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백영진,김민성,나호상 대한설비공학회 2014 International Journal Of Air-Conditioning and Refr Vol.22 No.1
In order to compare the performance of the carbon dioxide, propane and isobutane heat pumps formoderate to high temperature heating, the three heat pump cycles were optimized using a simulationmethod. To fairly compare the performance of the cycles by using different working fluids,each cycle was optimized from the viewpoint of heating COP by two design parameters. The first is the gas cooler (or condenser) exit temperature and the other is the ratio of the overall heatconductance of the gas cooler to the combined overall heat conductance of the gas cooler and theevaporator. The inlet and outlet temperatures of secondary fluid of the gas cooler (or condenser)were fixed at 40/90°C and 40/150°C. The heat source inlet temperature was fixed at 10°C. The°ow rates of both the heat source and the heat sink were also fixed. The results shows that thehydrocarbon heat pumps have 11–17% higher heating COP than carbon dioxide heat pump underthe simulation conditions considered in the present study. However, for a high temperatureheating, even though the isobutane heat pump shows the best performance, the carbon dioxideheat pump looks promising due to hydrocarbon heat pumps' high compression ratio.
윤형기,신광호,장기창,나호상,유성연 대한설비공학회 2006 설비공학 논문집 Vol.18 No.12
This is to characterize the fluid mechanics of surfactant water solutions, which exhibit drag reduction in the turbulent flow as compared to pure water. The emphasis is placed on those fluid characteristic aspects of drag reducing solutions which are relevant for application in closed circulation loops for the purpose of pumping power savings, like hydronic cooling and heating systems in buildings. The experiments are carried out with the solutions of the surfactant Beraid DR-IW 616 in concentration of 100∼3,000ppm.The following key parameters are focused in this study: surfactant concentration, solution temperature and pipe diameter.
300 kW급 소형 열병합발전기용 배열회수 시스템의 실증운전 성능분석에 관한 연구
김민성,백영진,박성룡,나호상 대한설비공학회 2010 설비공학 논문집 Vol.22 No.4
An exhausted heat recovery system for a small gas engine cogeneration plant was investigated. The system was designed and built in a 300kW class cogeneration demonstrative system. The basic performance was tested depending on load variation, and installed to a field site as a bottoming heat and power supply system. The exhaust gas heat exchangers (EGHXs) in shell-and-tube type and shell-and-plate type were tested. The entire efficiency of the cogeneration system was estimated between 85 to 90% under the 100% load condition, of which trend appears higher in summer due to the less thermal loss than in winter. Power generation efficiency and thermal efficiency was measured in a range of 31∼33% and 54∼57%, respectively.
수배관 절환 방식 수열 히트펌프의 난방 운전 특성에 대한 실험적 연구
김기봉,장기창,왕은석,나호상,조준현,최봉수,허재혁,이길봉 대한기계학회 2023 大韓機械學會論文集B Vol.47 No.2
The present study conducted experiment on heating and reverse-cycle operation using a low-temperature heat source. A 20 kW scale water switchable experimental device is built to develop a river water heat pump system with a heat source mix technology that can provide cooling and heating energy irrespective of the temperature characteristics of the heat source. Even at 4°C and 4.5°C, the river water heat pump demonstrates good efficiency, with COPh values of 3.05 and 3.15, respectively. The reverse-cycle operation experiment is conducted using three different methods, switching the water side valve momentarily each time the evaporator's water output temperature reaches -1°C. In the reverse-cycle operation, the inlet and outlet temperatures of the evaporator circulating water are compensated to prevent supercooling of the plate. An optimal operation control pattern to prevent supercooling is determined to be possible through reverse-cycle operation. 본 연구에서는 저온 열원 활용을 위한 난방 및 역사이클 운전에 대한 연구를 실험적으로 수행하였다. 열원의 온도 특성에 상관없이 냉·난방 에너지를 공급할 수 있는 열원 믹스 기술을 적용한 하천수 히트펌프 시스템 개발을 위해 20 kW 규모의 수절환이 가능한 실험 장치를 구축하였다. 하천수 히트펌프는 저온 열원인 4°C, 4.5°C에서도 COPh가 각각 3.05, 3.15로 좋은 효율을 보였다. 저온 열원 활용을 위한 운전 전략 중 역사이클 운전은 증발기의 물 출구 온도가 -1°C에 도달하면, 물 측 밸브를 순간적으로 절환하는 역사이클 운전 실험을 3가지 방법으로 진행하였다. 역사이클 운전은 증발기 순환수의 입·출구 온도가 보상되어 전열판의 과냉각을 방지하는 최적의 운전 제어 패턴이 가능할 것으로 판단된다.