Slug length estimation for gas-liquid slug flow in T-shaped microdevices with liquid film

13th IFAC Symposium on Dynamics and Control of Process Systems, including Biosystems DYCOPS 2022, Busan, Republic of Korea, 14–17 June 2022To realize stable long-term operation of microdevices with gas-liquid slug flow, the slug lengths have to be monitored and controlled, because they influence mass transfer performance. In this study, an experimental investigation was carried out to analyze the gas-liquid slug flow in a T-shaped microdevice with a liquid film. The experimental result showed that the pressures in gas and liquid feeding tubes oscillate periodically along the formation of a pair of gas and liquid slugs. Then, the correlation equation between the liquid film thickness and the number of capillaries was identified on the basis of the experimental data. Based on these results, a method for estimating slug lengths and liquid film thickness from measurements of feed pressure and feed flowrate was developed. The developed method is non-invasive and does not affect slug formation or the manner of gas-liquid slug flow. Its effectiveness was assessed through an experimental case study, and the relative root mean square errors of estimated slug lengths were within 8.5%. The result show that the developed method can be applied to the monitoring of slug lengths

CFD-based Design of Multi-tube Heat Exchange Type Compact Reactor

The production capacity of compact reactors with micrometer or millimeter-scale channels or tubes is increased by numbering-up. In previous studies, a multi-channel plate type reactor and a multi-tube type reactor (MTR) were developed and applied to extraction and reaction operations. Fluid distribution has often been evaluated to design these reactors, but temperature control, which is critical to the reaction, has not been fully considered. It is important to solve this problem and establish a design method. In this study, computational fluid dynamics (CFD)-based design was performed so as to achieve the uniform flow and temperature distributions among the reaction tubes in the MTR, where an exothermic reaction proceeds in each tube with an immobilized catalyst and the reaction temperature is controlled by a coolant flowing outside the tubes. Effects of multi-tube arrangement of lattice, concentric circles and single circle, shell cross-sectional shape of circle, rectangle and ring, and reaction tubes with or without catalyst-free inert sections on the reactor performance were investigated by CFD. The usefulness of a two-step approach of designing the MTR after designing the double-tubular reactor was confirmed through a case study on parallel reactions

マイクロリアクタの形状設計と操作

京都大学0048新制・論文博士博士(工学)乙第12950号論工博第4126号新制||工||1628(附属図書館)32249京都大学大学院工学研究科化学工学専攻(主査)教授 長谷部 伸治, 教授 前 一廣, 教授 吉田 潤一学位規則第4条第2項該当Doctor of Philosophy (Engineering)Kyoto UniversityDFA

Optimal channel design and sensor placement in flow distributors for detecting blockage of parallelized microreactors

When the production capacity of micro chemical plants is increased by numbering-up approach, it is important to realize the uniform flow distribution among the parallelized microreactors. In addition, a blocked microreactor needs to be identified as early as possible to achieve the stable long-term operation of micro chemical plants. In this research, a system that can detect a blocked microreactor by using just two flow sensors is developed. The performance of the developed system is maximized by adjusting the channel size and sensor placement in the flow distributors. The effectiveness of the developed system and the optimal design result is demonstrated by computational fluid dynamics simulation

Operation policy for micro chemical plants with external numbering-up structure

Microreaction Technology IMRET 9: Proceedings of the Ninth International Conference on Microreaction Technology - IMRET9 Special IssueOne of the critical operational issues of micro chemical plants with external numbering-up structure is to keep a uniform flow distribution among parallelized microdevices even when blockage occurs in one or more microdevice. Since it is not practical to install flow controllers in all the microdevices, a simple and effective operation policy against blockage occurrence needs to be developed. In this research, micro chemical plants having four or eight parallelized microdevices are constructed to analyze the influence of blockage on the flow distribution among the parallelized microdevices. The numerical and experimental results show that pressure drop control is superior to total flow control. In addition, two control structures based on pressure drop control, pumping pressure control and pressure drop control over the parallelized section, are investigated. It is clarified that the latter control structure enables us to successfully keep the flow rate in each unblocked microdevice at a normal level when blockage occurs. Pressure drop control over the parallelized section is applied to a micro chemical plant having four parallelized micro heat exchangers, and its validity is demonstrated

ICNMM2007-30109 OPTIMAL SHAPE DESIGN OF PRESSURE-DRIVEN MICROCHANNELS USING ADJOINT VARIABLE METHOD

ABSTRACT The shape of microchannels is an important design variable to achieve the desired performance. Since most microchannels are, at present, designed by trial and error, a systematic optimal shape design method needs to be established. Computational fluid dynamics (CFD) is often used to rigorously examine the influence of the shape of microchannels on heat and mass transport phenomena in the flow field. However, the rash combination of CFD and the optimization technique based on evaluating gradients of the cost function requires enormous computation time when the number of design variables is large. Recently, the adjoint variable method has attracted the attention as an efficient sensitivity analysis method, particularly for aeronautical shape design, since it allows one to successfully obtain the shape gradient functions independently of the number of design variables. In this research, an automatic shape optimization system based on the adjoint variable method is developed using C language on a Windows platform. To validate the effectiveness of the developed system, pressure drop minimization problems of a 180° curved microchannel and a branched microchannel in incompressible flows under constant volume conditions are solved. These design examples illustrate that the pressure drop of the optimally designed microchannels is decreased by about 20 % ~ 40 % as compared with that of the initial shape