http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
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 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.