• Title/Summary/Keyword: Refrigeration cycle

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Performance Characteristics of Refrigeration Cycles with Ejector using Refrigerants (이젝터를 적용한 냉동사이클의 냉매종류별 성능특성)

  • Yoon, Jung-In;Kim, Chung-Lae;Son, Chang-Hyo
    • Journal of Power System Engineering
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    • v.21 no.1
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    • pp.24-29
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    • 2017
  • Studies in liquid-vapor ejector, which performs a great efficiency in refrigeration cycle is highly concerned. This paper is based on basic refrigeration cycle and three ejector refrigeration cycles and the comparison and contrasts about when 6 different refrigerants are applied to such refrigeration cycles. All cycles had a percentage increase of COP from 4 to 74% when ejector was applied, and the source of increasement was the decrease of total work done due to ejector's pressure recovery function. When R-245fa is applied to cycle (d), results showed that COP was the most superior in such cycle, R-245fa showed high volume entrainment ratio in all cycles. Future studies in refrigeration cycles will require more knowledge and experiments on ejector's appliance to refrigeration cycles and the actuation of such functions.

Analysis of combined cycle for desalination process and $CO_2$ refrigeration system (담수화 공정과 이산화탄소 냉동 시스템의 복합사이클 해석)

  • 신지영
    • Journal of Advanced Marine Engineering and Technology
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    • v.24 no.1
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    • pp.41-48
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    • 2000
  • The characteristics of a combined cycle for the production of fresh water and air-conditioning was analyzed. The combined cycle consisted of an open water cycle and a $CO_2$ refrigeration cycle interlinked in the pre-heater of the water cycle, which is the condenser of the refrigeration cycle. The oprating conditions and criteria for the fresh water production and air-conditioning was described and their effects on the total system were evaluated. The results indicated an increase of desalinated water with the increase of hot water temperature, which resulted in the decrease of cooling capacity of the refrigeration system in this study. However, the energy saving correspond to the pre-heating of the water cycle by the condensing of the refrigeration system shows the avilable advantage of the proposed cycle as compared to other single purpose plants for desalination.

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Performance Analysis of R404A Refrigeration System with Internal Heat Exchanger Using R744 as a Secondary Refrigerant (R744를 2차 냉매로 사용하는 내부열교환기 부착 R404A 냉동시스템의 성능 분석)

  • Oh, Hoo-Kyu;Son, Chang-Hyo;Yi, Wen-Bin;Jeon, Min-Ju
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.25 no.10
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    • pp.548-554
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    • 2013
  • A thermodynamic analysis of the R404A refrigeration system with an internal heat exchanger using R744 as a secondary refrigerant is presented in this paper to optimize the design for operating parameters of the system. The main results are summarized as follows: The COP increases with increasing subcooling and superheating degree of R404A, internal heat exchanger and compression efficiency of the R404A cycle and evaporating temperature of the R744 cycle and decreasing temperature difference of the cascade heat exchanger and condensing temperature of the R404A cycle. The mass flow ratio decreases with increasing evaporating temperature of the R744 cycle and internal heat exchanger efficiency of the R404A cycle and decreasing subcooling and superheating degree of the R744 cycle, temperature difference of the cascade heat exchanger and condensing temperature of the R404A cycle.

Heating and Cooling System using the Sewage Source Absorption Refrigeration and Heat Pump Cycle (하수열을 이용한 냉난방시스템에 관한 연구)

  • Lee, Yong-Hwa;Shin, Hyun-Joon;Yoon, Hee-Chul;Park, Hyun-Gun
    • Journal of the Korean Solar Energy Society
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    • v.27 no.4
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    • pp.19-26
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    • 2007
  • This paper concerns the study of absorption refrigeration and heat pump cycle to use sewage. Simulation analysis on the double-effect absorption refrigeration cycle with parallel and two-stage heat pump cycle has been performed. The working fluid is Lithium Bromide and water solution. The absorption refrigeration cycle use sewage as a cooling water for the absorber and condenser, and absorption refrigeration cycle does that as a chilled water for the evaporator of the first stage cycle. And the two-stage cycle consists of coupling double-effect with parallel and single effect cycle so that the first stage absorber and condenser produces heating water to evaporate refrigerant in the evaporator of the second stage. The effects of operating variables such as a absorber temperature on the coefficient of performance have been studied for absorption refrigeration and heat pump cycle.

Performance comparison of refrigeration cycle using R134a with the vapor-liquid ejector (증기-액 이젝터를 적용한 R134a 냉동사이클의 성능 비교)

  • Yoon, Jung-In;Kim, Chung-Lae;Son, Chang-Hyo
    • Journal of Advanced Marine Engineering and Technology
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    • v.39 no.9
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    • pp.890-894
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    • 2015
  • Recently, research on high-efficiency refrigeration cycles that apply an ejector to basic cycles has progressed actively. The role of the ejector and the performance of refrigeration cycles are subordinate to ejector locations. In this study, the performance of three refrigeration cycles with different ejector locations is compared and analyzed. The results showed an increased COP in all cycles due to the application of the ejector, with the highest increase of 44% compared to a basic refrigeration cycle. The ejector refrigeration cycle proposed in this study presents the highest COP, 3.47. Moreover, the decrease in condensation capacity in Bergander's cycle, Xing's cycle, and our proposed ejector refrigeration cycle went up to 21%. In refrigeration cycles applying the ejector, the pressure ratio of the ejector, the vapor fraction of discharge, and compression ratio are important factors for COP enhancement. For this reason, detailed and accurate control of these is significant.

Modelling of a High Efficiency Refrigeration System with Heat Storage for Reverse Cycle Hot Gas Defrost

  • Ardiyansyah, Ardiyansyah;Choi, Kwang-Il;Oh, Jong-Taek;Oh, Hoo-Kyu
    • International Journal of Air-Conditioning and Refrigeration
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    • v.15 no.4
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    • pp.175-181
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    • 2007
  • A computer model of a high efficiency refrigeration system equipped with heat storage for reverse cycle-hot gas defrost (the stored heat is used during defrost cycle of the system) is presented. The model was developed based on both theoretical and empirical equations for the compressor, evaporator, condenser and the heat storage equipment. Simulations of the prototype system were carried out to investigate refrigeration system performance under various operating conditions during refrigeration cycles. The simulations of the evaporator during defrost cycles at 30 and $40^{\circ}C$ hot gas refrigerant temperature were also performed which resulted on shorter defrost time but only slight increase in defrost efficiency. These information on energy efficiency and the defrost time required are important in order to avoid excessive parasitic load and temperature rise of the refrigerated room.

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

  • Noh, Sanggyun
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.15 no.5
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    • pp.3327-3335
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    • 2014
  • In this study, comparison works have been performed for single-stage and multi-stage refrigeration cycle using propane as a refrigerant in order to cool down the natural gas stream. A comparative analysis has been performed for a single, two, three and four stage refrigeration cycle using propane as a refrigerant for cooling the natural gas stream. For the simulation, natural gas feedstock properties supplied by KOGAS were utilized and Peng-Robinson equation of state model was used. As the number of compression stages increase, the condenser heat duty is decreased. The refrigeration heat duty for a four-stage refrigeration cycle is decreased by 20.36% compared to that for a single-stage refrigeration cycle. Moreover, the total refrigerant circulation rate for a four-stage refrigeration system is was reduced by 14.53% compared to the single stage refrigeration cycle. The total compression power for a four-stage compression was reduced by 41.61% compared to the single stage compression.

An Optimization Study on the Reliquefaction of Boil-Off Gas from Liquefied Petroleum Gas Storage Tank (액화석유가스 저장탱크로부터 발생하는 증발가스 재액화 공정의 최적화에 대한 연구)

  • NOH, SANGGYUN
    • Transactions of the Korean hydrogen and new energy society
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    • v.30 no.5
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    • pp.395-400
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    • 2019
  • Comparative studies between single- and two-stage refrigeration cycle using propane as a refrigerant have been performed for a vapor recompression refrigeration cycle. PRO/II with PROVISION release 10.2 from AVEVA company was used, and the Soave-Redlich-Kwong equation of state model with Twu's alpha function was selected for the modeling and optimization of the refrigeration cycle for the reliquefaction of BOG coming out from the LPG storage tank. In two-stage refrigeraton cycle, 24.8% of compressor power was reduced compared to that of single-stage refrigeration cycle through the optimization works.

Performance analysis of $CO_{2}$ refrigeration cycle with two-phase ejector (2상류이젝터를 이용하는 $CO_{2}$ 냉동사이클의 성능해석)

  • Lee Yoon-Hwan
    • Journal of Advanced Marine Engineering and Technology
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    • v.29 no.8
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    • pp.946-952
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    • 2005
  • The $CO_{2}$ refrigeration cycle is expected to reduce the compressor work and increase the COP by applying two-phase ejector as a device for the recovery of dissipated expansion energy. In this study, the performance of the cycle was simulated and effects of the ejector shapes on the performance of the $CO_{2}$ refrigeration cycle were investigated. The following results were obtained through the cycle simulation. The COP of the $CO_{2}$ refrigeration cycle with two-phase ejector flow which expansion is occured in the isentropic manner is increased by a maximum of 24 $\%$ than the basic cycle with expansion valve If the velocity nonequilibrium in the mixing process is assumed the COP of the cycle is increased with the increase of the length and the decrease of the section area of the mixing tube. The best cycle performance is obtained when the divergent angle of diffuser is 7.

Analysis of a Refrigeration Cycle Driven by Refrigerant Steam Turbine (냉매증기터빈에 의해 구동되는 냉동사이클의 해석)

  • 정진희
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.14 no.10
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    • pp.801-810
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    • 2002
  • We have analyzed a combined cycle employing refrigerant Rankine cycle and simple refrigeration cycle with one working fluid. Although this cycle shows promising aspects such as simplicity, it does not have a good efficiency to compete with the other existing technologies because of high temperature at the exit of the turbine. However, by introducing a recuperator, it is found that the cycle efficiency can be improved up to the level much higher than other technology's efficiency.