• 제목/요약/키워드: Integral-Fin Tube

검색결과 18건 처리시간 0.022초

낮은 핀관 (low-fin tube)의 응축 열전달 성능에 관한 실험적 연구 (An Experimental Study on Condensation Heat Transfer of Low-Finned Tubes)

  • 김내현;정인권;김경훈
    • 설비공학논문집
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    • 제7권2호
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    • pp.298-309
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    • 1995
  • Low-fin tubes are widely used to enhance condensation heat transfer. In this study, condensation heat transfer experiment was conducted on the low-fin tube using R-11. Three different fin densities-787 fpm (fins per meter), 1102 fpm. 1378 fpm-were tested. The results show that low-fin tube enhances the condensation heat transfer considerablely. The enhancement increases as the fin density increases. It was also found that the fin shape and height have a significant effect on the condensation heat transfer coefficient. Slender or high fins showed a higher condensing heat transfer coefficient compared with fat, low fins. For the tube with 1378 fpm, however, excessive fin height decreased the condensing heat transfer coefficient. The reason may be attributed to the increasing condensate retention angle as the fin density increases. The experimental data are compared with existing prediction models. Results show that Webb's surface tension model predicted the data best (within ${\pm}20%$), which confirms that surface tension plays the major role in low-fin tube condensation.

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낮은 핀 관의 응축 열전달 성능에 관한 연구 (A Study on the Condensation Heat Transfer of Low Integral Fin Tubes)

  • 한규일;박성국
    • 수산해양기술연구
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    • 제32권1호
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    • pp.67-77
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    • 1996
  • The heat transfer performance of R - 11 vapor condensing on integral fin tubes has been studied using fin tubes having the fin density from 748 to 1654 fins per meter. Electric heater supplied heat energy to the boiler to generate R - 11 vapor over the range of 25-60W. Condensation rates of each tubes were tested under the condition of cooling water flow rate from 400l/h to 2500l/h. For the seven fin tubes tested, the best performance has been obtained with a tube having a fin density of 1417fpm and a fin height of 1.3mm. This tube has yielded a maximum value of the heat transfer coefficient of 16500W/$m_2$K, at a vapor to wall temperature difference of 3K. Experimental results of integral fin tubes have been compared with available predictive models such as Beatty - Katz's analysis, Webb's analysis, Sukhatme's analysis and Rudy's empirical relation. The experimental results were shown to be in good agreement with that of the Sukhatme's analysis.

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공작기계 절삭유 냉각용 낮은 핀관의 열전달 성능에 관한 연구 (A Study on the Performance of Heat Transfer of Low Fin Tubes Used in Cooling of the Cutting Oil of the Machine Tool)

  • 조동현
    • 한국공작기계학회:학술대회논문집
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    • 한국공작기계학회 1998년도 추계학술대회 논문집
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    • pp.125-133
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    • 1998
  • Nine tubes with trapezoidal integral-fins having fin densities from 748 to 1654fpm and 10,30 grooves and finned tubes with caves of 0.55 and 0.64mm height respectively are tested. A plain tube having same diameter as the finned tubes is also tested for comparison. In case of condensation CFC-11 condensates at saturation state of 32$^{\circ}C$ on the outside surface cooled by inside cooling water flows. And in case of boiling the refrigerant evaporates at a saturation state of 1bar on the outside tube surface and heat is supplied by hot water which circulates inside of the tube. The tube having fin density of 1299fpm and 30grooves has the best condensation overall heat transfer coefficient. However, as far as boiling heat transfer coefficient concerns, fin tubes with cave show higher value than low fin tube having fin density of 1299fpm and 30 grooves.

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터보 냉동기용 핀튜브에 관한 연구 ( I ) - 응축 열전달에 관하여 - (A Study on Finned Tube Used in Turbo Refrigerator( I ) -for Condensation Hear Transfer-)

  • 조동현;한규일;김시영
    • 수산해양교육연구
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    • 제5권1호
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    • pp.31-44
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    • 1993
  • Through the early 1900's, the evolution of the surface condenser was closely tied to the development of steam engine and the turbine. As the chemical and petroleum industries evolved in the 1900's, the use of surface condensers in many different processes. Today, industry uses condensers in many shapes and sizes. The actual condensation process occurs on the outside surface of tubes. The nature of this surface geometry affects the condenser's heat transfer performance. The first condensers were built with plain tubes. As tube manufacturing techniques advanced, manufacturers started making tubes with integral fins. In the 1940's, fin densities were limited to about 600 to 700 fins per meter(fpm) because of manufacturing procedure. Today new manufacturing techniques allow production of tubes with fin densities ranging from 750 to 1600 fpm. The integral-fin tubes investigated in this paper are nominally 19 mm diameter. Eight tubes have been used with trapezodially shaped integral-fins having fin density from 748 to 1654 fpm and 10, 30 grooves. For comparison, tests are made using a plain tube having the same inside diameter and an outside diameter equal to that at the root of the fins for the finned tubes. Betty and Katz's theoretical modelis is used to predict the R-11 condensation coefficient on horizontal integral-fin tubes having 748, 1024 and 1299 fpm. Experiments are carried out using R-11 as working fluid. The refrigerant condensates at a saturation state of $30^{\circ}C$ on the outside tube surface cooled by coolant. The amount of noncondensable gases present in the test loop is reduced to a negligible value by repeated purging. For a given heat input to the boiler and given cooling water flow rate, all test data are taken at steady state. The observed heat transfer enhancement for the finned and grooved tubes significantly exceeded that to be expected on grounds of increased area. For the eight fin tubes and one plain tube tested, the best performance has been obtained with a tube having a fin density of 1299 fpm, and a fin bight of 1.2mm and 30 grooves.

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터보 냉동기용 핀 튜브에 관한 연구(II) - 비등 열전달에 관하여 - (A Study on Finned Tube Used in Turbo Refrigerator(II) - on boiling heat transfer -)

  • 한규일;김시영;조동현
    • 수산해양교육연구
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    • 제5권2호
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    • pp.119-127
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    • 1993
  • This work studies for heat transfer and pressure drop performance of integral inner and outer fin tubes, designed to enhance the heat transfer performance of smooth tubes for in recipro and turbo refrigerator or high performance compact heat exchangers. Eight different inner spiral fin copper tubes with integral fin at outside surfaces were employed to improve boiling heat transfer coeffcient. For comparison, tests were made using a plain tube having the inside diameter and an outside diameter equal to that at the root of the fins for the finned tubes. Pool boiling heat transfer is investigated experimentally and theoretically on single tube arrangement. The refrigerant evaporates at a saturation state of 1 bar on the outside tube surface heated by hot water. The refrigerant R11 ($CFCl_3$) was used at a pressure of $P_s=1bar$ as a convenient test fluid with a boiling temperature of $T_s=23.6^{\circ}C$. The observed heat transfer enhancement of boiling for finned tubes significantly exceeded that to be expected on grounds of increased area. The maximum Vapor - side enhancement(i.e., vapor - side heat transfer coefficient of finned tube/vapor - side coefficient for plain tube) was found to be around 4 at 1299fpm - 30grooves tube.

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자동차용 리시버/건조기 일체형 응축기의 성능해석 (Performance Analysis of Integral Receiver/Dryer Condenser for Automobile)

  • 원성필
    • 설비공학논문집
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    • 제19권3호
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    • pp.245-252
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    • 2007
  • The important problems from the point of view of preventing global warming are to save the power consumption of automotive air-conditioning systems and reduce the refrigerant amount filled. To achieve such requirements, integral receiver/dryer (R/D) condensers were developed recently. Typical integral R/D condensers have extra headers that play the role of R/D. Except an extra header and somewhat complex tube array resulting from the extra header, the most integral R/D condensers have almost the same specification that tube has multi channels, fin has louvers, flow in tube is parallel, etc. When integral condensers are applied, it is known that the refrigerating effect increases, resulting from the increase of subcooling degree in condenser, and the refrigerant amount used saves. In spite of several merits, integral condensers have not been applied a lot. That is why there is an uncertainty in performance, using integral condensers. The objective of this study is to theoretically optimize the tube array in an integral R/D condenser that is really being applied to some vehicles. The tube array has a great effect on the performance of the integral condenser as well as common ones. Through computer simulation, we could see that the tube array, 14-6-3-5-3-4, in the same condenser was the best, comparing heat release rate, pressure drop, etc. to the real array, 17-5-3-3-2-5. It should be noted that the optimization is based on the condenser performance only.

톱니형 휜이 부착된 원주의 근접후류특성 연구 (IV) - 와형성영역의 유동비교 - (Characteristics of Near Wake Behind a Circular Cylinder with Serrated fins (IV) - Comparison of Vortex Formation Regions -)

  • 류병남;김경천;부정숙
    • 대한기계학회논문집B
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    • 제27권3호
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    • pp.357-366
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    • 2003
  • An experimental study is performed to investigate characteristics of near of wakes of circular cylinders with serrated fins using a hot-wire anemometer for various freestream velocities. The main focus of this paper is to investigate a reason why a vortex formation length is increased suddenly. Velocity of the fluid which flow through fins decreases as fin's height and freestream velocity increases and fin pitch decreases, and a thickness of boundary layer increases. The finned tube has a lower velocity gradient when the higher boundary layer grows. This velocity gradient on finned tube makes a weak shear force in the wake and moves to downstream in a state of lower momentum transfer between the freestream and the wake. The phenomenon makes a vortex formation length increased suddenly. The fluctuations of the velocity distributions on the finned tube and (equation omitted) = 1.0 contour line in the vortex formation region decreases when the fin height increases and the pitch decreases.

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.