• Title/Summary/Keyword: Vapor compression system

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Experimental Study on the Performance of Refrigeration System with an Ejector

  • Lee, Won-Hee;Kim, Yoon-Jo;Kim, Min-Soo
    • International Journal of Air-Conditioning and Refrigeration
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    • v.10 no.4
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    • pp.201-210
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    • 2002
  • Experimental investigation on the performance of dual-evaporator refrigeration system with an ejector has been carried out. In this study, a hydrofluorocarbon (HFC) refrigerant R134a is chosen as a working fluid. The condenser and two-evaporators are made as concentric double pipes with counter-flow type heat exchangers. Experiments were peformed by changing the inlet and outlet temperatures of secondary fluids entering condenser, high-pressure evaporator and low-pressure evaporator at test conditions keeping a constant compressor speed. When the external conditions (inlet temperatures of secondary fluid entering condenser and one of the evaporators) are fixed, results show that coefficient of performance (COP) increases as the inlet temperature of the other evaporator rises. It is also shown that the COP decreases as the mass flow rate ratio of suction fluid to motive fluid increases. The COP of dual-evapo-rator refrigeration system with an ejector is superior to that of a single-evaporator vapor compression system by 3 to 6%.

Analysis and Experiment on The Performance of an Autocascade Refrigeration System Using Carbon Dioxide As a Refrigerant (이산화탄소를 냉매로 사용하는 오토캐스케이드 냉동기의 성능에 관한 해석 및 실험)

  • 김성구;김민수
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.13 no.5
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    • pp.411-421
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    • 2001
  • The purpose of this study is to investigate the performance of an autocascade refrigeration system by simulation and experiment using refrigerant mixtures of R744/134a and R744/290 as working fluid. Variations of mass flow rate of refrigerant, compressor work refrigeration capacity and COP with respect to mass fraction of R744/134a and R744/290 mixture were presented under different operating conditions. Performance test has been executed by ASRAE standard. Experimental results show as the composition of R744 in the refrigerant mixture increases, heating and coling capacity are enhanced, but COP trends to decrease. Experimental results are compared with those from the simulation.

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이젝터가 부착된 냉동시스템의 성능실험

  • 이원희;김윤조;김민수
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.13 no.10
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    • pp.993-1001
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    • 2001
  • Experimental investigation on the performance of dual-evaporator refrigeration system with an ejector has been carried out. In this study, a hydrofluorocarbon (HFC) refrigerant R134a is chosen as a working fluid. The condenser and two-evaporators are made as concentric double pipes with counter-flow type heat exchangers. Experiments were performed by changing the inlet and outlet temperatures of secondary fluids entering condenser, high-pressure evaporator and low-pressure evaporator at test conditions keeping a constant compressor speed. When the external conditions (inlet temperatures of secondary fluid entering condenser and one evaporator) are fixed, results show that coefficient of performance (COP) increases as the inlet temperature of the other evaporator rises. It is also shown that the COP decreases as the mass flaw rate ratio of suction fluid to motive fluid increases. The COP of dual-evaporator refrigeration system with an ejector is superior to that of a single-evaporator vapor compression system by 3 to 6%.

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A Study on Pump Down Operation Performance of Refrigerator (냉동기 펌프다운 운전성능에 관한 연구)

  • Kim, Chul-Soo;Chung, Han-Shik;Jeong, Hyo-Min
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.18 no.12
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    • pp.964-970
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    • 2006
  • Vapor compression refrigerators have much critical variables such as the controls of temperature and pressure switches, control durations and operating hours of electronic valves. This study compares and analyzes the data which is obtained from system controlling of the evaporation temperatures which are generally used in automatic pump down operating systems. Through this study, the automatic evaporation control operation system will be more ideal for the system to keep the proper temperature distribution depending on the purpose of evaporation side. The automatic pump down control operation is more appropriate for the system to aim at the effective use of evaporation side without using the temperature difference. And this test will be proved that the changes at the low pressure side didn't have significant impacts on the high pressure side.

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

  • 김제봉;김수연;정평석;조경철
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.15 no.3
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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.

Simulation of Solar/Absorption Cooling Hybrid System and Examination of Its Operating Condition (태양열을 이용한 흡수식 냉방시스템의 시뮬레이션과 운전조건의 검토)

  • Her, Jae-Young;Lee, Sang-Yong
    • The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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    • v.14 no.1
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    • pp.1-11
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    • 1985
  • Solar/absorption cooling system was analyzed and its operating condition was examined. For the system, the optimum size of absorption refrigerator and collector area should be determined. As the temperature of water supplied to the generator increases, the collector efficiency decreases whereas the coefficient of performance of absorption refrigerator increases up to a certain point, and vice versa for decreasing of the temperature of water supplied to the generator . Thus if the reeling load is given, the appropriate operating condition can be determined between the two opposing trends by simulation program. As an example of the simulation, the case of Jejudo province was studied. Under the conditions (such as weather data and prices of components, etc.) given en the sample calculation, the result shows that the optimum temperature of water supplied to the generator turned out to be $80.3^{\circ}C$, and still shows a large economical disadvantage in present stage compared to the case of conventional vapor compression cooling/heating combined heat pump system.

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A Study on the Decrease of Compressor Discharge Temperature Using Subcooling Bypass Technology (Subcooling Bypass Technology를 적용한 압축기 토출 냉매 온도 감소에 관한 연구)

  • Kwak, Kyung-Min;Bai, Cheol-Ho
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.21 no.6
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    • pp.326-332
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    • 2009
  • The purpose of the study is to decrease the refrigerant temperature at the outlet of the compressor under high thermal load conditions for air cooled vapor compression refrigeration system. The subcooling bypass line called subcooling bypass technology(SBT) is installed to the window type A/C system to investigate the performance test. The standard air calorimeter test method is applied to measure the refrigerant temperature at the outlet of the compressor, cooling capacity, power consumption, and system EER. The refrigerant temperature at the outlet of the compressor decreases as the bypass rate increases. When the bypass rate is 8.2%, the refrigerant temperature at the outlet of the compressor decreases $2.8^{\circ}C$ while the cooling capacity and EER are the same as the conventional A/C unit.

Simulation of the Mixed Propane Refrigeration Cycle Using a Commercial Chemical Process Simulator (상용성 화학공정모사기를 활용한 혼합냉매 이용 냉동사이클의 전산모사)

  • Cho, Jung-Ho;Kim, Young-Woo
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.10 no.11
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    • pp.3253-3259
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    • 2009
  • In this study, a computer simulation has been performed for the refrigeration cycle using mixed refrigerants in order to decrease the process stream temperature to $-20^{\circ}C$. Refrigerant supply temperature was assumed to be $-30^{\circ}C$ considering the temperature difference as $10^{\circ}C$ with process stream. Peng-Robinson equation of state model was selected for the computer simulation. A new alpha function proposed by Twu et al was used for an accurate prediction of pure component vapor pressure experimental data. One fluid mixing rules were used for the estimation of mixture vapor-liquid equilibria calculations. A commercial process simulator, PRO/II with PROVISION was utilized for the simulation of the overall refrigeration process. In order to minimize the compressor power consumption, we have optimized the two-stage compression system by varying the first stage compressor outlet pressure. Finally, we could obtain the minimum total power 755.7kW at the first stage compressor outlet pressure, 6 bar.

Experimental Study of Adoption of Alternative Refrigerant for Avionic Equipment Cooling System (항공전자기기용 냉각시스템의 대체냉매 적용에 관한 실험적 연구)

  • Kang, Hoon;Jung, Jongho;Jung, Minwoo;Chi, Yongnam;Yoo, Yongseon;Choi, Heeju;Byeon, Youngman;Kim, Youngjin;Oh, Kwangyoon;Kim, Yongchan
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.37 no.5
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    • pp.431-439
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    • 2013
  • A cooling system is adopted to control the thermal load from the avionic equipments in an aircraft for stable operation. In this study, an avionic cooling system was designed and manufactured by adopting a vapor compression cycle with a closed-loop air-circulation system to investigate the operating characteristics of an alternative refrigerant. The performance characteristics of a cooling system adopting R236fa as an alternative refrigerant were experimentally determined by varying the refrigerant charging amount, expansion valve opening, and compressor rotation speed. The experimental results were analyzed and compared with those of a cooling system adopting R124 as a refrigerant. The possibility of the adoption of R236fa as an alternative refrigerant was verified, and design solutions were suggested to improve the system efficiency.

A Study on Optimizing Drying Performance of Air Dryer (에어 드라이어 제습성능 최적화 프로그램 개발)

  • Park, Won-Ki;Lee, Hi-Koan;Yang, Gyun-Eui;Mun, Sang-Don
    • Transactions of the Korean Society of Automotive Engineers
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    • v.18 no.6
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    • pp.70-75
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    • 2010
  • Compressed air represents an energy source and an force-transmission medium for brake systems on medium-heavy and heavy-duty commercial vehicles. However, one disadvantage is the tendency of air to absorb moisture in the form of water vapor. This water vapor condenses once the air, which is heated during compression, cools back to ambient temperature upon emerging from the air compressor. The resulting condensation assumes the form of moisture in pneumatic lines, air tanks, cylinders and valve assemblies and can have negative consequences for the brake system and vehicle safety. The pneumatic systems on today's vehicles are equipped with air dryers, in which the supplied air is dried according to the adsorption principle. In the systems, the compressed air flows through a granular desiccant with molecular sieves which captures the water molecules.