scholarly journals Prediction of Droplet Production Speed by Measuring the Droplet Spacing Fluctuations in a Flow-Focusing Microdroplet Generator

Micromachines ◽  
2019 ◽  
Vol 10 (12) ◽  
pp. 812 ◽  
Author(s):  
Wen Zeng ◽  
Dong Xiang ◽  
Hai Fu
Keyword(s):  
Fluid Flow ◽  
Efficient Method ◽  
Immiscible Fluids ◽  
Droplet Generation ◽  
Flow Focusing ◽  
Flow Conditions ◽  
Flow Rates ◽  
Wide Range ◽  
Droplet Production ◽  
Monodisperse Droplets

In a flow-focusing microdroplet generator, by changing the flow rates of the two immiscible fluids, production speed can be increased from tens to thousands of droplets per second. However, because of the nonlinearity of the flow-focusing microdroplet generator, the production speed of droplets is difficult to quantitatively study for the typical flow-focusing geometry. In this paper, we demonstrate an efficient method that can precisely predict the droplet production speed for a wide range of fluid flow rates. While monodisperse droplets are formed in the flow-focusing microchannel, droplet spacing as a function of time was measured experimentally. We discovered that droplet spacing changes periodically with time during each process of droplet generation. By comparing the frequency of droplet spacing fluctuations with the droplet production speed, precise predictions of droplet production speed can be obtained for different flow conditions in the flow-focusing microdroplet generator.

scholarly journals Precise detection of the size of monodisperse droplets considering the fluctuations induced by the droplet generation process

2021 ◽  
Author(s):  
Wen Zeng ◽  
Hai Fu
Keyword(s):  
Droplet Size ◽  
Detection Method ◽  
Droplet Microfluidics ◽  
Generation Process ◽  
Time Varying ◽  
Electrical Detection ◽  
Flow Focusing ◽  
Wide Range ◽  
Droplet Production ◽  
Monodisperse Droplets

Abstract For droplet microfluidics, the electrical-detection method which can precisely detect the size of monodisperse droplets is demonstrated in this paper. In a Flow-focusing microdroplet generator, three pairs of the microelectrodes are allocated along the microchannel, and during the passing-by process of each droplet, both the length, the velocity and the production speed of the droplets can be obtained from the experimental measurements of the time-varying capacitance between each pair of the microelectrodes. Particularly, for different geometries of the Flow-focusing microchannel, the method of the electrical-detection is validated experimentally over a wide range of the typical conditions of monodisperse droplet production. In addition, the droplet size measured by the electrical-detection method is compared with that by the method of image processing, and the detection precision of the electrical-detection method is verified experimentally. Most importantly, by calculating the root-mean-square value of the droplet lengths for three pairs of the microelectrodes, the detection precision of the droplet size can be increased drastically.

scholarly journals Modeling of Droplet Generation in a Microfluidic Flow-Focusing Junction for Droplet Size Control

Micromachines ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 590
Author(s):  
Ali M. Ibrahim ◽  
Jose I. Padovani ◽  
Roger T. Howe ◽  
Yasser H. Anis
Keyword(s):  
Numerical Model ◽  
Droplet Size ◽  
Size Control ◽  
Continuous Phase ◽  
Immiscible Fluids ◽  
Droplet Generation ◽  
Flow Rate Ratio ◽  
Flow Focusing ◽  
Flow Rates ◽  
Microfluidic Flow

In this paper, we study the parameters that affect the generation of droplets in a microfluidic flow-focusing junction. Droplets are evaluated based on the size and frequency of generation. Droplet size control is essential for microfluidic lab-on-a-chip applications in biology, chemistry, and medicine. We developed a three-dimensional numerical model that can emulate the performance of the physical system. A numerical model can help design droplet-generation chips with new junction geometries, different dispersed and continuous phase types, and different flow rates. Our model uses a conservative level-set method (LSM) to track the interface between two immiscible fluids using a fixed mesh. Water was used for the dispersed phase and mineral oil for the continuous phase. The effects of the continuous-to-dispersed flow rate ratio (Qo/Qw) and the surfactant concentration on the droplet generation were studied both using the numerical model and experimentally. The numerical model was found to render results that are in good agreement with the experimental ones, which validates the LSM model. The validated numerical model was used to study the time effect of changing Qo/Qw on the generated droplet size. Properly timing when the flow rates are changed enables control over the size of the next generated droplet, which is useful for single-droplet size modulation applications.

scholarly journals Negative Pressure Provides Simple and Stable Droplet Generation in a Flow-Focusing Microfluidic Device

Micromachines ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 662
Author(s):  
Nikita A. Filatov ◽  
Anatoly A. Evstrapov ◽  
Anton S. Bukatin
Keyword(s):  
Microfluidic Device ◽  
Negative Pressure ◽  
Low Cost ◽  
Control Valve ◽  
Droplet Microfluidics ◽  
Droplet Generation ◽  
Electric Signal ◽  
Absolute Pressure ◽  
Flow Focusing ◽  
Wide Range

Droplet microfluidics is an extremely useful and powerful tool for industrial, environmental, and biotechnological applications, due to advantages such as the small volume of reagents required, ultrahigh-throughput, precise control, and independent manipulations of each droplet. For the generation of monodisperse water-in-oil droplets, usually T-junction and flow-focusing microfluidic devices connected to syringe pumps or pressure controllers are used. Here, we investigated droplet-generation regimes in a flow-focusing microfluidic device induced by the negative pressure in the outlet reservoir, generated by a low-cost mini diaphragm vacuum pump. During the study, we compared two ways of adjusting the negative pressure using a compact electro-pneumatic regulator and a manual airflow control valve. The results showed that both types of regulators are suitable for the stable generation of monodisperse droplets for at least 4 h, with variations in diameter less than 1 µm. Droplet diameters at high levels of negative pressure were mainly determined by the hydrodynamic resistances of the inlet microchannels, although the absolute pressure value defined the generation frequency; however, the electro-pneumatic regulator is preferable and convenient for the accurate control of the pressure by an external electric signal, providing more stable pressure, and a wide range of droplet diameters and generation frequencies. The method of droplet generation suggested here is a simple, stable, reliable, and portable way of high-throughput production of relatively large volumes of monodisperse emulsions for biomedical applications.

scholarly journals Simultaneous Droplet Generation with In-Series Droplet T-Junctions Induced by Gravity-Induced Flow

Micromachines ◽  
2021 ◽  
Vol 12 (10) ◽  
pp. 1211
Author(s):  
Khashayar Bajgiran ◽  
Alejandro Cordova ◽  
Riad Elkhanoufi ◽  
James Dorman ◽  
Adam Melvin
Keyword(s):  
Single Cell ◽  
High Throughput ◽  
Droplet Diameter ◽  
Droplet Microfluidics ◽  
Droplet Generation ◽  
Single Experiment ◽  
Flow Rates ◽  
Wide Range ◽  
Significant Difference ◽  
Gravity Driven Flow

Droplet microfluidics offers a wide range of applications, including high-throughput drug screening and single-cell DNA amplification. However, these platforms are often limited to single-input conditions that prevent them from analyzing multiple input parameters (e.g., combined cellular treatments) in a single experiment. Droplet multiplexing will result in higher overall throughput, lowering cost of fabrication, and cutting down the hands-on time in number of applications such as single-cell analysis. Additionally, while lab-on-a-chip fabrication costs have decreased in recent years, the syringe pumps required for generating droplets of uniform shape and size remain cost-prohibitive for researchers interested in utilizing droplet microfluidics. This work investigates the potential of simultaneously generating droplets from a series of three in-line T-junctions utilizing gravity-driven flow to produce consistent, well-defined droplets. Implementing reservoirs with equal heights produced inconsistent flow rates that increased as a function of the distance between the aqueous inlets and the oil inlet. Optimizing the three reservoir heights identified that taller reservoirs were needed for aqueous inlets closer to the oil inlet. Studying the relationship between the ratio of oil-to-water flow rates () found that increasing resulted in smaller droplets and an enhanced droplet generation rate. An ANOVA was performed on droplet diameter to confirm no significant difference in droplet size from the three different aqueous inlets. The work described here offers an alternative approach to multiplexed droplet microfluidic devices allowing for the high-throughput interrogation of three sample conditions in a single device. It also has provided an alternative method to induce droplet formation that does not require multiple syringe pumps.

Modeling of Droplet Generation by a Modified T-Junction Device Using COMSOL

2014 ◽  
Vol 705 ◽  
pp. 112-116 ◽  
Author(s):  
Lei Lei ◽  
Hong Bo Zhang ◽  
Donald J. Bergstrom ◽  
Bing Zhang ◽  
Wen Jun Zhang
Keyword(s):  
Numerical Study ◽  
Cross Flow ◽  
Droplet Generation ◽  
Comsol Multiphysics ◽  
Generation Process ◽  
Flow Conditions ◽  
Key Factors ◽  
Flow Rates ◽  
Junction Device ◽  
Simulation Results

This paper presents a numerical study of the formation of droplets in a novel two-dimensional T-junction device by using a commercial CFD package: COMSOL Multiphysics. Numerical simulations were carried out for different flow conditions. Different flow rates lead to four regimes: continuous flow, droplet generation, detached, and stalled. The capillary number of the cross-flow turns out to be the key factors in the droplet generation process. The simulation results are validated by comparison to the existing experimental data.

scholarly journals Experimental Study of The Influence of Fluid Flow Rate on The Risk of Rock Destruction

2021 ◽  
Author(s):  
Sudad H Al-Obaidi
Keyword(s):  
Fluid Flow ◽  
Flow Rate ◽  
Design Flow ◽  
Fluid Flow Rate ◽  
Reservoir Properties ◽  
Rock Destruction ◽  
Flow Rates ◽  
Wide Range ◽  
Deformation Properties ◽  
Gas Fields

The stresses acting in the vicinity of wells have a significant impact on the flow properties of the reservoir and, as a result, on the flow rate of oil wells. The magnitude of such stresses depends on the deformation properties of the rock and on the oil pressure at the bottom of the well. In this work, an attempt to study the effect of flow fields (formation flow rate, well flow rates) on rocks in near-wellbore zones was performed. For this purpose, the correlation of such indicators as the fluid flow rate and the risk of destruction of the rocks of the productive deposits of one of the gas fields were experimentally studied. The experiments were performed on chosen core samples with quite wide range of flow and volumetric reservoir properties. It was concluded that the rock samples of the productive deposits of the studied formation do not collapse under the influence of pressure gradients corresponding to the design flow rates.

Numerical Analysis of the Fluid Flow in the First Stage of a Two-Stage Centrifugal Pump With a Vaned Diffuser

2013 ◽  
Vol 135 (7) ◽  
Author(s):  
H. Stel ◽  
G. D. L. Amaral ◽  
C. O. R. Negrão ◽  
S. Chiva ◽  
V. Estevam ◽  
...  
Keyword(s):  
Fluid Flow ◽  
Flow Pattern ◽  
Centrifugal Pump ◽  
Pressure Rise ◽  
Single Equation ◽  
Two Stage ◽  
Vaned Diffuser ◽  
Flow Rates ◽  
Wide Range ◽  
Pump Head

This work presents a numerical investigation of the fluid flow in the first stage of a two-stage centrifugal pump with a vaned diffuser. A computational fluid dynamics (CFD) analysis is performed by using the ANSYS-CFX software for a wide range of volumetric flow rates and also for different rotor speeds. The numerical results are validated against measured values of pressure rise through the impeller and diffuser of the first stage with an overall good agreement. Nevertheless, not only the best efficiency point evaluated numerically is overestimated in comparison with the measured two-stage pump values but also the computed hydraulic efficiency of the first stage. Investigation of the flow pattern for different flow rates reveals that the flow becomes badly oriented for part-load conditions. In such cases, significant levels of turbulence and blade orientation effects are observed, mainly in the diffuser. In spite of different flow rates or rotor speeds, the flow pattern is quite similar if the flow dimensionless coefficient is kept constant, showing that classical similarity rules can be applied in this case. By using such rules, it was also possible to derive a single equation for the pump head to represent the whole operational range of the pump.

scholarly journals Flow Conditions for PATs Operating in Parallel: Experimental and Numerical Analyses

Energies ◽  
2019 ◽  
Vol 12 (5) ◽  
pp. 901 ◽  
Author(s):  
Mariana Simão ◽  
Modesto Pérez-Sánchez ◽  
Armando Carravetta ◽  
Helena Ramos
Keyword(s):  
Numerical Models ◽  
Maximum Flow ◽  
Experimental Tests ◽  
Single Mode ◽  
Electrical Equipment ◽  
Average Error ◽  
Flow Conditions ◽  
Flow Rates ◽  
Head Losses ◽  
Wide Range

Micro-hydro systems can be used as a promising new source of renewable energy generation, requiring a low investment cost of hydraulic, mechanical, and electrical equipment. The improvement of the water management associated with the use of pumps working as turbines (PATs) is a real advantage when the availability of these machines is considered for a wide range of flow rates and heads. Parallel turbomachines can be used to optimize the flow management of the system. In the present study, experimental tests were performed in two equal PATs working in parallel and in single mode. These results were used to calibrate and validate the numerical simulations. The analysis of pressure variation and head losses was evaluated during steady state conditions using different numerical models (1D and 3D). From the 1D model, the installation curve of the system was able to be defined and used to calculate the operating point of the two PATs running in parallel. As for the computational fluid dynamics (CFD) model, intensive analysis was carried out to predict the PATs′ behavior under different flow conditions and to evaluate the different head losses detected within the impellers. The results show system performance differences between two units running in parallel against a single unit, providing a greater operational flow range. The performance in parallel design conditions show a peak efficiency with less shock losses within the impeller. Furthermore, by combining multiple PATs in parallel arrangement, a site’s efficiency increases, covering a wide range of applications from the minimum to the maximum flow rate. The simulated flow rates were in good agreement with the measured data, presenting an average error of 10%.

Microchannel Device for Droplet Generation, Mixing, and Phase Separation for Continuous Counter-Current Flow Extraction

2013 ◽  
Author(s):  
Norbert Kockmann ◽  
Alexander Holbach
Keyword(s):  
Phase Separation ◽  
Organic Phase ◽  
Chemical Engineering ◽  
Glass Plate ◽  
Process Intensification ◽  
Droplet Generation ◽  
Operation Conditions ◽  
Wide Range ◽  
Microchannel Device ◽  
Monodisperse Droplets

Process intensification is a major goal in chemical engineering, which is often obtained by miniaturized devices with enhanced heat and mass transfer characteristics. This work shows a microchannel device for liquid-liquid extraction and reactions with integrated droplet generation, enhanced mixing and phase separation. Monodisperse droplets with diameters in the range from 0.3 to 0.7 mm are generated by co-current jet flow with different operating modes of aqueous and organic phase. Flow regime maps indicate operation conditions for small and monodisperse droplets of the organic phase. A glass plate with a single microstructured channel serves for sufficient residence time and intensive mixing between the two phases. At the outlet, a wider channel leads to droplet coalescence and agglomeration at a hydrophobic wall and outlet tube for the organic phase. A complete phase separation was possible over a wide range of flow rates. The closed channel setup of droplet generation, mixing and phase equilibrium, and finally phase separation allows for countercurrent switching of the plates. This arrangement needs additional pumps to overcome the pressure drop over the plates, at least one pump more than the number of plates.

Automation of Process Control in Chemical Plant

2015 ◽  
Vol 2 (1) ◽  
pp. 6-12
Author(s):  
Agus Sugiarta ◽  
Houtman P. Siregar ◽  
Dedy Loebis
Keyword(s):  
Process Control ◽  
Pid Control ◽  
Control Algorithm ◽  
Chemical Engineering ◽  
Chemical Plant ◽  
Raw Material ◽  
Flow Rates ◽  
Material Supply ◽  
Wide Range ◽  
Inherent Problem

Automation of process control in chemical plant is an inspiring application field of mechatronicengineering. In order to understand the complexity of the automation and its application requireknowledges of chemical engineering, mechatronic and other numerous interconnected studies.The background of this paper is an inherent problem of overheating due to lack of level controlsystem. The objective of this research is to control the dynamic process of desired level more tightlywhich is able to stabilize raw material supply into the chemical plant system.The chemical plant is operated within a wide range of feed compositions and flow rates whichmake the process control become difficult. This research uses modelling for efficiency reason andanalyzes the model by PID control algorithm along with its simulations by using Matlab.

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