• Proceedings of the Korean Society of Marine Engineers Conference
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• 2006.06a
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• pp.55-56
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• 2006

냉매 충전량과 이차유체의 입구조건은 $CO_2$용 열펌프시스템의 성능실험에서 중요한 제어변수이다. 따라서, 열펌프사이클의 적용과 난방성능 향상을 위해 제어변수의 특성을 조사하는 것이 필요하다. 본 논문에서, $CO_2$용 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 COP가 최대가 되는 냉매충전량이 존재함을 나타낸다. 또한, 난방성능은 가스쿨러내 이차유체의 질량유량의 증가에 따라 증가하였다. 가스냉각기내 2차유체의 입구은도가 $10^{\circ}C$에서 $40^{\circ}C$로 증가하면, 난방용량, 압축일량, 토출압력은 각각 -8.57%, -35.89%, 32.78%로 변화했으며, 증발기 2차유체의 입구 온도가 감소하였을 때 난방COP는 감소하는 경향을 보였다.

• Journal of Energy Engineering
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• v.12 no.4
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• pp.253-258
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• 2003

Manual type manifold gauge has been used for charging the refrigerant in the refrigeration systems. In this case, the refrigerant is released to the ambient during the hose-switching period. :he objectives of this study are to develop a novel automatic refrigerant charging system, and to quantify the effect of the automatic systems on the reduction of the non-condensable gas and the contamination of the compressor oil. The automatic charging system makes the pressure test, vacuum test, and refrigerant charging work very simple and easy because the charging hose does not have to be switched many times. It is found that the amount of water in the SiO$_2$and the compressor oil reduces to l/4 times of that for the manual type manifold gauge and the refrigerant is not released to the ambient at all when the automatic charging system is adopted.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.35 no.6
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• pp.357-365
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• 2022

Refrigerant mischarging is one of the most frequently occurring failure modes in air conditioners, and both undercharging and overcharging degrade cooling performance. Therefore, it is important to accurately determine the amount of charged refrigerant. In this study, a support vector machine (SVM) model was developed to multi-classify the refrigerant mischarge through steady-state identification via fuzzy clustering techniques. For steady-state identification, a fuzzy clustering algorithm was applied to the air conditioner operation data using the difference between moving averages. The identification results using the proposed method were compared with those using existing steady-state determination techniques studied through the inversed Fisher's discriminant ratio (IFDR). Subsequently, the main features were selected using minimum redundancy maximum relevance (mRMR) considering the correlation among candidate features, and an SVM multi-classification model was devised using the derived features. The proposed method achieves satisfactory accuracy and robustness from test data collected in the new domain.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.5
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• pp.359-364
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• 2002

A popular type of residential air conditioner is the split system which has two separate units: indoor and outdoor units During field installation of the split system, the potential exists for not setting the charge exactly to the manufacturer´s specifications. The objective of this study is to investigate the effects of the refrigerant charge on the performance of the air conditioner. An air conditioner with capillary tube expansions was tested for various refrigerant charges. The results indicated that the more charge resulted in the more flowrate of the refrigerant. The flowrate of the refrigerant was one of the most important factors to understand the e(sects of the charge on the performance of the air conditioner with capillary tube expansions. Under-charge results in wide region of superheated vapor of the refrigerant in the evaporator, while over-charge results in high temperature of the liquid refrigerant in the evaporator.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.12 no.5
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• pp.486-493
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• 2000

A theoretical model for the transient performance of vapor-compression air-conditioning system has been developed to evaluate the influence of the refrigerant charge on the system performance. A set of mass and energy equations for the simulation of the heat exchangers and the capillary tube and a polytropic compression model for the compressor are used. The present model successfully predicts the transient behavior of the vapor-compression air-conditioner from the startup. As the refrigerant charge is increased, both the evaporating and condensing pressures increase gradually, and the cooling rate and the COP show a maximum in the range of 0.75-0.8 kg of refrigerant charge. This amount of refrigerant mass is determined to be the optimum charge of the model system. Also, the effect of outdoor air temperature on the optimum refrigerant charge is discussed.

• Proceedings of the SAREK Conference
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• 2005.11a
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• pp.427-432
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• 2005

This study developed a program for detecting charged refrigerant amount in system air-conditioner. System air-conditioner is an air-conditioning system with multiple indoor units. Due to the complexity of the system, it is more difficult to detect the refrigerant amount charged in system air-conditioner than in a general single air-conditioner. Experiments were performed for 6 HP outdoor units with 3 indoor units in a psychrometric calorimeter. The experimental amount of charged refrigerant were ranged from 60% to 140% with 10% increasement. Fuzzy algorithm were emploeed for detecting the charged refrigerant amount in a system air-conditioner. The experimental data were used for curve fitting for general ranges for indoor and outdoor temperature conditions. membership function were determined for whole ranges of experimentally measured data and rulebase were defined for each amount of refrigerant charge. Developed program successfully predicted the measured data within 10% resolution range.

• Journal of Advanced Marine Engineering and Technology
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• v.31 no.5
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• pp.558-566
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• 2007

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.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.4
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• pp.1568-1575
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• 2013

There has been an increasing interest in the market of vehicle maintenance and repair equipments to decrease air pollution. However, most of the existing air conditioning system equipment in Korea have poor performance as well as non-protection against air pollution. The purpose of this paper is to develop the monitoring technology of recovering and recharging refrigerant for air conditioning system, and also to develop its related diagnostic system. This technology and system can supply the exact amount of refrigerant from the charger to the air conditioning system by precisely diagnosing and monitoring their statuses. This technology can also control recovering and recharging of refrigerant exactly by altering the recovering pressures of refrigerant according to circumstance temperatures.

• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.2
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• pp.203-211
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• 1998

The system performance of an automobile air conditioning system with variations of charging conditions has been investigated experimentally. An automobile air conditioning system was composed of laminated type evaporator, parallel flow type condenser, swash plate type com-pressor, externally equalized thermostatic expansion valve and receiver drier. The objective of this study was to quantify the influence of the refrigerant charge under the steady state operation of an automobile air conditioning system. The results indicated that a 10% undercharge caused a 10% reduction in the capacity of evaporator.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.5
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• pp.410-417
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• 2005

The cooling performance of a transcritical $CO_{2}$ cycle varies significantly with a variation of refrigerant charge amount. In this study, the performance of the $CO_{2}$ system was measured and analyzed by varying refrigerant charge amount at a standard test condition. Besides, the losses of the major components in the $CO_{2}$ system were estimated by evaluating entropy generation with refrigerant charge amount. The losses in the expansion device and the gascooler show the major portion of the total loss. For undercharging conditions, the expansion loss dominates the overall system performance, while the gascooler loss increases significantly with an increase of refrigerant charge amount.