• 설비공학논문집
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• 제16권3호
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• pp.203-210
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• 2004

This paper describes the potential advantages in applying evaporative cooling to air-cooled condensers. The cooling characteristics of an air-cooled condenser with its surface fully covered with thin water film are investigated and compared with that of an air-cooled condenser with usual dry surface. By applying the evaporative cooling, the cooling performance of the condenser is shown to improve enormously. When the outdoor air is 35$^{\circ}C$ and 40% in relative humidity, the condensing temperature of the refrigerant is decreased by 2$0^{\circ}C$. Even when the incoming air is fully saturated with water vapor, the evaporation from the wet surface occurs to cause a decrease in the condensing temperature by 1$0^{\circ}C$. The main reason for this improvement is assessed as the addition of an efficient cooling mechanism which is the water evaporation resulting in latent heat absorption.

• 한국자동차공학회논문집
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• 제12권5호
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• pp.205-210
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• 2004

Sub-cooled hybrid condenser(SCHC) which have been developed through this study is an appliance of integrating a condenser with a receiver dryer, which were previously separated. It is supposed that the development of sub-cooled hybrid condenser will be able to reduce not only weight, size, production process and cost, but also quite improve in capability, which will be of great use for the technological development and research of an air conditioning system whose importance is higher in a car. Through the present study it was found that the developed SCHC increases in the degree of sub-cooling by 10∼100% compared to conventional condenser. The excessive sub-cool has improved the cooling performance by 10%, and that leads to the reduction in evaporator outlet air temperature $1.5^{\circ}C$. Additionally, it is expected that sub-cooled hybrid condenser weights less by 100g than the previous condensers which has equal super heat.

• 대한기계학회논문집 C: 기술과 교육
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• 제3권3호
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• pp.201-207
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• 2015

공랭식 응축기(ACC, Air Cooled Condenser)는 공기를 냉매로 이용하여 저압 스팀을 응축하는 설비로써 사막이나 내륙 등 물이 부족한 지역에서 주로 사용된다. 공랭식 응축기의 성능은 풍속이나 대기온도와 같은 외기 조건에 의해 크게 영향을 받으므로 성능 저하 개선을 위해 여러 장치들이 설치된다. 본 연구에서는 풍속에 의한 ACC 성능 변화를 확인하고 윈드 스크린에 의한 성능 개선 효과를 분석하기 위해 CFD 해석을 수행하였다. CFD 는 질량 보존, 운동량 보존 등 미분방정식을 차분방정식으로 변환하여 검사 체적에 대해 속도, 온도 등을 계산하는 기법이다. 풍속이 3m/s 에서 7m/s 로 상승할 때, ACC 에 설치된 팬 공급 유량은 약 15.76% 감소하며 ACC 유입 공기 온도는 $5.55^{\circ}C$ 증가한다. 윈드 스크린을 적절히 설치한 경우, 풍속이 7m/s 이고 윈드 스크린이 설치되지 않은 경우에 비해 팬 공급 유량이 약 5.18% 증가하며 ACC 유입 공기 온도 상승은 $2.08^{\circ}C$ 감소하는 효과가 있다.

• 설비공학논문집
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• 제9권3호
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• pp.292-299
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• 1997

Ammonia has been used as refrigerant for more than 100 years in absorption as well as in compression systems. Due to its poisonous and inflammable properties, however, its use has been mainly on heavy industrial plants in which regular maintenance are available. For these systems, condensers are generally water-cooled. This is suitable for large systems over 20 RT but is not suitable for small systems. In order to apply ammonia for a small system, it is important to adopt an air-cooled condenser. In this study, simple numerical analysis of an air-cooled condenser for an ammonia refrigeration system has been carried out. The condenser is designed as horizontal tubes with plate fins attached at the outer surface to enhance the air-side heat transfer rate. Effects of fin shape and arrangement are studied in detail. Since the local heat transfer coefficient is highest at the leading edge, heat flux is highest at the edge and decreases along the distance. Conditions of inlet air are also varied in the study and condenser length that is required for full condensation is calculated. The results show that it is important to enhance both the air-side and internal heat transfer coefficients.

• International Journal of Air-Conditioning and Refrigeration
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• 제6권
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• pp.104-112
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• 1998

Ammonia has been used as refrigerant for more than 100 years in absorption as well as in compression systems. Due to its poisonous and inflammable properties, however, its use has been mainly on heavy industrial plants in which regular maintenance is available. For these systems, condensers are generally water∼cooled. This is suitable for large systems over 20RT but is not suitable for small systems. In order to apply ammonia for a small system, it is important to adopt an air-cooled condenser. In this study, simple numerical analysis of an air-cooled condenser for an ammonia refrigeration system has been carried out. The condenser is designed as horizontal tubes with plate fins attached at the outer surface to enhance the air-side heat transfer rate. Effect of fin shape and arrangement are studied in detail. Since the local heat transfer coefficient is highest at the leading edge, heat flux is highest at the edge and decreases along the distance. Conditions of inlet air are also varied in the study and condenser length that is required for full condensation is calculated. The results show that it is important to enhance both the air-side and internal heat transfer coefficients.

• 대한기계학회논문집B
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• 제22권7호
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• pp.1001-1012
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• 1998

This paper reports the analysis of dynamic characteristics of air-cooled condenser. At first, there is an assumption that the superheated vapor flows into the condenser inlet. And in order to consider the effect of pressure change in the dynamic characteristics of the condenser the combined system of condenser and compressor was used. By using the equation of energy balance and the equation of mass balance, the basic equation for describing the dynamic characteristics of condenser can be derived. The transfer function for describing dynamic response of the condenser to flow rate change outlet can be obtained from using linearizations and Laplace transformations of the equation. From this transfer function, analytical investigation which affects the frequency responses of condenser has been made. Through this study, it became possible that the information about the dynamic characteristics of air-cooled condenser is offered. While the average heat transfer coefficient of the refrigerant side necessary for the theoretical calculation of the dynamic characteristics is given by calculation method for the tube length and pressure drop of air-cooled condenser.

• 한국자동차공학회논문집
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• 제11권5호
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• pp.70-76
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• 2003

An experimental study was performed to understand the heat transfer and fluid dynamic characteristics of Sub-Cooled Hybrid Condenser (SCHC), which conventional condenser and receiver dryer are integrated into. SCHC also employs a sub-cooled refrigerant passages at the end of the condenser in order to supply perfect liquid refrigerant to the expansion unit. Throughout the present study, it was found that the developed SCHC increases in the degree of sub-cooling by 10~100% compared to conventional condenser. The excessive sub-cooling has improved the cooling performance by 10%, and that leads reduction in evaporator outlet air temperature by $1.5^{\circ}C$. Also found through the study is that the refrigerant pressure drop across SCHC is fairly increased due to insertion of the desiccant cartridge in the receiver tank which is composed of zeolite, filter and supporter plate.

• 플랜트 저널
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• 제10권4호
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• pp.24-28
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• 2014

본 연구에서는 150 MW 화력발전소를 기준하여 발전소 건설지역의 최저 대기온도 $-17.1^{\circ}C$부터 최대 대기온도 $36.7^{\circ}C$까지를 $3^{\circ}C$의 일정한 간격으로 구분하여 복수기 압력이 증기터빈의 배압조건을 만족하는 대기온도별 송풍기 수량을 검토하였다. 공랭식 복수기는 대기온도 및 송풍기 운전수량 변화에 따른 냉각공기 순환량에 영향을 받아 운전조건이 변경이 되므로, 대기온도가 복수기 설계기준온도 이상의 경우에는 공랭식 복수기 송풍기의 운전수량을 최대로 해야 하고, 대기온도가 복수기 설계기준온도 미만의 경우에는 증기터빈 배압 운전조건을 만족하는 범위 내에서 송풍기 운전수량을 변화시켜 공랭식 복수기에 가해지는 공기 순환량을 감소시키는 것이 안정적인 발전소 운영을 하는 것임을 확인하였다.

• 대한기계학회논문집B
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• 제36권8호
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• pp.811-819
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• 2012

공랭식 응축기는 대기중의 공기를 이용해 스팀을 응축수로 전환시키는 발전용 냉각설비이다. 추운 겨울철, 공랭식 응축기는 열교환부 관내의 응축수가 동결되어 튜브 자체가 터지는 심각한 동파 문제를 수반한다. 이는 기존 공랭식 응축기 시스템이 가지는 튜브 출구의 구조적 문제로 인한 응축되지 않은 스팀 및 비응축성 기체의 역류가 주요 원인이 된다. 따라서 본 연구에서는 유사 모의 공랭식 응축기 시스템을 설계 및 제작하여 기존의 공랭식 응축기 시스템이 가지고 있는 문제점을 구현하고, 이를 해결하기 위한 설계가 가능함을 실험적으로 증명하였다. 기존 공랭식 응축기 시스템의 작동 원리와 유사한 조건에서 실시한 실험에서 역류에 의한 튜브 동결을 관찰할 수 있었다. 반면 신개념 공랭식 응축기 시스템을 적용한 실험에서는 역류 및 동결 발생없이 열교환이 잘 이루어짐을 확인할 수 있었다.

• International Journal of Air-Conditioning and Refrigeration
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• 제8권1호
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• pp.14-28
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• 2000

The frequency response characteristics of a condenser were numerically studied for the control of refrigeration and air conditioning systems. The important parameters, such as the refrigerant flow rate, refrigerant temperature, air velocity, and air temperature at the condenser inlet, were analyzed. Superheated vapor, two phase, and subcooled liquid domain in condenser can be described by using the energy balance equation and the mass balance equation in refrigerant and tube wall, the basic equation for describing the dynamic characteristics of condenser can be derived. The transfer function for describing dynamic response of the condenser to disturbances can be obtained from using linearizations and Laplace transformations of the equation. From this transfer function, analytical investigation which affects the frequency responses of condenser has been made. Block diagrams were made based on the analytic transfer function; dynamic responses were evaluated in Bode diagrams on the frequency response. Through this study, it became possible that the information about the dynamic characteristics of air-cooled condenser is offered. The results may be used for determining the optimum design parameters in actual components and entire systems. Also, the mathematical models, frequency response may be used to help understanding, evaluate optimum design parameters, design control systems and determine on setting the best controller for the refrigeration and air-conditioning systems.