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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.
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.
손창효(Son, Chang-Hyo) 한국산학기술학회 2008 한국산학기술학회논문지 Vol.9 No.2
본 논문은 수평 이증관식 열교환기 내 프레온계 냉매의 대체냉매인 탄화수소계 냉매(R-290과 R-600a)의 증발 열전달 계수에 대한 실험적 결과를 나타내었다. 증발기의 내관 내경은 각각 10.07 ㎜와 6.54 ㎜의 2가지를 사용하였다. 증발실험은 질량유속 35.5~210.4 ㎏/㎡s이고, 냉각용량 0.95~10.1 ㎾인 조건에서 수행하였다. 실험결과를 요약하면, 탄화수소계 냉매 R-290과 R-600a의 증발 열전달 계수가 프레온계 냉매 R-22보다 높았다. 즉, R-22의 증발 열전달 계수에 비해, R-290와 R-600a는 각각 56.7~70.1%와 46.9~59.7% 정도 높았다. 실험데이터와 종래의 상관식을 비교한 결과, 모든 냉매와 관경에 대해서 Kandlikar 상관식이 가장 좋은 일치를 보였다. This paper presents the experimental results of evaporation heat transfer coefficients of HC(e.g. R290 and R600a), R-22 as a HCFCs refrigerant in horizontal double pipe heat exchangers, having four different inner diameters of 10.07 ㎜ and 6.54 ㎜ respectively. The experiments of the evaporation process were conducted at mass flux of 35.5~210.4 ㎏/㎡s and cooling capacity of 0.95~10.1 ㎾. The main results were summarized as follows : The average evaporation heat transfer coefficient of R-290 and R-600a was higher value than that of R-22. In comparison with R-22, the evaporation heat transfer coefficient of R-290 and 600a is approximately 56.7~70.1% and 46.9~59.7% higher, respectively. In comparison with experimental data and some correlations, the evaporation heat transfer coefficients are well matched with the Kandlikar’s correlation regardless of a type of refrigerants and tube diameters.
손창효(Chang-Hyo Son),이동건(Dong-Gun Lee),노건상(Gun-Sang Roh),박기원(Gi Won Park),오후규(Hoo-Kyu Oh) 한국마린엔지니어링학회 2003 한국마린엔지니어링학회 학술대회 논문집 Vol.2003 No.-
The heat transfer coefficient and pressure drop of CO₂(R-744) during gas cooling process of carbon dioxide in a horizontal tube were investigated. The experiments were conducted without oil in the refrigerant loop. The main components of the refrigerant loop consist of a receiver, a variable-speed pump, a mass flowmeter, an evaporator, and a gas cooled test section). The main components of the water loop consist of a variable-speed pump, an isothermal tank, and a flowmeter. The gas cooler is a counterflow heat exchanger with refrigerant flowing in the inner tube and water flowing in the annulus. The test section consists of smooth, horizontal stainless steel tube of 9.53 mm outer diameter and 7.75 mm inner diameter. The length of test section is 6 m. The refrigerant mass fluxes were 200 -300kg/(m2·s) and the inlet pressure of the gas cooler varied from 7.5 MPa to 8.5 MPa.<br/> The main results were summarized as follows: Pressure drop of CO2 increases with increasing gas cooler pressure. The friction factors of CO2 in a horizontal tube are showed relatively good agreement with correlation predicted by Blasius. The heat transfer coefficient of CO₂ in transcritical region increases with decreasing gas cooler pressure and decreasing mass flux of CO2. Most of correlations proposed in a transcritical region showed significant deviations with experimental data except for those predicted by Gnielinski.<br/>
수평관내 이산화탄소의 냉각열전달과 압력강하 특성에 관한 연구
손창효(Son C. H.),김종열(Kim J. R.),노건상(Roh G. S.),구학근(Ku H. G.),박기원(Park G. W.),오후규(Oh H. K.) 한국마린엔지니어링학회 2005 한국마린엔지니어링학회 학술대회 논문집 Vol.2005 No.-
This paper presents the heat transfer and pressure drop characteristics during cooling process of carbon dioxide in a horizontal tube. The test section is a tube in tube type heat exchanger with refrigerant flowing in the inner tube and water flowing in the annulus. It was made of a stainless steel tube with the inner diameter of 7.75[㎜], the outer diameter of 9.53[㎜] and length of 6000[㎜]. The refrigerant mass fluxes were 200~400[㎏/㎡s] and the average pressure varied from 7.5[㎫] to 10.0[㎫]. The main results were summarized as follows : The heat transfer coefficient of supercritical CO₂ increases in decrease of the gas cooler pressure. And the heat transfer coefficient increases with respect to the increase of the refrigerant mass flux. Among some correlations proposed in a transcritical region, Bringer-Smith's correlation has some analogy with experimental results. The pressure drop decreases in increase of the gas cooler pressure and increases with respect to increase the refrigerant mass flux.
손창효(Son, Chang-Hyo) 한국산학기술학회 2007 한국산학기술학회논문지 Vol.8 No.6
본 논문은 세관내 R-134a의 유동특성을 실험적으로 조사한 것이다. 이에 대한 실험장치는 마그네틱 기어 펌프, 증발기, 수액기, 사이트 글라스, 응축기, 계측기로 구성된다. 유동양식을 관찰하기 위한 사이트 글라스는 증발기 입출구에 설치하였다. 실험은 세관내 R-22와 R-134a의 유동특성을 살펴보기 위해서 수행되었다. 이에 대한 실험변수인 냉매질량 유속은 100에서 1000 ㎏/㎡s이고, 포화온도는 30℃이다. 증발과정 중의 유동양식에서 2 ㎜의 세관내 환상유동은 8 v관의 대구경관에 비해 저건도와 저질량유속에서 발생하였다. 본 실험결과와 종래의 유동양식 선도와 비교한 결과, 2 ㎜의 세관내 증발 유동양식은 Baker, Mandhane, Taitel-Dukler의 유동양식 선도와는 큰 차이를 보였지만, Dobson의 유동양식 선도와는 좋은 일치를 보였다. The flow characteristics of R-134a in a small diameter tube was investigated experimentally. An experimental apparatus was consisted of a magnetic gear pump, an evaporator, a sight-glass, a condenser and a measurement instruments. The sight-glass for flow pattern observations was located at the inlet and outlet of the evaporator. The experiment was carried out to show the flow characteristics of R-134a in a small diameter tube. Mass flux of refrigerants was ranged from 100 to 1000 ㎏/㎡s, the saturation temperature was 30℃. In the flow patterns during evaporation, the annular flow in a 2 ㎜ inner diameter tube occurred at a relatively lower quality and mass velocity, compared to that in a 8 ㎜ inner diameter tube. The evaporation flow pattern in a small diameter tube has been shown major deviations with the Baker, Mandhane and Taitel-Dukler’s flow pattern maps but it was similar to the Dobson’s flow pattern map.