• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.5
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• pp.1220-1226
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• 2007

As the industry of 21C has been developed, the gas industry has grown and it has not only the convenience but also the riskiness fer using. Especially, the energy and environment problems have been getting serious after the modern industry revolution. Therefore, the demand of gas as an eco-friendly energy source is getting increased. With the demand of gas, the installation and use of gas boiler is also increased, so human life injury by the waste gas(CO) of boiler goes on increasing every year. Therefore, we want to find out the harm to human body through the study on the concentration of CO by the length of the curved exhaust tube of boiler. The allowable concentration of CO is 50ppm. The length of the one-meter-three-curved tube after three minutes is applicable to 50ppm of the threshold limit values of CO. Also, five meters exceed the threshold limit values of CO after five minutes. Strangely, the concentration of CO is under the threshold limit values from two to four meters.

• Korean Journal of Bronchoesophagology
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• v.16 no.2
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• pp.131-137
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• 2010

Background: Montgomery T-tube is widely used to maintain airway in many cases. Market-available tubes are not always fit to the trachea of each patient and need some modification such as trimming. Complications do happen in prolonged use like tracheostomy tubes. To overcome above limitations, we designed custom-made T-tube using CT data with the aid of 3D reconstruction software. Material and Method: Boundaries were extracted from neck CT data of normal person and processed by surface rendering methods. Real laryngotracheal model and tracheal inner surface-mimicking tube model were made with plaster and rubber. The main tube was designed by accumulation of circles or simple closed curves made from boundaries. Stomal tube was made by accumulation of squares due to limitation of software. Measurement data of tracheal lumen were used to custom-made T-tubes. Tracheal lumen residing portion (vertical limb) was made like circular cylinder or simple closed curved cylinder. Stomal portion (horizontal limb) was designed like square cylinder. Results: Custom made T-tube with cylindric vertical limb and horizontal limb of square cylinder was designed. Conclusion: CT data was helpful in making custom made T-tube with 3D reconstruction technique. If suitable materials are available, commercial T-tube can be printed out from 3D printers.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.1
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• pp.218-228
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• 1991

Since heat exchangers are composed of bank of tubes, the knowledge on the flow and heat transfer characteristics of the tube bank are required for the optimum design and selection of heat exchangers. In this paper, the turbulent flow fields and heat transfers normal to a staggered tube bank are solved numerically employing K-.epsilon. 2 equation turbulence model and non-orthogonal coordinate transformation for the treatment of curved surface of tubes. Predicted mean Nusselt numbers of tube bank agree reasonably well with Grimision's correlation

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.9 no.3
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• pp.160-168
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• 2000

Hydroforming is a metal forming process that enables circular metal tubes to be formed in to the parts with the complex cross section along the curved axial direction. Recently this hydroforming process is largely used for the production of the automotive parts. This paper presents the results of tube bending and hydroforming simulations in cases of the varying weld line positions of the tube. Ten cases of prebending and hydroforming simulations are carried out to find the optiaml weld line position.

• 한국전산유체공학회:학술대회논문집
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• 2009.04a
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• pp.97-103
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• 2009

A numerical study of the flow characteristics inside a U-type circular tube is carried out in this paper. The numerical simulations carried out by using a Navier-Stokes code which is commercially available. Before detailed numerical simulations, validation of present numerical approach is made by comparing numerical solutions with experimental data. Numerical simulations are performed to study the effect of curvature on the flow characteristics inside a U-type tube. Numerical solutions show that a significant effect on the secondary flow structure in the cross section of the tube, especially in the curved section is shown when the curvature ratio, ratio of curvature to tube diameter, is smaller than about 3.5. As the curvature ratio decreases below 3.5, a counter rotating vortex is found below the primary vortex in the cross section of the tube. Another dramatic change of the flow structure is the formation of streamwise separation zone when the curvature ratio is decreased below 1.25.

• Journal of computational fluids engineering
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• v.14 no.3
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• pp.105-114
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• 2009

A numerical study of the flow characteristics inside a U-type circular tube is carried out in this paper. The numerical simulations carried out by using a Navier-Stokes code which is commercially available. Before detailed numerical simulations, validation of present numerical approach is made by comparing numerical solutions with experimental data. Numerical simulations are performed to study the effect of curvature on the flow characteristics inside a U-type tube. Numerical solutions show that a significant effect on the secondary flow structure in the cross section of the tube, especially in the curved section is shown when the curvature ratio, ratio of curvature to tube diameter, is smaller than about 3.5. As the curvature ratio decreases below 3.5, a counter rotating vortex is found below the primary vortex in the cross section of the tube. Another dramatic change of the flow structure is the formation of streamwise separation zone when the curvature ratio is decreased below 1.25.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.1
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• pp.262-273
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• 1991

In the present study, the steady, incompressible, isothermal, developing flow in a 90.deg. rectangular cross sectional strongly curved duct with aspect ratio 1:1.5 and Reynolds number of 9.4*10$^{4}$ has been investigated. Measurements of components of mean velocities, pressures, and corresponding components of the Reynolds stress tensor are obtained with a hot-wire anemometer and pitot tube. In general, flow in a curved duct is characterized by the secondary vortices which are driven mainly by centrifugal force-radial pressure gradient imbalance, and the stress field stabilizing effects near the convex wall and destablizing effects close to the concave wall. It was found that the secondary mean velocities attain values up to 39% of the bulk velocity and are largely responsible for the convections of Reynolds stress in the cross stream plane. Therefor upstream of the bend the Reynolds stress are low. Corresponding to the small boundary layer thickness. At successive planes, large values of Reynolds stress were observed near the concave surface and the side wall.

• Proceedings of the Korean Nuclear Society Conference
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• 2005.05a
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• pp.519-520
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• 2005

• The Journal of the Acoustical Society of Korea
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• v.23 no.5
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• pp.353-361
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• 2004

Propagation of the guided waves in a steam generator (SG) tube was investigated. Dispersion curves and the incident angles corresponding to the specific modes were calculated for the SG tube. The modes of guided wave were identified by time-frequency diagrams obtained by short time Fourier transform. Group velocities were also determined from the time-frequency diagrams obtained at the different separations of transducers. In experiment. distinct mode conversion was not observed when the guided ultrasound passed curved region of the S/G tube. The optimum mode of guided wave for the inspection of SG tube was suggested and verified by experiments.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.1 no.4
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• pp.265-275
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• 1989

An experimental study of decaying swirl air flow has been obtained by tangential inlet in a straight tube with Reynolds number range 20,000~40,000. The friction factor, swirl angle, velocity profiles and turbulent intensity are measured by using micro-manometer and hot-wire anemometer. It is found that the swirl flow behaviors depend on the swirl intensity along the test tube.