scholarly journals Novel Preparation of Monodisperse Microbubbles by Integrating Oscillating Electric Fields with Microfluidics

Micromachines ◽  
2018 ◽  
Vol 9 (10) ◽  
pp. 497 ◽  
Author(s):  
Anjana Kothandaraman ◽  
Anthony Harker ◽  
Yiannis Ventikos ◽  
Mohan Edirisinghe
Keyword(s):  
Electric Fields ◽  
Bubble Size ◽  
Bubble Diameter ◽  
Size Variation ◽  
Processing Parameters ◽  
Resonance Phenomenon ◽  
Stainless Steel Capillary ◽  
Food Engineering ◽  
Set Up ◽  
Viscous Solutions

Microbubbles generated by microfluidic techniques have gained substantial interest in various industries such as cosmetics, food engineering, and the biomedical field. The microfluidic T-junction provides exquisite control over processing parameters, however, it relies on pressure driven flows only; therefore, bubble size variation is limited especially for viscous solutions. A novel set-up to superimpose an alternating current (AC) oscillation onto a direct current (DC) field is invented in this work, capitalising on the possibility to excite bubble resonance phenomenon and properties, and introducing relevant parameters such as frequency, AC voltage, and waveform to further control bubble size. A capillary embedded T-junction microfluidic device fitted with a stainless-steel capillary was utilised for microbubble formation. Furthermore, a numerical model of the T-junction was developed by integrating the volume of fluid (VOF) method with the electric module; simulation results were attained for the formation of the microbubbles with a particular focus on the flow fields along the detachment of the emerging bubble. Two main types of experiments were conducted in this framework: the first was to test the effect of applied AC voltage magnitude and the second was to vary the applied frequency. Experimental results indicated that higher frequencies have a pronounced effect on the bubble diameter within the 100 Hz and 2.2 kHz range, whereas elevated AC voltages tend to promote bubble elongation and growth. Computational results suggest there is a uniform velocity field distribution along the bubble upon application of a superimposed field and that microbubble detachment is facilitated by the recirculation of the dispersed phase. Furthermore, an ideal range of parameters exists to tailor monodisperse bubble size for specific applications.

Bubble Size Reduction in a Fluidized Bed by Electric Fields

2003 ◽  
Vol 1 (1) ◽  
Author(s):  
Flip Kleijn van Willigen ◽  
J. Ruud van Ommen ◽  
Jan van Turnhout ◽  
Cor van den Bleek
Keyword(s):  
Electric Fields ◽  
Bubble Size ◽  
Fluidized Beds ◽  
Gas Flow ◽  
Bubble Diameter ◽  
Size Reduction ◽  
Length Scale ◽  
Similar Reduction ◽  
Bed Material ◽  
Bed Expansion

The reduction of the size of bubbles can improve both selectivity and conversion in gas-solid fluidized beds. Results are reported of the reduction of bubble size by the application of electric fields to uncharged, polarizable particles in fluidized beds. It is shown how average bubble diameters can be drastically reduced, with little change of the bed expansion. A literature review shows that to maintain smooth fluidization, electric fields in the direction of the gas flow, with a relatively low alternating frequency, are optimal. To measure average bubble diameters, a spectral decomposition technique of pressure fluctuation time series is used. Using this method, based on non-intrusive measurements, a characteristic length scale for bubble diameters can be found. It is shown experimentally, using video analysis, that this length scale is of constant proportionality for a given bed material and bed dimensions. The proportionality of the length scale to bubble diameter is independent of measuring height or gas velocity. With this, we have a tool for measuring bubble diameters in both 2-D and 3-D fluidized beds. Electric fields were applied to fluidized beds using thin wire electrodes placed inside the column. Both 2-D and 3-D columns were tested over a range of frequencies and field strengths. For Geldart A glass beads, an optimal range was determined at 5-20 Hz and 400-1600 V/cm fields. The reduction of bubble diameter was measured to be up to 25% for this system. Larger Geldart B glass particles show a larger reduction of bubble diameters - up to 85%. For these particles, the optimal frequency was at a higher range, 20-70 Hz. At higher frequencies (up to 100 Hz), bubble size reduction is less, but still substantial. Experiments in the 3-D column using Geldart A particles show a similar reduction in bubble diameters.

Fringe fields are important when examining molecular orientation in a cold ammonia beam

2021 ◽  
Author(s):  
Paul Bertier ◽  
Brianna Heazlewood
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Molecular Orientation ◽  
Molecular Beam ◽  
Buffer Gas ◽  
State Distribution ◽  
Experimental Apparatus ◽  
Set Up ◽  
A Minor ◽  
Fringe Fields

Abstract External fields have been widely adopted to control and manipulate the properties of gas-phase molecular species. In particular, electric fields have been shown to focus, filter and decelerate beams of polar molecules. While there are several well-established approaches for controlling the velocity and quantum-state distribution of reactant molecules, very few of these methods have examined the orientation of molecules in the resulting beam. Here we show that a buffer gas cell and three-bend electrostatic guide (coupled to a time-of-flight set-up) can be configured such that 70% of ammonia molecules in the cold molecular beam are oriented to an external electric field at the point of detection. With a minor alteration to the set-up, an approximately statistical distribution of molecular orientation is seen. These observations are explained by simulations of the electric field in the vicinity of the mesh separating the quadrupole guide and the repeller plate. The combined experimental apparatus therefore offers control over three key properties of a molecular beam: the rotational state distribution, the beam velocity, and the molecular orientation. Exerting this level of control over the properties of a molecular beam opens up exciting prospects for our ability to understand what role each parameter plays in reaction studies.

scholarly journals Development of Bubble Characteristics on Chute Spillway Bottom

Water ◽  
2018 ◽  
Vol 10 (9) ◽  
pp. 1129
Author(s):  
Ruidi Bai ◽  
Chang Liu ◽  
Bingyang Feng ◽  
Shanjun Liu ◽  
Faxing Zhang
Keyword(s):  
Size Distribution ◽  
Bubble Size ◽  
Dissipation Rate ◽  
Bubble Diameter ◽  
Bubble Size Distribution ◽  
Impact Zone ◽  
Air Bubble ◽  
Air Supply ◽  
Bubble Characteristics ◽  
The Impact

Chute aerators introduce a large air discharge through air supply ducts to prevent cavitation erosion on spillways. There is not much information on the microcosmic air bubble characteristics near the chute bottom. This study was focused on examining the bottom air-water flow properties by performing a series of model tests that eliminated the upper aeration and illustrated the potential for bubble variation processes on the chute bottom. In comparison with the strong air detrainment in the impact zone, the bottom air bubble frequency decreased slightly. Observations showed that range of probability of the bubble chord length tended to decrease sharply in the impact zone and by a lesser extent in the equilibrium zone. A distinct mechanism to control the bubble size distribution, depending on bubble diameter, was proposed. For bubbles larger than about 1–2 mm, the bubble size distribution followed a—5/3 power-law scaling with diameter. Using the relationship between the local dissipation rate and bubble size, the bottom dissipation rate was found to increase along the chute bottom, and the corresponding Hinze scale showed a good agreement with the observations.

Bubble Formation From Porous Plates in Liquid Cross-Flow

2018 ◽  
Author(s):  
Thomas Shepard ◽  
Eric Ruud ◽  
Henry Kinane ◽  
Deify Law ◽  
Kohl Ordahl
Keyword(s):  
Size Distribution ◽  
Bubble Size ◽  
Bubble Diameter ◽  
Bubble Formation ◽  
Cross Flow ◽  
Rectangular Channels ◽  
Gas Liquid Flow ◽  
Liquid Flows ◽  
Processing Techniques ◽  
The Impact

Controlling bubble diameter and bubble size distribution is important for a variety of applications and active fields of research. In this study the formation of bubbles from porous plates in a liquid cross-flow is examined experimentally. By injecting air through porous plates of various media grades (0.2 to 100) into liquid flows in rectangular channels of varying aspect ratio (1–10) and gas/liquid flow rates the impact of the various factors is presented. Image processing techniques were used to measure bubble diameters and capture their formation from the porous plates. Mean bubble diameters ranged from 0.06–1.21 mm. The present work expands upon the work of [1] and further identifies the relative importance of wall shear stress, air injector pore size and gas to liquid mass flow ratio on bubble size and size distribution.

scholarly journals Acoustic Measurement in a Rectangular Bubble Column to Determine Bubble Size and Interfacial Area for Aqueous Solutions of Ethylene Glycol

2019 ◽  
Vol 8 (2) ◽  
pp. 994-998
Keyword(s):  
Ethylene Glycol ◽  
Bubble Size ◽  
Bubble Column ◽  
Bubble Diameter ◽  
Water System ◽  
Interfacial Area ◽  
Bed Height ◽  
Specific Interfacial Area ◽  
Bubble Sizes ◽  
Distributor Plate

Bubble sizes in bubble column affect the bubble induced mixing of phases, interfacial area and transfer processes. Acoustic technique is used to measure bubble size distribution in a rectangular bubble column of cross section 0.2m x 0.02m for air sparged into water and aqueous solutions of ethylene glycol. Five condenser mikes at intermediate distance of 0.05 m measured above the distributor plate were used to find out the variation of bubble size as the bubbles move up. Sauter-mean bubble diameter and specific interfacial area were estimated from bubble size distribution at several superficial air velocity, static bed height, distance above the distributor plate and ethylene glycol concentration. The BSD exhibited mono-modal distribution and indicated non-uniform homogeneous bubbling regime. Sauter-mean bubble diameter is independent of superficial gas velocity, static bed height and concentration of EG, although, the values were higher than that for air-water system. Sauter-mean bubble diameter decreases as the bubbles move up indicating bubble breakup to take place once the bubbles leave the sparger. The value of interfacial area increases as the static bed height decreases and distance above the distributor plate increases. For air-ethylene glycol solution the values of specific interfacial area are about 200% higher than that observed in case of air-water system. The acoustic technique may be used to measure local values of bubble sizes and specific interfacial area.

scholarly journals Processing parameters for electrospinning poly(methyl methacrylate) (PMMA)/titanium isopropoxide composite in a pump-free setup

2018 ◽  
Vol 1 ◽  
pp. 27
Author(s):  
Leah Nyangasi ◽  
Dickson Andala ◽  
Charles Onindo ◽  
Alphonse Wanyonyi ◽  
Josphine Chepngetich
Keyword(s):  
Methyl Methacrylate ◽  
Polymer Solution ◽  
Solution Concentration ◽  
Titanium Isopropoxide ◽  
Processing Parameters ◽  
Solution Viscosity ◽  
Poly Methyl Methacrylate ◽  
Size And Morphology ◽  
Set Up ◽  
Almost All

Background: Electrospinning is a technique for producing nanofibers, useful in many fields of nanotechnology. The size and morphology of the nanofibers obtained depends on the polymer solution properties, the parameters of the equipment and the conditions of the surrounding. In almost all reported electrospinning set ups, a pump ,which regulates the flow of the polymer solution, has been included as one of the requirements. In this study, the effects of solution concentration, viscosity, voltage and the distance from the tip of the syringe to the aluminum collector on the morphology and diameters of poly(methyl methacrylate)(PMMA) fibers were investigated, using a pump-free electrospinning set up. Methods: Varied PMMA concentration (50 -120 mg/mL), voltage (10-18 kV) and distance (5 – 18 cm) of electrospinning were studied and the optimum electrospinning conditions identified.  PMMA/ titanium isopropoxide solution of ratio 1:2 was prepared, electrospun at optimized conditions (15 kV, 18 cm, Dichloromethane/Dimethylformamide 60:40) and the fibers obtained analyzed using a scanning electron microscope. Results: Solutions of PMMA whose concentrations were less than 50 mg/mL, produced beads on fibers, whereas those at ~ 100 mg/mL formed the best bead-free fibers of diameter 350±50 nm. The results showed a direct dependence of fiber diameter on the solution viscosity. Fibers of larger diameters were obtained when the distance from the tip of the syringe to the aluminum collector and voltage were increased but at higher distances (>18 kV) fewer fibers were collected. When the voltage was steadily increased, the fibers broadened and the diameters were non-uniform due to splaying and splitting. Increasing the distance between the pipette-tip and the collector from 10 to 18 cm resulted in reduced electric field which in turn yielded fewer fibers. Conclusions: The results obtained in a pump free set-up were comparable to those eletrospun in the presence of a pump.

scholarly journals Impact of High-Intensity Pulsed Electric Fields on Bioactive Compounds in Mediterranean Plant-based Foods

2009 ◽  
Vol 4 (5) ◽  
pp. 1934578X0900400 ◽  
Author(s):  
Pedro Elez-Martínez ◽  
Robert Soliva-Fortuny ◽  
Olga Martín-Belloso
Keyword(s):  
Electric Fields ◽  
Bioactive Compounds ◽  
High Intensity ◽  
Processing Parameters ◽  
Heat Treatments ◽  
Processing Technologies ◽  
Nonthermal Processing ◽  
Liquid Products ◽  
Health Related ◽  
Mediterranean Plant

Novel nonthermal processing technologies such as high-intensity pulsed electric field (HIPEF) treatments may be applied to pasteurize plant-based liquid foods as an alternative to conventional heat treatments. In recent years, there has been an increasing interest in HIPEF as a way of preserving and extending the shelf-life of liquid products without the quality damage caused by heat treatments. However, less attention has been paid to the effects of HIPEF on minor constituents of these products, namely bioactive compounds. This review is a state-of–the-art update on the effects of HIPEF treatments on health-related compounds in plants of the Mediterranean diet such as fruit juices, and Spanish gazpacho. The relevance of HIPEF-processing parameters on retaining plant-based bioactive compounds will be discussed.

An Electroscope System Based on Electric Field Measurement Method for UHV Transmission Lines

2009 ◽  
Vol 10 (2) ◽  
Author(s):  
Fan Yang ◽  
Wei He ◽  
Tao Chen ◽  
Xiaochu Luo ◽  
Yongchang Fu
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Transmission Lines ◽  
Field Measurement ◽  
Measurement Method ◽  
Electric Field Measurement ◽  
Set Up ◽  
Global Regularization ◽  
Uhv Transmission Lines ◽  
Internet Network

The paper describes an electric field measurement method based electroscope system to check the electrification state of ultra-high voltage transmission lines, which is composed of three parts: 1) Measuring terminal; 2) Central sever; 3) GPRS and Internet network. The measuring terminal was used to measure the electric field and the location of the measuring points, then the measured data was sent to the central sever by GPRS and Internet network, and requested for an electricity state confirmation.When the sever received a request from a terminal, the electric fields and locations of the measuring points were obtained first, then according to the location of the measuring points, the server searches the corresponding objective transmission lines in the database and read their parameters. According to the parameters of the measuring points and transmission lines, a calculation would be carried out to confirm the electrification state of the transmission lines. For the confirmation calculation, equations for the electric field inverse problem of the transmission lines were set up first, then global regularization and damped Gauss Newton (DGN) method were used to solve the inverse problem.A 500kV double loops transmission line was taken as an example to verify the validity of this method. The electric field and location of 11 measuring points were measured by the measuring terminal firstly, and then sent to the central sever. Electrification state was confirmed by the central sever.

Measurement on Temperature Distribution of Metal Powder Stream in Laser Fabricating

2011 ◽  
Vol 101-102 ◽  
pp. 994-997 ◽  
Author(s):  
Jian Bo Lei ◽  
Zhen Wang ◽  
Yun Shan Wang
Keyword(s):  
Temperature Distribution ◽  
Temperature Gradient ◽  
Thermal Radiation ◽  
Metal Powder ◽  
Visible Region ◽  
Digital Signal ◽  
Processing Parameters ◽  
Measurement Results ◽  
Set Up ◽  
Powder Temperature

In order to study temperature distribution of metal powder stream in laser fabricating, its thermal radiation in visible region was detected by CCD. Based on Planck’s radiation law, the relation between molten powder temperature and its visible thermal radiation could be set up. The thermal radiation image signal of powder stream was transformed to digital signal which was used to analyzing its temperature distribution. It was shown that crosswise dimension of molten powder was about 2.5mm in diameter at the distance of 5mm from power nozzle. The powder out from powder nozzle was heated rapidly by laser. Temperature of powder in central axis regions was the highest which was nearly 2000K at the power of 1100w. The temperature gradient of powder at the edge of laser stream was greatly. The measurement results could be used to optimize the design of powder nozzle and processing parameters of laser fabricating.

Expert System of the Parameter Optimization in the Heavy-Duty Cutting Processing

2006 ◽  
Vol 532-533 ◽  
pp. 1140-1143
Author(s):  
Yu Quan Chen ◽  
Zhen Jia Li ◽  
Deng Hui Zhu ◽  
Zhen Bo Wang ◽  
Jin Xing Guo
Keyword(s):  
Expert System ◽  
Knowledge Base ◽  
Programming Language ◽  
Parameter Optimization ◽  
Computer Technology ◽  
Metal Cutting ◽  
Processing Parameters ◽  
Heavy Duty ◽  
Sql Sever ◽  
Set Up

This paper is focused on using the method of computer technology combined with the knowledge of experts to determine heavy-duty cutting processing parameters according to the relevant theories of metal cutting. This “Expert System of the Parameter Optimization in the Heavy-duty Cutting Processing” is based on the VC++6.0 programming language and SQL Sever 2000. It is divided into two subsystems, turning and milling machining. Taking the turning machining subsystem for example, by using methods of generating expression combined with frame representation, this paper classifies and generalizes related knowledge, and combines the knowledge base with the data base to set up the knowledge base of the subsystem. Also this paper introduces the process of inferential mechanism of the optimizing modules of cutters and machining engagements.

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