• Title/Summary/Keyword: Outdoor air conditioning system

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Simulation Study on the Performance Characteristics in the Solar Hybrid R744 Heat Pump for Residential Applications (주거용 태양열 하이브리드 이산화탄소 열펌프 시스템의 성능특성에 관한 해석적 연구)

  • Kim, Won-Seok;Cho, Hong-Hyun
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.23 no.10
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    • pp.678-686
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    • 2011
  • Simulation study on the operating characteristics in the solar hybrid R744 heat pump system for residential applications was carried out with heat pump operating temperature, outdoor temperature and solar radiation. As a result, collector operating time is decreased by 1.5 hours due to the increase of water temperature in the heat storage tank when the heat pump operating temperature rises. Heat pump operating time is reduced by 19.4% owing to the high temperature of a heat storage tank. Besides, indoor heating time is decreased from 10.3 to 5.5 hours as the indoor temperature increases from $3^{\circ}C$ to $11^{\circ}C$. In addition to, when the solar radiation rises from 10 to 20 MJ/$m^2$, the maximum outlet temperature of a solar collector is increased from $65^{\circ}C$ to $71^{\circ}C$.

Experimental Study on the Performance Improvement of a Simultaneous Heating and Cooling Heat Pump in the Cooling-main Operating Mode (냉방주체 운전모드에서 동시냉난방 열펌프 성능향상에 관한 실험적 연구)

  • Chung, Hyun-Joon;Joo, Young-Ju;Kang, Hoon;Kim, Yong-Chan;Choi, Jong-Min
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.20 no.5
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    • pp.314-320
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    • 2008
  • The cooling load in winter is significant in buildings and hotels because of the usage of office equipments and the improved wall insulation. Hence, a multi~heat pump is required to cover heating and cooling simultaneously for each indoor unit. In this study, the operating characteristics and performance of a simultaneous heating and cooling heat pump in the cooling-main operating mode were investigated experimentally. The system adopted a variable speed compressor using R410A with four indoor units and one outdoor unit. In the cooling-main mode, the heating capacity decreased due to reduction of flow rate to the indoor unit under heating mode operation. The EEV opening was adjusted to increase flow rate to the indoor unit under heating mode operation. The total capacity and COP in the cooling-main mode increased by 20.5% and 29.2%, respectively, compared with those in the cooling-only mode.

Cooling Performance of a Hybrid Refrigeration System for Telecommunication Equipment (통신기기 냉각용 하이브리드 냉방시스템의 성능특성)

  • Jeon, Jong-Ug;Kim, Yong-Chan;Choi, Jong-Min
    • Proceedings of the SAREK Conference
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    • 2006.06a
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    • pp.489-494
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    • 2006
  • Electronic and telecommunication industries are constantly trying to develop compact components having high power density. Therefore, a proper heat dissipation method is very important to allow reliable operation of the telecommunication equipment. In this study, a hybrid refrigeration system for a telecommunication equipment room was designed to save energy consumption and improve reliability of the compressor In addition, the performance of the hybrid refrigeration system was measured with a variation of outdoor load. The designed hybrid refrigeration system for the telecommunication equipment shelter saved the energy approximately 50%e at the mode switch temperature of $8.3^{\circ}C$.

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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 2016 (설비공학 분야의 최근 연구 동향 : 2016년 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.29 no.6
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    • pp.327-340
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    • 2017
  • This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during 2016. 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 flow, heat and mass transfer, the reduction of pollutant exhaust gas, cooling and heating, the renewable energy system and the flow around buildings. CFD schemes were used more for all research areas. (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 of the long-term performance variation of the plate-type enthalpy exchange element made of paper, design optimization of an extruded-type cooling structure for reducing the weight of LED street lights, and hot plate welding of thermoplastic elastomer packing. In the area of pool boiling and condensing, the heat transfer characteristics of a finned-tube heat exchanger in a PCM (phase change material) thermal energy storage system, influence of flow boiling heat transfer on fouling phenomenon in nanofluids, and PCM at the simultaneous charging and discharging condition were studied. In the area of industrial heat exchangers, one-dimensional flow network model and porous-media model, and R245fa in a plate-shell heat exchanger were studied. (3) Various studies were published in the categories of refrigeration cycle, alternative refrigeration/energy system, system control. In the refrigeration cycle category, subjects include mobile cold storage heat exchanger, compressor reliability, indirect refrigeration system with $CO_2$ as secondary fluid, heat pump for fuel-cell vehicle, heat recovery from hybrid drier and heat exchangers with two-port and flat tubes. In the alternative refrigeration/energy system category, subjects include membrane module for dehumidification refrigeration, desiccant-assisted low-temperature drying, regenerative evaporative cooler and ejector-assisted multi-stage evaporation. In the system control category, subjects include multi-refrigeration system control, emergency cooling of data center and variable-speed compressor control. (4) In building mechanical system research fields, fifteenth 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, renewable energies, etc. Proposed designs, performance tests using numerical methods and experiments provide useful information and key data which could be help for improving 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 analyses of indoor thermal environments controlled by portable cooler, the effects of outdoor wind pressure in airflow at high-rise buildings, window air tightness related to the filling piece shapes, stack effect in core type's office building and the development of a movable drawer-type light shelf with adjustable depth of the reflector. The subjects of building energy were worked on the energy consumption analysis in office building, the prediction of exit air temperature of horizontal geothermal heat exchanger, LS-SVM based modeling of hot water supply load for district heating system, the energy saving effect of ERV system using night purge control method and the effect of strengthened insulation level to the building heating and cooling load.

Simulation Study on the Performance Characteristics of $CO_2$ microchannel gascooler with Operation Conditions ($CO_2$용 마이크로채널 가스쿨러의 운전조건 변화에 따른 성능특성에 관한 해석적 연구)

  • Shin, Eun-Sung;Bae, Kyung-Jin;Kim, Byeong-Cheol;Cho, Hong-Hyun
    • Proceedings of the SAREK Conference
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    • 2009.06a
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    • pp.1090-1095
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    • 2009
  • The purpose of this study is to determine the performance characteristics for the micro-channel gascooler with various operating conditions. The performance of four kind of HX models were analyzed and optimized with the variation of refrigerant inlet temperature, air velocity, outdoor temperature. As a result, Model B showed the maximum capacity and high performance could be maintained for wide operating conditions. Beside, the micro-channel heat exchanger could be appled to $CO_2$ system appropriately because of a small pressure drop and high heat transfer rate.

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An Experimental Study on Thermal and Environmental Characteristics of Various Heating Systems in the Residential House (주거용 건물의 난방 방식별 열적성능 및 실내환경 특성 평가를 위한 실험적 연구)

  • Lee, Choong-Kook;Cho, Sung-Hwan
    • Proceedings of the SAREK Conference
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    • 2005.11a
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    • pp.121-128
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    • 2005
  • This is about experimental comparison study between convective heating and radiation heating system to use the design criteria for residential house. Experiment was done in EC(environment chamber) under simultaneous outdoor condition for 4 kinds of heating system such as CRHP(Ceiling Radiant Heating Panel), BEHC( Bottom Electric Heating Coil Mat), EFCU( Electric Fan Coil Unit) and CEHU( Convective Electric Heating Unit). Result show that CRHP ,which is radiation heating system, can consume more 23% energy than convective heating system when it is operated by dry bulb temperature but can save 1 ${\sim}$ 10% when operated by glove temperature and 27% when operated by MRT.

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Energy Saving Effect of the Night Purge Control using ERV in a School Building (전열교환형 환기시스템을 이용한 학교건물의 나이트 퍼지 적용 효과 분석)

  • Kim, Su-Yeon;Won, Jung-kwan;Kim, Jae-Hyung;Song, Doo-Sam
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.28 no.11
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    • pp.421-427
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    • 2016
  • The indoor temperature of a building increases during the day due to solar radiation. This behavior is significant in school buildings that are finished with high thermal capacity materials. Moreover, in school buildings, windows cannot be opened until the class has finished owing to the security policy of schools. Consequently, classrooms maintain a high temperature throughout the morning. It is thus important to remove the indoor heat before the commencement of classes in order to reduce the cooling energy needed. The Energy Recovery Ventilator (ERV) system is currently being installed in school buildings for ventilating the classrooms. Night-purge control using ERV can be a good strategy to cool the classroom in advance of the operation of the cooling system. However, the optimal operation method of the ERV for night-purge control has not yet been reported. In this study, the effect of night-purge control with ERV in school buildings is analyzed by simulation method. The results of this study showed that the energy saving effect of night-purge control with ERV is most effective in the case of 2 hours operation prior to the commencement of the first lass and when enthalpy based outdoor air cooling is used.

Strategy to Maintain the Smith Predictor Controller in the District Heating System for Apartment Buildings (지역난방 공동주택 시스템에서 Smith Predictor 제어기 적용성 연구)

  • Jung, Sang-Hoon;Moon, Youn-Jin;Ha, Jae-Sun;Cho, Sung-Hwan
    • Proceedings of the SAREK Conference
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    • 2009.06a
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    • pp.1025-1030
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    • 2009
  • It is known that the classical tuning formula for typical PID controllers in general provides unsatisfactory results for industrial plants where the time delay exceeds the dominant lag time. For this reason, alternative strategies have been studied in order to cope with this problem and the most popular scheme is the Smith Predictor(SP). In this paper, the dynamic model of a unit apartment in the district heating system, which is the control process effected by the dead-time, is developed, and the on/off room temperature control method with the SP simulate using Matlab-Simulink. The simulation results show that the SP works effectively in outdoor temperature variation.

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Simulation on a 2-Stage Compression $CO_2$ Cycle (2단압축 이산화탄소 사이클의 성능특성에 대한 해석적 연구)

  • Ryu, Chang-Gi;Cho, Hong-Hyun;Cho, Sung-Wook;Kim, Yong-Chan
    • Proceedings of the SAREK Conference
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    • 2005.11a
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    • pp.404-409
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    • 2005
  • In this paper a 2-stage $CO_2$ cycle was simulated to predict the performance characteristics with operating parameters. The simulation results showed similar tendency compared to the measured system pressure, capacity, COP etc. System characteristics were analyzed with the variations of outdoor temperature and EEV opening. In the simulation, the highest COP was 2.7 at 30-30 Hz and it decreased as compressor frequency increased. Besides, system COP can be increased by optimizing EEV opening.

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A Study on the Method of Estimating Optimum Supply Water Temperature Considering the Heating Load and the Heat Emission Performance of Radiant Floor Heating Panel (난방부하와 온수온돌의 방열성능을 고려한 적정 공급온수온도 산출방법에 관한 연구)

  • Choi, Jeong-Min;Lee, Kyu-Nam;Ryu, Seong-Ryong;Kim, Yong-Yee;Yeo, Myoung-Souk;Kim, Kwang-Woo
    • Proceedings of the SAREK Conference
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    • 2006.06a
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    • pp.795-800
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    • 2006
  • A common approach to achieve better thermal comfort with hydronic radiant floor heating system is supply water temperature control. This is the control method through which supply water temperature is varied with outdoor temperature. In this study, a comprehensive, yet simple calculation method to find optimum supply water temperature is evaluated by combining heat loss from the building and heat emission from the hydronic radiant floor heating system. And then the control performance of suggested calculation method is confirmed through experiment. It is shown that indoor air temperature is stably maintained around the set point.

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