• 제목/요약/키워드: Low fin tube

검색결과 81건 처리시간 0.027초

액화질소 초저온과 이원냉동 초저온 냉열의 비교 실험적 연구 (A Study on the Cold Energy for Liquefied Nitrogen Gas and Cascade Refrigeration System)

  • 김철수;장현순;정효민;정한식
    • 동력기계공학회지
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    • 제11권1호
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    • pp.56-62
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    • 2007
  • This paper represents the cold energy for liquefied nitrogen gas and cascade refrigerator. In this study, the vaporizer of liquefied nitrogen gas has the fin coil tube type with the dimension of inside diameter of 10mm and outside diameter of 12mm. Also, the total length of vaporizer is 20,000mm. The main experimental parameters are the mean velocity in duct and the supplied flow-rates of liquefied nitrogen gas. For the cascade refrigeration system, the refrigerants are ethane(R 170) in the high pressure stage and R 22 in the low pressure stage.

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분리형 히트파이프의 저발열량 연료가스 예열시스템에 대한 적용연구 (Application of a Large Scale Heat Pipe System to Preheating the Fuel Gas of Low Heating Value)

  • 박흥수;유갑종;이진호;이용국
    • 대한기계학회논문집B
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    • 제23권9호
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    • pp.1085-1097
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    • 1999
  • A separate heat pipe system capacity of 3,700kW has been developed and applied to preheating the blast furnace gas for recovery of the waste heat from boiler. The system is designed to preheat the blast furnace gas up to $126^{\circ}C$ by using tho boiler exhaust gas of which temperature is $180^{\circ}C{\sim}220^{\circ}C$. The arrangement of the fin tubes as well as the shape of the fin has been carefully determined to minimize the fouling problems. The heat pipe system was found to be stable in circulation of the working fluid and the range of the temperature variation of the preheated blast furnace gas was within $10^{\circ}C$. It was proved through a long-term test that the selected tube arrangement and the shape of the fins are proper to prevent the fouling problems and that the pay-back period of the system Is within one year.

설비공학 분야의 최근 연구 동향 : 2013년 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 2013)

  • 이대영;김사량;김현정;김동선;박준석;임병찬
    • 설비공학논문집
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    • 제26권12호
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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.

열전달 촉진관에서 2원 혼합냉매의 외부 응축열전달계수 (Condensation Heat Transfer Coefficients of Binary Refrigerant Mixtures on Enhanced Tubes)

  • 김경기;서강태;채순남;정동수
    • 설비공학논문집
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    • 제14권2호
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    • pp.161-167
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    • 2002
  • In this study, external condensation heat transfer coefficients (HTCs) of two non-azeotropic refrigerant mixtures of HFC32/HFC134a and HF0134a/HCF0123 at various compositions were measured on both low fin and Turbo-C enhanced tubes of 19.0 mm outside diameter All data were taken at the vapor temperature of 39$^{\circ}C$ with a wall subcooling of 3- 8 K. Test results showed that HTCs of the tested mixtures on the enhanced tubes were much lower than the ideal values calculated by the mass fraction weighting of the pure compo- nents'HTCs. Also the reduction of HTCs due to the diffusion vapor film was much larger than that of a plain tube. Unlike HTCs of pure fluids, HTCs of the mixtures measured on enhanced tubes increased as the wall subcooling increased, which was due to the sudden break up of the vapor diffusion film with an increase in wall subcooling. Finally, heat transfer enhancement ratios for mixtures were found to be much lower than those of pure fluids.

단일진공관 태양열집열기의 형상변화 및 접촉저항에 따른 집열효율 연구 (Study on Thermal Efficiency according to Configuration Change and Contact Resistance of Solar Collector with Single Evacuated Tube-type)

  • 최보원;양영준
    • 에너지공학
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    • 제23권4호
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    • pp.189-195
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    • 2014
  • 신재생에너지 분야 중 특히 태양에너지를 이용하는 분야는 자원의 무한 및 청정성 때문에 그 사용량이 증가 추세에 있다. 우리나라에서 태양열에너지의 이용률이 전체 에너지 사용량 중 아직 미미한 실정이지만, 근래 정부의 정책적 지원에 힘입어 이 분야에 대한 연구가 활발히 이루어지고 있다. 본 연구는 태양열집열기의 형상 변화에 따른 집열효율을 조사하기 위하여 단일진공관 태양열집열기를 이용한 실험 및 이중진공관 태양열집열기와의 비교 실험을 수행하였다. 그 결과, 본 실험장치에서 히트 파이프의 최고온도의 차이로부터 태양열집열기 형상 변화에 따른 집열효율의 변화를 확인할 수 있었다. 또한 본 연구대상 태양열집열기의 히트파이프의 온도가 비교대상 태양열집열기보다 높음에도 불구하고 방열핀의 온도가 낮게 관측되었다. 이것은 본 연구대상의 태양열집열기는 히트파이프 방열부인 헤드부와 방열핀 사이의 접촉저항이 비교대상의 접촉저항보다 크다는 것을 나타내며, 집열효율을 높이기 위해서는 태양열집열기의 여러 부분의 성능개선뿐만 아니라 접촉저항에 의한 집열손실도 감소시켜야 함을 확인할 수 있었다.

상변화물질을 이용한 축열시스템에서 핀에 의한 열전달 촉진 연구 (Heat Transfer Enhancement by Fins in a Latent Heat Storage System Using Phase Change Material)

  • 한승구;한귀영
    • 에너지공학
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    • 제5권2호
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    • pp.115-122
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    • 1996
  • 망초를 이용한 저온 잠열축열시스템에서 핀을 설치한 전열관에서 방열과정중의 열전달 특성을 살펴보았다. 잠열물질의 과냉각과 상분리를 방지하기위해 3.0 wt% $Na_2$B$_4$O$_{7}$10$H_2O$와 2.2 wt% acrylic acid sodium sulfate가 조핵제 및 증점제로 사용되었다. 축열조는 높이가 530 mm, 직경이 74 mm이고 열전달관은 높이가 480 mm, 직경이 13.5 mm인 이중관으로 되어있으며 열전달 유체로는 물을 사용하였다. 축열재로부터 열을 치수하는 방열과정에서 열회수율은 열전달 유체의 유입온도와 유량에 크게 의존하였다. 핀이 설치되지 않은 전열관과의 비교실험을 통하여 핀에 의한 열전달 촉진은 얇은 핀의 경우에는 열전달계수의 증가가 미미하였지만 두꺼운 핀을 사용한 경우에는 같은 조업조건에서 열전달계수가 약 60% 정도 증가하였다. 실험적으로 결정된 총괄 열전달계수는 핀이 없는 경우에는 약 150-260 w/$m^2$K이었고 두꺼운 핀을 사용한 전열관에서는 230-530 W/$m^2$K정도였다. 총괄 열전달계수의 크기와 핀에 의한 전열면적을 기준으로 한 핀의 효율은 두꺼운 핀의 경우에는 약 0.26, 얇은 핀의 경우에는 0.05 정도로 계산되었다.다.

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저온 조건에서 핀-관 열교환기의 공기측 열전달 및 압력손실 (Air-side Heat Transfer and Pressure Drop of a Fin-and-Tube Heat Exchanger Under Low Temperature Condition)

  • 김내현
    • 한국산학기술학회논문지
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    • 제18권4호
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    • pp.15-20
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    • 2017
  • 최근 들어 가정용 공조기가 겨울철에 히트 펌프로도 사용된다. 이 때 실외기는 저온의 외기와 열전달을 하며 관내의 냉매를 증발시킨다. 반면 여름철에 냉방기로 사용될 경우 실외기는 고온의 외기와 열전달을 통해 관 내의 냉매를 응축시킨다. 즉, 동일한 열교환기가 여름철에는 응축기로, 겨울철에는 증발기로 사용되고 외기 조건도 겨울철의 저온에서 여름철의 고온까지 넓은 범위에 놓이게 된다. 본 연구에서는 표준 설계 온도 조건에서 얻어진 j와 f 인자가 저온 운전 시에도 무리없이 적용 가능한지를 실험을 통하여 확인하였다. 이를 위하여 2열 루버 핀-관 열교환기에 대하여 외기 온도를 변화시키며 일련의 실험을 수행하였다. 또한 관 내측의 브라인의 유량이 미치는 영향도 살펴보았다. 실험 결과 외기의 온도 변화가 j와 f 인자에 미치는 영향은 무시할 만 하였다. 모든 j와 f 인자는 각각 9%, 3% 내에서 일치하였다. 따라서 표준 조건에서 얻어진 j와 f 인자를 저온 조건에 사용하여도 무리가 없다고 판단된다. 또한 관 내측 유량 변화가 j와 f 인자에 미치는 영향이 미미한 것으로 미루어 관 내측 상관식의 적용이 적절하다고 판단된다.

비공비 혼합냉매 R-410A를 적용한 납작한 알루미늄 마이크로 멀티 튜브에서의 마찰손실에 관한 연구 (A study on the friction head loss in flat aluminum micro multi tubes with nonazeotropic refrigerant mixtures R-410A)

  • 이정근;민경호
    • Design & Manufacturing
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    • 제13권2호
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    • pp.37-43
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    • 2019
  • This study conducted a research as to condensation heat transfer friction loss headby using three types of flat micro multi-channel tubes with different processing of micro-fin and number of channels inside the pipes and different sizes of appearances. In addition, identical studies were conducted by using smoothing circular tubes with 5mm external diameter to study heat enhancement factor and pressure drop penalty factor. 1) The friction head loss showed an increase as the vapor quality and mass flux increased. In case of saturation temperature, it shows an increase as it gets lower. These factors are the reason occurring as the lower the saturation temperature is, the higher the density of refrigerant vapor gets. The influence of heat flux is similar as the dryness is low, but as it gets higher, it lowers in heat flux, and as the high temperature of high heat flux, it is a factor that occurs as the density gets lower. 2) RMS error of the in case of friction head loss, it showed to be predicted as 0.45~0.67 by Chisholm, Friedel, Lockhart and Martinelli. 3) As forfriction head loss penalty factor, the smaller the aspect ratio is, the larger the penalty factor gets, and as for the effect of micro-fin, the penalty factor increased because it decreases to the gas fluid the way groove for the refrigerant's flow.

착상조건에서 R134a와 R1234yf를 적용한 핀-관 형태의 증발기 성능 비교 (Performance Comparison of Fin-Tube Type Evaporator using R134a and R1234yf under the Frost Condition)

  • 신윤찬;김진현;조홍현
    • 한국산학기술학회논문지
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    • 제16권9호
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    • pp.5795-5801
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    • 2015
  • 식생활의 향상 및 다양화로 신선한 제품에 대한 요구가 증가하고 있으며, 이에 따라 냉장 및 냉동식품의 저온유통 또한 점차 증가되고 있다. 현재 냉동산업에는 주로 R134a 냉매가 사용되고 있으며 GWP(Global Warming Potential)가 1300으로써 매우 높아 지구온난화에 영향을 미친다. 이를 대체하기 위한 냉매로써 R1234yf 냉매가 있으며, GWP는 4로써 매우 낮다. 냉동탑차 냉장시스템에 사용되는 증발기는 저온조건에서 작동되기 때문에 서리가 형성되어 시스템의 성능을 급격히 감소시킨다. 따라서, 본 연구에서 R134a와 R1234yf 냉매를 작동유체로 사용한 증발기의 성능을 착상조건 하에서 다양한 운전조건으로 분석하였다. 해석결과, 서리성장 조건에서 공기측 입구온도, 상대습도, 증발온도 변화에 대하여 R134a 증발기의 성능이 R1234yf 증발기보다 더욱 민감하게 나타났으며 서리의 성장 또한 R134a 증발기가 더 크게 나타났다.

설비공학회 분야의 최근 연구 동향 : 2015년 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 2015)

  • 이대영;김사량;김현정;김동선;박준석;임병찬
    • 설비공학논문집
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    • 제28권6호
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    • pp.256-268
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    • 2016
  • This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during 2015. 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 were carried out in the areas of flow, heat and mass transfer, cooling and heating, and air-conditioning, the renewable energy system and the flow inside building rooms. Research issues dealing with air-conditioning machines and fire and exhausting smoke were reduced. CFD seems to be spreading to more research areas. (2) Research works on heat transfer area were carried out in the categories of heat transfer characteristics, pool boiling and condensing heat transfer and industrial heat exchangers. Researches on heat transfer characteristics included the economic analysis of GHG emission, micro channel heat exchanger, effect of rib angle on thermal performance, the airside performance of fin-and-tube heat exchangers, theoretical analysis of a rotary heat exchanger, heat exchanger in a cryogenic environment, the performance of a cross-flow-type, indirect evaporative cooler made of paper/plastic film. In the area of pool boiling and condensing, the bubble jet loop heat pipe was studied. In the area of industrial heat exchangers, researches were performed on fin-tube heat exchanger, KSTAR PFC and vacuum vessel at baking phase, the performance of small-sized dehumidification rotor, design of gas-injection port of an asymmetric scroll compressor, effect of slot discharge-angle change on exhaust efficiency of range hood system with air curtain. (3) In the field of refrigeration, various studies were carried in the categories of refrigeration cycle, alternative refrigeration/energy system, system control. In the refrigeration cycle category, a cold-climate heat pump system, $CO_2$ cascade systems, ejector cycles and a PCM-based continuous heating system were investigated. In the alternative refrigeration/energy system category, a polymer adsorption heat pump, an alcohol absorption heat pump and a desiccant-based hybrid refrigeration system were investigated. In the system control category, turbo-refrigerator capacity controls and an absorption chiller fault diagnostics were investigated. (4) In building mechanical system research fields, eighteen 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, and renewable energies, piping 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 was mostly focused on indoor environment and building energy. The main researches of indoor environment were related to the user and location awareness technology applied dimming lighting control system, the lighting performance evaluation for light-shelves, the improvement evaluation of air quality through analysis of ventilation efficiency and the evaluation of airtightness of sliding and LS window systems. The subjects of building energy were worked on the energy saving estimation of existing buildings, the developing model to predict heating energy usage in domestic city area and the performance evaluation of cooling applied with economizer control. The studies were also performed related to the experimental measurement of weight variation and thermal conductivity in polyurethane foam, the development of flame spread prevention system for sandwich panels, the utilization of heat from waste-incineration facility in large-scale horticultural facilities.