• Title, Summary, Keyword: Sub-cooler

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Performance Characteristics of a Vapor Injection Heat Pump System with Different Sub-cooler Capacity (과냉각 열교환기 용량 변화에 따른 인젝션 히트펌프의 성능 특성)

  • Choi, Jong Min;Park, Yong-Jung;Kang, Shin-Hyung
    • Transactions of the Korea Society of Geothermal Energy Engineers
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    • v.10 no.3
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    • pp.17-23
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    • 2014
  • One major breakthrough in the field of heating, ventilation and air conditioning has been the development of heat pumps. Heat pump systems offer economic alternatives for recovering heat from different sources for use in various industrial, commercial and residential applications. In recent years, the heat pump has been tipped to have a very good potential for hot water production. This paper investigated the performance of a vapor injection heat pump with the variation of sub-cooler capacity at heating mode. The heating capacity of the vapor injection heat pump slightly increased with an increment of sub-cooler capacity, while COP didn't increase continuously. The 20% capacity of sub-cooler comparing with system capacity could be used as a standard to select sub-cooler capacity.

Experimental Study on Compact type CO2 Gas Cooler(1) - Heat Flowrate and Pressure Drop in a Multi-Tube-In-Tube Helical Coil Type Gas Cooler - (CO2 가스쿨러용 콤팩트열교환기 개발에 관한 연구(1) -다중관식 헬리컬 코일형 가스냉각기내 CO2의 열유량과 압력강하-)

  • Oh, Hoo-Kyu;Son, Chang-Hyo
    • Journal of Advanced Marine Engineering and Technology
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    • v.34 no.1
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    • pp.30-36
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    • 2010
  • The heat flowrate and pressure drop of $CO_2$ in a multi-tube-in-tube helical coil type gas cooler were investigated experimentally. The mass flowrate of $CO_2$ and coolant were varied from 0.06 to 0.075 [kg/s], respectively and the cooling pressure of gas cooler were from 8 to 10 [MPa]. The heat flowrate of $CO_2$ in the test section is increased with the increase in mass flowrate of coolant, the cooling pressure and mass flowrate of $CO_2$. The pressure drop of $CO_2$ is decreased with the decrease in mass flowrate of coolant and $CO_2$, but decreased with increase in cooling pressure of $CO_2$. The heat flowrate of $CO_2$ in the multi-tube-in-tube helical coil type gas cooler is greatly higher than that of $CO_2$ in the double pipe type gas cooler, while the pressure drop of $CO_2$ in the multi-tube-in-tube helical coil type gas cooler is greatly lower than that of $CO_2$ in the double pipe type gas cooler. Therefore, in case of the application of $CO_2$ at the multi-tube-in-tube helical coil type gas cooler, it is expected to carry out the high-efficiency, high-performance and compactness of gas cooler.

Experimental Study on Heat Transfer Performance of CO2 in a Multi-Tube Type Gas Cooler of Inner Diameter Tube of 1.77 mm (내경 1.77 mm의 다중관식 가스냉각기내 CO2 전열 성능에 대한 실험적 연구)

  • Son, Chang-Hyo
    • Transactions of the Korean hydrogen and new energy society
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    • v.19 no.5
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    • pp.439-444
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    • 2008
  • The heat capacity and pressure drop of $CO_2$ and coolant in a multi-tube type gas cooler were investigated experimentally. The main components of the refrigerant loop are a receiver, a $CO_2$ compressor, a mass flow meter, an evaporator and a multi-tube type gas cooler as a test section. The mass flowrate of $CO_2$ and coolant were varied from 0.06 to 0.075 [kg/s], respectively and the cooling pressure of gas cooler were from 8 to 10 [MPa]. The heat capacity of $CO_2$ in the test section is increased with the increment in mass flowrate of coolant, the cooling pressure and mass flowrate of $CO_2$. The pressure drop of $CO_2$ is decreased with the decrease in mass flowrate of coolant and $CO_2$, but decreased with increase in cooling pressure of $CO_2$. The heat capacity of $CO_2$ per unit heat transfer area of gas cooler is greatly high. Therefore, in case of the application of $CO_2$ at the multi-tube type gas cooler, it is expected to carry out the high-efficiency, high-performance and compactness of gas cooler.

Experimental Study on Compact type CO2 Gas Cooler(2) - Experiments and Predictions on Heat Flowrate and Pressure Drop - (CO2 가스쿨러용 콤팩트열교환기 개발에 관한 연구(2) - 열유량과 압력강하에 관한 실험 및 예측 -)

  • Oh, Hoo-Kyu;Son, Chang-Hyo
    • Journal of Advanced Marine Engineering and Technology
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    • v.34 no.2
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    • pp.259-266
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    • 2010
  • The heat flowrate and pressure dorp of $CO_2$ in a multi-tube-in-tube helical coil type gas cooler were predicted using LMTD method and compared with the experimental data. The mass flowrate of $CO_2$ and coolant were varied from 0.06 to 0.075 [kg/s], and the cooling pressure of gas cooler were from 8 to 10 [MPa], respectively. The LMTD method is used to predict the heat flowrate and pressure drop of supercritical $CO_2$ during in-tube cooling. The equations used by LMTD method were Gnielinski correlation for $CO_2$ and Dittus-Boelter correlation for coolant, respectively. The equation used to predict the pressure drop of $CO_2$ and coolant is Blasius correlation. In comparison of heat flowrate and pressure drop of $CO_2$ measured by experiment to that predicted by LMTD method, the experimental heat flowrate and pressure drop of $CO_2$ in the multi-tube-in-tube helical coil type gas cooler shows a relatively good agreement with that predicted by LMTD method.

An Experimental Study on Oil Effect of CO2 in Heat Pump Outdoor Heat Exchanger (CO2용 실외열교환기의 오일 영향에 따른 성능변화에 대한 실험적 연구)

  • Lee, Jin-Gwan;Chang, Young-Soo;Kim, Seo-Young;Kim, Yong-Chan
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.23 no.4
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    • pp.243-250
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    • 2011
  • In order to investigate the effects of PAG oil concentration on heat transfer performance and pressure drop during gas cooling process of $CO_2$, the experiments on fin-tube heat exchanger of $CO_2$ heat pump were performed. The experimental apparatus consists of a gas cooler, a heater, a chiller, a mass flow meter, a pump and measurement system. Experiments were conducted in various experimental conditions, which were inlet temperature($110^{\circ}C$), mass flow rates (50, 55, 60, 65, 70 g/s) and PAG oil concentration(0 to 2.6 wt%). Heat transfer rate decreased with the increase of the oil concentration and the decrease of inlet pressure. And pressure drop increased with the increase of the oil concentration and mass flow rate of refrigerant. The COP reduction by deterioration of gas cooler performance with oil concentration was analyzed. When inlet pressure of gas cooler is 100 bar, the COP reduction was estimated by 6% under 1 wt% of oil concentration.

Performance Characteristics of Water-Chilling Heat Pump Using CO2 on the Variation of Secondary Fluid Conditions (2차 유체 조건 변화에 대한 CO2용 수냉식 열펌프의 성능 특성에 관한 연구)

  • Son, Chang-Hyo;Oh, Hoo-Kyu
    • Journal of Advanced Marine Engineering and Technology
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    • v.31 no.5
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    • pp.543-551
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    • 2007
  • The performance characteristics of water-chilling heat pump using $CO_2$ with respect to variation of inlet temperature and mass flow rate of secondary fluid 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 ate made of copper. The gas cooler and the evaporator consist of 6 and 4 straight sections respectively arranged in parallel, each has 2.4 m length. The experimental results were summarized as the followings : As inlet temperature of secondary fluid in the gas cooler increases from $10^{\circ}C$ to $40^{\circ}C$, the compressor work, heating capacity and heating COP were varied to 37.8%, -13%, -35.9%, respectively. The heating capacity, compressor work, heating COP were turned into 23.3%, 6.42%, 13.1%, respectively when ass flow rate of secondary fluid in the evaporator increases from 70 g/s to 150 g/s. The above tendency is similar with performance variation with respect to temperature variation of secondary fluid in the conventional vapor compression cycle.

Experimental Study on the Performance Characteristics of a CO2 Air-conditioning System for Vehicles (자동차용 CO2 에어컨 시스템의 성능 특성에 관한 실험적 연구)

  • Lee, Daewoong
    • Transactions of the Korean Society of Automotive Engineers
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    • v.23 no.1
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    • pp.18-24
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    • 2015
  • In this study, a $CO_2$ air-conditioning system was investigated with different types of electrically driven compressors, parallel flow type gas cooler, four-pass type evaporator, internal heat exchanger integrated with accumulator, and electric expansion valve. The experimental study was conducted under various operating conditions (ie., different rotational compressor speeds, air inlet temperatures and air velocity coming into heat exchangers). The experimental results showed the cooling capacity was 3.5kW at $35^{\circ}C$ ambient temperature when the vehicle was idle (ie., the worst condition for cooling off the gas cooler). In terms of performance effect of the compressor, the e-RP model had a slightly better cooling capacity and coefficient of performance than the e-GR model under the same test conditions. An experimental equation for optimum cooling-performance control was also suggested based on the results. A high-pressure control algorithm for the super critical cycle was determined to achieve both maximum cooling performance and efficient energy consumption. The results from the experimental equation coincided with those of previous experimental studies.

Conceptual Development of a Subminiature Cool Pad Applying Sorption Cooling Effect (흡습 냉각 원리를 이용한 소형 냉각 패드에 관한 연구)

  • 황용신;이대영;김우승
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.16 no.2
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    • pp.121-127
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    • 2004
  • This paper describes conceptual development and idea-verification of a sub-miniature portable cooler which dose not necessitate any pre-cooling nor any external energy supply. The basic principle of the cooling mechanism is the vaporization of water and sub-sequent cooling due to the evaporative latent heat loss. In this work, the vaporization of the water is stimulated by desiccant material to improve the cooling effect. The evaporative cooling caused by the desiccant is modeled and analyzed considering the sorption characteristics of the desiccant. In addition, the portable cooler is fabricated in the shape of a thin pad, and its cooling characteristics are tested and compared with the analytic results.

Heat Transfer Characteristics During Gas Cooling Process of Carbon Dioxide in a Horizontal Tube (수평관내 초임계 영역의 Co2 냉각 열전달 특성)

  • Son, Chang-Hyo;Lee, Dong-Gun;Oh, Koo-Kyu;Jeong, Si-Young;Kim, Young-Lyoul
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.28 no.3
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    • pp.289-295
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    • 2004
  • The heat transfer coefficient and pressure drop during gas cooling process of carbon dioxide in a horizontal tube were investigated. The experiments were conducted without oil in the refrigerant loop. The main components of the refrigerant loop are a receiver, a variable-speed pump, a mass flowmeter, an evaporator, and a gas cooler(test section). The main components of the water loop consist of a variable-speed pump, an isothermal tank, and a flowmeter. The gas cooler is a counterflow heat exchanger with refrigerant flowing in the inner tube and water flowing in the annulus. The test section consists of smooth, horizontal stainless steel tube of the outer diameter of 9.53mm and of the inner diameter of 7.75mm. The length of the test section is 6m. The refrigerant mass fluxes were 200∼300kg/(m2$.$s) and the inlet pressure of the gas cooler varied from 7.5㎫ to 8.5㎫. The main results were summarized as follows : Pressure drop of CO2 increases with increasing gas cooler pressure. The friction factors of CO2 in a horizontal tube show a relatively good agreement with the correlation by Blasius. The heat transfer coefficient of CO2 in transcritical region increases with decreasing gas cooler pressure and decreasing mass flux of CO2. Most of correlations proposed in a transcritical region showed significant deviations with experimental data except for those predicted by Gnielinski.

Analysis of Heat Transfer Performance of a Gas Cooler of CO2 Heat Pump for Water Heating (온수제조용 CO2 히트펌프의 가스쿨러 열전달 성능 해석)

  • Kwon, Jeong-Tae;Lee, Chang-Kyung;Baek, Dong-Seok;Kwon, Young-Chul
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.14 no.11
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    • pp.5317-5322
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    • 2013
  • This study presents a prediction method for heat transfer performance of a gas cooler of $CO_2$ heat pump using ${\epsilon}$-NTU method, and compared the results with the experimental data from the open literature. The heat transfer rate, refrigerant side outlet temperature and water side outlet temperature were calculated by using EES(Engineering Equation Solver)program in multi-tube-in-tube type $CO_2$ heat pump gas cooler. Analysis was performed in two methods : The first method performed without dividing into the test section by applying an analysis of the mean properties(mean analysis). The second method, tube length divided into 50 sections, was applied to the local properties(local analysis). From the present study, a good agreement at the local analysis was obtained between the analytical and experimental results by 0.3~1.1%, 1.31~1.88% and 3.12~5.18% for heat transfer rate, water and refrigerant side outlet temperatures, respectively.