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수평관내 $CO_2$의 초임계 영역내 열전달에 관한 연구
오후규,이동건,손창효,Oh Hoo-Kyu,Lee Dong-Geon,Son Chang-Hyo 한국마린엔지니어링학회 2005 한국마린엔지니어링학회지 Vol.29 No.5
The cooling heat transfer coefficient of $CO_2$(R-744) in a horizontal tube was investigated experimentally. The experiments were conducted without oil in a closed refrigerant loop which was driven by a magnetic gear pump. The main components of the refrigerant loop are a receiver, a variable-speed pump. a mass flow meter. a pre-heater and gas cooler(test section). The test section consists of a smooth, horizontal stainless steel tube of 7.75 mm inner diameter. The experiments were conducted at mass flux of 200 to $400\;kg/m^{2}s$ and the inlet cooling pressure of 7.5 MPa to 10.0 MPa. The variation of heat transfer coefficient tends to decrease as cooling pressure of $CO_2$ increases. The heat transfer coefficient with respect to mass flux increases as mass flux increases. The pressure drop of $CO_2$ in the gas cooler shows a relatively good agreement with that predicted by Blasius's correlation. The local heat transfer coefficient of $CO_2$ agrees well with the correlation by Bringer-Smith.
오후규(Hoo-Kyu Oh),전민주(Min-Ju Jeon),유태근(Tae-Guen Yu),장승일(Seung-Il Jang),손창효(Chang-Hyo Son) 한국마린엔지니어링학회 2006 한국마린엔지니어링학회 학술대회 논문집 Vol.2006 No.-
The heat transfer of CO₂ has a greater effect on nucleate boiling more than convective boiling. Mass flux of CO₂ does not effect nucleate boiling too much. In comparison with test results and existing correlations, it is necessary to develop reliable and accurate predictions determining the evaporative heat transfer coefficient of CO₂ in a horizontal tube.
R744-R404A용 캐스케이드 냉동시스템의 성능 분석
오후규(Hoo Kyu Oh),최경민(Kyoung Min Choi),이대훈(Dae Hun Lee),전민주(Min Ju Jeon),손창효(Chang Hyo Son) 한국마린엔지니어링학회 2010 한국마린엔지니어링학회 학술대회 논문집 Vol.2010 No.10
In this paper, cycle performance analysis of R744-R404A cascade refrigeration system is presented to offer the basic design data for the operating parameters of the system. The main results were summarized as follows : The COP of cascade refrigeration system increases with the increasing subcooing degree, but decreases with the increasing superheating degree. The COP of this system increases with the decreasing condensing temperature, and increases with the increasing evaporating temperature. Therefore, superheating and subcooling degree, evaporating and condensing temperature of R744-R404A cascade refrigeration system have an effect on the COP of this system.
R744를 2차 냉매로 사용하는 내부열교환기 부착 R404A 냉동시스템의 성능 분석
오후규(Hoo-Kyu Oh),손창효(Chang-Hyo Son),이문빈(Wen-Bin Yi),전민주(Min-Ju Jeon) 대한설비공학회 2013 설비공학 논문집 Vol.25 No.10
A thermodynamic analysis of the R404A refrigeration system with an internal heat exchanger using R744 as a secondary refrigerant is presented in this paper to optimize the design for operating parameters of the system. The main results are summarized as follows: The COP increases with increasing subcooling and superheating degree of R404A, internal heat exchanger and compression efficiency of the R404A cycle and evaporating temperature of the R744 cycle and decreasing temperature difference of the cascade heat exchanger and condensing temperature of the R404A cycle. The mass flow ratio decreases with increasing evaporating temperature of the R744 cycle and internal heat exchanger efficiency of the R404A cycle and decreasing subcooling and superheating degree of the R744 cycle, temperature difference of the cascade heat exchanger and condensing temperature of the R404A cycle.