bubble size on underwater noise spectra

This paper describes the interpretations of underwater noise spectra of rainfall on water bodies. It uses a simple methodology of measurement of bubbles of various sizes up to 10mm in diameter and the comparison of resonating frequencies of the above bubbles with theoretical calculations. The underwater noise of rainfall is a combined effect of drop impacts and bubble bursting. The rain drop size during actual rainfall varies between 0.8 and 5mm in diameter and the underwater bubble sizes can vary from 0.5mm to 10mm in diameter. The detailed description of the experimental results of the underwater spectrum of natural light rain and artificially generated rain are presented. By analyzing the resonating frequencies of underwater bubbles for different type of rainfall, it is plausible to interpret the underwater noise spectrum of rainfall on water bodies and then predict the amount of rainfall.

Behaviour of bubble clusters in a turbulent flotation cell

The rate of capture of particles decreases as the particle size increases in froth flotation. It has been postulated that the upper size range of particles that can be recovered in conventional machines could be extended by the use of bubble clusters [1].This study is concerned with the behaviour of bubble clusters in turbulent flotation cell. The breakup and re-formation of clusters and the effect of bubble size and impeller speed on the behaviour of clusters have been investigated. The apparatus used was essentially a laboratory flotation cell, agitated by a Rushton turbine. The cell was modified to allow pre-formed clusters to rise out of a fluidized bed and into the path of the rotating impeller. The events were captured using a digital camera, and the images were analysed to give the sizes of the bubbles and clusters.In the first part of the investigation, a collector was used but no frother. Under these conditions, the bubble diameter was effectively controlled by the collector concentration, and it varied considerably. It was found that the sizes of clusters decrease with increasing shear rate at low impeller speeds, and at higher speeds the clusters are broken up into bubbles and particles.In the second part, frother was used at a concentration above the critical coalescence concentration, to control the bubble size, which remained essentially constant at this concentration. The bubbles were too small to be broken by the action of the impeller, so they always remained at the same size. In this case it was found that when the impeller speed was increased, two stages of formation were observed, the fragmentation and equilibrium stages. In the fragmentation stage, at low impeller speeds, the clusters were loose and filamentous, and as the energy input increases, they rupture and re-form. In the second stage, above a critical impeller speed, dense clusters formed whose size was relatively insensitive to the energy input.

Effect of Bubble Size on Aeration Process

Effect of Bubble Size on Aeration Process

The effect of bubble size on the efficiency and economics of harvesting microalgae by foam flotation.

The effect of bubble size and rise velocity on the efficiency of a foam flotation microalgae harvesting unit was determined. Three sparger and input airflow combinations were used: (1) limewood sparger with constant airflow, (2) ceramic flat plate sparger with constant airflow and (3) ceramic flat plate sparger with an oscillating airflow. The ceramic sparger with oscillating flow generated the smallest bubbles within the liquid pool and the largest bubbles within the foam phase. This delivered the highest levels of biomass recovery due to enhanced bubble-algae collision and attachment efficiencies. The smaller bubbles generated by the ceramic sparger under constant or oscillating airflow had significantly faster rise velocities when compared to the larger bubbles produced by the limewood spargers. The faster velocities of the smaller bubbles were due to momentum transfer to the liquid phase. Analyses of the harvest economics revealed that the ceramic flat plate sparger with an oscillating airflow delivered the best overall cost-benefit relationship.

Foam Simulation Faces Several Numerical Challenges

This article, written by Special Publications Editor Adam Wilson, contains highlights of paper SPE 166232, ’Numerical Challenges in Foam Simulation: A Review,’ by W.R. Rossen, SPE, Delft University of Technology, prepared for the 2013 SPE Annual Technical Conference and Exhibition, New Orleans, 30 September-2 October. The paper has not been peer reviewed. Foam simulation brings various numerical challenges. Some of these problems are largely cosmetic, creating, for instance, fluctuating fluxes and pressure gradient but no significant effect on final recovery. Others severely influence the whole progress of the flood. This paper discusses the origin of the challenges, how to recognize them, how they can be mitigated, and whether they arise from a correct representation of foam physics or are the unintended result of attempts to solve other numerical problems. Introduction Injected gas [carbon dioxide (CO2), hydrocarbon gas, nitrogen, or steam] can be very effective at displacing oil in enhanced- oil-recovery (EOR) processes, but ultimate recovery suffers from poor sweep efficiency. Poor sweep efficiency arises from reservoir heterogeneity, viscous instability, and gravity override of gas. Foam can address all three causes of poor sweep efficiency. Foam is a dispersion of gas separated by water films called lamellae that separate the gas into bubbles; the lamellae are stabilized by surfactant. Thus, foam requires the presence of gas, water, and surfactant. Two fundamental approaches exist for representing the effect of foam on gas mobility. Population-balance models introduce lamella density (number of lamellae per unit volume of gas phase) as a separate variable and perform a balance on lamellae at each location in the formation, along with material balances on water, gas, surfactant, and oil. Thus, an additional partial-differential equation must be solved at each location and timestep, along with those for saturations of the phases. The model then represents gas mobility as a function of lamella density and other factors. Local-equilibrium (LE) models assume that the processes of lamella creation and destruction are always and everywhere at local steady state. It is possible to adapt a population-balance model to LE by setting the expressions for lamella creation and destruction equal to each other. Most LE models, however, represent the effect of bubble size implicitly in relations for gas mobility as a function of water and oil saturations, surfactant concentration in the aqueous phase, and other factors. Foam can be injected in at least four ways: 1. In coinjection, gas and aqueous surfactant solution are injected simultaneously from a single well. Foam forms in the surface facilities where the fluids meet, in the tubing, or shortly after the fluids enter the formation. 2. In surfactant-alternating-gas (SAG) injection, gas and surfactant solution are injected in separate slugs from a single well. Foam forms in the formation where gas meets previously injected surfactant solution or when surfactant solution meets previously injected gas. 3. It is possible to dissolve some surfactants directly into supercritical CO2. Then, there is no need to inject aqueous surfactant solution; injected CO2 with dissolved surfactant forms foam as it meets water in the formation. 4. Surfactant solution and gas can be injected simultaneously from different sections of a vertical well (gas injected below the surfactant solution) or from parallel horizontal wells (gas injected from the lower well). As far as we know, this approach has not been tested with foam in the field. Simulating each of these injection methods involves particular challenges.

Power induced by bubbles of different sizes and frequencies on to hollow fibers in submerged membrane systems

To shed light onto the relationship between sparging conditions and fouling control in submerged hollow fiber membranes, the effects of bubble size and frequency on the hydrodynamic conditions induced in membrane system were studied. Two general classes of bubbles were considered: coarse (0.75–2.5 mL) and pulse (100–500 mL). The power transferred (Ptrans) onto membranes could be used to characterise the multiple effects induced under different sparging conditions. Ptrans is proportional to root mean square of shear stress (τrms), the area of zone of influence (i.e. the fraction in the system where high velocity and high vorticity (turbulence) are induced by the bubble) and their rise velocity. At a given sparging rate, the power transferred onto membranes was less with coarse bubble sparging than pulse bubble sparging and increased with the size of pulse bubbles. For all cases, the power transfer efficiency was consistently higher for pulse bubble sparging than for coarse bubble sparging. The power transfer efficiency to the system was greatest for the small pulse bubbles considered when a small amount of power is required for fouling control. However, when fouling is extensive, large pulse bubbles may be required to generate the required amount of power for fouling control.

Modeling investigation of mass transfer of gas–liquid concurrent flow processes

This paper presents a modeling investigation of mass transfer of gas–liquid concurrent flow processes to explore the effect of bubble scale. CO2 capture with MEA aqueous solution is selected as a working system to evaluate the modeling results. The rate-controlling step is first determined and the effects of bubble size, gas–liquid volume ratio and diffusion coefficient on mass transfer coefficients are respectively discussed, with bubble size ranging between 10μm and 1cm and gas–liquid volume ratio ranging between 6.5:1 and 321:1. For both gas-resistance-controlled and liquid-resistance-controlled processes, as bubble size decreases from 1cm to 10μm, the overall mass-transfer coefficient increases by three orders of magnitude and volumetric mass-transfer coefficient increases by six orders of magnitude, indicating the decrease in bubble size intensifies the mass transfer processes both by reducing mass transfer resistance and increasing interfacial area obviously. The modeling results are in good agreement with the experimental data. This study could be useful for designing micro-devices and optimizing gas–liquid microdispersion processes.

The Effect of Bubble-Induced Turbulence on the Interfacial Area Transport in Gas-Liquid Two-Phase Flow

In the present work, two common modelling concepts taking into account the influence of bubbles on the turbulence of the liquid phase with available models in open literature were implemented in the EAGLE (Elaborated Analysis of Gas-Liquid flow Evolution) code and assessed against experimental data of Hibiki et al. (2001). The EAGLE code has been developed at KAERI based on the two-fluid model for a multi-dimensional analysis of two-phase flow with the implementation of non-drag force, standard k-ε turbulence model, and the interfacial area transport equation. In order to investigate the bubble size effect on two-phase flow evolution and to provide a data set for developing the physical models to describe the bubble-induced turbulence effect and also for validating the EAGLE code, a series of local parameter measurements as well as visualization tests were conducted in air-water vertical-upward flow condition in which the initial bubble size is controlled by a specially designed bubble generator. The numerical results and experimental data were compared, analysed and discussed in this paper.

Noncontact Bubble Manipulation in Microchannel by Using Photothermal Marangoni Effect

A noncontact bubble manipulation by an optically induced local surface tension gradient is described in this paper. In microfluidic devices, the effects of interfacial phenomena become dominant with decreasing of the length scale. An appropriate control of the local gradient of the interfacial properties can provide a powerful method for bubble handling in the microfluidic system. Here, the photothermal technique is used to induce the gradient in surface tension around a microbubble. The thermocapillary force around the bubble is induced and controlled by local laser focusing. The bubble in a microchannel filled with silicone oil with varied viscosity was examined to verify experimentally the optical manipulation method of bubbles based on the photothermal Marangoni effect. As a result, three applications of bubble manipulation by using photothermal Marangoni effect are obtained: detachment from channel wall, trapping in liquid phase, and transportation in the channel. Additionally, minimum optical power for the manipulation was evaluated. The effects of bubble size, liquid viscosity, and irradiated optical power on the manipulation characteristics can be summarized by a dimensionless number that is a ratio of the thermocapillary force to viscous drag force for the bubble.

泡沫状電解質を用いた電気めっき法における気泡粒径の効果

泡沫状電解質を用いた電気めっき法における気泡粒径の効果

A Numerical Study on Bubble Detachment from Solid Wall and Formation of Jet inside Detached Bubble

A numerical study dedicated to observe bubble detachment phenomena from solid wall has been carried out. The Comsol Multiphysics's level set method has been chosen to perform numerical simulations. Numerical results are clearly evidencing bubble detachment and formation of jet inside detached bubble, which after deforming bubble maneuver inside with relatively higher velocity. Detachment time is found to be a direct function of bubble size and shows linear behavior for various fluids. Detailed study reveals that there exists a bubble size effect on jet formation.

Acid mist and bubble size correlation in copper electrowinning

The average bubble size and the amount of acid mist generated during copper electrowinning were measured under a variety of operating conditions. In the absence of surfactants, the amount of generated acid mist decreased as the average bubble size increased. In contrast, in the presence of FC-1100, a surfactant typically used to supress acid mist, acid mist showed little correlation with the average bubble size. The significant change in the bubble burst mechanism, due to the presence of surfactant molecules in the solution/air interface, is believed to be the reason for the suppression of the effect of bubble size on acid mist.

CFD analysis of two‐phase turbulent flow in internal airlift reactors

AbstractThe hydrodynamic performance of three internal airlift reactor configurations was studied by the Eulerian–Eulerian k–ε model for a two‐phase turbulent flow. Comparative evaluation of different drag and lift force coefficient models in terms of liquid velocity in the riser and downcomer and gas holdup in the riser was highlighted. Drag correlations as a function of Eötvös number performed better results in comparison to the drag expressions related to Reynolds number. However, the drag correlation as a function of both Reynolds and Eötvös numbers fitted well with experimental results for the riser gas holdup and downcomer liquid velocity in configurations I and II. Positive lift coefficients increase the liquid velocity and decrease the riser gas holdup, while opposite results were obtained for negative values. By studying the effects of bubble size and their shape, the smaller bubbles provide a lower liquid velocity and a gas holdup. The effects of bubble‐induced turbulence and other non‐drag closure models such as turbulent dispersion and added mass forces were analysed. The gas velocity and gas holdup distributions, liquid velocity in the riser and downcomer, vectors of velocity magnitude and streamlines for liquid phase, the dynamics of gas holdup distribution and turbulent viscosity at different superficial gas velocities for different reactor configurations were computed. The effects of various geometrical parameters such as the draft tube clearance and the ratio of the riser to the downcomer cross‐sectional area on liquid velocities in the riser and the downcomer, the gas velocity and the gas holdup were explored. © 2011 Canadian Society for Chemical Engineering

Tuning a multi-fluid model for gas lift simulations in wells

A multi-fluid formulation based on the k–ɛ turbulence closure is used for modeling bubbly flow in vertical pipes. Each bubble-size group is considered as a separate dispersed phase. The current k–ɛ based multi-fluid models suffer from the problem of large overprediction of void fraction peak and lead to satisfactory results in limited ranges. In this study, first, we establish a model for gas lift simulations in wells. For this purpose, we propose new modified lift and wall force coefficients by tuning the model with many experimental databases. As shown here, the tuned multi-fluid model is able to predict flows in all the three bubbly flow subregimes, namely the wall-peak, core-peak, and transition subregimes, with reasonable accuracy. The predictions by the tuned model are compared with other numerical simulations, as well. Finally, the tuned model is used to simulate gas-lift problems in oil wells and the performance of eight empirical and semi-empirical correlations for predicting pressure drop is investigated, carefully. It is observed that, there is a correlation (i.e. Guet, S., Ooms, G., Oliemans, R.V.A., Mudde, R.F., 2004. Bubble size effect on low liquid input drift-flux parameters. Chem. Eng. Sci. 59, 3315–3329) which predicts gravitational pressure drop in very good agreement with the tuned multi-fluid model in all ranges of bubble diameters, including the wall-peak and core-peak regimes.

Effects of Bubble Size in Foam Fractionation on Removal of Organic Carbon, Protein, and Trace Elements from the Closed Recirculating Culture of Japanese Flounder Paralichthys olivaceus

Effects of Bubble Size in Foam Fractionation on Removal of Organic Carbon, Protein, and Trace Elements from the Closed Recirculating Culture of Japanese Flounder <I>Paralichthys olivaceus </I>

Yoon–Luttrell collision and attachment models analysis in flotation and their application on general flotation kinetic model

We theoretically used the models of Yoon and Luttrell for collision and attachment efficiencies to show the effect of fluid flow condition, the effect of bubble size and velocity and particle surface hydrophobicity in flotation system, and in order to demonstrate the effect of particle density on the attachment behavior we incorporate the correct expression for the maximum collision angle developed by Dukhin collision model in the Yoon–Luttrell attachment efficiency applied for two minerals species such as the quartz and chalcopyrite. Then we used the expression of the analytical model that enables the calculation of the flotation rate constant of particles derived by Pyke et al., developed under turbulent condition and with including the efficiency of collision using the generalized Sutherland equation (GSE), the attachment efficiency using modified Dobby–Finch model, and stability of bubble–particle aggregate includes the various forces acting between the bubble and the attached particle. Some results are obtained revealing the positive inertial effect for the quartz and galena particles under defined flotation data conditions by incorporating in the flotation rate constant mentioned above, the collision and attachment efficiency models of Yoon–Luttrell developed for potential flow condition with assuming that the bubble surface is completely mobile and the particle inertia is ignored. The results show also the influence of the increasing of the bubble velocity to determine the particle size range between the models considering the inertial effect and those who ignored the particle Inertia.

Effect of Bubble Size and Angle of Tapering Upriser Pipe on the Performance of Airlift Pumps

Airlift pumps are devices with the ability to lift liquid phase by injecting the gas phase. Parameters that affect the performance of these pumps are divided into two groups. The first group contains design parameters such as diameter of the pipe, tapering angle of the upriser pipe, and the submergence ratio, which is the ratio of immersed length to the total length of the upriser. The second group includes operating parameters such as the gas flow rate, bubble diameter, bubble distribution, and inlet gas pressure. In this research, the performance of an airlift pump is investigated numerically for different submergence ratios and different diameter of the upriser pipe. For this purpose, an airlift pump with a riser length of 914 mm and different diameters (6, 8, and 10 mm) and seven tapering angles (0°, 0.25°, 0.5°, 1°, 1.5°, 2°, and 3°) is numerically modeled and analyzed. Different submergence ratios are used: 0.4, 0.6, and 0.8. The numerical results are compared with the existing experimental data in the literature and show reasonable agreement. The results indicate that decrease in size of the bubble diameter increases mass flow rate of liquid at constant submergence ratios. The present study reports the improved performance of this pump with decrease in bubble size and increase in angle of tapering upriser pipe. Moreover, the results show that the tapering upriser pipe with 3° tapering angle gives the highest efficiency at nearly all submergence ratios. Further, the highest efficiency of the pump is shown to be at the largest submergence ratio.