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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.
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.