CHEMICAL ENGINEERING JOURNAL
·
2020
·
IF 10.652
Yanyan Liu,Qiankun Zhao,Jun Yue,Chaoqun Yao,Guangwen Chen
The mass transfer of slug flow, a widely applied flow pattern in microreactors, is still difficult to predict mainly due to the competing nature between convection and diffusion. This work focused on the influence of the mixing mechanism on the mass transfer performance under gas–liquid and liquid–liquid slug flow, in both continuous slugs and dispersed droplets. Colorimetric study with the resazurin oxidation system was implemented, where the mass transfer resistance was constantly located in the aqueous phase. In the hydrophilic glass microreactor, the convection featured by intensive internal circulation and/or inter-slug leakage flow dominated diffusion, leading to nearly-constant k L a along the channel under given flow rates. However, in the hydrophobic PTFE capillary, the stagnant region constituted a significant share in the aqueous droplet, indicating the prominent role of diffusion against convection therein. As a result, k L a values decreased along the main channel length in fixed operating conditions. Accordingly, prediction models were respectively correlated depending on mixing mechanisms. Moreover, mass transfer contributions from the bubble and droplet formation stages were also investigated. This work is expected to shed light on judicious process design and reliable predictions in microreactor operations.
研究领域:
化学工程
·
生物工程
✓ 已验证
产品关联
DOI
高影响因子
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
·
2017
·
IF 3.458
Chunying Zhu,Yutao Lu,Taotao Fu,Youguang Ma,Huai Z. Li
The gas-liquid two-phase flow and mass transfer with fast chemical reaction in a microchannel were investigated experimentally. Result showed that the bubble volume decreased exponentially with its movement along the channel in a quickly reactable absorbent. The volumetric mass transfer coefficient k L a increased with gas flow rate, while it was insensitive to liquid flow rate under experimental conditions, although the mass transfer coefficient k L increased with liquid flow rate. In slug-bubbly flow regime, the k L decreased when increasing gas flow rate, but inverse tendency was found for slug flow pattern. Both k L and k L a increased with the increase of absorbent concentration. A new correlation for predicting the volumetric mass transfer coefficients k L a was proposed by taking the enhancement factor E of chemical reaction into account.
研究领域:
化学工程
·
传质与反应工程
✓ 已验证
产品关联
DOI
高影响因子
CHINESE JOURNAL OF CHEMICAL ENGINEERING
·
2024
·
IF 3.7
Min An,Chengxiang Wang,Qing Liu,Mengya Wang,Zhirong Yang,Wenpeng Li,Guoli Zhou,Jingtao Wang,Jinli Zhang
Combining the advantages of high efficiency, low-pressure drop, and large throughput, the pore array-enhanced tube-in-tube microchannel (PA-TMC) is a promising microreactor for industrial applications. However, most of the mass transfer takes place in the upstream pore region, while the contribution of the downstream annulus is limited. In this work, helical wires were introduced into the annulus by adhering to the outer surface of the inner tube. Mixing behavior and mass transfer of liquid–liquid two-phase flow in PA-TMC with different helical wires have been systematically studied by a combination of experiments and volume of fluid (VOF) method. The introduction of helical wires improves the overall volumetric mass transfer coefficient K L a by up to 133% and the mass transfer efficiency E by up to 117%. The simulation results show that the helical wire brings extra phase mixing regions and increases the specific interface area, while accelerating the fluid flow and expanding the area of enhanced turbulent dissipation rate. Influences of helical wires in various configurations are compared by the comprehensive index I concerning the pressure drop and mass transfer performance simultaneously and a new correlation between K L a and specific energy consumption ϕ is proposed. This research deepens the understanding of the mixing behavior and mass transfer in the PA-TMCs and provides practical experience for the process intensification of microchannel reactors.
研究领域:
化学工程
·
传热传质学
·
微流控技术
✓ 已验证
产品关联
DOI
高影响因子
ENVIRONMENTAL SCIENCE & TECHNOLOGY
·
2023
·
IF 11.4
Ting Wu,Zhibing Yang,Ran Hu,Yi-Feng Chen
Colloids are ubiquitous in the natural environment, playing an important role in facilitating the transport of absorbed contaminants. However, due to the complexities arising from two-phase flow and difficulties in three-dimensional observations, the detailed mechanisms of colloid transport and retention under two-phase flow are still not well understood. In this work, we visualize the colloid transport and retention during immiscible two-phase flow based on confocal microscopy. We find that the colloid transport and retention behaviors depend strongly on the flow rate and pore/grain size. At low levels of saturation (high flow rate) with the wetting liquid mainly present as pendular rings, the colloids can aggregate at the liquid filaments in small-grain packings and are uniformly distributed in large-grain packings. Through theoretical analysis of the pendular ring geometry, we elucidate the mechanism responsible for the strong dependence of colloid clogging behavior on solid grain size. Our results further demonstrate that even at dilute concentrations, colloids can alter the flow paths and the wetting fluid topology, suggesting a strong two-way coupling dynamics between immiscible two-phase flow and colloid transport and calling for improved predictive models to incorporate the overlooked clogging behavior.
研究领域:
环境科学
·
流体力学
✓ 已验证
DOI
高影响因子
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
·
2018
·
IF 3.891
Yaran Yin,Chunying Zhu,Rongwei Guo,Taotao Fu,Youguang Ma
The dynamics of the gas-liquid two-phase flow are of great significance for the heat and mass transfer performance in a microreactor. In this paper, the flow pattern, void fraction and frictional pressure drop of gas-liquid two-phase flow of CO 2 and MEA/[Bmim][BF 4 ] aqueous solution accompanied by the chemical reaction in a 400 μm square microchannel were investigated experimentally by a high-speed camera and pressure sensor. Three kinds of flow regimes were observed: slug-bubbly flow, slug flow and slug-annular flow. The void fraction and frictional pressure drop in the slug flow regime were mainly investigated, and the applicability of models without consideration of the mass transfer proposed in the literature was assessed. Considering the effect of chemical absorption, two correlations were proposed with the Hatta number for predicting the two-phase void fraction and Chisholm parameter C , which showed good prediction performance.
研究领域:
化学工程
·
传热与传质
✓ 已验证
产品关联
DOI
高影响因子
AICHE JOURNAL
·
2023
·
IF 3.7
Jingwei Zhang,Jianhong Xu,Zhuo Chen
Micro-packed beds have the advantages of excellent heat and mass transfer efficiency and high safety, which have been successfully applied to hydrogenation and oxidation reactions. The dispersion behavior of multiphase flow is closely related to mass transfer and reaction performance. However, the study of dispersion law in micro-packed beds is not sufficient. This work investigated the dispersion behavior of gas–liquid/liquid–liquid two-phase flow in micro-packed beds. The average size and distribution of droplets/bubbles were measured in different systems. Key parameters that affect the dispersion characteristics of the two phases were observed experimentally, including gas/liquid phase flow rate, size of the packing, and physical parameters of the systems. The experimental results showed that gas–liquid and liquid–liquid dispersion processes exhibited different characteristics due to the different physical parameters of liquid and gas as the dispersed phase. The fracture driving force of the gas–liquid process was mainly from the continuous liquid phase, while the fracture driving force of the liquid–liquid process came from both the dispersed phase and the continuous phase.
研究领域:
化学工程
·
传热传质学
✓ 已验证
产品关联
DOI
高影响因子
Reaction Chemistry & Engineering
·
2019
·Vol. 4
·期 4
·715-723
·
IF 3.935
Hao Feng,Xun Zhu,Biao Zhang,Rong Chen,Qiang Liao,Dingding Ye,Jian Liu,Ming Liu,Gang Chen,Kun Wang
The hydrodynamic characteristics of gas–liquid two-phase flow can significantly affect the performance of gas–liquid–solid microreactors. Using nitrobenzene hydrogenation as the reference heterogeneous catalytic reaction, the two-phase reacting flow behavior was visualized and characterized. Distinct differences in the length evolution, migration velocity and residence time of gas slugs were noticed for the reaction and non-reaction cases. The interface retraction of a gas slug was observed, which was mainly due to the hydrogen consumption at the gas pressure accumulation stage. Moreover, effects of the gas and liquid flow rates as well as the inlet nitrobenzene concentration on the two-phase flow behaviors and microreactor performance were also investigated. The results suggested that increasing the gas flow rate could enhance nitrobenzene conversion, but this effect was inhibited by the reduced residence time at high gas flow rates. Higher nitrobenzene concentration could enhance the interface retraction and extend the residence time, and together promote aniline production but in a trade-off with the conversion. This work reveals the intrinsic interaction between two-phase flow behaviors and catalytic reaction in microreactors, which can play a significant role in the development of microreactor technology.
研究领域:
化学工程
·
催化反应工程
✓ 已验证
DOI
高影响因子
JOURNAL OF POWER SOURCES
·
2024
·
IF 8.1
Yuan Zhou,Shaojie Zheng,Xiao Cheng,Liu Liu,Hao Lei,Nianbing Zhong,Zhichao Deng,Wenqian Zhang,Xuefeng He
Direct liquid fuel cells (DLFCs) offer a promising alternative energy solution by directly utilizing "liquid sunshine fuels", thereby avoiding the complexities of hydrogen storage systems. Despite their potential, DLFC performance is often compromised by gas bubble accumulation at the anode, which reduces the active electrochemical surface area and disrupts fuel transport. In this study, we introduce an inspired Janus electrode with combined hydrophobic and hydrophilic properties designed to shorten the gas diffusion pathway, promoting efficient in-situ bubble release and improving mass transfer. Using visualization techniques, finite element analysis, and mechanical modeling, we investigated the dynamic behavior and transport mechanisms of gas bubbles. The results demonstrate that DLFCs equipped with Janus electrodes achieve superior performance at high current densities, reducing voltage fluctuations and optimizing gas-liquid two-phase flow. This work suggests that Janus electrodes can effectively overcome the bubble-induced limitations in conventional DLFCs.
研究领域:
能源科学
·
材料科学
✓ 已验证
产品关联
DOI
高影响因子
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
·
2019
·
IF 4.346
Hao Feng,Xun Zhu,Rong Chen,Qiang Liao
In this work, the gas consumption characteristics were investigated by gas-liquid two-phase flow in a capillary microreactor using the catalytic hydrogenation of nitrobenzene as a reference gas-liquid reaction. Image processing technique was used to measure the gas consumption from the variation in the gas phase through the recorded images. The influence of the inlet nitrobenzene concentration and both the gas and liquid flow rates on the gas consumption and the microreactor performance was investigated. The experimental results showed that there existed a discrete hydrogen consumption process, i.e. the waiting stage and inburst stage. Hydrogen consumption was mainly attributed to the waiting stage in each bubble formation cycle. Minimal hydrogen was consumed in the inburst stage. In addition, there was a clear difference between the H 2 consumption rates under each operating condition. As the gas flow rate and nitrobenzene concentration increased, the H 2 consumption rate was gradually decreased with each successive formation cycle. Although the consumption rate was gradually reduced with each successive formation cycle with increasing liquid flow rate, the downward trend became increasingly gradual and clearly stabilized at 20 μL/min. The microreactor performances under different operating conditions were also investigated. The results showed that the nitrobenzene conversion was first increased and then gradually decreased with increasing the gas flow rate, whereas it was gradually decreased with increasing both the liquid flow rate and nitrobenzene concentration. The results obtained in this work are beneficial for not only understanding process intensification but also promoting the use of microreactor technology in additional industrial applications.
研究领域:
化学工程
·
催化反应
✓ 已验证
产品关联
DOI
高影响因子
AICHE JOURNAL
·
2020
·Vol. 66
·期 8
·e16260
·
IF 3.519
Chong Shen,Qibo Zheng,Minjing Shang,Li Zha,Yuanhai Su
In this work, an automatic liquid–liquidtwo-phase flow pattern recognition platform was developed to help circumvent the difficulties in labor-intensive hydrodynamics studies. Trained by about 30,000 of human-labeled flow pattern images, a convolutional neural network was built with the expert-level ability in the flow pattern recognition tasks and then coupled with automatic pump feeding system and online high-speed camera monitoring system to realize the high-throughput experimentation platform for microchannels. Effects of important factors such as flow rate, viscosity, interfacial tension, and so on were studied, and different flow pattern maps were obtained. With these thousands of flow pattern data in hand, we eventually drew the generalized liquid–liquidtwo-phase flow map and then proposed the relatively prudent criteria for slug flow operation window in the microchannel. This study extended the applications of artificial intelligence on microreactor technology or microfluidics, and in particular facilitated understanding complex hydrodynamics and flow patterns.
研究领域:
微流体技术
·
流体力学
·
人工智能应用
✓ 已验证
产品关联
DOI
高影响因子
INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH
·
2023
·
IF 4.2
Bin Jiang,Rongwei Guo,Taotao Fu,Chunying Zhu,Youguang Ma
For gas–liquid two-phase flow in comb-shaped microchannels, operating conditions could change the flow pattern and the uniformity of flow distribution and further affect the mass transfer performance. In this study, the hydrodynamics and mass transfer of gas–liquid two-phase flow in comb-shaped microchannels are investigated. Four flow patterns are observed: single-phase or foam flow, slug-bubbly flow, slug flow, and compact slug flow. When the flow pattern is slug flow, the flow distribution and velocity distribution in the microchannel are ideal, and its mass transfer performance is close to that of a single microchannel. Before the appearance of slug flow, the uniformity of flow distribution and mass transfer performance are improved with the increase of the ratio of gas–liquid flow rate. After the appearance of slug flow, the uniformity of flow distribution and mass transfer performance are deteriorated with the increase of the ratio of gas–liquid flow rate.
研究领域:
化学工程
·
流体力学
·
微流控
✓ 已验证
产品关联
DOI
高影响因子
CHEMICAL ENGINEERING SCIENCE
·
2022
·
IF 4.889
Chenghao Gao,Sida Ling,Zhuo Chen,Yundong Wang,Jianhong Xu
Droplet microfluidic technology refers to the technique of preparing and controlling microscale monodisperse droplets by shear force and interfacial tension of two immiscible phases accurately, which has a wide range of applications in biomedicine, chemical reaction enhancement, nanoparticle preparation, and other fields due to its efficient mass and heat transfer, easy manipulation, rapid response, and high throughput. In the application of droplet microfluidic technology, coalescence often occurs due to the structural complexity of microchannels, which limits the practical application performance. The mechanism of droplet coalescence has been widely studied in conventional reactors, among which the liquid film drainage theory is the most widely accepted. To achieve accurate control of the droplet coalescence process, there have been many studies on droplet coalescence in microchannels. A variety of microchannel structures have been proposed and the mechanism and influencing factors of double droplets coalescence have been explored. However, most of the existing studies on coalescence are based on cross structures, mainly studying the coalescence of double droplets in confined systems. There is still a lack of research on the coalescence process of droplet swarms, which is more widespread in practical applications. Therefore, this work used the rectangular expansion structure to realize the droplet coalescence and explored the effects of two-phase flow rate, continuous phase viscosity, surfactant concentration, and the size of expanding channel on the droplet coalescence behavior. The coalescence types, probabilities, and size distributions of microdroplet swarms under different factors were summarized. The time distribution of liquid film drainage in the droplet coalescence process and the influence of various factors on it were further analyzed based on the liquid film drainage theory.
研究领域:
微流控技术
·
生物医学工程
✓ 已验证
产品关联
DOI
高影响因子
危险品化学品经营许可证（带存储）