scholarly journals Liquid Flow and Mass Transfer Behaviors in a Butterfly-Shaped Microreactor

Micromachines ◽  
2021 ◽  
Vol 12 (8) ◽  
pp. 883
Author(s):  
Haicheng Lv ◽  
Zhirong Yang ◽  
Jing Zhang ◽  
Gang Qian ◽  
Xuezhi Duan ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Flow Pattern ◽  
Liquid Flow ◽  
Two Phase Flow ◽  
Flow Behavior ◽  
Dynamics Simulation ◽  
Mixing Efficiency ◽  
Phase Flow ◽  
Two Phase ◽  
Flow Rates

Based on the split-and-recombine principle, a millimeter-scale butterfly-shaped microreactor was designed and fabricated through femtosecond laser micromachining. The velocity fields, streamlines and pressure fields of the single-phase flow in the microreactor were obtained by a computational fluid dynamics simulation, and the influence of flow rates on the homogeneous mixing efficiency was quantified by the mixing index. The flow behaviors in the microreactor were investigated using water and n-butanol, from which schematic diagrams of various flow patterns were given and a flow pattern map was established for regulating the flow behavior via controlling the flow rates of the two-phase flow. Furthermore, effects of the two-phase flow rates on the droplet flow behavior (droplet number, droplet size and standard deviation) in the microreactor were investigated. In addition, the interfacial mass transfer behaviors of liquid–liquid flow were evaluated using the standard low interfacial tension system of “n-butanol/succinic acid/water”, where the dependence between the flow pattern and mass transfer was discussed. The empirical relationship between the volumetric mass transfer coefficient and Reynold number was established with prediction error less than 20%.

Upward Vertical Two-Phase Flow Through an Annulus—Part II: Modeling Bubble, Slug, and Annular Flow

1992 ◽  
Vol 114 (1) ◽  
pp. 14-30 ◽  
Author(s):  
E. F. Caetano ◽  
O. Shoham ◽  
J. P. Brill
Keyword(s):  
Flow Pattern ◽  
Annular Flow ◽  
Two Phase Flow ◽  
Flow Behavior ◽  
Bubble Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Flow Through ◽  
Physical Phenomena ◽  
Good Agreement

Mechanistic models have been developed for each of the existing two-phase flow patterns in an annulus, namely bubble flow, dispersed bubble flow, slug flow, and annular flow. These models are based on two-phase flow physical phenomena and incorporate annulus characteristics such as casing and tubing diameters and degree of eccentricity. The models also apply the new predictive means for friction factor and Taylor bubble rise velocity presented in Part I. Given a set of flow conditions, the existing flow pattern in the system can be predicted. The developed models are applied next for predicting the flow behavior, including the average volumetric liquid holdup and the average total pressure gradient for the existing flow pattern. In general, good agreement was observed between the experimental data and model predictions.

Predicting Compositional Two-Phase Flow Behavior in Pipelines

1986 ◽  
Vol 108 (3) ◽  
pp. 207-210 ◽  
Author(s):  
H. Furukawa ◽  
O. Shoham ◽  
J. P. Brill
Keyword(s):  
Mass Transfer ◽  
Computational Algorithm ◽  
Two Phase Flow ◽  
Flow Behavior ◽  
Phase Flow ◽  
Temperature Profiles ◽  
Balance Equations ◽  
Two Phase ◽  
Liquid Phases ◽  
Retrograde Condensation

A computational algorithm for predicting pressure and temperature profiles for compositional two-phase flow in pipelines has been developed. The algorithm is based on the coupling of the momentum and energy balance equations and the phase behavior of the flowing fluids. Mass transfer between the gas and the liquid phases is treated rigorously through flash calculations, making the algorithm capable of handling retrograde condensation. Temperatures can be predicted by applying the enthalpy balance equation iteratively. However, it was found that the explicit Coutler and Bardon analytical solution for the temperature profile yields nearly identical results for horizontal and near horizontal flow.

scholarly journals Mixing Efficiency Analysis on Droplet Formation Process in Microchannels by Numerical Methods

Processes ◽  
2019 ◽  
Vol 7 (1) ◽  
pp. 33 ◽  
Author(s):  
Jin-yuan Qian ◽  
Xiao-juan Li ◽  
Zhi-xin Gao ◽  
Zhi-jiang Jin
Keyword(s):  
Mass Transfer ◽  
Disperse Phase ◽  
Two Phase Flow ◽  
Efficiency Analysis ◽  
Mixing Efficiency ◽  
Phase Flow ◽  
Transfer Enhancement ◽  
Two Phase ◽  
Mass Transfer Enhancement ◽  
The Cross

Liquid–liquid two-phase flow in microchannels has attracted much attention, due to the superiority of mass transfer enhancement. One of the biggest unresolved challenges is the low mixing efficiency at the microscale. Suitable mixing efficiency is important to promote the mass transfer of two-phase flow in microchannels. In this paper, the mixing efficiency in three junction configurations, including a cross-shaped junction, a cross-shaped T-junction, and a T-junction, is investigated by the volume of fluid (VOF) method coupled with user-defined scalar (UDS) model. All three junction configurations are designed with the same hydraulic diameter of 100 μm. Mixing components are distributed in the front and back parts of the droplet. The mixing efficiency in the droplet forming stage and the droplet moving stage are compared quantitatively. Results show that different junction configurations create very different mixing efficiencies, and the cross-shaped T-junction performs best, with relatively lower disperse phase fractions. However, with an increase of the disperse phase fraction, the cross-shaped junction is superior.

Flow Pattern Transition in Pipes Using Data-Driven and Physics-Informed Machine Learning

2020 ◽  
Author(s):  
André M. Quintino ◽  
Davi L. L. N. da Rocha ◽  
Roberto Fonseca Jr. ◽  
Oscar M. H. Rodriguez
Keyword(s):  
Machine Learning ◽  
Experimental Data ◽  
Flow Pattern ◽  
Liquid Flow ◽  
Two Phase Flow ◽  
Data Driven ◽  
Phase Flow ◽  
Two Phase ◽  
Flow Pattern Transition ◽  
Gas Liquid Flow

Abstract Flow pattern is an important engineering design factor in two-phase flow in the chemical, nuclear and energy industries, given its effects on pressure drop, holdup, and heat and mass transfer. The prediction of two-phase flow patterns through phenomenological models is widely used in both industry and academy. In contrast, as more experimental data become available for gas-liquid flow in pipes, the use of data-driven models to predict flow-pattern transition, such as machine learning, has become more reliable. This type of heuristic modeling has a high demand for experimental data, which may not be available in some industrial applications. As a consequence, it may fail to deliver a sufficiently generalized transition prediction. Incorporation of physics in machine learning is being proposed as an alternative to improve prediction and also to reduce the demand for experimental data. This paper evaluates the use of hybrid-physics-data machine learning to predict gas-liquid flow-pattern transition in pipes. Random forest and artificial neural network are the chosen tools. A database of experiments available in the open literature was collected and is shared in this work. The performance of the proposed hybrid model is compared with phenomenological and data-driven machine learning models through confusion matrices and graphics. The results show improvement in prediction performance even with a low amount of data for training. The study also suggests that graphical comparison of flow-pttern transition boundaries provides better understanding of the performance of the models than the traditional metric

Flow Regime Evolution in Long, Serpentine Microchannels With a Porous Carbon Paper Wall

2008 ◽  
Author(s):  
Julie E. Steinbrenner ◽  
Eon Soo Lee ◽  
Fu-Min Wang ◽  
Chen Fang ◽  
Carlos H. Hidrovo ◽  
...  
Keyword(s):  
Fuel Cell ◽  
Flow Regime ◽  
Liquid Flow ◽  
Liquid Water ◽  
Two Phase Flow ◽  
Pem Fuel Cells ◽  
Carbon Paper ◽  
Phase Flow ◽  
Two Phase ◽  
Flow Rates

An important function of the gas delivery channels in Proton Exchange Membrane (PEM) fuel cells is the evacuation of liquid water created at the cathode. The resulting two-phase flow can become an obstacle to reactant transport and a source of parasitic losses. The present work examines the behavior of two-phase flow in 500 μm × 500 μm × 60 cm channels with distributed water injection through a porous carbon paper wall to gain understanding of the physics of flows relevant to fuel cell water management challenges. Flow regime maps based on local gas and liquid flow rates are constructed for experimental conditions corresponding to current densities between 0.5 and 1 A/cm2 and stoichiometric coefficients from 1 to 4. Flow structures are analyzed along the entire length of the channel. It is observed that slug flow is favored to plug flow at high air flow rates and low liquid flow rates. Stratified flow dominates at high liquid flow rates. Along the axial flow direction, the flow regime consistently transitions from intermittent to wavy to stable stratified flow. This progression is quantified using a parameter of flow progression which characterizes the degree of development of the two-phase flow toward the stable stratified condition. This parameter is discussed in relation to fuel cell operating conditions. It provides a metric for analyzing liquid water removal mechanisms in the cathode channels of PEM fuel cells.

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