• 설비공학논문집
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• 제10권1호
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• pp.44-55
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• 1998

The evaluation of aluminum flat tube and louver fin heat exchangers for a condenser in residential air-conditioning applications has been conducted. A series of tests for two-different brazed aluminum heat exchangers was performed and the results were compared with conventional fin and tube heat exchangers for residential air-conditioning system. Refrigerant charge amount for a window-system air-conditioner with the brazed aluminum condenser is decreased by 35% and the volume and material of heat exchanger can be reduced by 50% compared to the conventional fin and tube heat exchangers.

• 한국산학기술학회논문지
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• 제22권1호
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• pp.31-36
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• 2021

최근에 지구온난화 문제로 인하여 자동차 공조시스템은 GWP 지수가 높은 R134a 냉매를 대체할 수 있는 대체 냉매를 적용하고 있다. 본 연구에서는 R1234yf 냉매를 사용하여 내부열교환기와 가면용량형 팽창밸브인 TXV를 적용한 자동차 공조시스템의 성능특성을 해석하였다. 상용 소프트웨어인 Amesim을 이용하여 주요 부품인 압축기, 응축기, 팽창장치, 증발기와 내부열교환기를 모델링을 하여 외기온도와 응축기 휜 피치 변화에 따른 냉동사이클 시뮬레이션을 수행하였다. 외기온도가 30℃에서 40℃로 증가함에 따라 시스템의 냉방용량은 3.1% 감소하고, 압축기 소비동력은 17.1% 증가하였다. 또한, 응축기의 휜 피치를 0.8 mm에서 1.4 mm로 증가시키면서, 사이클 성능특성을 해석하였다. 휜 피치가 1.0 mm 클 경우에 응축기의 방열량은 감소하였고, COP는 5.9% 까지 감소하였다. 응축기 휜 피치가 1.0 mm 보다 작은 0.8 mm에서는 시스템 성능에 큰 변화가 없어 휜 피치 1.0 mm에서 최적의 성능을 나타내는 것으로 분석되었다.

• Journal of Mechanical Science and Technology
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• 제17권11호
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• pp.1801-1811
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• 2003

An experimental study was conducted to investigate the effects of air-side fouling and cleaning on the performances of various condenser coils used in unitary air-conditioning systems. A total of six condenser coils with different fin geometry and row number were tested. Performance tests were performed at three different conditions: clean-as-received, after fouling, and after cleaning. In all cases, it was observed that the fouling was mostly confined to the frontal face of the heat exchanger as reported in the previous investigations. The amount of deposited dust was more dependent on fin geometry for the single-row heat exchangers than for the double-row heat exchangers. The predominant effect of fouling was to cause a more significant increase in air-side pressure drop than a degradation in heat transfer performance. For the single-row heat exchangers, the pressure drop increased by 28 to 31%, while the heat transfer performance decreased by 7 to 12% at the standard air face velocity of 1.53 m/s depending on fin shape. For the double-row heat exchangers, the pressure drop increased by 22 to 37%, and heat transfer performance decreased by only 4-5% at the same air face velocity. Once the contaminated coils were cleaned according to the given cleaning procedure the original performance of the heat exchangers could almost be recovered completely. The pressure drop could be restored within 1 to 7% and the heat transfer performance could be recovered to within 1 to 5% of the originally clean heat exchangers. Therefore, it is concluded that a periodic application of the specified cleaning technique will be effective in maintaining the thermal performance of the condenser coils.

• 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.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2006년도 하계학술발표대회 논문집
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• pp.483-488
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• 2006

In this study, newly-developed slim electronic panel cooler with aluminum PF condenser and evaporator was tested and the results are compared with imported panel cooler with fin-tube heat exchangers. The PF heat exchangers significantly (approximately 45%) reduced the refrigerant charge. The air-side pressure drop was also reduced, which resulted in the reduction of the sound level of the panel cooler. The effect of the condenser size was also investigated.

• 설비공학논문집
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• 제6권4호
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• pp.388-398
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• 1994

Computer simulation model for predicting more accurately the heat transfer performance of the evaporator and condenser which have significantly affected on the performance of air-conditioner has been suggested. In this model oil and micro-fin tube used in a actual unit are considered to simulate the more realistic case. The effects of oil and micro-fin tube on the performance of an air-conditioner have been investigated. It is found that the present model requires higher pressure than the existing model due to the characteristics of the tube considered. However, it turns out that the present model is very close to an actual cycle. As the amount of oil inside the tube increases, condensation heat transfer coefficient shows a linear decrease irrespective of a kind of oil, while evaporation heat transfer coefficient increases slightly in the oil with low viscosity and decreases exponentially in the oil with high viscosity. Pressure drop in both evaporator and condenser increases linearly irrespective of a kind of oil. It is also found that the effect of the variation of oil concentration on the magnitude of two-phase region is negligible.

• International Journal of Air-Conditioning and Refrigeration
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• 제15권1호
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• pp.25-33
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• 2007

The investigation has been made into the prediction of heat exchange performance of a counter flow type double-tube condenser for natural refrigerant mixtures composed of Propane/n-Butane or Propane/i-Butane in a smooth tube and micro-fin tube. Under various heat transfer conditions, mass flux, pressure drop and heat transfer coefficient of the mixed refrigerants were calculated using a prediction method, when the length of condensing tube, total heat transfer rate, mass flux and outlet temperature of coolant were maintained constant. Also, the predicted results were compared with those of HCFC22. The results showed that the mixed refrigerants of Propane/n-Butane or Propane/i-Butane could be substituted for HCFC22, while the pressure drop and overall heat transfer coefficient of the refrigerants were evaluated together.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.2292-2297
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• 2008

Recently, a study on condensers for refrigerators has focused on new model which will cost less and will be more efficient. Some widely used condensers for domestic refrigerators are wire-and-tube type condenser, hot-wall type condenser, and spiral type condenser. Some companies which use the spiral type condenser at the moment try to develop a new type condenser which will cost less and will be as efficient as the spiral type. The new type condenser consists of a steel tube, steel plates and louver fins attached to the tube. The tube and the plate are bent into a single-passage serpentine shape.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2009년 추계학술대회논문집
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• pp.135-144
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• 2009

In this study, the heat transfer and fluid flow characteristics of a condenser for a refrigerator are analyzed with the numerical method. The main objective of the study is to obtain basic data in order to develop a new type of condenser focused on an influence of thermal resistance of air side and thermal contact resistance on the heat transfer performance. The CFD technique was used for whole study, and experiments were performed in order to verify the reliability of the numerical analysis and predict the thermal contact resistance. In this study, a heat exchanger sample was made of a part of condenser to make the experimental and numerical analysis simple and efficient. Water was used for the inner working fluid of the heat exchanger, and an experimental apparatus was composed concisely. A heat exchanger sample of tube type was used to verify the reliability of numerical analysis, and a heat exchanger of fin and tube type was used to predict the ratio of thermal contact resistance to the overall thermal resistance.