• Journal of the Korean Institute of Gas
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• v.14 no.1
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• pp.1-7
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• 2010

In this paper, cycle performance analysis of $NH_3-CO_2$(R717-R744) two-stage cascade refrigeration system is presented to offer the basic design data for the operating parameters of the system. The operating parameters considered in this study include subcooling and superheating degree, compressor efficiency, and condensing and evaporating temperature in the ammonia(R717) high temperature cycle and the carbon dioxide low temperature cycle. The main results were summarized as follows : The COP of two-stage cascade refrigeration system increases with the increasing subcooling degree, but decreases with the increasing superheating degree. The COP of two-stage cascade refrigeration system decreases with the increasing condensing temperature, but increases with the increasing evaporating temperature. And the COP of two-stage cascade refrigeration system increases with increasing the compressor efficiency. Therefore, superheating and subcoolng degree, compressor efficiency, and evaporating and condensing temperature of $NH_3-CO_2$(R717-R744) two-stage cascade refrigeration system have an effect on the COP of this system.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2012.05a
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• pp.626-629
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• 2012

In this paper, Actual refrigeration system and the data were analyzed in order to provide basic design data of Refrigeration system using the characteristic curve of the refrigerant. On the basis of the characteristic curve of the refrigerant developed simulation program and data of refrigeration system equipment data consisting of compressor, condenser, Receiver content, expansion valve, evaporator, liquid separator, leading to changes in temperature and Moliere were analyzed.

• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.747-749
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• 2002

초전도 마그네트 시스템의 냉각방법 중, 액체 헬륨등의 극저온 유체를 이용한 액체냉각방식이 극저온 냉동기를 이용한 직접 전도냉각 방식에 비해 신뢰도가 높은 열적 안정성으로 인하여 현재도 많은 초전도 마그네트 시스템이 액체냉각방식을 이용하고 있다. 그러나, 고가의 극저온 액체의 재충전으로 인하여 경제성이 낮고 취급이 불편한 단점이 있다 이러한 액체냉각방식의 단점을 보완하고자 극저온 유체를 시스템 안에서 직접 응축하여 재충전을 하지 않는 재응축형 시스템을 개발하여 실험하였다. 실험에 사용한 초전도 마그네트 시스템은 상온보아 1270 mm. 최대자장 0.3 T로 설계되었고, 금속 전류도입선과 HTS 전류도입선을 복합적으로 사용하였으며, 복사차폐막 냉각용 극저온 냉동기와 헬륨 재응축용 극저온 냉동기를 사용하였다. 초전도 마그네트는 200 A에서 1600 gauss의 자장으로 운전하였고 극저온 용기에서는 0.05 bar의 압력으로 액체 헬륨이 증발하지 않고 유지되었다.

• Journal of Advanced Marine Engineering and Technology
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• v.35 no.1
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• pp.40-45
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• 2011

The purpose of research is to understand the characteristics of refrigeration system having a liquid-vapor phase separator after expansion device and precooling heat exchanger. After expansion process of typical refrigerant of freezer, R134a, the cold vapor of the expanded refrigerant mixture is separated in the liquid-vapor separator and introduced in the precooling heat exchanger to enable the liquid refrigerant to be subcooled. The analysis results showed that the increasing rate of refrigeration capacity and COP can be 8.6% and 1.4%, each. The cause of these performance improvements is due to the difference of the slope of saturated vapor and saturated liquid lines in Mollier diagram of refrigerant.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.33 no.3
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• pp.37-42
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• 2004

흡수식 냉동기의 구성요소에 관한 성능향상 및 배열을 이용한 코제네레이션 시스템의 소개한다. 1997년 12월에 개최된 지구온난화 방지 교토회의(COP3-기후변동협조조약 제3회 체결국 회합)에서, 일본은 2008년-2012년까지 온실효과가스의 배출량을 1990년도 시점을 기준으로 6% 삭감하기로 합의하였다. 이러한 배경에 따라 $CO_2$ 배출량의 삭감에 대한 새로운 공업기술의 전개가 진행되고 있으며, 일본의 냉동공조산업 분야에서도 코제네레이션이라는 에너지 절약 관점으로부터 흡수식 냉동기가 다시 주목을 받게 되는 계기가 되었다.(중략)

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.28 no.5
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• pp.347-358
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• 1999

암모니아는 독성, 가연성 및 동 재질의 부식성 등의 단점은 있지만 CFC계 냉매가 개발되기 전에는 우수한 열역학 및 열전달 특성 때문에 냉매로서 가장 많이 사용되어져 왔다. 미국에서는 약120년, 일본에서는 약 80년 전부터 암모니아가 냉동 사이클에 사용되었고, 따라서 축적된 관련 기술 수준도 놀고 경험도 많은 편이다. 지금도 미국에서는 상업용 냉동기의 80% 정도가 암모니아를 냉매로 사용하고 있다. 우리나라도 냉동창고 냉동용으로는 암모니아 시스템이 널리 사용되고 있다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.9
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• pp.1971-1978
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• 2011

In RFID-based cold-storage systems, product locations are recognized as the logical locations of RFID readers which are attached to the entrance of the cold rooms. However, through these methods, product locations can be incorrect in many different situations of a storage. Cold storage rooms have a huge rage in temperature, and the product in the cold-storage spoils easily. Therefore, highly precise product locations is very important for the product quality In this paper, a new approach is suggested to manage the storage location inaccuracy by adding two readers to existing forklift and attaching RFID tags to the ceiling. One reader recognizes ceiling tags to acquire location data, and the other recognizes product tags to acquire product detail data loaded on the forklift. The product can be seamlessly tracked and traced in realtime by monitoring and analyzing data gathered from these readers. Through the proposed location management method, the effectiveness of the product management in cold-storage can be improved consequently.

• Journal of Energy Engineering
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• v.7 no.2
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• pp.231-240
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• 1998

The global environmental problems such as CFC, energy losses in heat recovery system as well as summer peak time power demands, the development of high efficiency absorption refrigeration systems is one of the most promising method in this problems. The absorption refrigeration system to utilize treated sewage is available for environmental protection and energy conservation. Simulation analysis on the double-effect absorption refrigeration cucles with parallel or series flow type has been performed. LiBr+LiI+LiCl+LiNO$_3$ solution was selected as the new working fluid. The main purpose of this study is evaluating the possibilities of effective utilization of treated sewage as a cooling water for the absorber and condenser. The other purpose of the present study is to determine the optimum designs and operating conditions based on the operating constraints and the coefficient of performance in the parallel or series flow type. In this study, we found out the characteristic of new working solution through the cycle simulation and compared LiBr solution to evaluate. The absorption refrigeration machine using the new working fluid was obtained better results COP rise and compactness of system by comparison with LiBr solution.

• Journal of Advanced Marine Engineering and Technology
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• v.35 no.2
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• pp.182-188
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• 2011

In this paper, analysis on the performance characteristics of R744-R404A cascade refrigeration system is presented to offer the basic design data for the operating parameters of the system. The operating parameters considered in this study include subcooling and superheating degree, compressor efficiency, and condensing and evaporating temperature in R404A high- and R744 low-temperature cycle, respectively. The main results were summarized as follows : It was observed that the highest COP of the system is achieved by higher superheating degree in R744 cycle than that in R404A cycle. The COP of the system increased by giving the subcooling degree in both cycles. The COP of the cascade system is the highest value when the system is operated at an optimum evaporation temperature.

• Proceedings of the KSME Conference
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• 2005.11a
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• pp.28.2-28.2
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• 2005