• 한국기계가공학회지
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• 제10권4호
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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.

• Journal of Advanced Marine Engineering and Technology
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• 제24권4호
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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.

• 한국기계가공학회지
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• 제10권6호
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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.

• 대한기계학회논문집
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• 제9권6호
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• pp.699-705
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• 1985

본 논문에서는 자연 및 강제순환 모두를 실험 했으며 사용한 리브붙이 관은 관의 두께와 직경, 리브수, 리브 피치(Pitch), 높이 및 폭등을 사용 하려는 열교환기 나 보일러에 합당하도록 설계, 선정하면, 그 적용 범위는 매우 넓다고 생각돼 연구 검 토 하고자 한다.

• 한국산학기술학회논문지
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• 제17권3호
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• pp.716-723
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• 2016

전열 촉진관은 흡수식 냉동기에 널리 사용되고 있다. 본 연구에서는 흡수식 냉동기의 재생기에 주로 사용되는 평활관, 리브 튜브, 코류게이트 튜브, 플로랄 튜브에 대하여 관 내측 열전달계수 및 마찰계수를 측정하였다. 실험 결과 열전달계수 및 마찰계수는 코류게이트 튜브에서 가장 크게 나타나고 다음으로 리브 튜브에서 크게 나타났다. 한편 플로랄 튜브의 열전달계수 및 마찰계수는 평활관 값과 4% 내에서 일치하였다. 이로부터 플로랄 튜브의 열전달 및 압력손실 특성이 수력직경으로 적절히 표현될 수 있음을 알 수 있다. 실험 데이터로부터 코류게이트 튜브와 리브 튜브의 B(e+)와 g(e+) 상관식을 구하였는데 코류게이트 튜브의 B(e+)와 g(e+)는 기존 상관식의 예측치와 20% 내에서 일치하였다. 본 연구 결과는 고온 영역에서 재생기용 전열촉진관의 관 내측 열전달 계수 및 마찰계수 산정에 활용될 수 있을 것이다.

• 대한기계학회논문집
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• 제11권1호
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• pp.105-109
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• 1987

본 연구는 열교환기의 설치 및 사용목적에 따라 전열관내유동이 경사류가 될 때 특히 자연순환(2*$10^{6}$＜Gr＜15*$10^{6}$)의 경우와 강제순환(3,000＜Re＜ 40,000)의 경우에 대해서 열전달특성과 유동마찰에 의한 손질을 규명하는데 있다. 사용되는 관은 평골관과 ribbed관이며 관경사각을 수평면에 대하여 0˚,22.5˚,45˚, 90˚로 변화시켰다.

• 설비공학논문집
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• 제4권4호
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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.

• Journal of Advanced Marine Engineering and Technology
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• 제20권1호
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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.

• 한국자동차공학회논문집
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• 제4권5호
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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.

• International Journal of Aeronautical and Space Sciences
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• 제18권3호
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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.