• 제목/요약/키워드: Multi-stage refrigeration

검색결과 18건 처리시간 0.024초

프로판 냉매를 활용한 단일 및 다단 냉동 사이클의 전산모사 비교 연구 (A comparative study on the simulation of single-stage and multi-stage refrigeration cycle using propane as a refrigerant)

  • 노상균
    • 한국산학기술학회논문지
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    • 제15권5호
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    • pp.3327-3335
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    • 2014
  • 본 연구에서는 천연가스의 냉각을 위한 프로판을 냉매로 사용한 단일 및 다단 냉동 사이클에 대한 소요 에너지를 비교하였다. 이를 위해서 천연가스의 온도를$ -37.00^{\circ}C$까지 냉각시키기 위해서 프로판을 냉매로 사용하여 1단 압축 및 2단, 3단, 4단 압축을 이용한 냉동 사이클에 대한 비교 연구를 수행하였다. 전산모사를 위해 한국가스공사로부터 제공받은 천연가스 조성을 적용하였으며, 열역학 모델식으로는 Peng-Robinson 상태방정식을 적용하였다. 냉동기 압축 단수가 증가할수록 응축기의 heatduty는 점점 줄어드는 것을 알 수 있었다. 4단 압축공정의 경우 1단 압축공정에 비해 응축기의 heatduty는 약 20.36% 정도 감소하였으며 냉매의 총 순환 유량은 약 14.53% 감소하였다. 또한 4단 압축공정의 경우 1단 압축공정에 비해 압축기의 총 소요 동력은 약 41.61% 감소함을 알 수 있었다.

천연가스 액화를 위한 캐스케이드 냉동사이클의 전산모사에 대한 연구 [2]: 다단 캐스케이드 냉동 사이클에 적용 (A Simulation Study on the Cascade Refrigeration Cycle for the Liquefaction of the Natural Gas [2]: An Application to the Multistage Cascade Refrigeration Cycle)

  • 조정호;김유미
    • 한국산학기술학회논문지
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    • 제12권2호
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    • pp.1013-1019
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    • 2011
  • 본 논문에서는 천연가스를 액화시키기 위해서 프로판, 에틸렌 및 메탄 냉매를 이용한 다단 캐스케이드 냉동사이클에 대한 전산모사를 PRO/II with PROVISION 8.3에 내장되어 있는 Peng-Robinson 상태방정식을 활용하여 수행하였다. 천연가스의 조성은 한국가스공사로부터 제공받은 것을 적용하였으며, 유량은 연간 500만톤으로 가정하였다. 프로판 냉매의 공급온도는 $-40^{\circ}C$로, 에틸렌 냉매의 공급온도는 $-95^{\circ}C$로 메탄 냉매의 공급온도는 $-155^{\circ}C$로 각각 정하였으며, 천연가스와 각각의 냉매의 최소 접근온도는 $3^{\circ}C$로 정하였다. 다단 냉동을 위한 프로판 냉동 사이클은 3단 냉동을 가정하였으며, 에틸렌 냉동 사이클은 2단 냉동을 그리고 메탄 냉동 사이클은 3단 냉동을 가정하였다. 메탄 냉매에 의해서 $-152^{\circ}C$까지 냉각된 천연가스는 줄-톰슨 팽창에 의해서 $-162^{\circ}C$까지 냉각되어 액화가 일어나도록 하였다. 결론적으로 캐스케이드 냉동 사이클과 줄-톰슨 팽창을 통한 천연가스의 액화율은 몰 비로 91.71%이며, 액화천연가스 1.0 kg/hr당 0.433 kW의 압축 일이 필요함을 알 수 있었다.

Temperature Characteristics of Cascade Refrigeration System by Pressure Adjustment

  • Chung Han-Shik;Jeong Hyo-Min;Kim Yeong-Geun;Rahadiyan Lubi
    • Journal of Mechanical Science and Technology
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    • 제19권12호
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    • pp.2303-2311
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    • 2005
  • Super low temperature has many applications nowadays, from the chemical processing, automotives manufacturing, plastic recycling, etc. Considering of its wide application in the present and the future, study of the super-low temperature refrigeration system should be actively carried out. Super low state temperature can be achieved by using multi-stage refrigeration system. This paper present the development and testing of cascade refrigerator system for achieving super-low temperature. On this experiment, two different types of HCFCs refrigerants are utilized, R-22 and R-23 were applied for the high stage and the low-pressure stage respectively. The lowest temperature in the low-pressure evaporator that can be achieved by this cascade refrigeration system is down to $-85^{\circ}C$. This experiment is aimed to study the effect of inlet pressure of the low-pressure stage evaporator and low-pressure stage compressors inlet pressure characteristics to the overall temperature characteristics of cascade refrigeration system.

3단 응축 고온/고효율 열펌프의 전산해석 (Compute simulation of a three-stage condensation heat pump)

  • 이윤학;정동수;김종보
    • 설비공학논문집
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    • 제10권3호
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    • pp.303-314
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    • 1998
  • In this study, the performance of a multi-stage condensation heat pump was examined. Computer simulation programs were developed for 1-stage, 2-stage, and 3-stage heat pumps and R11, R123, R141b were tested as working fluids. The results showed that coefficients of performance(COPs) of an optimized 3-stage condensation heat pump are 25∼40% higher than those of a conventional 1-stage heat pump. The increase in COP, however, differed among the fluids tested. The improvement in COP largely stems from the decrease in average LMTD values in the condensers of the multi-stage system. For the 3-stage condensation heat pumps, optimized UA values of three condensers were determined to be 30∼40% of the UA value of the total condenser regardless of the working fluid. When the amount of cooling water entering into the intermediate and high-stage subcoolers is roughly 10% of the total condenser cooling water respectively, the optimum performance was achieved for the 3-stage condensation heat pump.

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변형 Roebuck 압축기를 이용한 J-T 네온 냉각시스템의 열역학적 설계 (Thermodynamic Design of J-T Neon Refrigeration System Utilizing Modified Roebuck Compression Device)

  • 정제헌;정상권
    • 설비공학논문집
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    • 제15권5호
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    • pp.432-438
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    • 2003
  • This paper describes a modified Roebuck compression device as a potential compression device of a rotating cryogenic refrigeration system in superconducting machine such as generator or motor. The conventional cryogen transfer method from stationary refrigeration system to rotating system can be eliminated by an on-board cryogenic refrigeration system that utilizes well-designed multi-stage modified Roebuck compression device. This paper shows basic thermodynamic analysis of modified Roebuck compression device and its application for compressing neon at 77 K with substantial pressure ratio when the rotor diameter is 0.8 m with rotating speed of 3600 rpm. The device does not require any moving part in rotating frame, but two separate thermal reservoirs to convert thermal energy into mechanical compression work. The high temperature thermal reservoir is atmospheric environment at 300 K and the low temperature thermal reservoir is assumed as a liquid nitrogen bath at 77 K. The concept of the compression device in this paper demonstrates its usefulness of generating high-pressure neon at 77 K for rotating J-T neon refrigeration cycle of superconducting rotor.

불균형 데이터를 갖는 냉동 컨테이너 고장 판별 및 원인 분석을 위한 기계학습 모형 개발 (Development of machine learning model for reefer container failure determination and cause analysis with unbalanced data)

  • 이희원;박성호;이승현;이승재;이강배
    • 한국융합학회논문지
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    • 제13권1호
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    • pp.23-30
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    • 2022
  • 냉동 컨테이너의 고장은 큰 비용의 손실을 야기하지만, 현재 냉동 컨테이너의 알람 체계는 효율성이 떨어진다. 기존에 냉동 시스템의 시뮬레이션 데이터를 활용한 연구는 존재하지만, 냉동 컨테이너의 실제 운영 데이터를 활용한 연구는 부족하다. 이에 본 연구는 실제 냉동 컨테이너 운영 데이터를 활용하여 고장 원인을 분류하였다. 실제 데이터에서는 데이터 불균형이 발생하였으며 ENN-SMOTE, 클래스 가중치를 둔 Logistic 회귀분석과 본 연구에서 개발한 2-stage 알고리즘을 비교하여 데이터 불균형문제를 해결하였다. 2-stage 알고리즘은 XGboost, LGBoost, DNN을 사용하여 첫 번째 단계에서는 고장 및 정상을 분류하고, 두 번째 단계에서는 고장의 원인을 분류하는 알고리즘이다. 2-stage 알고리즘에서 LGBoost를 사용한 모델이 99.16%의 정확도로 가장 우수하였다. 본 연구는 데이터 불균형을 해결하기 위해 2-stage 알고리즘을 활용한 최종모델을 제안하며 이는 다른 산업에도 활용할 수 있을 것으로 사료된다.

Performance of A Three-Stage Condensation Heat Pump

  • Lee, Yoon-Hak;Jung, Dong-Soo;Kim, Chong-Bo
    • International Journal of Air-Conditioning and Refrigeration
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    • 제7권
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    • pp.55-68
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    • 1999
  • In this study, computer simulation programs were developed for single-stage, two-stage, and three-stage condensation heat pumps and their performance with CFC11, HCFC123, HCFC141b was examined under the same external conditions. The results showed that the coefficient of performance(COP) of an optimized 'non-split type' three-stage condensation heat pump is 25-42% higher than that of a conventional single-stage heat pump. The increase in COP, however, differed among the fluids tested. The improvement in COP is largely due to the decrease in average LMTDs in condensers, which results in the decrease in thermodynamic irreversibility in heat exchange process. For the three-stage heat pump, the highest COP is achieved when the total condenser area is evenly distributed among the three condensers. For the two-stage heat pump, however, the optimum distribution of the total condenser area varies with an individual working fluid. For the three-stage system, 'splitting the condenser cooling water'for the use of intermediate and high pressure subcoolers helps increase the COP further. When the individual cooling water entering the intermediate and high pressure subcoolers is roughly 10% of the total condenser cooling water, the maximum COP is achieved showing roughly an 11% increase in COP as compared to that of the 'non-split type' heat pump.

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초기투자비와 1차 에너지소비량을 고려한 에너지시스템의 다중최적 설계 방법론 (A Multi-objective Optimization Method for Energy System Design Considering Initial Cost and Primary Energy Consumption)

  • 공동석;장용성;허정호
    • 설비공학논문집
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    • 제26권8호
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    • pp.357-365
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    • 2014
  • This paper proposed a multi-objective optimization method for building energy system design using primary energy consumption and initial cost. The designing of building energy systems is a complex task, because life cycle cost and efficiency of building are determined by decisions of engineer during the early stage of design. Therefore, methods such as pareto analysis that can generate various alternatives for decision making are necessary. In this study, the optimization is performed using the NSGAII and case study was carried out for feasibility of the proposed method. As a result, alternative solutions can be obtained for the optimal building energy system design.

Transient cooling operation of multistage thermoelectric cooler (TEC)

  • Park, Jiho;Jeong, Sangkwon
    • 한국초전도ㆍ저온공학회논문지
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    • 제23권3호
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    • pp.55-59
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    • 2021
  • A thermoelectric cooler (TEC) is promising as an alternative refrigeration technology for the sake of its inherent advantages; no-moving parts and refrigerant-free in its operation. Due to the compactness, reliability and excellence in temperature stability, TECs have been widely used for small cooling devices. In recent years, thermoelectric devices have been attractive technologies that not only serve the needs of cooling and heating applications but also meet the demand for energy by recycling waste heat. In this research paper, multistage TEC is proposed as a concept of demonstrating the idea of transient cooling technology. The key idea of transient cooling is to harnesses the thermal mass installed at the interfacial level of the stages. By storing heat temporally at the thermal mass, the multistage TEC can readily reach lower temperatures than that by a steady-state operation. The multistage TEC consists of four different sizes of thermoelectric modules and they are operated with an optimized current. Once the cold-part of the uppermost stage is reached at the no-load temperature, the current is successively supplied to the lower stages with a certain time interval; 25, 50 and 75 seconds. The results show the temperatures that can be ultimately reached at the cold-side of the lowermost stage are 197, 182 and 237 K, respectively. It can be concluded that the timing or total amount of the current fed to each thermoelectric module is the key parameter to determine the no-load temperature.

설비공학 분야의 최근 연구 동향 : 2016년 학회지 논문에 대한 종합적 고찰 (Recent Progress in Air-Conditioning and Refrigeration Research : A Review of Papers Published in the Korean Journal of Air-Conditioning and Refrigeration Engineering in 2016)

  • 이대영;김사량;김현정;김동선;박준석;임병찬
    • 설비공학논문집
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    • 제29권6호
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    • pp.327-340
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    • 2017
  • This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during 2016. It is intended to understand the status of current research in the areas of heating, cooling, ventilation, sanitation, and indoor environments of buildings and plant facilities. Conclusions are as follows. (1) The research works on the thermal and fluid engineering have been reviewed as groups of flow, heat and mass transfer, the reduction of pollutant exhaust gas, cooling and heating, the renewable energy system and the flow around buildings. CFD schemes were used more for all research areas. (2) Research works on heat transfer area have been reviewed in the categories of heat transfer characteristics, pool boiling and condensing heat transfer and industrial heat exchangers. Researches on heat transfer characteristics included the results of the long-term performance variation of the plate-type enthalpy exchange element made of paper, design optimization of an extruded-type cooling structure for reducing the weight of LED street lights, and hot plate welding of thermoplastic elastomer packing. In the area of pool boiling and condensing, the heat transfer characteristics of a finned-tube heat exchanger in a PCM (phase change material) thermal energy storage system, influence of flow boiling heat transfer on fouling phenomenon in nanofluids, and PCM at the simultaneous charging and discharging condition were studied. In the area of industrial heat exchangers, one-dimensional flow network model and porous-media model, and R245fa in a plate-shell heat exchanger were studied. (3) Various studies were published in the categories of refrigeration cycle, alternative refrigeration/energy system, system control. In the refrigeration cycle category, subjects include mobile cold storage heat exchanger, compressor reliability, indirect refrigeration system with $CO_2$ as secondary fluid, heat pump for fuel-cell vehicle, heat recovery from hybrid drier and heat exchangers with two-port and flat tubes. In the alternative refrigeration/energy system category, subjects include membrane module for dehumidification refrigeration, desiccant-assisted low-temperature drying, regenerative evaporative cooler and ejector-assisted multi-stage evaporation. In the system control category, subjects include multi-refrigeration system control, emergency cooling of data center and variable-speed compressor control. (4) In building mechanical system research fields, fifteenth studies were reported for achieving effective design of the mechanical systems, and also for maximizing the energy efficiency of buildings. The topics of the studies included energy performance, HVAC system, ventilation, renewable energies, etc. Proposed designs, performance tests using numerical methods and experiments provide useful information and key data which could be help for improving the energy efficiency of the buildings. (5) The field of architectural environment was mostly focused on indoor environment and building energy. The main researches of indoor environment were related to the analyses of indoor thermal environments controlled by portable cooler, the effects of outdoor wind pressure in airflow at high-rise buildings, window air tightness related to the filling piece shapes, stack effect in core type's office building and the development of a movable drawer-type light shelf with adjustable depth of the reflector. The subjects of building energy were worked on the energy consumption analysis in office building, the prediction of exit air temperature of horizontal geothermal heat exchanger, LS-SVM based modeling of hot water supply load for district heating system, the energy saving effect of ERV system using night purge control method and the effect of strengthened insulation level to the building heating and cooling load.