• 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.

• 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.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.2
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• pp.113-120
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• 2010

An experimental investigation was carried out to examine the evaporative heat transfer characteristics of R-134a in a micro-channel heat exchanger. The micro-channel heat exchanger used in this study was a sort of plate heat exchanger. Micro-channels were fabricated on the SUS304 plate by the photo-etching process: 13 sheets of plates were stacked and bonded by the diffusion bonding process. The effects of the evaporating temperature, mass flux of R-134a, and inlet temperature of water were examined. As the difference between the inlet temperatures of R-134a and water increased, the heat transfer rate increased. The evaporative heat transfer coefficients obtained in this study range from 0.67 to 6.23 kW/$m^2{\cdot}^{\circ}C$. The experimental correlation for the Nusselt number as a function of the Reynold number and $\Theta$ was suggested for the micro-channel heat exchanger.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.1
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• pp.9-18
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• 2010

There are two kinds of models in two-phase pressured drop; homogeneous flow model and separated flow model. Many previous researchers have developed correlations for two-phase pressure drop in a microchannel. Most correlations were modified Lockhart and Martinelli's correlation, which was based on the separated flow model. In this study, experiments for adiabatic liquid water and nitrogen gas flow in rectangular microchannels were conducted to investigate two-phase pressure drop in the rectangular microchannels. Two-phase frictional pressure drop in the rectangular microchannels is highly related with flow regime. Homogeneous model with six two-phase viscosity models: $Owen^{(21)}$'s, $MacAdams^{(22)}$'s, Cicchitti et ${al.}^{(23)}$'s, Dukler et ${al.}^{(24)}$'s, Beattie and ${Whalley}^{(25)}$'s, Lin et ${al.}^{(26)}$'s models and six separated flow models: Lockhart and $Martinelli^{(27)}$'s, ${Chisholm}^{(31)}$'s, Zhang et ${al.,}^{(15)}$'s, Lee and ${Lee}^{(5)}$'s, Moriyama and ${Inue}^{(4)}$'s, Qu and $Mudawar^{(8)}$'s models were assessed with our experimental data. The best two-phase viscosity model is Beattie and Whalley's model. The best separated flow model is Qu and Mudawar's correlation. Flow regime dependency in both homogeneous and separated flow models was observed. Therefore, new flow pattern based correlations for both homogeneous and separated flow models were individually proposed.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.1540-1545
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• 2004

Measurement of concentration fields in a micro-channel is the crucial technology in the area of Lab-on-a-chip to be used for various bio-chemical applications. It is wel-known that the only possible way to measure the concentration field in the micro-channel is using micro-LIF(Laser Induced Fluorescence) method. However, an accurate concentration field at a given cross plane in a micro-channel has not been made so far due to the limit of light illumination. The present study demonstrates a novel method to provide an ultra thin laser sheet beam having 5 microns thickness by a micro focus laser line generator. Nile Blue A was used as fluorescent dye for LIF measurement. The laser sheet beam illuminates an exact plane of concentration measurement in the micro-channel to increase the signal to noise ratio and reduce the depth uncertainty considerably.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.59-60
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• 2011

본 논문에서는 기존의 PCR 장비가 가지고 있는 낮은 경제성, 장비의 대형화, 긴 분석 시간 등과 같은 단점을 해결하기 위하여 ATMEGA128 마이크로 칩을 사용 continuous-flow PCR 칩의 온도를 제어 하였다. Polydimethylsiloxane (PDMS)와 산화 인듐-주석(Indium tin-oxide, ITO) 유리 기판을 사용하여 continuous-flow PCR 칩을 제작하였고 PDMS를 주조 하여 마이크로 채널을 형성하였다. 또한 유리 기판위에 ITO 전극을 패터닝하여 마이크로 히터를 제작하였다. 이 결과 continuous-flow PCR 칩에서 빠르고 정확한 온도 제어를 통한 DNA 중합 효소 연쇄반응 결과를 얻을 수 있었다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.11a
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• pp.15-18
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• 2006

Recently, experimental visualization of microscale fluid transport has attacted considerable attention in designing microelectromechanical systems. Fluid-surface interactions on hydrophobic and hydrophilic surfaces can play a key role in passively controlling microfluidics. Here we investigate the slip boundary condition depending on the surface characteristics; hydrophilic, hydrophobic wettabilities. Using the micro-PIV, velocity profiles are measured in the glass (hydrophilic), PDMS (hydrophobic) microchannels.

• 순환기질환의공학회:학술대회논문집
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• 2005.12a
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• pp.43-46
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• 2005

• Proceedings of the KSME Conference
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• 2005.11a
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• pp.55.2-55.2
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• 2005

• Proceedings of the KSME Conference
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• 2005.11a
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• pp.90.1-90.1
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• 2005