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경사진 헬리컬 코일형 가스냉각기의 관형상에 따른 CO2냉각 열전달 특성
손창효,오후규 대한설비공학회 2007 설비공학 논문집 Vol.19 No.9
The cooling heat transfer coefficient of CO2 (R-744) for tube and coil diameter (CD), inclined angle of tube and coil pitch of inclined helical coil type copper tubes were investigated experimentally. The main components of the refrigerant loop are a receiver, a variable- speed pump, a mass flow meter, a pre-heater and a inclined helical coil type gas cooler (test section). The test section consists of a smooth copper tube of 2.45 and 4.55mm inner diameter (ID). The refrigerant mass fluxes were varied from 200 to 800[kg/m2s] and the inlet pressures of gas cooler were 7.5 to 10.0[MPa]. The heat transfer coefficients of CO2 in inclined helical coil tube with 2.45mm ID are 5∼10.3% higher than those of 4.55mm ID. The heat transfer coefficients of 41.35mm CD are 8∼32.4% higher than those of 26.75mm CD. Comparison between 45° and 90° of coil angle, the heat transfer coefficients of 45° are higher than those of 90°. For coil pitch of gas cooler, the heat transfer coefficients of inclined helical coil gas cooler with coil pitch of 5 mm are similar to those of 10 and 15mm.
헬리컬 코일형 가스냉각기 내 CO2의 냉각 열전달 특성
손창효,전민주,오후규 한국마린엔지니어링학회 2007 한국마린엔지니어링학회지 Vol.31 No.6
The cooling heat transfer coefficient and pressure drop of CO2 (R-744) in helical coil copper tubes were investigated experimentally. The main components of the refrigerant loop are a receiver, a variable-speed pump, a mass flow meter, a pre-heater and a inclined helical coil type gas cooler (test section). The test section consists of a smooth copper tube of 2.45 and 4.55 mm inner diameter. The refrigerant mass fluxes were varied from 200 to 600 [kg/m2s] and the inlet pressures of gas cooler were 7.5 to 10.0 [MPa]. The heat transfer coefficients of CO2 in helical coil tubes increase with the increase of mass flux and gas cooling pressure of CO2. The pressure drop of CO2 in the gas cooler shows a relatively good agreement with those predicted by Ito’s correlation developed for single-phase in helical coil tubes. Though a few correlation available with the data, the local heat transfer coefficient of CO2 agrees well with those presented by Pitla et al. among the predictions. However, at the region near pseudo-critical temperature, the experiment data indicate higher values than the Pitla et al. correlation.
2차 유체 조건 변화에 대한 CO2용 수냉식 열펌프의 성능 특성에 관한 연구
손창효,오후규 한국마린엔지니어링학회 2007 한국마린엔지니어링학회지 Vol.31 No.5
The performance characteristics of water-chilling heat pump using CO2 with respect to variation of inlet temperature and mass flow rate of secondary fluid was investigated experimentally. An experimental apparatus is consisted of a compressor, a gas cooler, an expansion valve, an evaporator and a liquid receiver. All heat exchangers used in the test rig are counter-flow-type heat exchangers with concentric dual tubes, which are made of copper. The gas cooler and the evaporator consist of 6 and 4 straight sections respectively arranged in parallel, each has 2.4 m length. The experimental results were summarized as the followings : As inlet temperature of secondary fluid in the gas cooler increases from 10℃ to 40℃, the compressor work, heating capacity and heating COP were varied to 37.8%, -13%, -35.9%, respectively. The heating capacity, compressor work, heating COP were turned into 23.3%, 6.42%, 13.1%, respectively when mass flow rate of secondary fluid in the evaporator increases from 70 g/s to 150 g/s. The above tendency is similar with performance variation with respect to temperature variation of secondary fluid in the conventional vapor compression cycle.
외기 온도 변화에 따른 액화 공기 발전소 저온 공기를 활용한 냉방시스템 성능분석
손창효,윤정인,설성훈,이준혁,최재원,차승윤 한국동력기계공학회 2023 동력시스템공학회지 Vol.27 No.2
Recently, the government is planning to utilize new and renewable energy, and research on ESS is being conducted for the storage and stabilization of generated electricity. In particular, research on LAES is being conducted among several ESSs, and this paper conducted a study on the cooling system associated with LAES. A simulation was conducted using Hysys as a cooling method in which low-temperature air discharged after power generation using liquefied air is supplied to the room. As a result, an energy saving rate of about 75 to 94% was shown at a heat load of 5RT, and the energy saving rate increased as the consumption of low-temperature air increased. The data in this paper are provided as basic data for cooling system design using LAES. 최근 정부는 신재생에너지를 활용하는 계획이 진행되고 있으며, 생산된 전력의 저장 및 안정화를위해 ESS에 대한 연구가 진행되고 있다. 특히, 여러 ESS 사이에서 LAES에 대한 연구가 진행되고 있으며, 본 논문은 LAES와 연계된 냉방시스템에 대한 연구를 진행하였다. 액화 공기를 활용한 발전 후 토출되는저온 공기를 실내로 급기하는 냉방방식으로 Hysys를 통한 시뮬레이션을 진행하였다. 그 결과, 5 RT의 열부하에서 약 75~94%의 에너지 절감률을 보였으며, 저온 공기의 소모량을 늘릴수록 에너지 절감률이 높아지는 결과를 얻었다. 본 논문의 자료는 LAES를 활용한 냉방시스템 설계의 기초 자료로 제공된다.
냉매 충전량에 따른 CO<sub>2</sub>용 수냉식 열펌프의 성능 특성에 관한 연구
손창효,유태근,장승일,오후규,Son, Chang-Hyo,Yu, Tae-Guen,Jang, Seong-Il,Oh, Hoo-Kyu 한국마린엔지니어링학회 2007 한국마린엔지니어링학회지 Vol.31 No.5
The performance characteristics of water-chilling heat pump using $CO_2$ with respect to variation of refrigerant charge amount was investigated experimentally. An experimental apparatus is consisted of a compressor, a gas cooler, an expansion valve, an evaporator and a liquid receiver. All heat exchangers used in the test rig are counter-flow-type heat exchangers with concentric dual tubes, which are made of copper. The gas cooler and the evaporator consist of 6 and 4 straight sections respectively arranged in parallel, each has 2400 mm length. The experimental results summarize as the followings : As the refrigerant charge ratio of $CO_2$ heat pump system increases, the discharge pressure and compressor ratio increases, but mass flow rate of refrigerant decreases. Also the compressor work increases with the increase of refrigerant charge ratio. However, the heating and cooling capacity of $CO_2$ heat pump decreases as the refrigerant charge ratio increases. The maximum heating COP of $CO_2$ heat pump system presented at 0.25 refrigerant charge ratio. It is possible to confirm the optimum charge ratio of $CO_2$ heat pump system by the viewpoint of heating COP.