• Title/Summary/Keyword: Microchannel Reactor

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Computational Fluid Dynamics Study of Channel Geometric Effect for Fischer-Tropsch Microchannel Reactor (전산유체역학을 이용한 Fischer-Tropsch 마이크로채널 반응기의 채널 구조 영향 분석)

  • Na, Jonggeol;Jung, Ikhwan;Kshetrimayum, Krishnadash S.;Park, Seongho;Park, Chansaem;Han, Chonghun
    • Korean Chemical Engineering Research
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    • v.52 no.6
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    • pp.826-833
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    • 2014
  • Driven by both environmental and economic reasons, the development of small to medium scale GTL(gas-to-liquid) process for offshore applications and for utilizing other stranded or associated gas has recently been studied increasingly. Microchannel GTL reactors have been prefrered over the conventional GTL reactors for such applications, due to its compactness, and additional advantages of small heat and mass transfer distance desired for high heat transfer performance and reactor conversion. In this work, multi-microchannel reactor was simulated by using commercial CFD code, ANSYS FLUENT, to study the geometric effect of the microchannels on the heat transfer phenomena. A heat generation curve was first calculated by modeling a Fischer-Tropsch reaction in a single-microchannel reactor model using Matlab-ASPEN integration platform. The calculated heat generation curve was implemented to the CFD model. Four design variables based on the microchannel geometry namely coolant channel width, coolant channel height, coolant channel to process channel distance, and coolant channel to coolant channel distance, were selected for calculating three dependent variables namely, heat flux, maximum temperature of coolant channel, and maximum temperature of process channel. The simulation results were visualized to understand the effects of the design variables on the dependent variables. Heat flux and maximum temperature of cooling channel and process channel were found to be increasing when coolant channel width and height were decreased. Coolant channel to process channel distance was found to have no effect on the heat transfer phenomena. Finally, total heat flux was found to be increasing and maximum coolant channel temperature to be decreasing when coolant channel to coolant channel distance was decreased. Using the qualitative trend revealed from the present study, an appropriate process channel and coolant channel geometry along with the distance between the adjacent channels can be recommended for a microchannel reactor that meet a desired reactor performance on heat transfer phenomena and hence reactor conversion of a Fischer-Tropsch microchannel reactor.

Pressure Drop and Catalytic Dehydrogenation of NaBH4 Solution Across Pin Fin Structures in a Microchannel Reactor (마이크로 Pin Fin 화학반응기에서 수소화붕소나트륨 수용액의 압력강하 및 탈수소 화학반응 연구)

  • Jung, Ki Moon;Choi, Seok Hyun;Lee, Hee Joon
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.41 no.6
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    • pp.381-387
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    • 2017
  • Dehydrogenation from the hydrolysis of a sodium borohydride ($NaBH_4$) solution has been of interest owing to its high theoretical hydrogen storage capacity (10.8 wt.%) and potentially safe operation. An experimental study has been performed on the catalytic reaction rate and pressure drop of a $NaBH_4$ solution over both a single microchannel with a hydraulic diameter of $300{\mu}m$ and a staggered array of micro pin fins in the microchannel with hydraulic diameter of $50{\mu}m$. The catalytic reaction rates and pressure drops were obtained under Reynolds numbers from 1 to 60 and solution concentrations from 5 to 20 wt.%. Moreover, reacting flows were visualized using a high-speed camera with a macro zoom lens. As a result, both the amount of hydrogenation and pressure drop are 2.45 times and 1.5 times larger in a pin fin microchannel array than in a single microchannel, respectively.

Experimental Study of Interfacial Friction in NaBH4 Solution in Microchannel Dehydrogenation Reactor (마이크로채널 탈수소 화학반응기에서 수소화붕소나트륨 수용액의 계면마찰에 대한 실험연구)

  • Choi, Seok Hyun;Hwang, Sueng Sik;Lee, Hee Joon
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.38 no.2
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    • pp.139-146
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    • 2014
  • Sodium borohydride ($NaBH_4$) is considered as a secure metal hydride for hydrogen storage and supply. In this study, the interfacial friction of two-phase flow in the dehydrogenation of aqueous $NaBH_4$ solution in a microchannel with a hydraulic diameter of $461{\mu}m$ is investigated for designing a dehydrogenation chemical reactor flow passage. Because hydrogen gas is generated by the hydrolysis of $NaBH_4$ in the presence of a ruthenium catalyst, two different flow phases (aqueous $NaBH_4$ solution and hydrogen gas) exist in the channel. For experimental studies, a microchannel was fabricated on a silicon wafer substrate, and 100-nm ruthenium catalyst was deposited on three sides of the channel surface. A bubbly flow pattern was observed. The experimental results indicate that the two-phase multiplier increases linearly with the void fraction, which depends on the initial concentration, reaction rate, and flow residence time.

Analysis on Thermal Effects of Process Channel Geometry for Microchannel Fischer-Tropsch Reactor Using Computational Fluid Dynamics (전산유체역학을 이용한 Fischer-Tropsch 마이크로채널 반응기 반응채널구조에 따른 열적 효과 분석)

  • Lee, Yongkyu;Jung, Ikhwan;Na, Jonggeol;Park, Seongho;Kshetrimayum, Krishnadash S.;Han, Chonghun
    • Korean Chemical Engineering Research
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    • v.53 no.6
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    • pp.818-823
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    • 2015
  • In this study, FT reaction in a microchannel was simulated using computational fluid dynamics(CFD), and sensitivity analyses conducted to see effects of channel geometry variables, namely, process channel width, height, gap between process channel and cooling channel, and gap between process channels on the channel temperature profile. Microchannel reactor considered in the study is composed of five reaction channels with height and width ranging from 0.5 mm to 5.0 mm. Cooling surfaces is assumed to be in isothermal condition to account for the heat exchange between the surface and process channels. A gas mixture of $H_2$ and CO($H_2/CO$ molar ratio = 2) is used as a reactant and operating conditions are the following: GHSV(gas hourly space velocity) = $10000h^{-1}$, pressure = 20 bar, and temperature = 483 K. From the simulation study, it was confirmed that heat removal in an FT microchannel reactor is affected channel geometry variables. Of the channel geometry variables considered, channel height and width have significant effect on the channel temperature profile. However, gap between cooling surface and process channel, and gap between process channels have little effect. Maximum temperature in the reaction channel was found to be proportional to channel height, and not affected by the width over a particular channel width size. Therefore, microchannels with smaller channel height(about less than 2 mm) and bigger channel width (about more than 4 mm), can be attractive design for better heat removal and higher production.

Numerical Study of Heat and Mass Transfer Characteristics in Microchannel Steam Methane Reforming Reactor (마이크로채널 메탄 수증기 개질 반응기의 열 및 물질 전달 특성에 관한 수치해석 연구)

  • Jeon, Seung-Won;Lee, Kyu-Jung;Cho, Yeon-Hwa;Moon, Dong-Ju
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.36 no.9
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    • pp.885-894
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    • 2012
  • A numerical study of a microchannel steam methane reforming reactor has been performed to understand the characteristics of heat and mass transfer. The integration of Rh-catalyzed steam methane reforming and Pt-catalyzed methane combustion has been simulated. The reaction rates for chemical reactions have been incorporated into the simulation. This study investigated the effect of contact time, flow pattern (parallel or counter), and channel size on the reforming performance and temperature distribution. The parallel and counter flow have opposite temperature distribution, and they show a different type of reaction rate and species mole fraction. As the contact time decreases and channel size increases, mass transfer between the catalyst layer and the flow is limited, and the reforming performance is decreased.

PDMS/Glass Serpentine Microchannel Chip for PCR with Bubble Suppression in Sample Injection (시료주입시 기포발생이 억제된 반응조 형태의 중합효소연쇄반응용 PDMS/유리 바이오칩)

  • Cho Chul-Ho;Cho Woong;Hwang Seung-Yong;Ahn Yoo-Min
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.30 no.10 s.253
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    • pp.1261-1268
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    • 2006
  • This paper reports low-cost microreactor $(10{\mu}{\ell})$ biochip for the DNA PCR (polymerase chain reaction). The microbiochip $(20mm{\times}28mm)$ is a hybrid type which is composed of PDMS (polydimethylsiloxane) layer with serpentine micochannel $(360{\mu}m{\times}100{\mu}m)$ chamber and glass substrate integrated with microheater and thermal microsensor. Undesirable bubble is usually created during sample loading to PMDS-based microchip because of hydrophobic chip surface. Created bubbles interrupt stable biochemical reaction. We designed improved microreactor chamber using microfluidic simulation. The designed reactor has a coner-rounded serpentine channel architecture, which enables stable injection into hydrophobic surface using micropipette only. Reactor temperature needed to PCR reaction is controlled within ${\pm}0.5^{\circ}C$ by PID controller of LabVIEW software. It is experimentally confirmed that SRY gene PCR by the fabricated microreactor chip is performed for less than 54 min.

Microchannel Development for Fuel Processor of Automotive Applications (자동차탑재용 연료개질시스템을 위한 마이크로채널개발)

  • Bae Jung Myeon
    • 한국전기화학회:학술대회논문집
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    • 2003.07a
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    • pp.89-95
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    • 2003
  • Fuel processing is an enabling technology for faster commercialization under lack of hydrogen infrastructures. It has been reported that the development of novel catalysts that are active and selective for hydrocarbon reforming reactions. It has been realized, however, that with pellet or conventional honeycomb catalysts, the reforming process is mass transport limited. This paper reports the development of catalyst structures with microchannels that are able to reduce the diffusion resistance and thereby achieve the same production rate within a smaller reactor bed. These microchannel reforming catalysts were prepared and tested with natural gas and gasoline-type fuels in a microreactor (1-cm dia.) at space velocities of up to 250,000 per hour. These catalysts have also been used in engineering-scale reactors (10 kWe, 7-cm dia.) with similar product qualities. Compared to pellet catalysts. the microchannel catalysts enable a nearly 5-fold reduction in catalyst weight and volume.

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Intensified Low-Temperature Fischer-Tropsch Synthesis Using Microchannel Reactor Block : A Computational Fluid Dynamics Simulation Study (마이크로채널 반응기를 이용한 강화된 저온 피셔-트롭쉬 합성반응의 전산유체역학적 해석)

  • Kshetrimatum, Krishnadash S.;Na, Jonggeol;Park, Seongho;Jung, Ikhwan;Lee, Yongkyu;Han, Chonghun
    • Journal of the Korean Institute of Gas
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    • v.21 no.4
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    • pp.92-102
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    • 2017
  • Fischer-Tropsch synthesis reaction converts syngas (mixture of CO and H2) to valuable hydrocarbon products. Simulation of low temperature Fischer -Tropsch Synthesis reaction and heat transfer at intensified process condition using catalyst filled single and multichannel microchannel reactor is considered. Single channel model simulation indicated potential for process intensification (higher GHSV of $30000hr^{-1}$ in presence of theoretical Cobalt based super-active catalyst) while still achieving CO conversion greater than ~65% and $C_{5+}$ selectivity greater than ~74%. Conjugate heat transfer simulation with multichannel reactor block models considering three different combinations of reactor configuration and coolant type predicted ${\Delta}T_{max}$ equal to 23 K for cross-flow configuration with wall boiling coolant, 15 K for co-current flow configuration with subcooled coolant, and 13 K for co-current flow configuration with wall boiling coolant. In the range of temperature maintained (498 - 521 K), chain growth probability calculated is desirable for low-temperature Fisher-Tropsch Synthesis.

CURVED BOUNDARY TREATMENT OF THE LATTICE BOLTZMANN METHOD FOR SLIP FLOW SIMULATIONS (Slip flow 해석을 위한 격자볼츠만 방법의 곡면처리기법)

  • Jeong, Namgyun
    • Journal of computational fluids engineering
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    • v.19 no.3
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    • pp.77-84
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    • 2014
  • The lattice Boltzmann (LB) method has been used to simulate rarefied gas flows in a micro-system as an alternative tool. However, previous results were mainly focused on a simple geometry with flat walls because the LB method is modeled on uniform Cartesian lattices. When previous boundary conditions for the microflows are applied to curved walls, the use of them requires approximation of the curved boundary by a series of stair steps, and introduces additional errors. For macroflows, no-slip curved wall boundary treatments have been developed remarkably in order to overcome these limits. However, the investigations for the slip curved wall boundary have rarely been performed for microflows. In this work, a curved boundary treatment of the LB method for a slip flow has been introduced. The results of the LB method for 2D microchannel and 3D microtube flows are in excellent agreement with the analytical solutions.