• Title/Summary/Keyword: Air-cycle refrigeration

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An Analysis of the Performance of a Combined Expander-Compressor Unit for a CO2 Automotive Air Conditioning Cycle (차량용 CO2 에어컨 사이클 성능 향상을 위한 일체형 팽창기-압축기 성능 해석)

  • Choi, Jae Woong;Lim, Jeong Taek;Kim, Hyun Jin
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.30 no.3
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    • pp.107-115
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    • 2018
  • A design combining the use of a compressor and expander was introduced in order to improve the cycle performance of a $CO_2$ automotive air conditioning system. Both the compressor and expander used were of rotary vane type and were designed to share a common shaft in a housing. Numerical simulation was carried out to evaluate the merit of the combined unit. In a typical automotive air conditioning operating conditions, the COP of the system was improved by 8.7% by the application of the combined unit. The compressor input was reduced by 5.2% through use of the expander output. In addition, about 3.06% increase in the cooling capacity was obtained through isentropic expansion in the expander. Our study noted that, as the pressure difference between the gas cooler and the evaporator becomes larger, the COP of the system improved increases unless the mass flow rate in the expander exceeds that in the compressor.

Performance of adsorption heat pump with radial shape adsorber heat exchanger for air cooling (공냉식 방사형 열교환기를 갖는 흡착식 히트펌프의 성능)

  • Baek, N.C.;Yang, Y.S.;yoon, E.S.;Lee, J.K.;Joo, M.C.
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.9 no.1
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    • pp.73-81
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    • 1997
  • In this experimental study, the air cooling radial shape heat exchanger which influences on the COP and the cooling capacity by heat and mass transfer rate in the adsorbent bed was designed and applied to test its performance for adsorption heat pump(AHP). Zeolite-water was used for the adsorbent-adsorbat pair. As a result, the cooling COP and a cycle period of this adsorption heat pump are 0.28 and 2 hours, respectively, on the condition of none heat recovery from the adsorption reactor(absorber). The other results and recommendations are mainly related to improving the heat and mass transfer inside the absorber to reduce a cycle period.

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An experimental study on the performance of a window system air-conditioner using R407C and R410B (R407C 및 R410B 적용 창문형 에어컨의 성능에 관한 실험적 연구)

  • Kim, M.H.;Shin, J.S.;Kim, K.J.
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.9 no.4
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    • pp.536-544
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    • 1997
  • This study presents test results of a residential window system air-conditioner using R22 and two potential alternative refrigerants, R407C and R410B. A series of performance tests was performed for the basic and liquid-suction heat exchange cycle in a psychrometric calorimeter test facility. For R407C, the same rotary compressor was used as in the R22 system. However, compressor for the R410B system was modified to provide the similar cooling capacity. The evaporator circuit was changed to get a counter-cross flow heat exchanger to take advantage of zeotropic mixture's temperature glide, and liquid-line suction-line heat exchange cycle was also considered to improve the performance of the system. Test results were compared to those for the basic R22 system.

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Cycle Simulation of an Air Source Heat Pump Using Liquid Injection (액분사 사이클을 이용한 공기 열원 열펌프의 사이클 시뮬레이션)

  • 김욱중;홍용주;남임우;강원일;공용상
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.12 no.3
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    • pp.244-250
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    • 2000
  • An air source heat pump using liquid injection technique, which can be applied for very low temperature climate, has been simulated to examine the design options. Comparison between the simulation and experiment has been carried out to validate the simulation method. Effects of various design parameters such as liquid injection rate and injection pressure are Investigated to optimize the performance of the heat pump. Finally, optimal liquid infection rate and injection pressure to maintain sufficient heating capacity and moderate discharge refrigerant temperature are suggested when the heat pump was operated at very low outdoor temperature.

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Recent Progress in Air-Conditioning and Refrigeration Research: A Review of Papers Published in the Korean Journal of Air-Conditioning and Refrigeration Engineering in 2014 (설비공학 분야의 최근 연구 동향: 2014년 학회지 논문에 대한 종합적 고찰)

  • Lee, Dae-Young;Kim, Sa Ryang;Kim, Hyun-Jung;Kim, Dong-Seon;Park, Jun-Seok;Ihm, Pyeong Chan
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.27 no.7
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    • pp.380-394
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    • 2015
  • This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during 2014. 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 heat and mass transfer, cooling and heating, and air-conditioning, the flow inside building rooms, and smoke control on fire. Research issues dealing with duct and pipe were reduced, but flows inside building rooms, and smoke controls were newly added in thermal and fluid engineering research area. (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 for thermal contact resistance measurement of metal interface, a fan coil with an oval-type heat exchanger, fouling characteristics of plate heat exchangers, effect of rib pitch in a two wall divergent channel, semi-empirical analysis in vertical mesoscale tubes, an integrated drying machine, microscale surface wrinkles, brazed plate heat exchangers, numerical analysis in printed circuit heat exchanger. In the area of pool boiling and condensing, non-uniform air flow, PCM applied thermal storage wall system, a new wavy cylindrical shape capsule, and HFC32/HFC152a mixtures on enhanced tubes, were actively studied. In the area of industrial heat exchangers, researches on solar water storage tank, effective design on the inserting part of refrigerator door gasket, impact of different boundary conditions in generating g-function, various construction of SCW type ground heat exchanger and a heat pump for closed cooling water heat recovery were performed. (3) In the field of refrigeration, various studies were carried out in the categories of refrigeration cycle, alternative refrigeration and modelling and controls including energy recoveries from industrial boilers and vehicles, improvement of dehumidification systems, novel defrost systems, fault diagnosis and optimum controls for heat pump systems. It is particularly notable that a substantial number of studies were dedicated for the development of air-conditioning and power recovery systems for electric vehicles in this year. (4) In building mechanical system research fields, seventeen 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, and renewable energies, piping in the buildings. Proposed designs, performance performance tests using numerical methods and experiments provide useful information and key data which can improve 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 evaluation of work noise in tunnel construction and the simulation and development of a light-shelf system. The subjects of building energy were worked on the energy saving of office building applied with window blind and phase change material(PCM), a method of existing building energy simulation using energy audit data, the estimation of thermal consumption unit of apartment building and its case studies, dynamic window performance, a writing method of energy consumption report and energy estimation of apartment building using district heating system. The remained studies were related to the improvement of architectural engineering education system for plant engineering industry, estimating cooling and heating degree days for variable base temperature, a prediction method of underground temperature, the comfort control algorithm of car air conditioner, the smoke control performance evaluation of high-rise building, evaluation of thermal energy systems of bio safety laboratory and a development of measuring device of solar heat gain coefficient of fenestration system.

A Study on Regenerative OTEC System using the Condenser Effluent of Uljin Nuclear Power Plant (울진 원자력발전소 온배수를 이용한 재생식 해양온도차발전에 대한 연구)

  • Kang, Yun-Young;Park, Sung-Seek;Park, Yun-Beom;Kim, Nam-Jin
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.24 no.7
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    • pp.591-597
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    • 2012
  • For the past few years, the concern for clean energy has been greatly increased. Ocean thermal Energy Conversion(OTEC) power plants are studied as a viable option for the supply of clean energy. In this study, we examined the thermodynamic performance of the OTEC power system for the production of electric power. Computer simulation programs were developed under the same condition and various working fluids for closed Rankine cycle, regenerative cycle, Kalina cycle, open cycle, and hybrid cycle. The results show that the regenerative cycle showed the best system efficiency. And then we examined the thermodynamic performance of regenerative cycle OTEC power system using the condenser effluent from Uljin nuclear power plant instead of the surface water. The highest system efficiency of the condition was 4.55% and the highest net power was 181 MW.

Cycle performance of refrigeration and air-conditioning system using the hydrocarbon refrigerant R-290 (탄화수소계 냉매 R-290을 사용하는 냉동.공조 장치의 사이클 특성에 관한 연구)

  • 박기원
    • Journal of Advanced Marine Engineering and Technology
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    • v.23 no.4
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    • pp.447-452
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    • 1999
  • This paper describes the cycle performance of heat-pump system using R-22 and R-290. Experiments were performed in the smooth tube with inside diameter of 10.07mm and outside diameter of 12.07 mm and grooved inner tube having 75 fins with a height of 0.25mm Condensing temperatures were held constantly between 318K and 328 K while evaporating temperatures were varied from 257 K to 288 K mass velocities from 51 to $280 kg/m^2s$. From the experiments it was known that the evaporating temperature and condensing temperature had more affected by the compressor shaft power than the tube geometries. Cooling capacity of the R-22 and R-290 had similar values in the smooth and grooved inner tubes. The coefficient of performance(COP) was calculated using the compressor shaft power volumetric refrigeration capacity compression ratio and cooling capacity. The COP of the R-290 had slightly higher values than that of R-22 The major parameters affecting the heat pump cycle performance wee the refrigerant proper-ties and operating conditions rather than the geometric shapes of the heat exchanger

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Performance Characteristics and Economic Assessment of a River Water: Source Heat Pump System (하천수 열원 열펌프 시스템의 성능 특성 및 경제성 평가)

  • Park, Cha-Sik;Jung, Tae-Hun;Park, Hong-Hee;Kim, Yong-Chan
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.21 no.11
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    • pp.621-628
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    • 2009
  • The objectives of this study are to analyze the performance of a river water-source heat pump and to carry out economic assessment for the heat pump. The COP of the river water-source heat pump was 3-21% higher than that of the air-source heat pump because river water provides stable operating temperature compared with air temperature throughout the year. The economic analysis was carried out by comparing the initial and operating cost of the river water-source heat pump with those of the conventional air-source heat pump. The ratio of the life cycle operating cost to the life cycle cost increased with the increase of building capacity. The payback period was found to be less than 3.5 years when the capacity of the river water-source heat pump was larger than 10 RT.

The Cooling Performance Enhancement of a Variable Speed Heat Pump Using Gas Injection Technique (가스인젝션 기술을 적용한 공기열원 가변속 열펌프의 냉방성능 향상에 관한 연구)

  • Jeong, Min-Woo;Heo, Jae-Hhyeok;Jung, Hae-Won;Kim, Yong-Chan
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.21 no.8
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    • pp.425-432
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    • 2009
  • In this study, the improvement of cooling capacity by applying gas injection technique in a two-stage heat pump using R410A was experimentally investigated. A twin rotary type compressor with gas injection was applied to the heat pump system. The optimum refrigerant charge for the injection and the non-injection cycles was selected to achieve the maximum COP at the cooling standard condition. The injection cycle showed less optimum refrigerant charge than that of the non-injection cycle. The cooling performances of the injection and the non-injection cycles were measured and compared by varying compressor frequency from 40 to 90 Hz. The cooling capacity of the gas injection cycle was 1.6% -11.3% higher than that of the non-injection cycle. The COP of the gas injection cycle was 13.7% to 28.9% higher than that of the non-injection cycle at the same cooling capacity. The heat pump system showed stable operation after 30% of the injection valve opening.

Simulation on a Residential Heat Pump System Using $CO_2$ (이산화탄소를 적용한 주거용 냉난방 겸용 열펌프 시스템의 시뮬레이션)

  • 조홍현;이무연;김용찬
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.15 no.12
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    • pp.987-995
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    • 2003
  • The performance of a residential heating and cooling system with $CO_2$ is predicted by using a cycle simulation model. The simulations are conducted by varying design parameters and operating conditions. The efficiency of the transcritical cycle can be improved by utilizing the advantages in heat transfer characteristics of $CO_2$ and developing microchannel indoor and outdoor heat exchangers. For the designed system of this study, the predicted COP of the heat pump system is approximately 3.5 in the heating mode and 3.0 in the cooling mode. The predicted optimal discharge pressure for the heat pump system is approximately 11 MPa in the heating mode and 9 MPa in the cooling mode.