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수평 평활관 및 전열촉진관내 대체 냉매 R-407C의 응축 열전달 특성에 관한 연구
노건상,오후규,Roh, Geonsang,Oh, Hookyu 대한기계학회 1999 大韓機械學會論文集B Vol.23 No.2
This paper reports the experimental results on heat transfer characteristics of R-22 and R-407C(HFC-32/125/134a 23/25/52 wt%) condensing inside horizontal smooth and finned tubes. The test condensers used In the study are double pipe heat exchangers of 7.5 mm ID, 9.5 mm OD smooth tube, and 60 finned micro-fin tube with 8.53 mm ID, 9.53 mm OD. Each of these tubes was 4 000 mm long tubes connected with an U-bend. These U type two-path test tubes are divided In 8 local test sections for the identification of the local condensing heat transfer characterisitcs and pressure drop, U-bend effects on condensing flows. Inlet quality is maintained 1.0, and refrigerant mass velocity is varied from 102.0 to $301.0kg/m^2{\cdot}s$. From the results, it was found that the pressure drop of the R-407C Increased, and heat transfer coefficient decreased compared to those of R-22. In comparison condensing heat transfer characteristics of micro-fm tube with those of smooth tube, increasing of condensing heat transfer coefficient was found outstanding compared to the increasing ratio of pressure drop. Furthermore, pressure drop In U-bend showed at most a 30 % compared to the total pressure drop in the test section.
최경민(Kyoung-Min Choi),전민주(Minjoo Jeon),손창효(Changhyo Son),오후규(Hookyu Oh) 대한설비공학회 2010 대한설비공학회 학술발표대회논문집 Vol.2010 No.6
The condensation heat transfer coefficients of CO₂ in smooth and micro-fin tubes were investigated experimentally. The main components of the refrigerant loop are a receiver, a pump, a mass flow meter, a preheater and a condenser(test section). The water loop consists of a pump, an flow meter. The test sections are a micro-fin tube with 4.6 ㎜ inner diameter and smooth tube with 4.95 mm inner diameter. The experiments were conducted at mass flux of 800 to 2000 ㎏/㎡s, saturation temperature of 20 to 30℃. The main results were summarized as follows : the condensation heat transfer coefficients have an effect on the mass flux of R744, saturation temperature and tube shape. Therefore, it is necessary to develop reliable and accurate predictions determining the condensation heat transfer coefficient of CO₂ in the micro-fin tube.
평활관 및 마이크로핀관 내 초임계 이산화탄소의 냉각열전달 특성
이대훈(Daehun Lee),전민주(Minjoo Jeon),손창효(Changhyo Son),오후규(Hookyu Oh) 대한설비공학회 2010 대한설비공학회 학술발표대회논문집 Vol.2010 No.6
The cooling heat transfer characteristics of supercritical CO₂ in smooth and micro-fin tubes were investigated experimentally. The main components of the refrigerant loop are a receiver, a CO₂ compressor, a mass flow meter, an evaporator and a micro-fin tube as a test section. The test was conducted at mass flux from 1200 to 2000 ㎏/㎡s, inlet cooling pressure from 9 to 10 ㎫. The cooling heat transfer coefficients of the micro-fin tube are about 12~39% higher than those of the smooth tube. In comparison with test results and existing correlations, correlations failed to predict the cooling heat transfer coefficient of CO₂ in the micro-fin tube. Therefore, it is necessary to develop reliable and accurate predictions determining the cooling heat transfer coefficient of CO₂ in the micro-fin tube.
이산화탄소용 열펌프시스템의 성능특성에 관한 실험적 연구
장승일(Seong-Il Jang),전민주(Min-Ju Jeon),유태근(Tae-Guen Yu),손창효(Chang-hyo Son),오후규(Hookyu-Oh) 한국마린엔지니어링학회 2006 한국마린엔지니어링학회 학술대회 논문집 Vol.2006 No.-
냉매 충전량과 이차유체의 입구조건은 CO₂용 열펌프시스템의 성능실험에서 중요한 제어변수이다. 따라서, 열펌프사이클의 적용과 난방성능 향상을 위해 제어변수의 특성을 조사하는 것이 필요하다. 본 논문에서, CO₂용 열펌프 사이클의 성능 실험은 여러 가지 냉매 충전량에서 이차유체 입구조건에 변화를 주어 수행 되었다. 실험결과, 난방COP는 냉매 충전량이 증가함에 따라 1158g의 냉매 충전량에서 최대가 되었다가 감소하는 경향이 나타나며, 이는 COP,가 최대가 되는 냉매충전량이 존재함을 나타낸다. 또한, 난방성능은 가스쿨러내 이차유체의 질량유량의 증가에 따라 증가하였다. 가스냉각기내 2차유체의 입구온도가 10℃에서 40℃로 증가하면, 난방용량, 압축일량, 토출압력은 각각 -8.57%, -35.78%, 32.78%로 변화했으며, 증발기 2차유체의 입구 온도가 감소하였을 때 난방 COP는 감소하는 경향을 보였다.