• Title/Summary/Keyword: Air-cycle refrigeration

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Cooling Characteristics of Refrigerated Vehicles with Heat Storage Materials in Thermobank (냉동탑차의 Thermobank 열저장 매체에 따른 냉각성능 비교)

  • Mun, Je-Cheol;Choi, Kwang-Il;Oh, Jong-Taek;Kim, Jai-Hoon
    • Proceedings of the SAREK Conference
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    • 2009.06a
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    • pp.810-814
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    • 2009
  • A experimental study of a high efficiency transport refrigeration system for sliced-raw fish transportation is presented in this paper. The refrigeration system, that is powered by the car engine, is equipped with heat storage for reverse cycle-hot gas defrost; the stored heat is used during defrost cycle of the system. The heat storage has size $400(L){\times}350(W){\times}250(H)\;mm$ and made of fin-tube heat exchanger. System performance and container operating conditions are experimentally investigated and analyzed under cooling and defrosting conditions with heat storage materials. The water is faster about 30% than paraffin in cooling-down time of heat storage materials with load and unload.

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Performance Analysis of Vane Rotary Expander for $CO_2$ Cycles ($CO_2$ 사이클용 로타리 베인 팽창기 성능해석)

  • Kim, Ho-Young;Ahn, Jong-Min;Kim, Hyun-Jin;Cho, Sung-Oug
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.21 no.1
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    • pp.55-62
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    • 2009
  • Relatively low cycle performance of a conventional $CO_2$ system is partly due to significant increase in friction loss in the expansion process, since the pressure drop across the expansion device is considerably large compared to a conventional refrigeration cycle. To recover friction loss and increase refrigeration effect by providing isentropic expansion, a rotary vane type expander has been designed. Performance of the designed expander has been investigated by numerical simulation. With the pressure condition of 9 MPa/4.5 MPa and inlet temperature of $35^{\circ}C$, volumetric, isentropic, and mechanical efficiencies of the expander are calculated to be 58.1%, 101.1%, and 78.8%, respectively, resulting in total expander efficiency of 46.3%. With this expander, COP of a $CO_2$ refrigeration cycle is estimated to be improved by about 14%.

Capacity Modulation of a Heat Pump System by Changing the Composition of Refrigerant Mixtures (혼합냉매의 성분비 조절을 통한 열펌프의 용량조절)

  • 김민성;김민수;김용찬
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.12 no.3
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    • pp.258-266
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    • 2000
  • Experimental investigation and cycle simulation of a capacity modulation of a heat pump system using a hydrofluorocarbon (HFC) refrigerant mixture, R32/134a as an alternative to R22, have been done. In the cycle simulation, the refrigeration system was operated by assigning the temperatures of the external heat transfer fluids with the heat exchangers generalized by an average effective temperature difference. Heating capacity, cooling capacity, and coefficient of performance (COP) of the system were investigated at several operating conditions. Experimental apparatus which had a refrigeration part and a composition changing part was built, and the performance of the heat pump system filled with R32/134a mixture was investigated. A gas-liquid separator was used in the experiment to change the composition by collecting the vapor and the liquid Phase separately, The mass fraction of the charged refrigerant in the heat pump system was 40/60 and 70/30 by weight percentage. The composition of the refrigerant with initial composition of 40/60 varied from 29/71 to 41/59 in the refrigeration cycle. For the refrigerant with initial composition of 70/30, the composition varied from 65/35 to 75/25.

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Performance Analysis of 1MW Organic Rankine Cycle with Liquid-Vapor Ejector using Effluent from Power Plant (화력발전소 폐열에 따른 작동유체별 액-증기 이젝터를 적용한 1MW급 ORC의 성능 분석)

  • Kim, Hyeon-Uk;Yoon, Jung-In;Son, Chang-Hyo
    • Journal of Power System Engineering
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    • v.18 no.6
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    • pp.120-125
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    • 2014
  • In this paper, suitable working fluid of 1MW Organic Rankine Cycle(ORC) with liquid-vapor ejector using effluent from power plant is selected. The results of comparison performance of 5 refrigerants are as follows; R600a, R134a, R1270, R236fa, R235fa. The operating parameters considered in this study include the condensation capacity evaporation capacity and efficiency. As a result of comparison of basic ORC system and with liquid-vapor ejector, with ORC system presents the higher system efficiency since the ejector makes the turbine outlet pressure lower than condensation pressure through its pressure recovery. Also, this ejector ORC system is advantageous in miniaturizing the size of components owing to decrease of evaporation capacity and condensation capacity.

Performance Variation with Length of Internal Heat Exchanger in CO2 Cooling Cycle Using an Ejector (이젝터를 적용한 이산화탄소 냉동사이클의 내부열교환기 길이에 따른 성능 변화)

  • Kang, Byun;Cho, Hong-Hyun
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.24 no.2
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    • pp.147-154
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    • 2012
  • Recently, many researchers have studied the performance of the transcritical $CO_2$ refrigeration cycle in order to improve the system efficiency. In this study, the length of IHX in the $CO_2$ ejector cycle was varied so as to evaluate the performance improvement. As a result, compressor work and cooling capacity was increased by 3% and 5% as the length of internal heat exchanger was changed from 3 m to 15 m. The best COP was appeared at internal heat exchanger length of 12 m, and it was 3.01. Besides, the length of internal heat exchanger has a big effect to pressure lift ratio and entrainment ratio in the ejector $CO_2$ cycle and it may be changed with operating conditions and system specifications.

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.

A Study on the Cascade Hybrid Cooling/Refrigeration Cycle Equipped With Intercooler and Air-Cooled Condenser in Series (인터쿨러와 공랭식 응축기를 동시에 사용하는 냉방-냉동 겸용 캐스케이드 사이클에 대한 연구)

  • Kim, Nae-Hyun
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.20 no.7
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    • pp.353-362
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    • 2019
  • Thermodynamic analysis of cascade refrigeration systems has attracted considerable research attention. On the other hand, a system evaluation based on thermodynamic analyses of the individual parts, including the evaporator, condenser, intercooler, expansion valve, etc., has received less attention. In this study, performance analysis was conducted on a cascade refrigeration system, which has an individual cooling and refrigeration evaporator, and equips the intercooler and air-cooled condenser in a series in a lower cycle. The thermo-fluid design was then performed on the major components of the system - upper condenser, lower condenser, cooling evaporator, refrigeration evaporator, intercooler, compressor, electronic expansion valve - of 15 kW refrigeration, and 8 kW cooling capacity using R-410A. A series of simulations were conducted on the designed system. The change in outdoor temperature from 26 C to 38 C resulted in the cooling capacity of the lower evaporator remaining approximately the same, whereas it decreased by 9% at the upper evaporator and by 63% at the intercooler. The COP decreased with increasing outdoor temperature. In addition, the COP of the cycle with the intercooler operation was higher that of the cycle without the intercooler operation. Furthermore, the increase in the upper condenser size by two fold increased the upper evaporator by 4%. On the other hand, the lower evaporator capacity remained the same. The COP of the upper cycle increased with increasing upper condenser size, whereas that of the lower cycle remained almost the same. When the size of the lower condenser was increased 2.8 fold, the intercooler capacity increased by 8%, whereas those of upper and the lower evaporator remained approximately the same. Furthermore, the COP of the lower cycle increased with an increase in the lower condenser. On the other hand, the change of the upper condenser was minimal.

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

  • 김용찬;조홍현;노현일;김영득;박윤철
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.14 no.6
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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.

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

  • Park, Kyoung Kuhn
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.24 no.11
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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
    • 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.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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