• 한국전산유체공학회:학술대회논문집
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• 2005.10a
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• pp.67-74
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• 2005

Fluid flow and heat transfer in rectangular duct system are measured and computed by commercial software of Star-CD for comparison between them. Three rectangular systems are investigated in this study. Those are a rectangular duct with 90 degree bended elbow, a rectangular duct with two branchs, and a circular cylinder in a rectangular duct. But heat transfer is studied only for last system. These investigations show us that the numerical solutions predict satisfactorily design factors (K-factor for the elbowed duct, distributions of flow rates into each branch from a duct, and Nusselt number around circular cylinder) even though there are some disagreements in velocity profiles and turbulent kinetic energy.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.71-74
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• 2002

Fluid flow in a rectangular duct system are measured by W laser doppler velocity meter, and also computed by commercial software of STAR-CD for comparison between then First, for a rectangular duct with 90 degree metered elbow, the fluid flow with Reynolds numbs's of 1,508 is predicted by assumption of both laminar and turbulent models. But, even though the Reynolds number is less than 2,300-3,000, the computation by turbulent model is close to the experimental data. Moeover, the computation by turbulent model for Reynolds number of 11,751 also predicts the experimental data satisfactorily. Second, for a rectangular duct with two branch ducts, the ratios between flow rates in the two branches are invariant to Reynolds number according to both of numerical and experimental results.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.4
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• pp.386-395
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• 2005

With the development of a living standard, the importance of indoor air conditioning system in all kinds of buildings and vehicles has increased. A lot of researches on energy losses in a duct and various kinds of flow pattern in branches or junctions have been carried out over many years, because the primary object of a duct system used in HVAC is to provide equal flow rate in the interior of each room by minimizing pressure drop. In this study, to get equal flow distribution in each branch, a blockage is applied to the rectangular duct system. The flow analysis for flow distribution of a rectangular duct with two branches was performed by CFD. By using SIMPLE algorithm and finite volume method, flow analysis is performed in the case of 3-D, incompressible, turbulent flow. Also, the standard $k-{\varepsilon}$ model and wall function method were used for analysis of turbulent fluid flow. The distribution diagrams of static pressure, velocity vector, turbulent energy and kinetic energy in accordance with variation of Reynolds number and blockages location in a rectangular duct show that flow distribution at duct outlets is improved by a blockage. In this rectangular duct system, mean velocity and flow rate distribution in two branch outlets are nearly constant regardless of variation of Reynolds number, and a flow pattern of the internal duct has a same tendency as well.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.9
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• pp.766-773
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• 2002

Flow distributions in a rectangular duct with two branch ducts are measured by 5 W laser doppler velocity meter. The fluid flows are also computed by commercial soft-ware of STAR-CD for comparison between them. The Reynolds numbers in the main duct are from 4,226 to 17,491. The ratios distributed into two branches from the main duct are in-variant to Reynolds numbers according to both of numerical and experimental results. However computed velocity profiles at exit of each branch are somewhat different from measured profiles at the same location.

• Journal of Advanced Marine Engineering and Technology
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• v.26 no.6
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• pp.670-678
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• 2002

Fluid flow in a rectangular duct with $90^{\circ}$ mitered elbow is measured by 5W laser doppler velocity meter. The fluid flow is also computed by commercial software of STAR-CD for comparison between measured and computed velocity profiles in the duct. Reynolds numbers for the comparison are 1,608 and 11,751 based on mean velocity and hydraulic diameter of the duct. First, the fluid flow of Reynolds number equal to 1,608 is predicted by assumptions of both laminar and turbulent models. But, even though the Reynolds number is less than 2,300~3,000, the computation by turbulent model is closed to the experimental data than that by laminar model. Second, the computation for Reynolds number of 11,751 by turbulent model also predicted the experimental data satisfactorily.

• Journal of Power System Engineering
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• v.15 no.5
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• pp.43-48
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• 2011

The article represents an experimental investigation on friction and turbulent flow characteristics of free airflow through a rectangular duct fitted with semicircular ribs of uniform height (e = 3.5 mm) on one principle wall. The aspect ratio of the rectangular duct was AR= 5 where the duct height (H) was of 30 mm. Four different rib pitches (P) of 28 mm, 35 mm, 42 mm and 49 mm were used for constant rib height to hydraulic diameter ratio (e/Dh = 0.07) and constant rib height to channel height ratio (e/H = 0.11). The experimental results show some significant effects on pressure drop as well as turbulent characteristics at various configurations among different numbers of rib arrangements varying Reynolds number in the range of 15000 to 30000. Pressure transducer and hot wire anemometer were used for data acquisition of this experiment.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.2
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• pp.290-301
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• 1992

An experimental study has been performed to investigate the characteristics of forced convective heat transfer in a rectangular duct with a 180.deg. bend. The Nusselt number of outer wall has maximum value near 105.deg. at which secondary flow is most active and the Nusselt number of inner wall has maximum value near the inlet of a duct. Near the outlet of a duct, the Nusselt number of outer wall decreases, the Nusselt number of inner wall increases and so those access each other through the influence of a straight duct attached to the end of a duct with a 180.deg. bend. Results of this experimental study would be the fundamental data when streamline curvature correction models are developed in the numerical study for forced convective heat transfer in a curved duct.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2352-2356
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• 2008

Heat transfer and performance characteristics have been investigated for a rectangular wavy duct with dimple or protrusion arrays. The test duct was 15mm in height and 105mm wide. The print diameter of the dimple/protrusion wall was 12.99mm and the depth/height of the dimple/protrusion was 3.75mm. Local heat transfer coefficients on the dimple/protrusion wall were measured using a transient TLC technique. The Reynolds number was varied from 3,000 to 10,000. For the wavy duct tested in this study, adverse static pressure characteristics occurred at turning region of the wavy duct due to secondary flows. For the wavy duct with protrusion array, higher heat transfer enhancement level of 7.4 times than smooth straight case in maximum was obtained at low Reynolds number due to the high heat transfer enhancement by vortex flows. Also, the protrusion array increased the performance level of 3.0 at low Reynolds number of 3,000.

• Journal of computational fluids engineering
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• v.3 no.2
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• pp.9-16
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• 1998

Predictive behaviors by the extended k-${\varepsilon}$ turbulence model and the standard k-${\varepsilon}$ turbulence model are compared. Grid dependency is tested with the H-type grid as well as the O-type grid. Computations have been performed on a circular-to-rectangular transition duct. The Reynolds number is 390,000 based on the bulk velocity at the inlet. The computed axial velocity contours, transverse velocity profiles, static pressure contours, peripheral skin friction coefficient, peripheral wall static pressure distributions and turbulence kinetic energy have been compared with experimental results. The computed results than those obtained with the standard k-${\varepsilon}$ turbulence model. Comparing to the computed results obtained with the H-type grid and O-type grid, those with H-type grid seem to agree well with experimental results.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.11
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• pp.910-917
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• 2003

Fluid flow in a rectangular duct for 90$^{\circ}$ bend elbow with the ratio of 1.5 between its curvature radius and width is measured by 5 W laser doppler velocity meter. The fluid flow is also computed by commercial software of STAR-CD for comparison between measured and computed velocity profiles in the duct. Reynolds numbers for the comparison are 11,643, 19,746 and 24,260. From the comparison, computation of principal velocity components in the duct predicts the experimental data somewhat satisfactorily even though those of minor velocity components and turbulent kinetic energy do not match with the experimental data quite well. K-factor for the bend elbow is computed to be average 0.086 while the equivalent ASHRAE data is 0.07.