Optical Measurement of Void Fraction and Bubble Size Distributions in a Microchannel

Ide, Hideo; Kimura, Ryuji; Kawaji, Masahiro

doi:10.1115/icnmm2006-96100

Cited by 6 publications

(7 citation statements)

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“…Which type describes well the gas hold‐up is mainly dependent on the channel size . Besides the channel size, there are many factors that can affect the gas hold‐up such as fluid property, experimental setup, channel length, and channel geometry . This study investigated the impact of the system pressure.…”

Section: Resultsmentioning

confidence: 99%

The effect of system pressure on gas‐liquid slug flow in a microchannel

et al. 2013

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Characteristics of gas-liquid two-phase flow under elevated pressures up to 3.0 MPa in a microchannel are investigated to provide the guidance for microreactor designs relevant to industrial application. The results indicate that a strong leakage flow through the channel corners occurs although the gas bubbles block the channel. With a simplified estimation, the leakage flow is shown to increase with an increase in pressure, leading to a bubble formation shifting from transition regime to squeezing regime. During the formation process, the two-phase dynamic interaction at the Tjunction entrance would have a significant influence on the flow in the main channel as the moving velocity of generated bubbles varies periodically with the formation cycle. Other characteristics such as bubble formation frequency, bubble and slug lengths, bubble velocities, gas hold-up, and the specific surface area are also discussed under different system pressures.

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Section: Resultsmentioning

confidence: 99%

The effect of system pressure on gas‐liquid slug flow in a microchannel

et al. 2013

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“…Figs. [16][17][18] show the estimates and measurements of five successive gas and liquid slug lengths in Table 2 Estimates and measurements of gas and liquid slug lengths. Table 2, it is confirmed that L G and L L in all cases are estimated accurately by using the proposed estimation method.…”

Section: Verification Of Developed Estimation Methodsmentioning

confidence: 99%

“…In the digital fiber-optic sensor unit, two neighboring optical probes are set along the flow direction at 4 mm interval. Using the signals from two optical probes placed a certain interval, the two signals can be cross-correlated to determine the time lag and then yield instantaneous superficial velocity of slug flow and slug lengths of gas and liquid [18]. According to the obtained superficial velocity, time-varying Q G and Q L are calculated.…”

Section: Gas-liquid Slug Flow In T-shaped Microreactorsmentioning

confidence: 99%

“…Thus, for a long period operation, process monitoring systems that can detect such unacceptable condition are necessary. Optical methods [17,18] and electrical methods [19] have been proposed as the measuring methods of void fraction in microchannels. Though these methods are applicable to the monitoring of slug lengths, there are some drawbacks.…”

Section: Introductionmentioning

confidence: 99%

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Estimation of gas and liquid slug lengths for T-shaped microreactors

Miyabayashi

Tonomura

Hasebe

2015

Chemical Engineering Journal

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h i g h l i g h t sGas and liquid slug lengths in a microreactor are estimated non-invasively. The oscillation cycle time of feed pressure measurement is used for the estimation. The estimation errors of the slug lengths were within 2% of the real values. a b s t r a c tMicroreactors with gas-liquid slug flow have an advantage over the conventional batch reactors in mass transfer between mutually immiscible fluids because of the internal circulation flow within the liquid slug. To realize stable long-term operation of microreactors with gas-liquid slug flow, the slug lengths in the microreactors have to be monitored and controlled, because they influence mass transfer performance. In this study, an experimental investigation is carried out to analyze the formation of gas-liquid slug flow in a T-shaped microreactor. The experimental result shows that the pressures in gas and liquid feeding tubes connected to the microreactor oscillate periodically along the formation of a pair of gas and liquid slugs. Based on this result, a method for estimating slug lengths from feed pressure measurements is developed. The method is non-invasive and does not affect slug formation or the manner of gas-liquid slug flow. Its effectiveness was assessed through experimental case studies using T-shaped microreactors having different gas-liquid confluence angles and different gas and liquid flow rates. The relative root mean square errors of estimated slug lengths were within 2% for one minute operation. The results clearly show that the proposed method can be applied to the real time monitoring of slug lengths.

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“…The studies of bubble dynamics in the microfluidic circumstances with numerical methods were also suggested [27,28]. Some other properties of the gas-liquid two-phase flow in microchannels were studied under different circumstances [29,30]. From the researches above, fundamental explanations and preliminary conclusions for the influence of gas bubbles in microfluidic systems could be drawn.…”

Section: Introductionmentioning

confidence: 97%

Dynamic Characterization of a Valveless Micropump Considering Entrapped Gas Bubbles

Li¹,

Liu

Jiang

2013

Journal of Heat Transfer

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Unexpected gas bubbles in microfluidic devices always bring the problems of clogging, performance deterioration, and even device functional failure. For this reason, the aim of this paper is to study the characterization variation of a valveless micropump under different existence conditions of gas bubbles based on a theoretical modeling, numerical simulation, and experiment. In the theoretical model, we couple the vibration of piezoelectric diaphragm, the pressure drop of the nozzleldiffuser and the compressibility of working liquid when gas bubbles are entrapped. To validate the theoretical model, numerical simulation and experimental studies are carried out to investigate the variation of the pump chamber pressure influenced by the gas bubbles. Based on the numerical simulation and the experimental data, the outlet flow rates of the micropump with different size of trapped gas bubbles are calculated and compared, which suggests the influence of the gas bubbles on the dynamic characterization of the valveless micropump.

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Optical Measurement of Void Fraction and Bubble Size Distributions in a Microchannel

Cited by 6 publications

References 0 publications

The effect of system pressure on gas‐liquid slug flow in a microchannel

The effect of system pressure on gas‐liquid slug flow in a microchannel

Estimation of gas and liquid slug lengths for T-shaped microreactors

Dynamic Characterization of a Valveless Micropump Considering Entrapped Gas Bubbles

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