• Title/Summary/Keyword: Vapor compression system

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Optimization of Evaporator for a Vapor Compression Cooling System for High Heat Flux CPU (고발열 CPU 냉각용 증기 압축식 냉각 시스템의 증발기 최적화)

  • Kim, Seon-Chang;Jeon, Dong-Soon;Kim, Young-Lyoul
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.32 no.4
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    • pp.255-265
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    • 2008
  • This paper presents the optimization process of evaporator for a vapor compression cooling system for high heat flux CPU. The CPU thermal capacity was given by 300W. Evaporating temperature and mass flow rate were $18^{\circ}C$ and 0.00182kg/s respectively. R134a was used as a working fluid. Channel width(CW) and height(CH) were selected as design factors. And thermal resistance, surface temperature of CPU, degree of superheat, and pressure drop were taken as objective responses. Fractional factorial DOE was used in screening phase and RSM(Response Surface Method) was used in optimization phase. As a result, CW of 2.5mm, CH of 2.5mm, and CL of 484mm were taken as an optimum geometry. Surface temperature of CPU and thermal resistance were $33^{\circ}C\;and\;0.0502^{\circ}C/W$ respectively. Thermal resistance of evaporator designed in this study was significantly lower than that of other cooling systems such as water cooling system and thermosyphon system. It was found that the evaporator considered in this work can be a excellent candidate for a high heat flux CPU cooling system.

Experimental Studies on the Performance of a Transcritical Cycle for Hot Water Heating Using Carbon Dioxide (이산화탄소를 이용한 온수급탕용 초월임계사이클의 성능에 대한 실험적 연구)

  • 김성구;김민수
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.15 no.6
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    • pp.461-470
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    • 2003
  • The purpose of this study is to investigate the performance of a transcritical cycle for hot water heating using $CO_2$ as a working fluid. Some of the main parameters that affect the practical performance of the $CO_2$ system are discussed; the performance on the variation of refrigerant charge, changes in flow conditions of secondary fluids, and that with or without internal heat exchanger, The experimental results show that the optimum charge is approximately the same for various mass flow rates of the secondary fluid at gas cooler. The experimental results on the effect of secondary fluids are in general agreement with the experimental results of transcritical cycle in the open literature and show similar trend for conventional subcritical vapor compression cycles. The heat exchanger effectiveness increases with an increase of the heat exchange area of the internal heat exchanger regardless of the mass flow rate at the gas cooler.

Analysis of the Irreversibilities of a Vapor Compression Type Refrigerator (증기 압축식 냉동기의 비가역성 분석)

  • Shin, K.Y.;Jung, P.S.;Kim, S.Y.;Lee, S.C.
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.7 no.1
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    • pp.30-41
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    • 1995
  • The present paper investigated irreversibilities and energy flow of a vapor compression refrigerator. The entropy generation and the available energy dissipation in components of the system were analyzed by using experimental data. It was shown that the dissipated available energy in the compressor including electric motor was much more than those in other components. The effects of the pressure drop and heat loss on irreversibilities in the condenser and the evaporator were small in comparison with heat transfer.

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The Reduced Steam Consumptions in the Evaporation Process Using a Vapor Recompression (증기 재압축을 활용한 증발공정에서 스팀 절감에 대한 연구)

  • Noh, Sang Gyun
    • Clean Technology
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    • v.22 no.4
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    • pp.225-231
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    • 2016
  • In this study, modeling and optimization study have been performed to obtain $1,524.58kg\;h^{-1}$ of a solidified NaCl by evaporating a 21.0 wt% of NaCl aqueous solution in order to reduce the steam consumption from $3,139kg\;h^{-1}$ to $496kg\;h^{-1}$ using a two-stage evaporation and a vapor recompression processes. Aspen Plus release 8.8 at AspenTech was utilized for the modeling of two stage evaporation process and PRO/II with PROVISION release 9.4 at Schneider Electric was also used for the simulation of two-stage vapor recompression process with an inter-cooler. For the simulation of the evaporation process containing NaCl aqueous solution, Aspen Plus release 8.8 at AspenTech Inc. was utilized and for the modeling of vapor recompression process PRO/II with PROVISION release at Schneider Electric Inc. For the vapor recompression process, single stage compression and two-stage compression system was compared.

Dimensional Stability of Plastic Processing Wood Material - Compression Wood and Bentwood -

  • Hwang, Kweon-Hwan;Lee, Won-Hee
    • Journal of the Korea Furniture Society
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    • v.18 no.2
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    • pp.143-146
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    • 2007
  • This study was carried out to assess the dimensional stability of wood material treated by plastic processing for bentwood and compression wood. The evaluation method was different between two wood materials, but the treatments for them were very similar to each other. One of the main methods is heat treatment with sufficient water vapor. In bentwood, the used species were painted maple (Acer mono), bitter wood (Picrasma quassioides) and birch (Betula schmidtii). Steaming was the worst treatment method for dimensional stabilization of bentwood. The best results could be attained with PEG treatment for dimensional stabilization of bentwood. Dimensional stability of bitter wood was found to be conspicuous. However the steaming treatment at lower temperatures, i.e., about $130^{\circ}C$ was not suitable for dimensional stability of bentwood. In compression wood, the used specimen was Italian poplar wood (Populus euramericana). Two heat compressive pressing conditions, an open-press system and an air-tighten closed-press system, were used. The recovery rate was measured after boiling and/or absorbing in water to estimate the dimensional stability of heat compressed wood. The best dimensional stability of compressed wood in the air-tighten closed-press system was found to be better at $200^{\circ}C$ than $180^{\circ}C$. The best compression rate for dimensional stability was 73 percent.

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Performance analysis for load control of R744(carbon dioxide) transcritical refrigeration system using hot gas by-pass valve (핫가스 바이패스 밸브를 이용한 R744용 초임계 냉동사이클의 부하제어에 대한 성능 분석)

  • Roh, Geun-Sang;Son, Chang-Hyo
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.10 no.9
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    • pp.2189-2194
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    • 2009
  • The automatic hot gas by-pass technique is applied to control the capacity of refrigeration and air-conditioning system when operating at part load. In the scheme, the hot gas from the compressor is extracted and injected into the outlet of an evaporator through a hot gas by-pass valve. Thus, In this paper, the hot gas by-pass scheme for CO2 is discussed and analyzed on the basis of mass and energy conservation law. A comparative study of the schemes is performed in terms of the coefficiency of performance (COP) and cooling capacity. The operating parameters considered in this study include compressor efficiency, superheating degree, outlet temperature of gas cooler and evaporating temperature in the R744 vapor compression cycle. The main results were summarized as follows : the superheating degree, outlet temperature and evaporating temperature of R744 vapor compression refrigeration system have an effect on the cooling capacity and COP of this system. With a thorough grasp of these effect, it is necessary to design the compression refrigeration cycle using R744.

Performance Characteristic of the Compression-Absorption Hybrid Heat Pump Cycles (흡수압축 하이브리드 히트펌프 사이클의 성능특성)

  • Yoon J. I.;Kwon O. K.;Yang Y. M.
    • Journal of the Korean Institute of Gas
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    • v.3 no.1
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    • pp.14-20
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    • 1999
  • This study describes the results of Coefficient of Performance(COP) analysis by cycle simulation for two types of absorption-compression hybrid cycle using the Water/Lithium Bromide solution pair. These types are basic hybrid systems introducing a mechanical compression process into the refrigerant vapor phase of the single effect absorption cycle. In absorption-compression hybrid cycles, coefficient of performance is improved compared with absorption cycle. Hybrid cycle Type 2 is considered as a key technology to support energy utilization system, given its capability of utilizing waste heat to drive system with a high level of efficiency.

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Performance Analysis of a Seawater Ice Machine Applied Two-stage vapor compression refrigeration system for Various Refrigerants (2단 증기 압축식 냉동시스템을 적용한 해상용 제빙장치의 냉매에 따른 성능 분석)

  • Yoon, Jeong-In;Son, Chang-Hyo;Heo, Seong-Kwan;Jeon, Min-Joo;Jeon, Tae-Young
    • Journal of Power System Engineering
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    • v.20 no.2
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    • pp.85-90
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    • 2016
  • Coefficient of performance (COP) for two-stage compression system is investigated in this paper to develop seawater ice machine. The system performance is analyzed with respect to degrees of superheating and subcooling, condensing and evaporating temperatures, compression and mechanical efficiencies and mass flow ratio in an inter-cooler. The main results are summarized as follows : The COP of the system grows when the mass flow ratio, subcooling degree and evaporating temperature edge up. Contrariwise, the system performance descends in case that superheating degree and condensing temperature increase. The most effective factor for the COP is the mass flow rate ratio. Each refrigerant has different limitation for a value of the mass flow ratio in the inter-cooler because of difference in material property.

Design and Evaluation of Multiple Effect Evaporator Systems According to the Steam Ejector Position (증기 이젝터 위치에 따른 다중효용증발시스템의 설계 및 성능분석)

  • Kim, Deukwon;Choi, Sangmin
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.28 no.11
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    • pp.434-443
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    • 2016
  • The evaporation of water from an aqueous solution is widely used in the food, desalination, pulp, and chemical industries. Usually, a large amount of energy is consumed in the evaporation process to boil off water due to atmospheric pressure. As a way of improving the energy efficiency of the evaporation process, the combination of multiple effect evaporation and thermal vapor recompression has been proposed and has become a successful technique. In this study, 4 multiple-effect falling film type evaporators for sugar solution are designed and the energy efficiency of the system is analyzed in response to the selection of the steam ejector position. Energy efficiency is increased and vapor is more compressed in the steam ejector as the Thermal Vapor Recompression (TVR) is arranged in the rear part of the evaporator system. A simplified 0-dimensional evaporator model is developed using non-linear equations derived from mass balances, energy balances, and heat transfer equations. Steam economy is calculated to compare the evaporation performance of the 4 proposed evaporators. The entrainment ratio, compression ratio, and expansion ratio are computed to check the ejector performance.

Experimental Study on the Cooling Characteristics of an Environmental Control System for Avionic Reconnaissance Equipment (항공정찰장비용 환경제어시스템의 냉각특성에 관한 실험적 연구)

  • Kang, Hoon;Park, Hyung-Pil;Lee, Eung-Chan;Kim, Yong-Chan;Chi, Yong-Nam;Choi, Hee-Ju;Byeon, Young-Man;Kim, Young-Jin;Oh, Kwang-Yoon
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.21 no.9
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    • pp.519-526
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    • 2009
  • Environmental control system is adopted to control the thermal load from the avionic equipment in the reconnaissance pod which is mounted under a fighter aircraft, undergoing large and rapid environmental changes with the variations of flight altitude and velocity. In this study, an environmental control system was designed and built by adopting vapor compression cycle using R-124. The cooling performance characteristics of the system were measured varying operating parameters: thermal load in the pod, air mass flow rate through evaporator, condenser inlet air temperature, and air mass flow rate through condenser. The effects of the experimental parameters on the system performance were analyzed based on the experimental results. The problems on the designed system were also analyzed and the solutions were suggested to improve system efficiency and to obtain stable operation.