• Title/Summary/Keyword: Air-to-air heat pump

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A Study on the Heating Performance of Ground Source Heat Pump System (지중열원 열펌프 시스템의 난방성능 해석)

  • Woo Joung-Son;Kim Dae-Ki;Lee Se-Kyoun
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.16 no.12
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    • pp.1175-1182
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    • 2004
  • Installations of vertical boreholes for the ground source heat pump system are expensive to install. One way to reduce the initial cost is to increase the specific heat extraction rate of borehole system. However, as the specific heat extraction rate increases the temperature of borehole fluid decreases with the resultant lower Coefficient Of Performance in Heating(COPH) of heat pump system. The purpose of this study is to provide the basic informations about the performance of heat pump system with the specific heat extraction rate and soil thermal properties such as thermal conductivity and temperature. It is shown that the specific heat extraction rate is the most important parameter for the ground source heat pump system. To obtain the reasonable COPH value (COPH > 3) the heat extraction rate should be about 25 W/m or less. Accurate measurements of soil thermal properties are also very important to design the system properly. The effects of borehole thermal resistances are also examined in this study.

Recent Progress in Air-Conditioning and Refrigeration Research : A Review of Papers Published in the Korean Journal of Air-Conditioning and Refrigeration Engineering in 2013 (설비공학 분야의 최근 연구 동향 : 2013년 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.26 no.12
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    • pp.605-619
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    • 2014
  • This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during 2013. 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 fluid machinery, pipes and relative parts including orifices, dampers and ducts, fuel cells and power plants, cooling and air-conditioning, heat and mass transfer, two phase flow, and the flow around buildings and structures. Research issues dealing with home appliances, flows around buildings, nuclear power plant, and manufacturing processes are 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 general analytical model for desiccant wheels, the effects of water absorption on the thermal conductivity of insulation materials, thermal properties of Octadecane/xGnP shape-stabilized phase change materials and $CO_2$ and $CO_2$-Hydrate mixture, effect of ground source heat pump system, the heat flux meter location for the performance test of a refrigerator vacuum insulation panel, a parallel flow evaporator for a heat pump dryer, the condensation risk assessment of vacuum multi-layer glass and triple glass, optimization of a forced convection type PCM refrigeration module, surface temperature sensor using fluorescent nanoporous thin film. In the area of pool boiling and condensing heat transfer, researches on ammonia inside horizontal smooth small tube, R1234yf on various enhanced surfaces, HFC32/HFC152a on a plain surface, spray cooling up to critical heat flux on a low-fin enhanced surface were actively carried out. In the area of industrial heat exchangers, researches on a fin tube type adsorber, the mass-transfer kinetics of a fin-tube-type adsorption bed, fin-and-tube heat exchangers having sine wave fins and oval tubes, louvered fin heat exchanger were performed. (3) In the field of refrigeration, studies are categorized into three groups namely refrigeration cycle, refrigerant and modeling and control. In the category of refrigeration cycle, studies were focused on the enhancement or optimization of experimental or commercial systems including a R410a VRF(Various Refrigerant Flow) heat pump, a R134a 2-stage screw heat pump and a R134a double-heat source automotive air-conditioner system. In the category of refrigerant, studies were carried out for the application of alternative refrigerants or refrigeration technologies including $CO_2$ water heaters, a R1234yf automotive air-conditioner, a R436b water cooler and a thermoelectric refrigerator. In the category of modeling and control, theoretical and experimental studies were carried out to predict the performance of various thermal and control systems including the long-term energy analysis of a geo-thermal heat pump system coupled to cast-in-place energy piles, the dynamic simulation of a water heater-coupled hybrid heat pump and the numerical simulation of an integral optimum regulating controller for a system heat pump. (4) In building mechanical system research fields, twenty one studies were conducted to achieve effective design of the mechanical systems, and also to maximize the energy efficiency of buildings. The topics of the studies included heating and cooling, HVAC system, ventilation, and renewable energies in the buildings. Proposed designs, 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 is mostly focused on indoor environment and building energy. The main researches of indoor environment are related to infiltration, ventilation, leak flow and airtightness performance in residential building. The subjects of building energy are worked on energy saving, operation method and optimum operation of building energy systems. The remained studies are related to the special facility such as cleanroom, internet data center and biosafety laboratory. water supply and drain system, defining standard input variables of BIM (Building Information Modeling) for facility management system, estimating capability and providing operation guidelines of subway station as shelter for refuge and evaluation of pollutant emissions from furniture-like products.

An Experimental Study on the Heating Performance Characteristics of a Vapor Injection Heat Pump for Electric Vehicles (가스 인젝션을 적용한 전기자동차용 히트펌프의 난방성능 특성에 대한 실험적 연구)

  • Kim, Dongwoo;Jung, Jongho;Kim, Yongchan
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.26 no.7
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    • pp.308-314
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    • 2014
  • A heat pump has been considered as a thermal management unit for electric vehicles, including the heating and cooling of the cabin. However, the heat pump shows performance degradation at low outdoor temperatures or high compressor speeds. In this study, a R-134a heat pump for an electric vehicle was designed to improve system efficiency, by applying vapor injection with an internal heat exchanger. The heating performance characteristics of the vapor injection heat pump were analyzed at various compressor speeds and outdoor temperatures. The vapor injection heat pump showed 13.3% COP improvement over the non-injection heat pump, when the heating capacity was fixed at 5.2 kW. In addition, the heating capacity of the vapor injection system increased by 9.6%, as compared to the non-injection system.

Analytical Study on the Heating Performance Improvement of a CO2 Heat Pump Using Vapor Injection (가스인젝션을 적용한 이산화탄소 열펌프의 난방성능 향상에 관한 해석적 연구)

  • Jung, Jongho;Baek, Changhyun;Heo, Jaehyeok;Kim, Yongchan
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.24 no.11
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    • pp.767-776
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    • 2012
  • In this study, a simulation model for a $CO_2$ heat pump using vapor injection was developed and validated. It was used to predict the improvement of the heating performance of the $CO_2$ heat pump at various operating conditions. The simulation results showed consistent results with the measured data. The heating performances of the vapor injection and non-injection heat pumps were compared by varying the outdoor temperature and compressor frequency. The heating capacity of the vapor injection heat pump was 40% higher than that of the non-injection heat pump at the outdoor temperature of $-8^{\circ}C$. The performance of the vapor injection heat pump was consistently higher than that of the non-injection heat pump even when the compressor frequency was reduced to 35 Hz at the outdoor temperature of $-3^{\circ}C$.

Experimental Study on the Cooling Performance of Vertical Closed Loop Water to Water Ground Source Heat Pump System (물 대 물 방식 수직 밀폐루프 지열원 히트펌프 시스템의 냉방성능에 대한 실험적 연구)

  • Hong, Boo-Pyo;Choi, Kwang-Hwan
    • Journal of the Korean Solar Energy Society
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    • v.34 no.1
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    • pp.58-63
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    • 2014
  • A vertical closed loop ground source heat pump (GSHP) is used to produce heat from the low-grade energy source such as the outside air and ground source. It is known that a heat pump system type has better efficiency comparing to the electric heating system. This study only demonstrates that the vertical closed loop GSHP system is a feasible choice for space cooling of air conditioning. The coefficient of performance (COP) is the ratio of heat output to work supplied to the system in the form of electricity. For the vertical closed loop GSHP system in a cooling mode, the COP is the most commonly used way for judging the efficiency. For the purpose of this experiment, vertical closed loop GSHP system was installed in the laboratory and the experiment was executed. As a result, an average COP of vertical-closed loop GSHP system was 3.62 when the outside average temperature was $33^{\circ}C$.

Simulation of a two-stage absorption heat pump cycle using treated sewage (하수처리수 이용 흡수식 열펌프 사이클의 시뮬레이션)

  • 이용화;신현준;최국광
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.11 no.3
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    • pp.422-430
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    • 1999
  • This paper concerns the study of a two-stage absorption heat pump cycle to utilize treated sewage. This two-stage cycle consists of coupling double-effect with parallel or series flow type and single effect cycle so that the first stage absorber and condenser produces hot water to evaporate refrigerant in the evaporator of the second stage. The effects of operating variables such as absorber temperature on the coefficient of performance have been studied for two-stage absorption heat pump cycle. The working fluid is lithium bromide and water solution. The efficiency of the two-stage absorption heat pump cycle has been studied and simulation results show that higher coefficient of performance could be obtained for the first stage with parallel flow type. The optimum ratio of solution distribution can be shown by considering the COP, the crystallization of solution and the generator temperature.

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Transient Performance of a System Heat Pump with the Variation of Compressor Speed and EEV Openings (시스템 히트펌프의 압축기 주파수 및 전자팽창밸브 개도 변화에 따른 과도성능 특성)

  • Lee, Sang-Hyeok;Choi, Jong Min
    • Journal of the Korean Society for Geothermal and Hydrothermal Energy
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    • v.9 no.3
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    • pp.11-18
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    • 2013
  • Small and medium-size buildings employ a multi-distributed individual air-conditioning system utilizing package air conditioners instead of centralized cooling systems, which can allow easier building management and maintenance along with a diversification of facility use. Inverter driven system heat pumps have been developed to achieve not only easy distribution control allowing free combination of indoor units with different models and different capacities, but also wide applications to an intelligent air conditioning. In this study, the transient performance of a system heat pump was analysed with the variation of compressor speed and EEV openings. The superheat was selected as a control parameter of the system, because the variation of it was consistent with each indoor unit capacity.

An Experimental Study on the Performance of Heat Pump Assisted Batch Dryer Using HFC134a (HFC134a를 사용한 열펌프 건조기의 성능에 관한 실험적 연구)

  • Kim, Y.J.;Yim, C.S.
    • Solar Energy
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    • v.17 no.2
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    • pp.3-11
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    • 1997
  • In conventional heat and vent dryer, both sensible and latent heat could not be recovered from the exhaust air, but this problem could be solved by introducing a heat pump to a conventional dryer, having a connection with cooling, dehumidifying and heating of heat pump. In this work, HFC134a as a substitute refrigerant of CFC12 adopted in heat pump and a batch type is also introduced. The variables affected on the system performance are holding temperature of a drying chamber, bypass air ratio, degree of superheat and refrigerant flowrate, etc. The moisture contents were decreased curvilinearly in the range of $86{\sim}75%$ on the wet basis. Under the constant drying temperature, the face velocity plays an important role to the drying performance. The COPs are increased in accordance with the air velocity, on the other hand the SMERs are gradually decreased.

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An Experimental Study on Variable-Speed Control of an Ground-Water Circulation Pump for a Ground Source Multi-Heat Pump System (주거용 건물 지열원 멀티 히트펌프시스템의 지열순환펌프 가변유량제어에 관한 실증연구)

  • Song, Suwon
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.25 no.8
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    • pp.443-449
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    • 2013
  • The purpose of this study is to propose an enhanced variable-speed control method of ground-water circulation pumps using inlet and outlet ground-water temperature difference and analyze its effect for the ground source multi-heat pump system installed in a single-family house. As a result, it has shown to significantly reduce the electricity use of ground-water circulation pump and improve overall system Coefficient of Performance (COP) due to the proposed variable-speed control under partial load conditions after oversized and inefficient single-speed pump retrofit.

An Experimental Study on the Performance Improvement of an R32 Inverter Heat Pump System (R32 인버터 히트펌프 시스템의 성능향상에 관한 실험적 연구)

  • Park, Yun Ki;Ha, Man Yeoung
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.26 no.11
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    • pp.547-552
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    • 2014
  • As global warming in recent years has raised ever more critical concern, refrigerants with high global warming potentials (GWP) are facing the challenge of being phased out. R410A, with a GWP of 2,088, has been widely used in residential air-conditioning and heat pump systems. A potential substitute for R410A is R32, which has a GWP of 675. The present study presents experimental results of an inverter heat pump system that uses R32 as an alternative refrigerant to R410A. Drop-in tests with R32 indicated that the energy efficiency ratio of the system increased by 5.3% in cooling standard mode, and by 4.2% in heating standard mode at the same capacity; and that the cooling and heating capacity increased by about 12% at the same compressor operating frequency, while the annual performance factor (APF) of the system increased by 5.3%.