http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
한도영(Doyoung Han),박승호(Seungho Park) 대한설비공학회 2009 대한설비공학회 학술발표대회논문집 Vol.2009 No.-
Control methods for a CO₂ air-conditioning system should be different because of CO₂'s unique properties as a refrigerant. Especially, the high-side pressure of a CO₂ system should be controlled for the effective operation of a system. In this study, a fuzzy algorithm was developed for the control of the refrigerant pressure. The refrigerant pressure difference and its slope were used as input variables and the control signal difference for a electronic expansion valve was used as an output variable. The Min-Max method was used as an inference machine and the weight centroid method was used as a defuzzification tool. In order to identify the effectiveness of the control algorithm, an initial start-up test, an indoor temperature setpoint step change test, and an outdoor air disturbance test, were performed. Test results showed the good control of a CO₂ air-conditioning system with stable control signals. Therefore the pressure control algorithm developed for this study may be practically applied for the control of an electronic expansion valve.
CO₂의 상변화를 고려한 압력 제어 밸브 모델링 및 검증
최지아(Ji Ah Choi),장지성(Ji Seong Jang) 대한기계학회 2020 大韓機械學會論文集B Vol.44 No.9
최근 천연 냉매를 이용한 냉동·공조 시스템 연구가 활발히 진행되고 있다. 이 중 이산화탄소는 작동 압력이 상대적으로 높기 때문에 기존 냉동 · 공조 시스템에 비해 압력비가 작다. 또한, 지구 온난화 지수가 낮기 때문에 친환경적이다. CO₂ 냉매를 이용하는 압력 제어 밸브는 냉동·공조 사이클에서 유체가 기체, 액체, 이상 유동 상태인 모든 부분에 사용된다. 그러므로 본 연구에서는 상변화를 고려한 CO₂ 냉매용 압력제어 밸브의 분석 모델을 개발하고, 실험 결과와 비교를 통하여 검증하였다. Recently, industrial systems using natural refrigerants have been researched. Among these natural refrigerants, carbon dioxide, owing to its relatively high operating pressure, has a smaller pressure ratio compared with those of existing refrigeration systems. Furthermore, it is eco-friendly because it exhibits low global warming potential. The pressure control valve using CO₂ refrigerant is used for all parts where the fluid is gas, liquid and two-phase states in refrigeration and air-conditioning cycle. Therefore, in this study, an analysis model of pressure control valves using a CO₂ refrigerant was developed considering phase change; this model was verified by comparing them with experimental results.
CO₂-R134a용 2단 팽창식 오토 캐스케이드 냉동기의 성능특성 연구
정일영(Il Young Jung),문경록(Kyung Rok Mun),윤상국(Sang Kook Yun) 대한설비공학회 2018 설비공학 논문집 Vol.30 No.11
Air-cooled CO₂ refrigerators have several disadvantages, which have much difficulties to manufacture the components due to super-critical pressure over 130 bar, and to make efficient evaporation using ambient air in cold winter because of higher evaporation temperature. This research aims to overcome these disadvantages and to improve the energy efficiency by introducing a new lower-pressure two-stage expansion process in auto-cascade heat pump system. The CO₂-R134a zeotropic refrigerants in two-stage expansion in the effective flow configuration process of new auto-cascade refrigerator is considered. Results indicate that the new two-stage expansion system shows significant performance improvements as about 180% higher when high pressure of 50 bar, intermediate expansion pressure of 30 bar, and final low pressure of 7 bar are applied. It operates at a much lower evaporation temperature of -10℃ or below than original one-stage expansion system.
김보현(Bo Hyun Kim),장지성(Ji Seong Jang) 유공압건설기계학회 2018 드라이브·컨트롤 Vol.15 No.4
Pilot operated control valve for CO₂ refrigerant is a valve that can perform various functions according to the user"s intention by replacing pilot units, widely used for flow rate, pressure, and temperature control of refrigeration and air conditioning systems. In addition, CO₂ refrigerant, that requires high pressure and low critical temperature, can be installed and used in all positions of the refrigeration system, regardless of high or low pressure. In this paper, response characteristics are modeled and analyzed based on behavior of the main piston of the pilot-operated control valve. Although various factors influence operation of the main piston, this paper analyzes the effect of equilibrium pressure depending on valve installation position and application, and inlet and outlet orifice size of the load pressure feedback chamber to determine feedback characteristics of the main piston. As a result, it was possible to quantitatively analyze the effect of change in equilibrium and load pressure feedback chamber flow path size on the change in main piston dynamic and static characteristics.