General rules of bubble formation in viscous liquids in a modified step T-junction microdevice

Sheng, Lin; Chen, Yuchao; Wang, Kai; Deng, Jian; Luo, Guangsheng

doi:10.1016/j.ces.2021.116621

Cited by 36 publications

(28 citation statements)

References 53 publications

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“…According to the characteristic of short bubble formation in this capillary embedded step T‐junction microdevice, we defined three parameters, W neck (the width of the bubble neck), L (the length of the bubble), and W tail (the width of the bubble tail), to describe the bubble generation process, as depicted in Figure 9A. During the bubble formation process, four different forces, include the liquid inertia force, the gas inertia force, the gas–liquid interface tension force, and the viscous shearing force of the liquid phase, are the dominative forces to determine the bubble generation 39,40 . The general evolution rules of the three parameters and a typical dynamic generation process for the N 2 bubble in viscous glycerol–water solution are shown in Figure 9B,C, respectively.…”

Section: Resultsmentioning

confidence: 99%

High‐frequency formation of bubble with short length in a capillary embedded step T‐junction microdevice

et al. 2021

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The performances of slug flow gas–liquid reactors are mostly determined by slug length, especially for the high gas–liquid flow rate ratio condition. This work is the first time to report the short bubble generated with high frequency in a capillary embedded step T‐junction microdevice. The aspect ratio of bubble could be around 0.5 with a frequency higher than 750 s−1 when the gas–liquid flow rate ratio is even higher than 5. The specific surface area of the generated gas–liquid microdispersion system is larger than 10,400 m2/m3. The short bubble formation process includes two periods, and its formation mechanism is mainly because of the relatively higher pressure drop in the step T‐junction, which provides a much higher breakup force for the squeezing flow. Finally, two models are developed to predict the bubble frequency and volume. This work provides a highly promising dispersion technology for the gas–liquid process intensification in microreactors.

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Section: Resultsmentioning

confidence: 99%

High‐frequency formation of bubble with short length in a capillary embedded step T‐junction microdevice

et al. 2021

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“…It shows that the generation frequency in liquids with higher viscosities (89.8 and 151.9 mPa·s) has a negative relationship with the liquid phase flow rate. This phenomenon is primarily for the reason that the liquid phase pressure in the intersection of the T-junction is almost the same as the gas injection pressure (see Figure b), and the decrement degree of the gas phase flow rate is bigger than that of the Taylor bubble volume in this gas–liquid pressure ratio range; thus, the bubble generation frequency rule is in the decrement stage . However, Mi et al reported that the Taylor bubble generation frequency is only increased as the liquid phase flow rate increases in lower viscous liquids with viscosities of 1.0, 2.32, and 6.53 mPa·s under the same constant pressure-driven gas injection method.…”

Section: Resultsmentioning

confidence: 99%

Taylor Bubble Generation Rules in Liquids with a Higher Viscosity in a T-Junction Microchannel

Sheng

Chang

Deng

et al. 2022

Ind. Eng. Chem. Res.

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Generation of bubbles in a T-junction microdevice is vital to microfluidic applications for its advantages of easy fabrication and scaling-up, but the bubble generation in liquids with a higher viscosity in the T-junction is rarely reported for the unstable dispersion behavior under the constant flow rate-driven condition. Accordingly, this work investigates the bubble generation rules in liquids with a higher viscosity (45.6−240.5 mPa•s) under the constant-pressure method. It shows that the bubble formation process in higher viscous liquids contains three stages, expansion, shrinking, and necking, which are obviously different from the filling and squeezing stages in the lower viscous liquid. Importantly, the generation of satellite bubbles as a new bubble generation performance could be observed for the first time in the gas−liquid microdispersion process. The new dispersion mechanism and some novel phenomena are revealed by the interface evolution rules. Finally, a novel mathematical model is developed to predict the bubble length.

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“…The smaller characteristic size and larger specific surface area of microreactors significantly improve heat and mass transfer rates, 8–11 easily meet the requirements of isothermal conditions and effectively control the reaction selectivity. A smaller liquid holdup is conducive to the realization of intrinsic safety.…”

Section: Introductionmentioning

confidence: 99%

Determination of the kinetics of chlorobenzene nitration using a homogeneously continuous microflow

Cui

Song

et al. 2022

AIChE Journal

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The nitration of chlorobenzene with concentrated mixed acids is a fast and highly exothermic process, which suffers from considerable mass transfer resistance and poor heat transfer rates. The reaction kinetics has not been thoroughly reported before. In this work, a continuous‐flow microreactor system and a homogeneous reaction condition were proposed to obtain accurate chlorobenzene nitration kinetics parameters at high mixed acid concentrations. A general model for predicting the observed reaction rate constants was established. With a new method for estimating the equilibria associated with HNO3 in aqueous sulfuric acid, the rate constants based on nitronium ion and activation energies were obtained. Compared with batch reactors, the continuous‐flow microreactor system allows for a sufficient heat transfer efficiency and accurate residence time control, making it possible to study the reaction performance more quickly and sensitively. This work may provide a reliable reference for the kinetic study of similar processes.

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General rules of bubble formation in viscous liquids in a modified step T-junction microdevice

Cited by 36 publications

References 53 publications

High‐frequency formation of bubble with short length in a capillary embedded step T‐junction microdevice

High‐frequency formation of bubble with short length in a capillary embedded step T‐junction microdevice

Taylor Bubble Generation Rules in Liquids with a Higher Viscosity in a T-Junction Microchannel

Determination of the kinetics of chlorobenzene nitration using a homogeneously continuous microflow

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