• 제목/요약/키워드: Refrigeration Cycle

검색결과 445건 처리시간 0.027초

열교환기 전열용량이 냉동시스템의 성능에 미치는 영향 (Performance Characteristics with Capacities of Heat Exchangers of a Refrigeration System)

  • 김제봉;김수연;정평석;조경철
    • 설비공학논문집
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    • 제15권3호
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    • pp.187-195
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    • 2003
  • The geometric size and the refrigeration capacity of a refrigeration system are strongly dependent on the capacity of heat exchanger, which is one of the key design parameters. In this paper, the effect of the capacities of heat exchangers on the performance of a real refrigeration system operated in a vapor compression cycle was analyzed by the numerical simulation. From the results, the conditions that gave the maximum values of the refrigeration capacity or COP were respectively determined as a function of the capacities of condenser and evaporator under the given ambient and operating condition.

대체 프레온계 냉매를 이용하는 이원 냉동시스템의 성능예측 (Prediction on Performance of Cascade Refrigeration System using Alternative Freon Refrigerants)

  • 노건상
    • 한국기계기술학회지
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    • 제13권1호
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    • pp.73-79
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    • 2011
  • In this paper, cycle performance analysis of cascade refrigeration system using alternative FREON refrigerants are presented to offer the basic design data for the operating parameters of the system. The operating parameters considered in this study include subcooled and superheated degree, and evaporating and condensing temperature, temperature difference of cascade heat exchanger in cascade refrigeration system. The COP of cascade refrigeration system increases with the increasing subcooled degree, but there is no significant changes with the increasing superheated degree. The COP of cascade refrigeration system depends on evaporating and condensing temperatures of cascade heat exchanger. Therefore, subcooled degree, evaporating and condensing temperature of cascade heat exchanger using alternative FREON refrigerants have an effect on the COP of this system. In this paper, COP of cascade refrigeration system using R23 for low temperature system and R507A for high temperature system is higher 8 ~ 29 % than using R13 for low temperature system and R22 for high temperature system.

유기 랭킨 사이클로 구동되는 증기압축 냉동사이클의 성능 해석 (Performance Analysis of a Vapor Compression Cycle Driven by Organic Rankine Cycle)

  • 김경훈;진재영;고형종
    • 한국수소및신에너지학회논문집
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    • 제23권5호
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    • pp.521-529
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    • 2012
  • Since the energy demand for refrigeration and air-conditioning has greatly increased all over the world, thermally activated refrigeration cycle has attracted much attention. This study carries out a performance analysis of a vapor compression cycle (VCC) driven by organic Rankine cycle (ORC) utilizing low-temperature heat source in the form of sensible heat. The ORC is assumed to produce minimum net work which is required to drive the VCC without generating an excess electricity. Effects of important system parameters such as turbine inlet pressure, condensing temperature, and evaporating temperature on the system variables such as mass flow ratio, net work production, and coefficient of performance (COP) are thoroughly investigated. The effect of choice of working fluid on COP is also considered. Results show that net work production and COP increase with increasing turbine inlet pressure or decreasing condensing temperature. Out of the five kinds of organic fluids considered $C_4H_{10}$ gives a relatively high COP in the range of low turbine inlet pressure.

온배수를 이용한 혼합냉매용 해양온도차 발전 사이클의 성능 특성 (Performance Characteristics of a Mixed Refrigerant OTEC Power Cycle Using Hot Waste Water)

  • 윤정인;손창효;허정호;예병효;김현주;이호생
    • 동력기계공학회지
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    • 제17권6호
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    • pp.102-107
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    • 2013
  • In this paper, the performance analysis for evaporation capacity, total work and efficiency of the ocean thermal energy conversion(OTEC) power system using mixed refrigerant(R32,R152a) is conducted to find the effect of hot wasted water on OTEC power system. The system in this study is applied with two stage turbine, regenerator, cooler and separator on Organic Rankine Cycle. The commercial program HYSYS is used for the performance analysis. The main results were summarized as follows : The efficiency of the OTEC power cycle has a largely effect on the evaporation capacity and total work. As increasing temperature of heat source water, evaporator's capacity is decreased but total work increase. Otherwise, using hot wasted water bring effects not only increasing system efficiency but also declining evaporator's capacity. Thus With a thorough grasp of these effect, it is necessary to find way to use hot wasted water emitted by power plant and so on.

Design of closed-loop nitrogen Joule-Thomson refrigeration cycle for 67 K with sub-atmospheric device

  • Lee, C.;Lee, J.;Jeong, S.
    • 한국초전도ㆍ저온공학회논문지
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    • 제15권1호
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    • pp.45-50
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    • 2013
  • Closed-loop J-T (Joule-Thomson) refrigeration cycle is advantageous compared to common open loop $N_2$ decompression system in terms of nitrogen consumption. In this study, two closed-loop pure $N_2$ J-T refrigeration systems with sub-atmospheric device for cooling High Temperature Superconductor (HTS) power cable are investigated. J-T cooling systems include 2-stage compressor, 2-stage precooling cycle, J-T valve and a cold compressor or an auxiliary vacuum pump at the room temperature. The cold compressor and the vacuum pump are installed after the J-T valve to create sub-atmospheric condition. The temperature of 67 K is possible by lowering the pressure up to 24 kPa at the cold part. The optimized hydrocarbon mixed refrigerant (MR) J-T system is applied for precooling stage. The cold head of precooling MR J-T have the temperature from 120 K to 150 K. The various characteristics of cold compressor are invstigated and applied to design parameter of the cold compressor. The Carnot efficiency of cold compressor system is calculated as 16.7% and that of vacuum pump system as 16.4%. The efficiency difference between the cold compressor system and the vacuum pump system is due to difference of enthalpy change at cryogenic temperature, enthalpy change at room temperature and different work load at the pre-cooling cycle. The efficiency of neon-nitrogen MR J-T system is also presented for comparison with the sub-atmospheric devices. These systems have several pros and cons in comparison to typical MR J-T systems such as vacuum line maintainability, system's COP and etc. In this paper, the detailed design of the subcooled $N_2$ J-T systems are examined and some practical issues of the sub-atmospheric devices are discussed.

R744용 초임계 냉동사이클의 성능 분석 (Performance Analysis of R744(Carbon Dioxide) for Transcritical Refrigeration System)

  • 노건상;손창효
    • 한국산학기술학회논문지
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    • 제10권1호
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    • pp.32-38
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    • 2009
  • R744용 초임계 증기압축식 냉동시스템의 작동변수에 대한 기초설계자료를 제공하고자 냉동능력, 압축일량, 성적계수에 대한 사이클 성능분석을 실시하였다. 본 연구에서 고려된 작동변수는 R744 증기압축식 사이클의 과열도, 가스냉각기 출구온도, 증발온도이다. R744의 냉동능력은 과열도가 증가할수록 증가하는 반면, 증발온도와 가스냉각기 출구온도가 증가할수록 감소한다. 압축일량은 R744의 과열도와 냉각압력과 함께 증가하나 증발온도는 증가할수록 감소한다. 그리고 성적계수는 가스냉각기의 출구온도와 증발온도가 증가할수록 증가하는 반면, 과열도는 감소한다. 그러므로, R744용 초임계 증기압축식 냉동시스템의 냉동능력, 압축일량, 성적계수는 과열도, 가스냉각기 출구온도, 증발온도에 영향을 받는 것을 알 수 있었다. 따라서, R744용 초임계 증기압축식 냉동시스템을 설계할 경우에는 이러한 영향을 면밀하게 파악하여야 한다.

쇼케이스에서 고온가스 바이패스 및 단속운전 제상사이클의 성능특성에 관한 실험적 연구 (Experimental Study on the Performance Characteristics of Hot-gas Bypass and On-off Defrosting Cycle in a Showcase Refrigeration System)

  • 김용찬;조홍현;노현일;김영득;박윤철
    • 설비공학논문집
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    • 제14권6호
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    • pp.493-502
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    • 2002
  • During the defrosting process, the temperature in the cabinet of a showcase becomes high as compared to the setting point, which is not desirable for stored foods or materials. It is necessary to develop a more efficient defrosting method to prevent large temperature fluctuation. In this study, the performance of a showcase refrigeration system with three evaporators is investigated by employing a hot-gas bypass defrosting technology in the system under frosting and defrosting conditions. The operating characteristics are compared with those for the on-off defrosting method that has been widely used in current products. As a result, the hot-gas bypass defrosting method shows higher refrigerating capacity and less temperature fluctuation than the on-off method under frosting/defrosting conditions, while the power input is relatively high for the hot-gas bypass method.

열역학적 사이클의 제2법칙 효율의 정의에 대한 기본 연구 (Basic Study on the Definition of the Second Law Efficiencies of Thermodynamic Cycles)

  • 박경근
    • 설비공학논문집
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    • 제24권11호
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    • pp.792-798
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    • 2012
  • A general concept on the definition of the second law efficiencies of thermodynamic cycles is introduced. The efficiency is defined to be proportional to the entropy generation divided by the maximum possible entropy generation. This way of definition of the cycle efficiency is clear and concise and, moreover, follows faithfully the concept of the second law of thermodynamics. This definition is applied to heat engine, refrigerator and heat pump. The second law efficiencies of heat engine and refrigeration cycles are derived, which are the same as the existing ones, respectively. The second law efficiency of heat pump, however, finds to be different from the existing one. Discussion is given about the difference and its cause.

Research and Development of the Triple Effect Absorption Chiller-Heater Technology in Japan

  • Kashiwagi, Takao;Akisawa, Atsushi;Hamamoto, Yoshinori
    • 대한설비공학회지:설비저널
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    • 제33권3호
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    • pp.43-49
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    • 2004
  • This article reviews R&D of triple effect cycle developed in Japan. Most of the refrigeration and heat pump technologies are dominated by vapor compressor system. The vapor compressor system, however, is highly concerned with the environmental regulations , as most of the vapor compressor technologies are using CFCs or HCFCs which are known as ozone depleting and global warming gases. As a consequence, refrigeration technologists are trying to invent or to develop an alternative to vapor compressor refrigeration devices. Thermally driven, absorption technology is one of the possible alternatives. At the moment, absorption cycle is most promising technology The paper summarizes briefly the current research and development in advanced technologies of triple effect absorption chiller-heater in Japan.(omitted)

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