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이규정,Lee Kyu-Jung Korea Society of Computational Fluids Engineering 1998 한국전산유체공학회지 Vol.3 No.1
A numerical analysis of thermal stress over temperature variations near the crystal-melt interface is carried out for a floating-zone growth of Cadmium Telluride (CdTe). Thermocapillary convection determines crystal-melt interfacial shape and signature of temperature in the crystal. Large temperature gradients near the crystal-melt interface yield excessive thermal stresses in a crystal, which affect the dislocations of the crystal. Based on the assumption that the crystal is elastic and isotropic, thermal stresses in a crystal are computed and the effects of operating conditions are investigated. The results show that the extreme thermal stresses are concentrated near the interface of a crystal and the radial and the tangential stresses are the dominant ones. Concentrated heating profile increases the stresses within the crystal, otherwise, the pulling rate decreases the stresses.
이규정(Kyu-Jung Lee) 한국전산유체공학회 1998 한국전산유체공학회지 Vol.3 No.1
A numerical analysis of thermal stress over temperature variations near the crystal-melt interface is carried out for a floating~zone growth of Cadmium Telluride (CdTe), Thermocapillary convection determines crystal-melt interfacial shape and signature of temperature in the crystal. Large temperature gradients near the crystal-mel t interface yield excessive thermal stresses in a crystal, which affect the dislocations of the crystal. Based on the assumption that the crystal is elastic and isotropic, thermal stresses in a crystal are computed and the effects of operating conditions are investigated. The results show that the extreme thermal stresses are concentrated near the interface of a crystal and the radial and the tangential stresses are, the dominant ones, Concentrated heating profile increases the stresses within the crystal, otherwise, the pulling rate decreases the stresses.
마이크로채널 메탄 수증기 개질 반응기의 열 및 물질 전달 특성에 관한 수치해석 연구
전승원(Seung Won Jeon),이규정(Kyu Jung Lee),조연화(Yeon Hwa Cho),문동주(Dong Ju Moon) 대한기계학회 2012 大韓機械學會論文集B Vol.36 No.9
마이크로채널 메탄 수증기 개질 반응기의 열 및 물질 전달 특성을 이해하기 위한 수치해석 연구를 수행하였다. Rh-촉매의 메탄 수증기 개질 반응과 Pt-촉매의 메탄 연소 반응을 함께 모델링하였다. 화학 반응의 반응 속도를 해석 모델에 적용하였다. 접촉시간, 평행류·대향류 등 유동 패턴, 채널 크기 등이 개질 성능과 온도 분포에 미치는 영향을 관찰하였다. 평행류와 대향류는 서로 반대되는 온도 분포를 갖게 되고, 그로 인해 서로 다른 반응 속도와 화학종 몰분율을 나타낸다. 접촉시간이 짧아지고 채널 크기가 증가할수록 촉매층과 혼합물 유동 사이의 물질 전달이 제한되어 개질 성능은 감소하게 된다. 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.
3차원 채널 형상 변화에 따른 마이크로 채널 판형 열교환기의 열적 특성 수치해석
서장원(Jang-Won Seo),이규정(Kyu-Jung Lee),전승원(Seung-Won Jeon),이춘식(Chun-Sik Lee),문정은(Chung-Eun Moon) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5
The plate heat exchangers have been widely employed in the cooling systems for their compact size and high performance. In general, the flow passage of a compact plate heat exchangers are characterized by a small hydraulic diameter and low velocity. In this study, the microchannel plated heat exchangers were numerically investigated with I(straight), V, Y-channel shapes and Reynolds number under the counter flow. The material of micro-structured plate is STS304 and water is utilized as a working fluid. The averaged pressure drops from in let to outlet and total heat transfer rates were calculated. The results were compared with those of the straight micro channel.
조연화(Yeon Hwa Cho),이규정(Kyu Jung Lee),문동주(Dong Ju Moon),김윤호(Yoon Ho Kim) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.5
새롭게 제안된 형상의 마이크로채널 PCHE는 기존의 상용 열교환기에 비해 고성능, 고효율의 특성을 보이며 열교환을 수행한다. 본 연구에서는 I, Wavy, Beehive, Surf, I-Wavy, I-Beehive, I-Surf의 형상을 갖는 다양한 마이크로채널을 모델링하였다. 질량유속 변화에 따른 다양한 마이크로채널 내 유체의 유동 특성, 열전달, 압력강하를 살펴보았고 그 결과는 마이크로채널의 열전달 능력을 향상시키는데 향상시키는데 이용된다. I 채널은 새롭게 적용된 채널 형상과의 성능비교를 위해 해석을 수행하였다. 다양한 레이놀즈수 변화 하에서 고온측과 저온측 유체는 대향류 형태로 열교환이 이루어지도록 하였다. 수치해석 결과 Surf 형상이 다른 형상들보다 열교환 성능이 우수함을 확인하였다. The microchannel PCHE(printed Circuit Heat Exchanger) of the newly proposed shapes out-performs other existing commercial heat exchangers while retaining greater performance-effectiveness and energy-efficiency. Various microchannels with the shapes of I, Wavy, Beehive, Surf, I-Wavy, I-Beehive and I-Surf are computationally modeled in this study. Flow characteristics, heat transfer and pressure drop in the microchannel are investigated under the various mass flow rate conditions. The results are utilized to enhance the heat transfer performance of the microchannels. The I microchannel case is chosen to be benchmark case, whose results are compared with those of newly proposed microchannels. The counterflow is arranged at various Reynolds numbers of both hot and cold fluids. It is found that the shapes of surf is better than the others from the point of heat performance.