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경사진 헬리컬 코일 열교환기의 열전달 특성에 관한 연구
손창효,전민주,장승일,오후규,Son, Chang-Hyo,Jeon, Min-Ju,Jang, Seong-Il,Oh, Hoo-Kyu 한국마린엔지니어링학회 2007 한국마린엔지니어링학회지 Vol.31 No.6
The heat transfer coefficient and Pressure drop during gas cooling process of $CO_2$ (R-744) in inclined 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 2.45mm inner diameter. The refrigerant mass fluxes were varied from 200 to $600[kg/m^2s]$ and the inlet Pressures of gas cooler were 7.5 to 10.0 [MPa]. The heat transfer coefficients of $CO_2$ in the inclined helical coil tubes increases with the increase of mass flux and gas cooling pressure of $CO_2$. The pressure drop of $CO_2$ in the gas cooler shows a relatively good agreement with those Predicted by Ito's correlation developed for single-phase in a helical coil tube. The local heat transfer coefficient of $CO_2$ agrees well with the correlation by Pitla et al. However, at the region near pseudo-critical temperature. the experiments indicate higher values than the Pitla et al. correlation. Therefore. various experiments in the inclined helical coil tubes have to be conducted and it is necessary to develop the reliable and accurate prediction determining the heat transfer and pressure drop of $CO_2$ in the inclined helical coil tubes.
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.
인버터 주파수 제어에 따른 CO<SUB>2</SUB>용 수냉식 열펌프의 성능 특성
손창효(Son, Chang-Hyo) 한국산학기술학회 2010 한국산학기술학회논문지 Vol.11 No.12
본 논문은 압축기 인버터 주파수 제어에 따른 CO₂용 수냉식 열펌프의 성능 특성에 대해서 실험적으로 조사 하였다. 실험장치는 압축기, 가스냉각기, 팽창밸브, 증발기, 내부 열교환기, 수액기로 구성된다. 실험장치에 사용된 모 든 열교환기는 동관으로 제작된 이중관식 대향류형이다. 가스냉각기와 증발기는 2.4 m인 소시험부 6개와 4개로 각각 구성된다. 실험결과를 요약하면, 우선 증발기와 가스냉각기의 입구온도와 냉매유량이 일정한 조건하에서 압축기 인버 터 주파수가 증가할수록 압축비와 토출압력이 증가한다. 또한 인버터 주파수가 증가할수록 난방능력과 압축일량은 증 가하는 반면 성능계수는 감소한다. 그리고 증발기 입구 2차유체의 온도가 15℃에서 25℃로 증가함에 따라 압축비와 압축일량은 감소하지만 질량유량, 난방능력, 성능계수는 증가한다. 위의 이러한 경향은 종래의 프레온계 냉매 시스템 의 성능 변화와 유사하다. The performance characteristics of water-chilling heat pump using CO₂ for the control of inverter frequency 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 2.4m length. The experimental results summarize as the following: for constant inlet temperature of evaporator and gas cooler, as mass flow rate, compression ratio and discharge pressure increases with the inverter frequency. And heating capacity and compressor work increases, but coefficient of performance(COP) decreases with the inverter frequency of compressor. As inlet temperature of secondary fluid in the evaporator increases from 15℃ to 25℃, compression ratio and compressor work decreases, but mass flow rate, heating capacity and COP increases with the inverter frequency of compressor. The above tendency is similar with performance variation with respect to the variation of inverter frequency in the conventional vapor compression refrigeration cycle.
손창효(Chang-Hyo Son),오후규(Hoo-Kyu Oh) 대한설비공학회 2011 설비공학 논문집 Vol.23 No.6
This paper describes the analysis on freeze and refrigeration capacity of cold storage facilities for fisheries products during the last 15 years. And based on the analysis results, we prospect the number and scale of cold storage facilities in the near future. The main analysis results are summarized by the followings; Under the present conditions, the number and scale of our facilities is 879 and 3,586,824 ton, respectively. In comparison of the present and last 15 years ago, the business number increases about 22%, the accommodation capacity increases approximately 80%. In the reported update reference with the related data during the last 15 years, the capacity of cold storage facilities in 2011 expects to reach up to 4,600,000 ton. The newly established facility in 2011 has the function of a multi-purpose distribution center as well as the existing cold storage, but this facilities converges in the capital area. Therefore, in this paper, we provided the basic reference data for the present situation and prediction of our cold storage facilities. But it is necessary to investigate and analyse widely our cold storage facilities for fisheries products in the near future.
손창효(Son, Chang-Hyo) 한국산학기술학회 2008 한국산학기술학회논문지 Vol.9 No.3
수평관내 CO₂의 증발 열전달 계수를 실험적으로 조사하였다. 냉매 순환루프의 주요 구성품은 수액기, 변속 냉매 펌프, 질량 유량계, 예열기, 증발기(시험부)로 구성된다. 시험부는 내경 4.57㎜의 수평 평활 스텐레스관이다. 실험은 질량유속 400-900 ㎏/㎡s, 포화온도 5-20℃, 열유속 10-40 ㎾/㎡인 조건에서 수행하였다. 실험결과로부터 CO₂의 열전달은 대류비등보다는 핵비등에 더 많은 영향을 받는 것을 알 수 있었고, CO₂의 질량유속은 핵비등에 많은 영향을 미치지 않는 것으로 나타났다. 실험결과와 종래의 상관식을 비교해 본 결과, 기존의 상관식은 실험데이터를 과소예측하였지만, 정 등의 상관식은 좋은 일치를 보였다. 따라서, 수평관내 CO₂의 증발 열전달 계수를 예측할 수 있는 정확한 상관식의 개발이 필요하리라 판단된다. The evaporation heat transfer coefficient of CO₂ (R-744) in a horizontal tube was investigated experimentally. The main components of the refrigerant loop are a receiver, a variable-speed pump, a mass flow meter, a pre-heater and evaporator (test section). The test section consists of a smooth, horizontal stainless steel tube of inner diameter of 4.57㎜. The experiments were conducted at mass flux of 400 to 900 ㎏/㎡s, saturation temperature of 5 to 20℃, and heat flux of 10 to 40 ㎾/㎡. The test results showed the heat transfer of CO₂ has a greater effect on nucleate boiling more than convective boiling. Mass flux of CO₂ does not affect nucleate boiling too much. In comparison with test results and existing correlations, All of the existing correlations for the heat transfer coefficient underestimated the experimental data. However Jung et al.'s correlation showed a good agreement with the experimental data. Therefore, it is necessary to develope accurate predictions determining the evaporation heat transfer coefficient of CO₂ in horizontal tubes.