• Title/Summary/Keyword: Low temperature heat exchanger

검색결과 196건 처리시간 0.024초

난방운전 조건하에서 $CO_2$ 열펌프용 내부 열교환기의 열전달 특성에 대한 연구 (Study on Heat Transfer Characteristics of Internal Heat Exchanger for $CO_2$ Heat Pump under Heating Operating Condition)

  • 김대훈;이상재;최준영;이재헌;권영철
    • 에너지공학
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    • 제17권2호
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    • pp.116-123
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    • 2008
  • 본 연구에서는 $CO_2$ 열펌프에 사용되는 내부 열교환기를 난방조건에서 운전할 경우, 실험 및 수치적 방법으로 열전달량, 효율, 압력강하 등을 관찰하였다. 4가지 종류의 내부 열교환기를 사용하였다. 수치 해석은 단면분할법과 하디크로스 방법을 이용하여 유량, 길이, 운전조건, 내부 열교환기 종류에 따른 영향을 분석하고 실험을 통해 확인하였다. 유량이 증가함에 따라 열전달량이 약 25% 향상되었다. 마이크로 채널이 동심관에 비해 열전달량이 약 100% 크게 나타났다. 길이가 증가함에 따라 열전달 증가율은 감소하였다. 압력강하는 고압측에 비해 저압측이 크게 나타났으며, 동심관에 비해 마이크로 채널이 약 100% 크게 나타났다. 고온입구조건이 증가할수록, 저온입구조건이 감소할수록 열전달량은 약 3% 증가하였다. $CO_2$의 열전달 계산의 정확성을 위해 $CO_2$의 특성과 관형상을 고려할 수 있는 열전달 상관식의 개발이 필요하다.

가정용 흡수식 냉난방기 개발을 위한 재생기 성능실험 (Performance Experiment of Generator for Household Absorption Chiller and Heater)

  • 유선일;권오경;윤정인
    • 대한기계학회논문집B
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    • 제23권10호
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    • pp.1347-1354
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    • 1999
  • Recently, the markets of the air conditioner are enlarging. The market size will reach 2.0 billion won in 2000. Electric heat pumps have been utilized as main residential air conditioners. especially in Korea. They cause a surge up electric power demand during summer. Moreover, the use of HCFCs and HFCs causes serious problem to the global environment such as global warming and ozone layer destruction. Absorption chiller and heater could solve such problems. It was built and tested for analyzing the performance of the generator for absorption chiller and heater. Experiment was done with a high temperature generator, a low temperature generator, heat exchangers, a condenser and a solution tank. It was tested that the double effect series flow cycle with two kinds of solution cycle. Solution cycle B showed better than solution cycle A. Two kinds of heat exchanger were used, where one's heat transfer area is bigger than the other. Bigger one increased a little performance of absorption chiller and heater. But it was not economical. From this study, we got that the coefficient of performance(COP) is 0.82 and the capacity is 7.24 kW for an absorption chiller and heater.

초저온 액화 천연 가스용 기화기 핀의 승온 특성에 관한 수치 해석 (Numerical Analysis on the Increasing Temperature Characteristics of Vaporizer Fin for Liquefied Natural Gas with Super Low Temperature)

  • 이중섭;공태우;이효덕;정효민;정한식
    • 동력기계공학회지
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    • 제9권2호
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    • pp.81-87
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    • 2005
  • This study is numerical analysis on the increasing temperature characteristics of vaporizer fin for liquefied natural gas with super low temperature. Existing LNG vaporizers use the direct contact heat transfer mode where the extreme super low temperature LNG of $-162^{\circ}C$ flows inside of the tubes and about $20^{\circ}C$air flows on outside of the fin. Recently, the vaporizers with great enhanced performance compared to conventional type have been developed to fulfill these requirements. The vaporizing characteristic of LNG vaporizer with air as heat source has a fixed iced. These characteristic cause a low efficiency in vaporizer, total plant cost and installing space can be increased. The vaporizing characteristics of LNG via heat exchanger with air are analytically studied for an air heating type vaporizer. This study is intended to supply the design data for the domestic fabrication of the thickness and angle vaporizer fin. Governing conservation equations for mass, momentum and energy are solved by STAR-CD based on an finite volume method and SIMPLE algorithm. Calculation parameter is fin thickness, setup angle and LNG temperature. If the vaporization performance of the early stage and late stage of operating is considered, the case of ${\phi}=90^{\circ}$ was very suitable. In this paper was estimated that the heat transfer was most promoted in case of THF=2mm.

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CFC-대체냉매와 스크롤압축기를 사용한 냉동시스템 성능해석 (Performance Analysis of Refrigeration System Using the CFC-Alternative and Scroll Compressor)

  • 박희용;박경우
    • 설비공학논문집
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    • 제7권3호
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    • pp.366-381
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    • 1995
  • A performance analysis of refrigeration system using the HFC-134a and scroll compressor is performed numerically. The refrigeration system mainly consists of various standard components such as heat exchanger, compressor, and expansion device. The model for heat exchanger performance is based on a tube-by-tube method which is analyzed separately by considering the cross-flow heat transfer with the outdoor air flow and pressure drop. Compressor is used the scroll-type compressor which has many merits such as high efficiency, low noise and vibration, and small in size. Short-tube is included as an expansion device. Vapour and liquid line are also considered for the performance analysis of refrigeration system. Using the modeling of various components of refrigeration system, a performance comparison of CFC-12 and HFC-134a is performed numerically for the various outdoor air temperature and various values of short-tube diameter. As the results of this study, the refrigeration system performance decreases as the outdoor air temperature increases. And the optimum short-tube diameter based on COP is 1.37mm for this system.

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평판형 열교환기에서의 제빙억제를 위한 초음파의 영향 (Effect of ultrasonic waves on anti-freezing for plate-type heat exchanger)

  • 조기량;최광일;김온;박기원
    • Journal of Advanced Marine Engineering and Technology
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    • 제41권3호
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    • pp.176-181
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    • 2017
  • 본 연구는 저온환경에서의 평판형 열교환기에 대해 제빙을 억제할 수 있는 방법을 살펴보았으며, 그 방법으로 초음파의 발생에 따른 제빙특성을 관찰하였다. 본 실험에서 최적의 조건을 찾아내기 위해 에틸렌글리콜을 브라인으로 사용하고, 온도는 $-8{\sim}-16^{\circ}C$로 순환시켰으며, 제빙에 사용된 물은 1~3mm 두께로 공급하여 데이터를 기록하였다. 또한 초음파의 발생정도에 따른 변화를 확인하기 위해 출력을 조절하여 실험을 진행하였다. 그 결과 제빙억제 효과는 브라인 온도, 제빙두께, 초음파 주파수의 영향을 받는 것을 알 수 있었다.

설비공학 분야의 최근 연구 동향 : 2016년 학회지 논문에 대한 종합적 고찰 (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)

  • 이대영;김사량;김현정;김동선;박준석;임병찬
    • 설비공학논문집
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    • 제29권6호
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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.

산업폐수열원 이용 증기압축식/흡수식 하이브리드 히트펌프 시스템의 시뮬레이션 (Simulation of Compression/Absorption Hybrid Heat Pump System using Industrial Wastewater Heat Source)

  • 백영진;박성룡;장기창;라호상
    • 설비공학논문집
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    • 제16권12호
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    • pp.1117-1125
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    • 2004
  • In this study, in order to utilize the waste heat of industrial wastewater in the range of the relatively low temperature of 40~5$0^{\circ}C$ as a heat source, a hybrid heat pump system was considered by computer simulation method. In the simulation, an absorber, desorber and solution heat exchanger were modelled by UA values while a compressor and pump performance were specified by an isentropic efficiency. Simulation results show that the performance of hybrid heat pump can be up to 80% higher than that of conventional R134a heat pump when it makes a process hot water of 9$0^{\circ}C$ while the wastewater is cooled down to 2$0^{\circ}C$. As the absorber pressure increases, the system performance and deserter pressure increase with a favorable effect of a compressor discharge gas temperature drop.

저온 열원 HFC-134a 유기랭킨사이클의 출력 극대화 (Power Optimization of Organic Rankine-cycle System with Low-Temperature Heat Source Using HFC-134a)

  • 백영진;김민성;장기창;이영수;나호상
    • 대한기계학회논문집B
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    • 제35권1호
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    • pp.53-60
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    • 2011
  • 본 연구에서는 지열발전 등과 같은 저온 열원을 에너지원으로 하는 발전에 응용될 수 있는 HFC-134a 유기랭킨사이클의 출력 극대화를 수행하였다. 기존의 연구와는 달리, 본 연구에서는 열교환기해석에 유한체적법을 적용함으로써 작동유체의 열전달 및 압력강하 특성을 고려하였다. 또한, 열원과 냉각수의 입구온도 및 유량, 그리고 사이클을 구성하는 열교환기들의 총 전열면적을 구속 조건으로 함으로써, 기존 연구들에 비해 보다 현실적인 결과를 얻을 수 있도록 하였다. 사이클의 출력은 3 개의 설계인자를 이용하여 최적화 하였다. 시뮬레이션 결과, 출력을 극대화 시킬 수 있는 설계인자들의 최적조합이 존재함을 보였다. 또한, 출력 향상을 위해서는 증발과정의 개선이 우선적으로 필요함을 보였다.

비이온 계면활성제의 마찰 및 열교환효율 저감 특성 연구 (Study on the Drag Reduction and Heat Transfer Efficiency Reduction of the Non-Ionic Surfactant)

  • 조성환;태춘섭
    • 설비공학논문집
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    • 제19권2호
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    • pp.133-141
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    • 2007
  • The drag reduction (DR) and heat transfer efficiency reduction (HTER) of nonionic surfactant according to the fluid velocity, temperature and surfactant concentration were investigated experimentally. For this study, several kinds of new surfactant which contains amine-oxide and betaine were developed. And experimental apparatus equipped with two water storage tanks temperature controlled, pumps, testing pipe network, two flowmeters, two pressure gauges, heat exchanger, and data logging system was built. Results showed that existing alkyl ammonium surfactant (CTAC) had DR of $0.6{\sim}0.8$ for $1,000{\sim}2,000\;ppm$ in fluid temperature of $50{\sim}60^{\circ}C$ and had very low DR in fluid temperature over $70^{\circ}C$. And new amino oxide and betaine surfactant (SAOB) had lower DR in fluid temperature of $50{\sim}60^{\circ}C$ compared with CTAC but in fluid temperature of $70{\sim}80^{\circ}C$ DR was $0.6{\sim}0.8$ for 1$1,000{\sim}2,000\;ppm$.

저에너지주택의 지열히트펌프시스템 냉·난방 성능분석 (Heating and Cooling Performance Analysis of Ground Source Heat Pump System in Low Energy House)

  • 백남춘;김성범;신우철
    • 설비공학논문집
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    • 제28권10호
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    • pp.387-393
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    • 2016
  • A ground source heat pump system maintains a constant efficiency due to its stable heat source and radiant heat temperature which provide a more effective thermal performance than that of the air source heat pump system. As an eco-friendly renewable energy source, it can reduce electric power and carbon dioxide. In this study, we analyzed one year of data from a web based remote monitoring system to estimate the thermal performance of GSHP with the capacity of 3RT, which is installed in a low energy house located in Daejeon, Korea. This GSHP system is a hybrid system connected to a solar hot water system. Cold and hot water stored in a buffer tank is supplied to six ceiling cassette type fan coil units and a floor panel heating system installed in each room. The results are as follows. First, the GSHP system was operated for ten minutes intermittently in summer in order to decrease the heat load caused by super-insulation. Second, the energy consumption in winter where the system was operated throughout the entire day was 7.5 times higher than that in summer. Moreover, the annual COP of the heating and cooling system was 4.1 in summer and 4.2 in winter, showing little difference. Third, the outlet temperature of the ground heat exchanger in winter decreased from $13^{\circ}C$ in November to $9^{\circ}C$ in February, while that in summer increased from $14^{\circ}C$ to $17^{\circ}C$ showing that the temperature change in winter is greater than that in summer.