• Title/Summary/Keyword: Ribbed Tube

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A Study on Numerical Analysis for Flow Characteristics in Ribbed Tube (열교환기내 리브드 튜브의 유동 특성에 관한 수치해석적 연구)

  • Jeon, Jeong-Do;Jeon, Eon-Chan;Jeung, Hui-Gyun;Lee, Chi-Woo
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.10 no.4
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    • pp.115-120
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    • 2011
  • A ribbed tube consumes more power to transport the fluid by comparing with flat one. After the tangential velocity component occurs, its contact area with the ribbed tube becomes large and it enables the effective energy transportation. The flow characteristics vary according to the geometry of tube rib. This study aims to investigate the flow characteristics of fluids working at Reynolds numbers of 20,000, 40,000, 60,000 and 80,000 with the air at $15^{\circ}C$ in the ribbed test tube high 1mm and wide 8.48mm. As the flow characteristics are included with the states of fully developed hydrodynamical region, axial velocity vector distribution and non-dimensional velocity distribution, they are shown with the physical validity.

Characteristic of Heat and Mass Transfer on Inner Ribbed Notched Fin Tube Absorber (내면가공 핀튜브 흡수기의 열 및 물질전달특성)

  • 설원실;권오경;문춘근;정용옥;윤정인
    • Journal of Advanced Marine Engineering and Technology
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    • v.24 no.4
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    • pp.478-485
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    • 2000
  • An experimental study of the absorption process of water vapor into lithium bromide solution was performed. For the purpose of development of high performance absorption chiller-heater utilizing Lithium Bromide solution as working fluid, the absorber is the most effective to improve the performance of an absorber because it requires the largest heat transfer area in an absorption chiller-heater system. This paper introduces bare tube and inner ribbed notched fin tube for the absorber of absorption chiller-heaters. Inner ribbed notched fin tube has about 10∼20% higher heat and mass transfer performance than bare tube conventionally used in absorbers and the it is expected to perform high heat and mass transfer. This paper will provide important information on the selection of absorber tubes in commercial absorption chill-heaters.

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A Study on Numerical Analysis for Heat Transfer and Flow Characteristics in a Ribbed Tube (열교환기 내 리브드 튜브의 열전달 및 유체유동에 관한 수치 해석적 연구)

  • Jeon, Jeong-Do;Jeon, Eon-Chan;Jeung, Hui-Gyun;Lee, Chi-Woo
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.10 no.6
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    • pp.134-139
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    • 2011
  • This study was conducted on the characteristics of fluid flow and heat transfer in the ribbed tube used for a steam power plant. It was assumed that the air is incompressible and therefore, its density is not variable according to temperature. In addition, the gravity was ignored. A commercial code of computational fluid dynamics was used and standard k-$\epsilon$ model was used together with the energy equation included to calculate heat transfer. As Reynolds No. was low at the velocity distribution in the axial direction, the air reached hydro-dynamically fully developed region shortly but high Reynolds No. yielded late full hydro-dynamic development. The velocity distribution and non-dimensional temperature distribution were all physically reasonable and thus had a good agreement with the experimental result.

A Study on Heat Trasfer Characteristics of Smooth and Ribbed Tubes for Boiler (보일러용 裸管 및 리브붙이管 의 熱傳達 特性 에 관한 硏究)

  • 김종보;한승탁
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.9 no.6
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    • pp.699-705
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    • 1985
  • Heat transfer characteristics in terms of the tube wall-temperature and the enthalpy have been investigated utilizing ribbed (rifled) tubes in order to enhance heat transfer performance. Considerations were given for the cases of smooth tubes in order to compare with the case of ribbed tubes. The tilt angle of the experimental tubes are from 0.deg. to 90.deg. , in order to simulate the boiler water tubes having 15.deg.-90.deg. inclined angle in boiler nose and studded tubes (burner zones), Natural convection and forced convection (Re=1810) conditions were considered in the experiments. The experimental results for the effect for the tube inclination through a natural convection and forced convection are presented and it is shown that ribbed tubes permit an appreciable increase in heat transfer coefficients and consequently it means substantial reductions in boiler water wall tubes and heat exchanger surface areas.

An Experimental Study on Tube-Side Heat Transfer Coefficients and Friction Factors of the Enhanced Tubes Used in Regenerators of Absorption Chillers (흡수식 냉동기의 재생기에 사용되는 전열촉진관의 관 내측 열전달계수 및 마찰계수에 대한 실험적 연구)

  • Kim, Nea-Hyun
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.17 no.3
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    • pp.716-723
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    • 2016
  • Enhanced tubes are used widely in the heat exchangers of absorption chillers. In regenerators, corrugated, ribbed or floral tubes are commonly used. In this study, the tube-side heat transfer coefficients and friction factors of enhanced tubes were obtained experimentally using the Wilson Plot method. The results showed that the heat transfer coefficients and the friction factors were the largest for the corrugated tube, followed by the ribbed tube. The heat transfer coefficients and friction factors of the floral tube matched those of the smooth tube within 4%, which suggests that the heat transfer and friction characteristics of the floral tube may be accounted for properly by the hydraulic diameter. The B(e+) and g(e+) were obtained from the experimental data of the corrugated and ribbed tube. The B(e+) and g(e+) of the corrugated tube matched those of the existing correlation within 20%. The present results may be used for an assessment of the heat transfer and friction characteristics of the enhanced tubes for regenerators.

The effect of inclined ribbed tubes on heat transfer and friction loss (Ribbed 管의 管傾斜角이 熱傳達에 미치는 影響)

  • 박성찬;김종보
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.11 no.1
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    • pp.105-109
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    • 1987
  • Artificial roughness as a means of improving heat transfer gains more interest, especially for application to various heat exchanger. This study present experimental information for single-phase free and force convection heat transfer in a circular tube containing a internal spiral ribs. To examine the effect of inclined angle of tube, it was varied from 0 deg to 90 deg (0.deg., 22.5.deg., 45.deg., 90.deg.) with horizontal. Length of tube is 1.6m, and width, height and helix angle of rib are 4.2mm, 1.5mm, and 60 deg respectively. Water was used as a working fluid and test piece was heated with a constant heat flux by electric heater. Experiments have been performed with the range of modified Grashof number from 2 * 10$^{6}$ to 15 * 10$^{6}$ for free convection and with the range of Reynolds number from 3,000 to 40,000 for forced convection. Since the increase in heat transfer coefficients influence directly to the friction coefficient of the tube, the changes of the friction factors are also presented for several different cases considered in this investigation.

Fouling in Enhanced Tubes-Extension of Kern-Seaton Fouling Model to Repeated Ribbed Tubes (열전달 촉진관내의 화울링 해석-2차원 리브붙이관에 Kern-Seaton 화울링 모델 적용)

  • Kim, N.H.
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.4 no.4
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    • pp.289-298
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    • 1992
  • Fouling is "a major unsolved" area in heat transfer research. Currently, fouling researches are performed in every directions-fundamental aspects, modeling and cumulating experimental data. In this study, an attempt was made to extend the knowledge in enhanced tube fouling. The Kern-Seaton fouling model which was originally proposed for smooth tube fouling was extended to repeated rib tubes. Key parameters-mass transfer coefficient and wall shear stress-were modeled for repeated rib tubes. Some critical points related with the enhanced tube fouling-uncertainties in the mass transfer rate, wall shear stress modeling, deformation of roughness shape during fouling-were discussed, and some quantitative evaluations were made.

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Turbulent Flow and heat Transfer in the Annular Passage with Repeated-Ribbed Roughness on Both Walls (양측벽면에 반복돌출형 거칠기가 있는 이중관통로내의 난류유동과 열전달)

  • 안수환;김덕현
    • Journal of Advanced Marine Engineering and Technology
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    • v.20 no.1
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    • pp.1-12
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    • 1996
  • The fully developed tubulent momentum and heat transfer induced by the square- ribbed roughness elements on both the inner and outer wall surfaces in the concentric annuli are studied analytically based on a modified turbulence model. Heat transfer coefficients for two conditions, i.e, a) inner wall heated as constant heat flux and outer wall insulated b) inner wall insulated and outer wall heated as constant heat flux, are investigated. The analytical results of the fluid flow are verified by experiment. The experiment is done with a pitot tube and a X-type hot wire anemometer to measure the time mean velocity profiles, zero shear stress positions, maximum velocity profiles and friction factors, and etc. The resulting momentum and heat transfer are discussed in terms of various parameters, such as the radius ratio, the relative roughness, the roughness density, Nusselt number and Prandtl number.

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Turbulent Flow and Heat Transfer in an Annular Passage with Repeated-Ribbed Roughness on Both Walls (양측벽면에 반복돌출형 거칠기가 있는 이중관통로내의 난류운동과 열전달)

  • 안수환;이윤표
    • Transactions of the Korean Society of Automotive Engineers
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    • v.4 no.5
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    • pp.26-36
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    • 1996
  • The fully developed turbulent momentum and heat transfer induced by the square-ribbed roughness elements on both the inner and outer wall surfaces in concentric annuli are studied analytically based on a modified turbulence model. The analytical results of the fuid flow are verified by experiment. The experiment is done with a pitot tube and a X-type hot wire anemometer to measure the time mean velocity profiles, zero shear stress positions, maximum velocity positions and friction factors, and etc. shown in Fig.1. The resulting momentum and heat transfer are discussed in terms of various parameters, such as the radius ratio, the relative roughness, the roughness density, Reynolds number, Nusselt bumber and Prand시 number. The study demonstrates that certain artificial roughness elements may be used to enhance heat transfer rates with advantage from the overall efficiency point of view by investigating turbulent flows and heat transfer in Fig.1.

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Heat Transfer and Frictions in the Convergent/divergent Channel with Λ/V-shaped Ribs on Two Walls

  • Kim, Beom-soo;Lee, Myung-sung;Ahn, Soo-whan
    • International Journal of Aeronautical and Space Sciences
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    • v.18 no.3
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    • pp.395-402
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    • 2017
  • The local heat transfer and total pressure drops of developed turbulent flows in the ribbed rectangular convergent/divergent channels with ${\Lambda}/V-shaped$ ribs have been investigated experimentally. The channels have the exit hydraulic diameter ($D_{ho}$) to inlet hydraulic diameter ($D_{hi}$) ratios of 0.67 for convergence and 1.49 for divergence, respectively. The ${\Lambda}/V-shaped$ ribs with three different flow attack angles of $30^{\circ}$, $45^{\circ}$, and $60^{\circ}$ are manufactured with a fixed rib height (e) of 10 mm and the ratio of rib spacing (S) to height (e) of 10 on the walls. Thermal performances of the ribbed rectangular convergent/divergent channels are compared with the smooth straight tube under identical pumping power. The results show that the flow attack angle of $45^{\circ}$ with ${\Lambda}-shaped$ rib has the greatest thermal performance at all the Reynolds numbers studied in the convergent channel; whereas, the flow attack angle of $60^{\circ}$ with V-shaped rib has the greatest thermal performance over Reynolds number of 30,000 in the divergent channel.