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나인(Md. J. Nine),이경환(G. H. Lee),정효민(H. M. Jeong),정한식(H. S. Chung) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11
The article represents an experimental investigation on pressure drop and friction loss behaviors of free airflow through a rectangular duct fitted with semicircular ribs of uniform height on one principle wall. The aspect ratio of the rectangular duct is AR= 5, duct height was of H= 30 ㎜ and uniform rib heights (e = 3.5 ㎜m) were used for three different rib pitches of 30 mm, 35 ㎜ and 42 ㎜. For this cases, the rib height to hydraulic diameter ratio were e/D = 0.07 and rib height to channel height ratio were e/H = 0.11. The experimental results show some significant effects of static pressure near the wall and at various configurations and different numbers of rib arrangements within test section. Each result is compared with another among different configurations of rib arrangement over the 90 ㎝ X 15 ㎝ copper plate test section. The Reynolds number in the inlet of calculation domain was in a range of 10000 to 30000. Digital micro manometer and pressure transducer were used for taking static pressure of this experiment. Darcy friction factor was used and isothermal pressure drop had been considered in data evaluation. These experiment will be the preliminary investigation for turbulence analysis as heat transfer enhancement using periodic semicircular ribs.
이경환 (G. H. Lee ),라흐만 (M. Sq. Rahman ),김철표 (C. P. Kim ),정태휘 (T. W. Joung ),정효민(H. M. Jeong),정한식 (H. S. Chung ) 한국동력기계공학회 2009 한국동력기계공학회 학술대회 논문집 Vol.2009 No.6
Numerical analysis information of a complex discharge-passage will be very useful to improve hydrogen compression system. General information about an internal gas flow is presented by numerical analysis approach. Relating with hydrogen compressing system, which have an important role in hydrogen energy utilization, this should be a useful tool to observe the flow quickly and clearly. Flow characteristic analysis, including pressure and turbulence kinetic energy distribution of hydrogen gas from cylinder going to the chamber of a reciprocating compressor are presented in this paper. Discharge-passage model is designed based on real model of hydrogen compressor. Pressure boundary conditions are applied considering the real condition of operating system. The result shows pressure and turbulence kinetic energy are not distributed uniformly along the passage of the hydrogen compressing system. Path line or particles tracks help to demonstrate flow characteristics inside the passage. The existence of vortices and flow direction can be precisely predicted. Based on this result, the design improvement should be done. Consequently, development of the better hydrogen compressing system will be achieved.
이경환(G. H. Lee),심규진(K. J. Shim),이용훈(Y. H. Lee),정한식(H. S. Chung),정효민(H. M. Jeong) 한국동력기계공학회 2007 동력시스템공학회지 Vol.11 No.4
Pulsation is an inherent phenomenon in reciprocating compressors. It interacts with piping to cause vibrations and performance problems. Indiscriminately connecting to a compressor can be dangerous and cost money in the form of broken equipment and piping, poor performance, inaccurate metering, unwanted vibration, and sometimes noise. Piping connected to a compressor can materially affect the performance and response. To minimize these detrimental effects, reciprocating compressor system should be equipped by pulsation suppression system. The system usually comprises bottle volume, called snubber. Snubber is one of the most important parts in hydrogen compressing system. It has installed reciprocating hydrogen compressor. One of these components is snubber which has function to reduce pulsation waveform and to remove the impurities in the hydrogen gas. A snubber has an inclined plate as a buffer, which is installed inside snubber. When the pressure loss and the pulsation of pressure within a snubber is minimized, the snubber could get more applicability. Therefore, a study to find an optimum geometric size on a several snubbers which have different buffer width, has been conducted using a numerical analysis.
G. H. Lee(이경환),W. A. Akbar(악바르),K. J. Shim(심규진),H. Min. Jeong(정한식),H. S. Chung(정효민) 한국동력기계공학회 2008 동력시스템공학회지 Vol.12 No.1
수소 추출과 리포밍 과정, 연료 전지, 저장소로 구성된 수소 연료에 대한 연구는 세계적으로 번영하고 있는 중이다. 그러나 한국의 수소 스테이션에 대한 연구는 아직도 개발이 미미한 수준이다. 그리고 역시 수소 스테이션의 가장 중요한 부분인 수소 압축기에 대한 연구도 미흡하다. 수소압축기에서 가장 중요한 부분 중에 하나는 스너버인데 이것의 기능은 수소가스의 맥동압을 줄이고 불순물을 제거한다. 스너버 내부에는 버퍼라고 불리는 기울어진 판이 설치되어 맥동압을 줄이고 불순물을 제거하는 역할을 담당한다. 스너버 내부의 압력 손실과 맥동압이 최소가 될 때 스너버는 적절한 성능을 가졌다고 평가된다. 그러므로 이 연구의 목적은 수치해석을 통하여 스너버의 최적의 기하학적 크기와 버퍼의 각도에 따른 최적의 스너버를 찾는 것이다. 수치해석의 결과에서 다양한 버퍼각도에 따른 스너버의 독특한 특성을 볼 수 있다. 결과적으로 버퍼의 각도가 35°일때 최소의 압력손실율이 발생했고, 버퍼의 각도가 10°일 때 최소의 맥동압이 발생하였다.
이경환(G. H. Lee),라흐만(M. Sq. Rahman),김철표(C. P. Kim),정태휘(T. W. Joung),정효민(H. M. Jeong),정한식(H. S. Chung) 한국동력기계공학회 2009 동력시스템공학회지 Vol.13 No.3
Numerical analysis information of a complex discharge-passage will be very useful to improve hydrogen compression system. General information about an internal gas flow is presented by numerical analysis approach. Relating with hydrogen compressing system, which have an important role in hydrogen energy utilization, this should be a useful tool to observe the flow quickly and clearly. Flow characteristic analysis, including pressure and turbulence kinetic energy distribution of hydrogen gas from cylinder going to the chamber of a reciprocating compressor are presented in this paper. Discharge-passage model is designed based on real model of hydrogen compressor. Pressure boundary conditions are applied considering the real condition of operating system. The result shows pressure and turbulence kinetic energy are not distributed uniformly along the passage of the hydrogen compressing system. Path line or particles tracks help to demonstrate flow characteristics inside the passage. The existence of vortices and flow direction can be precisely predicted. Based on this result, the design improvement should be done. Consequently, development of the better hydrogen compressing system will be achieved.
H. S. Chung(정한식),M. Sq. Rahman(라흐만),G. H. Lee(이경환),J. S. Woo(우주식),B. H. Kim(김보한),H. M. Jeong(정효민) 한국동력기계공학회 2010 동력시스템공학회지 Vol.14 No.3
전 세계적으로 급속도로 인기가 더해가고 있는 수소에너지는 높은 전환 효율성, 재생성, 친환경적인 특징을 가지며 미래의 주 에너지가 될 것이다. 왕복동식 압축기를 통과한 후의 수소 가스의 압력은 높은 맥동압을 가진다. 스너버는 압축기의 한 구성품으로 맥동압을 낮추고 수소가스의 불순물을 제거하기 위해 사용된다. 이 연구에서의 실험은 스너버 시스템에 사용된 강관의 맥동에 관해 조사하기 위해서 수행되었다. 맥동압은 12 ㎐ ~ 60 ㎐의 모터속도에서 RMS값을 기준으로 0.1625% ~ 0.5305% 그리고 평균압력을 기준으로 0.1621% ~ 0.5277% 감소하였다. 압력손실은 RMS값을 기준으로 0.1092% ~ 1.4419%, 평균압력을 기준으로 0.1493% ~ 1.7507%로 측정되었다. CFD를 이용한 수치해석값은 실험값이 거의 비슷한 결과를 나타내고 강관 관로 내부 가스의 자세한 압력을 설명하기 위한 중요한 역할을 수행한다.
사각채널 내 주기적으로 배열된 반원 리브 영향의 유동해석
이경환(G. H. Lee),나인(Md. J. Nine),최순호(S. H. Choi),정효민(H. M. Jeong),정한식(H. S. Chung) 한국동력기계공학회 2011 동력시스템공학회지 Vol.15 No.2
The flow characteristics on the periodically arranged semi-circular ribs in a rectangular channel for turbulent flow have been investigated numerically. The aspect ratio of the rectangular channel was AR=5, the rib height to hydraulic diameter ratio was 0.07 and rib height to channel height ratio was e/H=0.117. The v2-f turbulence model and SST k-ω turbulence model were used to find the flow characteristics of near the wall which are suited for realistic phenomena. The numerical analysis results show turbulent flow characteristics and pressure drop at the near the wall as observed experimentally. The results predict that turbulent kinetic energy(k) is closely relative to the diffusion of recirculation flow. and v2-f turbulence model simulation results have a good agreement with experimental.
이경환(G. H. Lee),심규진(K. J. Shim),이용훈(Y. H. Lee),정한식(H. S. Chung),정효민(H. M. Jeong) 한국동력기계공학회 2007 한국동력기계공학회 학술대회 논문집 Vol.- No.-
The study about hydrogen fuel which consist of hydrogen extraction and reforming process, fuel cell equipment, and receptacle are flourishing all over the world. Currently, Korean hydrogen station is still underdeveloping. And also the most important part which is hydrogen compressor has not been developed. Snubber is one of the most important parts inhydrogen compressing system. It has installed reciprocating hydrogen compressor. One of these components is snubber which has function to reduce pulsation waveform and to remove the impurities in the hydrogen gas. Therefore, a snubber has a buffer. It is an inclined plate, attached inside snubber. The best snubber is the one which has the least pressure loss and the most pressure amplitude reduction. Furthermore, investigating geometric optimum size of with-buffer snubber has been done by numerical analysis approach.
이경환(G. H. Lee),악바르(Wanda Ali Akbar),심규진(K. J. Shim),정한식(H. S. Chung),정효민(H. Min Jeong) 한국동력기계공학회 2007 한국동력기계공학회 학술대회 논문집 Vol.- No.-
The studies about hydrogen fuel which consist of hydrogen extraction and reforming process, fuel cell equipment, and receptacle are flourishing all over the world. But, Korean hydrogen station is still underdeveloping. And also a hydrogen compressor which is the most important part at the hydrogen station, has not been developed. Snubber is one of the most important parts in hydrogen compressing system. Snubber has function to reduce pulsation waveform and to remove the impurities in the hydrogen gas. A snubber has an inclined plate as a buffer, which is installed inside snubber. When the pressure loss and the pulsation of pressure within a snubber is minimized, the snubber could get more applicability. Therefore, a study to find an optimum geometric size on a several snubbers which have different buffer width, has been conducted using a numerical analysis. The numerical results show the special characters of snubber according to various buffer angle. The minimum pressure loss ratio occurs when the buffer angle is 35. and the minimum pressure pulsation ratio occurs when the buffer angle 10.
이용훈(Y. H. Lee),박기태(G. T. Park),이경환(G. H. Lee),김필환(P. H. Kim),정효민(H. M. Jeong),정한식(H. S. Chung) 한국동력기계공학회 2007 한국동력기계공학회 학술대회 논문집 Vol.- No.-
Liquefied gas vaporizer means machine to vaporize the liquefied gas as liquid nitrogen(LN₂), liquefied natural gas(LNG), liquid oxygen(LO₂) etc. In the air type vaporizer, the frozen dew is also created by temperature drop (below 273 K) on vaporizer surface. This problem increases as the time progresses and humidity increases. In addition, the frozen dew gradually becomes frost deposit consequently, heat transfer through vaporizer decreases because frost deposit form adiabatic sheet. Because of this reason, recent vaporizer system is installed as parallel type, this vaporizer system needs more expensive installation costs and more space. This study carried out structure analysis on the material of vaporizer along the working fluid flow direction using liquefied super low temperature gas. The experimental study was investigated the heat transfer characteristics and performance on the tube length 4000 ㎜, 6000 ㎜ and 8000 ㎜ of three vaporizer models and was analyzed for evaluating the optimum efficiency on the vaporizer.