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미세제트 유동의 Stereoscopic micro-PIV측정
유청환,김형범 한국가시화정보학회 2007 한국가시화정보학회지 Vol.5 No.1
Micro-PIV(particle image velocimetry) has been widely used to measure the velocity of microflow. Although this micro-PIV method can give acurate 2D instantaneous velocity information of mea-surement plane, it cannot resolve the out of plane component of velocity vectors. Lots of the micro fluidicdevices generate three-dimensional flow and 3D measurement of velocity is useful to understand the phys-ics of micro flow phenomena. In this study, we constructed stereoscopic micro-PIV(SMPIV) system andapplied this method to the impinging micro jet flow. The results show that this method can produce acu-rate 3D reconstruction of micro jet flow. Micro-PIV(particle image velocimetry) has been widely used to measure the velocity of micro flow. Although this micro-PIV method can give accurate 2D instantaneous velocity information of measurement plane, it cannot resolve the out of plane component of velocity vectors. Lots of the micro fluidic devices generate three-dimensional flow and 3D measurement of velocity is useful to understand the physics of micro flow phenomena. In this study, we constructed stereoscopic micro-PIV(SMPIV) system and applied this method to the impinging micro jet flow. The results show that this method can produce accurate 3D reconstruction of micro jet flow.
미세제트 유동의 Stereoscopic micro-PIV측정
유청환(Cheong-Hwan Yu),김형범(Hyoung-Bum Kim) 한국가시화정보학회 2007 한국가시화정보학회지 Vol.5 No.1
Micro-PIV(particle image velocimetry) has been widely used to measure the velocity of micro flow. Although this micro-PIV method can give accurate 2D instantaneous velocity information of measurement plane, it cannot resolve the out of plane component of velocity vectors. Lots of the micro fluidic devices generate three-dimensional flow and 3D measurement of velocity is useful to understand the physics of micro flow phenomena. In this study, we constructed stereoscopic micro-PIV(SMPIV) system and applied this method to the impinging micro jet flow. The results show that this method can produce accurate 3D reconstruction of micro jet flow.
유청환(Cheong-Hwan Yu),이정호(Jungho Lee) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5
Liquid jet impingement cooling has been widely used in the iron/steel making industries and nucleate power plants as an effective method of removing high heat flux. Liquid jet impinging on hot surface passes through a phase change heat transfer such as single-phase forced convection, nucleate boiling, transition boiling, and film boiling. Especially, a strict understanding of boiling phenomena is significant to ensure high quality products in iron/steel making industry. An actual hot-steel cooling process requires wider band of nucleate boiling rather than transient boiling, because there are sudden changes in heat transfer rate within transient boiling regime. In this study, a variety of parameters has been experimentally considered to investigate the role of boiling in heat transfer characteristics of liquid jet impinging on hot surface extremely up to higher temperature of 900℃. The result shows a higher cooling rate with increased CHF (critical heat flux) by increasing flow rates.
Stereoscopic micro-PIV기법을 이용한 충돌제트 유동 측정
유청환(Cheong-Hwan Yu),김형범(Hyoung-Bum Kim) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.10
Micro flow measurement is important to understand the physics of micro fluidic devices such as MEMS actuator, pumps, etc. Micro-PIV became the essential tool for this purpose due to the good performance of it. Micro-PIV is basically two dimensional measurement method and many micro fluidic devices generate three dimensional flow. In this study, we developed stereoscopic micro-PIV(SMPIV) which is basically the combination of conventional stereoscopic PIV method with stereoscopic microscope. This SMPIV method is applied to the impinging jet flow for validating the performance. The results showed this SMPIV method can measure out-of-plane velocity of test plane precisely.
Effects of manifold geometries on flow distribution to parallel microchannels
Duckjong Kim,유청환,윤석호,최준석 대한기계학회 2011 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.25 No.12
For efficient scale up of microchannel devices, uniform flow distribution to parallel microchannels is very important. In the present work, a dimensionless geometric parameter indicating the optimal manifold configuration is derived through a numerical parametric study and validated by micro particle image velocimetry. It is clearly shown that the flow uniformity is maximized when the dimensionless parameter is about 0.8. This study presents a simple and systematic design methodology for a uniform flow distribution to multiple microchannels operating in parallel.
이정호(Jungho Lee),유청환(Cheong-Hwan Yu),도규형(Kyu Hyung Do) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.11
The analysis of the uncertainties in experimental measurements and results is a powerful tool, particularly when it is used in the planning and design of experiments. The uncertainty analysis, when used in the initial planning phase of an experiment, can identify such situations and save the experimentalist much time, money and embarrassment. The current study focuses on making detailed determination and estimation of the convective heat transfer coefficient as it is frequently encountered in the field of thermal engineering applications. The quantitative uncertainty analysis was carried out based on the ANSI/ASME PTC 19.1-2005 standard. The actual application of the uncertainty analysis is provided by the detailed example which is performed at the submerged impinging jet heat transfer case. The results show that the convective heat transfer coefficient can be determined by its individual contributors of measurands.
마찰용접 된 알루미늄 합금 6061-T6와 7075-T6의 기계적 특성과 표면에 관한 연구
유미화(Mihwa Yu),유청환(Chunghwan Yu),홍동표(Dongpyo Hong),김철생(Cheolsang kim),김연직(Yonjig Kim) 한국생산제조학회 2010 한국생산제조시스템학회 학술발표대회 논문집 Vol.2010 No.10
이번 연구의 목적은 기계, 건축, 자동차, 선박 등의 산업에서 경량화 소재로 많이 쓰이는 알루미늄 6061-T6와 7075-T6를 마찰용접하여 기계적인 특성과 표면을 연구하는데 있다. 마찰용접은 이종의 재료를 용접할 수 있고 또한 기계적인 물성이 뛰어나다. 이번 연구에서 최대인장강도는 모재인 6061-T6의 95%인 293 MPa정도였으며 그 시편의 비커스경도는 7075쪽이 최대 173 HV, 평균 160 HV였고 6061쪽은 거의 모든 값이 100 HV를 넘었다. 이는 다른 시편들보다 7075쪽은 15~20 HV 높은 값이고 6061쪽은 20~25 HV 높은 값이다. 현미경 조직관찰 결과 용접면으로부터 0.5~1mm 정도의 미세조직이 관찰되었으며, 회전의 영향으로 생긴 와류형태의 곡선을 발견할 수 있었다.