• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• 제31권11호
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• pp.15-19
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• 2002

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• 제31권11호
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• pp.20-26
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• 2002

• Journal of the Korean Institute of Gas
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• 제11권4호
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• pp.35-40
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• 2007

In this paper, evaporation heat transfer characteristics of propane and iso-butane in micro-fin tubes were investigated experimentally. Test section has a micro-fin tube with outside diameter of 12.70 mm, and 75 fins with a fin heights of 0.25 mm. The experimental results summarize as the followings: The average evaporation heat transfer coefficients of He's refrigerants is higher than those of HCFC22, and appeared in the order of iso-butane, propane with respect to the approaching of the high mass flux. The evaporation heat transfer coefficient of micro fin tube is about $10{\sim}80%$ higher than those of smooth tube. This results from the study can be used in the case of designing heat transfer exchanger using hydrocarbons as the refrigerant for the air-conditioning systems.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• 제10권5호
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• pp.569-580
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• 1998

In this study, condensation heat transfer coefficients(HTCs) of a plain tube, low fin tube, and Turbo-C enhanced tube for CFC-11, HCFC-123, CFC-12, HFC-l34a are measured and compared against each other. All data are taken at the vapor temperature of 39$^{\circ}C$ with a wall subcooling temperature 3~8$^{\circ}C$. Test results show that HTCs of a low vapor pressure refrigerant, HFC-123, for a plain, low fin, and Turbo-C tubes are 10.5~20.5%, 8.2~12.2%, 16.5~19.2% lower than those of CFC-11, respectively. On the other hand, HTCs of a medium vapor refrigerant, HFC-l34a, for a plain, low fin, and Turbo-C tubes are 20.6~31.8%, 0.0~8.0%, 13.2~20.9% higher than those of CFC-12, respectively. For all refrigerants tested, HTCs of Turbo-C tube are the highest among the three tubes showing almost 8 times increase in HTCs as compared to those of a plain tube. Nusselt's prediction equation for a plain tube yielded 12% deviation for all plain tube data while Realty and Katz's prediction equation for a low fin tube yielded 20% deviation for all low tube data.

• Journal of the Korea Academia-Industrial cooperation Society
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• 제16권11호
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• pp.7736-7744
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• 2015

Considering the significant waste of industrial energy, effective use of low temperature waste heat is extremely important. In this study, a heat pump cycle with double effect and double stage was realized, which escalates the hot water temperature from $50^{\circ}C$ to $70^{\circ}C$ using $160^{\circ}C$ high temperature heat source and $17^{\circ}C$ low temperature heat source. The steam generated in the first generator condenses in the first condenser generating steam in the second generator. The steam condenses in the second condenser and is provided to the second evaporator. Part of the water out of the second evaporator is supplied to the first evaporator, which evaporates using low temperature waste heat. The evaporated steam enters the first absorber and the second evaporator. The steam out of the second evaporator is absorbed into the solution at the second absorber. The hot water temperature is raised in the second condenser and in the second absorber. Proper flow rates and UA values, which satisfied temperature lift $20^{\circ}C$ and COP 1.6, were deduced through trior and error. The COP increases as the temperature of the high temperature water increases, hot water temperature decreases and flow rate increases, waste water temperature and flow rate increases, solution circulation rate decreases. On the other hand, the temperature rise of the hot water increases as the temperature of the high temperature water increases, hot water temperature increases and flow rate decreases, waste water temperature and flow rate increases, solution circulation rate increases. In addition, the COP and hot water temperature rise increase as UAs of the heat exchangers increase.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• 제13권2호
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• pp.122-133
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• 2001

Pool boiling heat transfer coefficients(HTCs) of HFC32/HFC134a, HFC125/HFC134a, HFC32/HFC125 and HFC32/HFC125/HFC134a were measured on a horizontal smooth tube. The experimental apparatus was specially designed to simulate the real heat transfer tube with the use of the secondary fluid of water. Data were taken in the order of decreasing heat flux starting at 80kW/$m^2\; and\; ending\; at\; 5kW/m^2$ in the pool temperature at $7^{\circ}C$. Test results showed that HTCs of these mixtures were 11~38% lower than those of ideal HTCs calculated by a linear mixing rule with pure fluids、 HTCs. Experimental data were compared with Stephan & Korner, Thome, Schlunder, Thome & Shakir、s correlations only to find that those correlations were not satisfactory for all fluids. Hence, a new correlation based on the present data was proposed which could be applied even to the ternary mixture. The correlation predicts the degradation of HTCs of mixtures well, showing a mean deviation of less than 15% for all the mixture data.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• 제31권11호
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• pp.8-14
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• 2002

가정용 룸에어컨이나 가정, 점포, 사무실에 사용하는 패키지에어컨은 쾌적한 주거 사무공간을 실현할 수 있기 때문에 최근 10년 동안에 광범위하게 보급되었고, 그 기술도 해마다 진보하고 있다. 그림 1에서 나타나듯이 2001년 가정용 룸에어컨의 국내생산 수량은 연간 600만대 수준이며, 패키지에어컨은 연간 약 80만대 수준이다. 2001년 기준으로 에어컨의 국내시장규모는 약 130만대로 세대 보급률이 약 40%에 도달하고 있다. 비록 패키지에어컨은 생산 수량면에서는 룸에어컨과 비교할 수 없지만, 한대의 냉방능력이 룸에어컨의 수배에서 수십배로 크기 때문에 전력에너지소비, 환경 등에 미치는 영향은 룸에어컨과 비견될 수 있다. 공조장치 보급에 따른 환경, 에너지 측면에서의 사회적 영향과 관심이 점차 커지고 있고, 이것을 개선하기 위한 기술개발이 활발하게 진행되고 있다. 에어컨을 포함한 공조장치의 다수는 효율이 좋은 증기 압축식 냉동사이클로써 구성되어 있으며, 증기 압축식 사이클에서 냉매가스를 압축하여 순환시키는 심장역할을 하고 있는 것이 압축기이다. 또한 압축기는 공조장치 전체의 전력소비의 80%에서 90%을 차지하고 있어 에너지절감 기술개발과 환경기술개발의 포인트가 되는 기구이다. 최근에 에어컨용 냉매압축기의 기술적인 개발동향을 정리하면 다음과 같은 경향으로 진행되고 있다. (1)오존층 파괴 지수가 제로인 친환경 HFC계와 자연냉매용 밀폐형 압축기기술 (2)로터리압축기의 성능향상 및 대용량화 기술 (3)압축기용 모터의 DC화통에 의한 모터 효율 향상 및 압축기 효율 향상 기술 (4)스크롤압축기의 압축비 변화의 대응, 고효율 유지, 대용량화 등 성능향상기술 (5)로터리, 스크롤, 왕복동 압축기를 이용한 용량가변기술 본 논고에서는 룸에어컨과 패키지에어컨에서 사용되고 있는 밀폐형 압축기에 대해서 그림 2에서 나타내고 있는 냉방능력 10tons(120,000Btu/h) 이하를 중심으로 상기의 최근 기술 동향을 간략하게 소개하고자 한다.

• Journal of the Korean Society of Marine Environment & Safety
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• 제27권6호
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• pp.839-845
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• 2021

In this study, it shows the efficiency of each refrigerant through simulation method for ORC (Organic Rankine Cycle) power generation that converts waste heat discarded by ship exhaust into electricity for the purpose of reducing CO₂ emission and increasing ship waste heat recovery. by Simulation was performed with waste heat from the exhaust gas which is relatively high temperature and cooling sea water which is relatively low temperature from ships. As a result of the sea water cooling ORC power generating system, efficiency of the working fluid with R717 is highest as a 2.86 % and the next working fluid is R152a, R134a, R143a and R125a.

• Journal of the Korea Academia-Industrial cooperation Society
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• 제14권11호
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• pp.5317-5322
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• 2013

This study presents a prediction method for heat transfer performance of a gas cooler of $CO_2$ heat pump using ${\epsilon}$-NTU method, and compared the results with the experimental data from the open literature. The heat transfer rate, refrigerant side outlet temperature and water side outlet temperature were calculated by using EES(Engineering Equation Solver)program in multi-tube-in-tube type $CO_2$ heat pump gas cooler. Analysis was performed in two methods : The first method performed without dividing into the test section by applying an analysis of the mean properties(mean analysis). The second method, tube length divided into 50 sections, was applied to the local properties(local analysis). From the present study, a good agreement at the local analysis was obtained between the analytical and experimental results by 0.3~1.1%, 1.31~1.88% and 3.12~5.18% for heat transfer rate, water and refrigerant side outlet temperatures, respectively.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• 제1권1호
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• pp.47-50
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• 1972

Farbwerke Hoechst 주식회사는 냉매 11, 12, 13 및 13B1의 열역학적 상태량(Thermodynamic Properties)을 결정하는 컴퓨터 프로그램밍을 가능케 하였다. 이들 프로그램밍은 냉동계산의 체계안에서 서브루우틴으로써 사용될 수 있다.