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Sun-Hwi Park(박선휘),Seon-Hwa Kim(김선화),Byung-Gon Kim(김병곤),Young-Jin Roh(노영진) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.11
Hydrogen energy is attracting attention as a future energy because it does not emit greenhouse gases and has a high calorific value per unit mass. In particular, the liquid hydrogen has a higher energy density than the gases of hydrogen, research on storage technology for hydrogen stations and hydrogen vehicles is being actively conducted. Since the hydrogen liquefaction process is an environment of cryogenic and high pressure, the reliability of mechanical performance of a heat exchanger operating in such an environment is required. In particular, in the resonance avoidance design of the tube structure of a fluid-induced vibration due to high-speed fluid movement, it is very important to understand the exciting force and the dynamic characteristics of the structure. In this study, in order to analyze the dynamic characteristics of the actual operating environment of the heat exchanger in the hydrogen liquefaction process based on the LNG precooling technology, process analysis, thermal calculation, and modal analysis were performed. Through this, the prediction of the excitation force of fluid-induced vibration and the resonance range of the dynamic characteristics of the heat exchanger tube structure were predicted.
박선휘(Sun Hwi Park),김선화(Seon Hwa Kim),노영진(Young Jin Roh),이선기(Seon Gi Lee) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.4
물을 작동 유체로 이용하는 기존의 수봉식 진공펌프의 경우, 물의 증기압에 따른 명확한 진공도 한계 특성을 갖게 된다. 진공도가 높아질수록 진공펌프 효율이 급격히 감소할 뿐만 아니라, 더 낮은 진공압력을 갖기 어려운 문제가 발생한다. 따라서 상기와 같은 문제를 해결하기 위해 저점도 저 증기압의 물질과 물의 수용액을 새로운 작동 유체로 선정하여 활용 가능 진공영역을 확장하고, 에너지 효율을 향상시키고자 한다. 본 연구에서 선정된 화합물은 폼상 칼륨으로 10~70%의 다양한 농도에서 성능실험을 하였다. 그 결과 모든 작동 유체에서 펌프의 내부 온도 증가로 인한 진공 성능 하락이 발생하였다. 하지만, 기존의 작동 유체인 물에 비해 수용액의 진공압력이 향상되었다. 또한 농도가 증가할수록 진공성능이 향상되는 것을 확인하였다. In the case of a liquid ring pump that uses water as the working fluid, there is a definite limit to the vacuum performance. As the degree of vacuum increases, the efficiency of the vacuum pump decreases rapidly, and it is difficult to have a lower vacuum pressure. Therefore, to solve these problems, we would like to expand the range of use of the liquid ring pump by selecting a new working fluid with low viscosity and low vapor properties. The compound selected in this study was potassium formate, and performance tests were performed at various concentrations of 10-40%. As a result, the vacuum performance decreased due to the increase in the internal temperature of the liquid ring pump for all working fluids. However, it has a lower vapor pressure than conventional water and the vacuum pressure of the pump is improved. In addition, it was confirmed that the pump performance improved as the concentration increased.
Sun-Hwi Park(박선휘),Seon-Hwa Kim(김선화),Chul-Woo Roh(노철우) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.11
Existing absorption heat pumps require significantly less compression, but COP is significantly lowered in the process of consuming a large amount of thermal energy to regenerate the absorbent solution. Just as steam compression heat pump technology is trying to reduce power consumption, absorption heat pump technology has continued to improve to reduce thermal energy consumption or lower the temperature of thermal energy. By converting to technology, it was attempted to achieve innovative COP by reducing the heating energy input, which was the root cause of the low COP of the absorption system, to 1/10 level. The technical approach of this study is to convert the thermal energy-based regeneration of the absorbent aqueous solution into a completely non-heating type. We produced a quasi-isothermal compression test facility that verifies the principle of the pressurization system of the working fluid to improve the efficiency of the nonheating regeneration process. The basic experiment was carried out by changing the type. A quasi-isothermal compression test facility was fabricated to verify the principle of the working fluid pressurization system to improve the efficiency of the non-heating regeneration process. Basic experiments were conducted by changing the pressurized pressure, air pocket size, temperature and pressure as well as the types of pressurized fluids such as air, water and ionic liquid.
일체형 삼점지지 고압 LNG 2차 펌프 rotor의 1차 mode 특성을 고려한 Balancing 벡터선도 연구
최병근(Byeong Keun Choi),박선휘(Sun Hwi Park),하정민(Jeong Min Ha),김효중(Hyo Jung Kim),김학은(Hack Eun Kim) 한국소음진동공학회 2016 한국소음진동공학회 학술대회논문집 Vol.2016 No.4
Balancing of rotating machinery can determines the life of the machine. before further damage occurs. The subject of this paper is a secondary high-pressure LNG Pump. This pump has a long shaft and integral type of rotor. Also, the shaft has three support points. This shape has difficulty correcting the unbalance using the existing two-plane balancing. Therefore balancing technology development is required. It simulated a high-pressure LNG Pump with Rotor and Shaft shape of the subject integrated using Pilot Rotor as previous studies to determine the optimal balancing rpm of the Lab Scale Shaft. By carrying out balancing at each rpm, we compared the amplitude, drew the graph and compared every aspect resulted from balancing at each rpm. Then, we check which rpm the most advantageous balancing occurs at.
노영진(Young Jin Roh),박선휘(Sun Hwi Park),김선화(Seonhwa Kim),박준현(Jun Hyun Park) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.4
수소 충전 차량용기와 같은 밀폐공간에서의 가스 누출 시 중대 사고의 개연성이 높으므로 수소를 생산, 수송, 저장하기 위한 제품의 개발과 더불어 안전 기술개발은 중요하다<sup>(1)(2)</sup>. 수소가스는 부력, 확산속도, 작은 분자크기 등으로 인해 다른 가스에 비해 점화시키기 어려울 뿐만 아니라 연소 상태를 유지하기가 어려우므로 수소화재가 발생하려면 적당한 수준의 수소농도, 산소농도 및 점화원이 존재하여야 한다. 또한 점화원의 측면에서 정전기는 위험장소에서의 정전기 관련 사고·재해가 발생하지 않도록 사전에 산업설비 및 인체 상호간의 시스템적 관점에서 발생수준을 안전한 상태로 관리하는 것이 무엇보다도 중요하다<sup>(3)(4)</sup>. 특히 점화원이 정전기인 경우, 정전기는 재현성이 없는 현상이기 때문에 측정 결과가 매우 분산되어 나타나고 재해의 대부분은 대전량이 어느 수준을 넘으면 반드시 발생하는 확정 현상이 아니고 어떤 빈도로 발생하는 확률 현상이다. 따라서 본 연구에서는 마찰에 의한 정전기 전위량 측정, 수소화재가 착화되는 최소 가스 누설량 측정하여 수소가스 누설과 정전기량의 상관관계를 분석하였다. 또한 누설되는 수소가스의 거동을 전산유체역학적 해석으로 검토하였다. 향후 수소가스 설비의 사고 예방 및 안전대책을 수립하는 참고자료로 활용하고자 한다. Generally, hydrogen gas is difficult to ignite compared to other gases due to buoyancy, diffusion rate, and small molecular size, and it is difficult to maintain a combustion state. Therefore, in order to generate hydrogen fire, the hydrogen concentration, oxygen concentration, and ignition source must exist appropriately. In addition, in terms of ignition sources, it is of utmost importance to manage the level of static electricity in a safe state in advance from a systemic point of view between industrial facilities and human bodies so that static electricity-related accidents and disasters do not occur in hazardous places. In particular, when the ignition source is static electricity, since static electricity is a phenomenon that has no reproducibility, the measurement results have scatters, and most of the disasters are not a definite phenomenon that necessarily occurs when the amount of charge exceeds a certain level, but a probability phenomenon that occurs at a certain frequency. Therefore, in this study, the correlation between the hydrogen gas leakage and the amount of static electricity was analyzed by measuring the amount of electrostatic potential due to friction and the minimum gas leakage at which the hydrogen fire is ignited. In addition, the behavior of the leaked hydrogen gas through computational fluid dynamics analysis will be used as references to establish accident prevention and safety measures for hydrogen gas facilities.