• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2010년 춘계학술대회논문집
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• pp.233-238
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• 2010

A two-dimensional laminar flow past a vertical plate in a microchannel is investigated. At far upstream and downstream from the plate in the microchannel, the plane Poiseuille flow exists. The Stokes flow for this microchannel is investigated analytically and then the laminar flow by numerical method. For the Stokes flow analysis, the method of eigenfunction expansion is used. From the results, the streamline pattern and the pressure distribution are plotted, and the additional pressure drop induced by the plate and the force exerted on the plate are calculated as functions of the length of the plate. For the laminar flow, finite difference method (FDM) is used to obtain the vorticity and the stream function. When the Reynolds number exceeds a critical value, a pair of viscous eddies appears behind the plate.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.1888-1893
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• 2007

In this study, the microchannel plated heat exchanger were numerically studied for the enhancement of heat transfer in the channel configuration. Unit cold and hot fluid region with the microchannel were modeled and periodic boundary condition at the side wall was applied to continuously repeating geometry. The material of micro-structured plate is STS304 and working fluid is water. Triangular obstacles were placed in micro channel to enhance heat transfer. The performance of microchannel plated heat exchangers were numerically investigated with various obstacle configuration and Reynolds number under the parallel and counter flows. Heat transfer rate has increased about 18% compared with straight channel, but pressure drop also increased about 3.5 times. The main factor of increasing of pressure drop and heat transfer rate is considered that the momentum was lost to collide against obstacles, generation of secondary flow and boundary layer separation, wake and vortex forming phenomena.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2007년도 동계학술발표대회 논문집
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• pp.229-234
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• 2007

Microscale heat transfer and microfluidics have become increasingly important to overcome some very complex engineering challenges. The use of very small passages to gain heat transfer enhancement is a well documented method for achieving high heat flux dissipation. As the passage size is decreased, the heat transfer performance increases but the pressure drop increases sharply when the passage size is reduced. In this study, the performance evaluation of micro plated heat exchangers under the counter flows with straight, V-shaped and Y-shaped channel are carried out.

• 대한기계학회논문집B
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• 제35권11호
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• pp.1119-1126
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• 2011

기존 마이크로채널 열교환기는 한 플레이트에 고온 또는 저온, 한 종류의 유체만이 흐르고 있다. 채널 내부를 흐르는 유체의 수직 방향으로는 다른 종류의 유체가 존재하지만, 수평 방향으로는 같은 종류의 유체가 존재한다. 그로 인해 수평 방향의 열전달률은 수직 방향에 비하여 낮게 나타나게 된다. 열교환기 성능 향상을 위하여 한 플레이트에서 고온, 저온 유동이 번갈아가며 존재하는 새로운 채널 배열을 제안하였다. 새로운 채널 배열을 위해서는 특별한 입구 및 출구 설계가 필요하다. 제안된 채널 배열을 통하여 기존 열교환기보다 높은 열전달률을 얻을 수 있다. Reynolds 수와 Prandtl수가 증가할수록 새로운 채널 배열로 인한 열 성능 향상이 증가하고, 고체와 유체의 열전도계수 비가 증가할수록 열 성능 향상은 감소한다.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2004년도 하계학술발표 논문집
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• pp.16-16
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• 2004

• Journal of Astronomy and Space Sciences
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• 제19권1호
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• pp.57-66
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• 2002

MCP(microchannel plate)와 지연산 양극판(delay line anode), 그리고 지연선 검출회로로 구성되는, 원자외선 분광기 에 사용될 2차원 지연선(delay line) 방식 의 위 치 검출기 (position sensitive detector)를 설계하고 그 중 지연선 검출회로를 제작하여 동작 및 분해능에 대한 시험을 수행하였다. 이 시험에서는 검출회로의 고유한 분해능을 확인하기 위하여 MCP와 양극판은 각파 특성이 잘 알려진 스티뮬레이션(stimulator)와 양극판 시뮬레이터(anode simulator)로 대체되었다. 제작된 검출회로는 안정적으로 동작하였으며 분광 및 영상 축 방향으로 각각 약 570ps와 약 100ps의 시간 분해능을 가지는 것을 확인하였다

• Journal of Astronomy and Space Sciences
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• 제18권2호
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• pp.145-152
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• 2001

태양의 극자외선 복사를 연구하기 위한 인공위성 탑재용 소형 극자외선 태양망원경의 공학 모형을 설계하였다. 극자외선 태양망원경은 $584.3AA$(He I)과 $629.7AA$(OV)의 두 파장대역에서 태양을 관측하기 위한 목적으로 설계되었다. 광학계는 Ritchey-Chr 샤두 방식이고, 망원경의 유효구경과 유효 초점 거리는 각각 80mm, 640mm이다. 회전 필터 휠을 사용하여 He I과 OV 방출선을 관측할 수 있도록 하였다. 검출기의 MCP (Microchannel Plate)는 채널 길이 대 직경의 비가 40:1인 Z-stack 타입이고, photocathode로서 KBr이 MCP 초점면에 코팅되며, MCP와 CCD는 fiber optic taper로 연결되도록 디자인하였다. 광학계 설계에 대한 분석은 광학계산용 상용 소프트웨어를 이용하였다.

• Journal of Advanced Marine Engineering and Technology
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• 제31권3호
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• pp.272-281
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• 2007

A numerical simulation on nitrogen gas flow in a long parallel plate microchannel was performed to obtain the effect of compressibility and rarefaction on gaseous flow in microchannels. The simulation was based on steady. two dimensional compressible Navier-Stokes and energy equations with noslip and first order slip boundary conditions. The channel was $1.2{\mu}m$ deep and $3000{\mu}m$ long. The Reynolds numbers were in the range of order from $10^{-2}$ to $10^{-1}$. So the flow was assumed to be laminar. The computations were performed on various pressure ratios. The outlet pressure was fixed to atmospheric pressure. The outlet Knudsen number was 0.0585, consequently the flow was in the slip flow regime. The computations were performed with the assumption of isothermal channel walls. The results were compared with the experimental data. The agreement was good.

• 전기학회논문지
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• 제57권1호
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• pp.137-141
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• 2008

Biochip, which implements bioanalytical process on a tiny surface, is one of candidates for medical diagnosis, drug screening, and molecular sensing. In general, a type of biochip based on microfluidics is composed of microcomponents including microchannel, pump, and valve, which require complicated processes. In this study, gray-scale photolithography(GSPL) was applied to fabricate a biochip with multiple layers. A mould for casting PDMS(polydimethylsiloxane) channel, was fabricated using GSPL. A gray-photomask was prepared by printing gray patterns on a high-quality glossy paper followed by photoreducing by 10:1 onto the photo-film. The formation of multiple layers was studied according to the change of gray level of pattern and the developing time. A biochip composed of a weir(multiple layer structure) and a reaction chamber in a single microchannel was fabricated in a glass plate. Finally, we investigated the application of biochip to antigen-antibody reaction by packing the microbead coated with antibody.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2006년 제4회 한국유체공학학술대회 논문집
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• pp.179-183
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• 2006

Surface roughness is present in most of the microfluidic devices due to the microfabrication techniques. This paper presents lattice Boltzmann method (LBM) results for laminar flow in a microchannel with surface roughness. The surface roughness is modeled by an array of rectangular modules placed on top and bottom side of a parallel-plate channel. In this study, LBGK D2Q9 code in lattice Boltzmann Method is used to simulate flow field for low Reynolds number in a micro-channel. The effects of relative surface roughness, roughness distribution, roughness size and the results are presented in the form of the product of friction factor and Reynolds number. Finally, a significant increase in Poiseuille number is detected as the surface roughness is considered, while the effect of roughness on the microflow field depends on the surface roughness.