• Title/Summary/Keyword: Heat pump

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Effects of Gas Injection on the Heating Performance of a Two-Stage Heat Pump Using a Twin Rotary Compressor with Refrigerant Charge Amount

  • Heo, Jae-Hyeok;Jeong, Min-Woo;Jeon, Jong-Ug;Kim, Yong-Chan
    • International Journal of Air-Conditioning and Refrigeration
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    • v.16 no.3
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    • pp.77-82
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    • 2008
  • For heat pumps used in a cold region, it is very important to obtain appropriate heating capacity. Several studies using a variable speed compressor and an additional heater have been performed to enhance heating capacity at low ambient temperatures. However, for outdoor temperature conditions below $-15^{\circ}C$, it is still difficult to obtain enough heating capacity above the rated value. In recent studies, the application of gas injection technique into a two-stage heat pump yielded noticeable heating performance improvement at low temperature conditions. In this study, the heating performance of a two-stage gas injection heat pump with a rated capacity of 3.5 kW was measured and analyzed by varying refrigerant charge amount and EEV opening at the standard heating condition. The heating performance of the two-stage gas injection heat pump was compared with that of a two-stage non-injection heat pump. The heating capacity and COP of the two-stage gas injection heat pump were improved by 2-10% at the optimal charging condition over those of the two-stage non-injection heat pump.

Performance Characteristics and Economic Assessment of Heat Pump Systems with the Various Heat Source (열원에 따른 열펌프의 성능 비교 및 경제성 평가)

  • Park, Cha-Sik;Park, Kyoung-Woo;Kwon, Oh-Kyung
    • Journal of the Korean Society for Geothermal and Hydrothermal Energy
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    • v.7 no.1
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    • pp.23-31
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    • 2011
  • The objectives of this study are to analyze the performance of a heat pump system with the various heat source and to carry out economic assessment for the heat pump system. The COP of the river water and ground source heat pump system was 20% higher than that of the air source heat pump system because river water and geothermal provide stable operating temperature compared with air temperature throughout the year. In addition, the economic assessment of a heat pump system using air, river water, and geothermal as a heat source was carried out. 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 3.3 and 4.5 years, respectively when the capacity of the river water and ground source heat pump was larger than 10 RT.

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 $-3^{\circ}C$.

Analytical Study on the Performance of Fuel Cell Driven Ground Source Heat Pump Heating and Cooling System of a Large Community Building (대형 Community 건물의 연료전지 구동 지열원 히트펌프 냉.난방 시스템 성능에 관한 해석적 연구)

  • Byun, Jae-Ki;Jeong, Dong-Hwa;Choi, Young-Dong;Cho, Sung-Hwan
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.21 no.6
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    • pp.355-366
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    • 2009
  • In the present study, fuel cell driven ground source heat pump system is applied to a large community building and performance of the heat pump system is computationally analyzed. Conduction heat transfer between brine pipe and ground is analyzed by TEACH code to predict the performance of heat pump system. Predicted COP of the heat pump system and the energy cost were compared with variation of the location of the objective building the water saturation rate of soil and the driven powers of heat pump system. Significant reduction of energy cost can be accomplished by employing the fuel cell driven heat pump system in comparison with the late-night electricity driven system. It is due to the low electricity production cost of fuel cell system and the application of recovered waste heat generated during electricity production process to the heating of large community building.

Performance Characteristics of Water-Chilling Heat Pump Using CO2 on Variation of Refrigerant Charge Amount (냉매 충전량에 따른 CO2용 수냉식 열펌프의 성능 특성에 관한 연구)

  • Son, Chang-Hyo;Yu, Tae-Guen;Jang, Seong-Il;Oh, Hoo-Kyu
    • Journal of Advanced Marine Engineering and Technology
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    • v.31 no.5
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    • pp.558-566
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    • 2007
  • The performance characteristics of water-chilling heat pump using $CO_2$ with respect to variation of refrigerant charge amount was investigated experimentally. An experimental apparatus is consisted of a compressor, a gas cooler, an expansion valve, an evaporator and a liquid receiver. All heat exchangers used in the test rig are counter-flow-type heat exchangers with concentric dual tubes, which are made of copper. The gas cooler and the evaporator consist of 6 and 4 straight sections respectively arranged in parallel, each has 2400 mm length. The experimental results summarize as the followings : As the refrigerant charge ratio of $CO_2$ heat pump system increases, the discharge pressure and compressor ratio increases, but mass flow rate of refrigerant decreases. Also the compressor work increases with the increase of refrigerant charge ratio. However, the heating and cooling capacity of $CO_2$ heat pump decreases as the refrigerant charge ratio increases. The maximum heating COP of $CO_2$ heat pump system presented at 0.25 refrigerant charge ratio. It is possible to confirm the optimum charge ratio of $CO_2$ heat pump system by the viewpoint of heating COP.

Investigation of Experimental Results Using the Drying Model for a Heat Pump Dryer (열펌프 건조 해석 모델을 이용한 측정 결과의 분석)

  • Lee, Kong-Hoon;Kim, Ook-Joong;Kim, Jong-Ryul;Lee, Sang-Ryoul
    • Proceedings of the KSME Conference
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    • 2008.11b
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    • pp.2268-2273
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    • 2008
  • The drying model has been used to obtain the fundamental information required to design the heat pump dryer with the simple thermodynamic model. In the model, the input conditions are crucial to obtain the acceptable results. The model includes one-stage heat pump cycle, simple drying process using the drying efficiency. The drying efficiency is defined with the conditions of inlet and outlet in the dryer. The experiment has been carried out in the pilot dryer with one-stage heat pump cycle. Refrigerant 134a is used in the heat pump cycle. In the dryer, some of drying air flows through the heat pump system and the rest of air bypasses the heat pump system and circulates through the drying chamber. Some operating conditions from the pilot dryer are used as input conditions of the model and the results are compared with experimental results for the validation.

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Evaluation of the Annual Performance of the Direct Expansion Vertical Closed-Loop Ground Source Heat Pump (직접순환식 수직밀폐형 지열원 열펌프의 연간 운전성능 평가)

  • Kim, Min-Sung;Woo, Joung-Son;Baik, Young-Jin;Jang, Jea-Chul;Kim, Ji-Young;Ra, Ho-Sang
    • 한국태양에너지학회:학술대회논문집
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    • 2012.03a
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    • pp.534-542
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    • 2012
  • Vertical closed-loop ground source heat pump systems(GSHP) have been installed widely in Korea since it can extract moderate temperature level of geothermal heat in a small area. As a ground heat exchanger, a vertical closed-loop type with brine circulation is mostly preferred since it is simple and less harmful to ground environment. However, it requires a secondary heat exchange loop between the refrigerant in a heat pump and the brine. By adding a geothermal heat exchanger in the secondary heat exchange loop, circulation pumps should be attached and the temperature difference between refrigerant and ground is increased, which are important parts of performance degradation. In this paper, annual and seasonal performances of direct expansion(DX) geothermal heat pump were estimated mathematically as an alternative of classical indirect geothermal heat pump based on the annual performance evaluation. As a result, DX geothermal heat pump showed 43% higher annual performance than the classical U-tube geothermal heat pump.

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Annual Performance Evaluation of Direct Expansion Vertical Closed-Loop Ground Source Heat Pump for Residential Application (주거용 직접순환식 수직밀폐형 지열원 열펌프의 연간 운전성능 평가)

  • Kim, Min-Sung;Baik, Young-Jin;Ra, Ho-Sang
    • Journal of the Korean Solar Energy Society
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    • v.32 no.3
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    • pp.114-122
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    • 2012
  • Vertical closed-loop ground source heat pump systems(GSHP) have been installed widely in Korea since it can extract moderate temperature level of geothermal heat in a small area. As a ground heat exchanger, a vertical closed -loop type with brine circulation is mostly preferred since it is simple and less harmful to ground environment. However, it requires a secondary heat exchange loop between the refrigerant in a heat pump and the brine. By adding a geothermal heat exchanger in the secondary heat exchange loop, circulation pumps should be attached and the temperature difference between refrigerant and ground is increased, which are important parts of performance degradation. In this paper, annual and seasonal performances of direct expansion(DX) geothermal heat pump were estimated mathematically as an alternative of classical indirect geothermal heat pump based on the annual performance evaluation. As results, DX geothermal heat pump showed 43% higher annual performance than the classical U-tube geothermal heat pump.

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.

Study on the Simulation of Heat Pump Heating and Cooling Systems to Resident Building (숙박업소 건물의 히트펌프 냉난방 시스템 적용을 위한 시뮬레이션 연구)

  • Choi, Young-Don;Han, Seong-Ho;Cho, Sung-Hwan;Kim, Du-Sung;Um, Chul-Jun
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.20 no.1
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    • pp.65-74
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    • 2008
  • In Korea, air source heat pump system is less efficient than conventional heat source facilities, such as ground source, river water, because the air temperature in winter season is so low that COP of air source heat pump system drops below 3.0. Therefore, the study on the application of heat pump heating and cooling systems is crucial for the efficient popularization of heat pump. In this work, we present the dynamic analysis of energy consumption for the large resident building by heat resistance-capacitance method. The system simulation of water storage air source heat pump is additionally performed by changing of sizes and locations of the hospital building. The computed results show that energy cost of water storage air source heat pump is low, so it is more economical than absorption chiller & heater.