• Journal of the Korean Institute of Gas
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• v.9 no.3 s.28
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• pp.1-8
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• 2005

We studied on the nondestructive evaluation of the elastic wave signals of locally wall thinned straight pipe. Wavelet transform was applied for the time-frequency analysis of waveforms obtained by fracture wave detector due to the dropping steel ball. The time-frequency analysis provides time variation of each frequency component involved in a waveform, which makes it possible to evaluate the shape of local wall thinning at each frequency. In this study, comparison by wavelet transform of the AE signals and monotonic bending tests without internal pressure are conducted on 1.91 inch diameter full-scale carbon steel pipe specimens. As the results of tests, fracture behaviors could be shown by the characteristic of mechanical strength of locally wall thinned pipes and the waveforms could be evaluated for the integrity insurance of the piping system according to the length and depth range of the deffeted shape pipes in the real field.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.8
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• pp.511-517
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• 2016

Three-dimensional models of stenosis blood vessels were prepared using a 3D printer. The models included a straight pipe with axisymmetric stenosis and a pipe that was bent $10^{\circ}$ from the center of stenosis. A refractive index matching method was utilized to measure accurate velocity fields inside the 3D tubes. Three different pulsatile flows were generated and controlled by changing the rotational speed frequency of the peristaltic pump. Unsteady velocity fields were measured by a time-resolved particle image velocimetry method. Periodic shedding of vortices occurred and moves depended on the maximum velocity region. The sizes and the positions of the vortices and symmetry are influenced by mean Reynolds number and tube geometry. In the case of the bent pipe, a recirculation zone observed at the post-stenosis could explain the possibility of blood clot formation and blood clot adhesion in view of hemodynamics.

• Journal of Korean Society of Water and Wastewater
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• v.30 no.3
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• pp.253-261
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• 2016

A variety of methods for detecting the location of an underground water pipeline are being used across the world; the current main methods used in South Korea, however, have the problems of low precision and efficiency and the limitations in actual application. On this, this study developed locator capable of detecting the location of a water pipe by the use of an IMU sensor, and technology for using the extended karman filter to correct error in location detection and to plot the location on the coordinate system. This study carried out a tract test and a road test as basic experiments to measure the performance of the developed technology and equipment. As a result of the straight line, circular and ellipse track tests, the 1750 IMU sensor showed the average error of 0.08-0.11%; and thus it was found that the developed locator can detect a location precisely. As a result of the 859.6-m road test, it was found that the error was 0.31 m in case the moving rate of the sensor was 0.3-0.6 m/s; and thus it was judged that the equipment developed by this study can be applied to long-distance water pipes of over 1 km sufficiently. It is planned to evaluate its field applicability in the future through an actual pipe network pilot test, and it is expected that locator capable of detecting the location of a water pipe more precisely will be developed through research for the enhancement of accuracy in the algorithm of location detection.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.1623-1628
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• 2004

Recently mini-channels or micro-channels are widely used for cooling the high density power electronic devices. Especially, the channels are used in small and high efficient equipments such as heat pipes and heat exchangers. Interfacial velocities between liquid and gas phases are very important in mini or micro-channels. In this paper, an experiment and a numerical analysis on the interfacial velocities were performed. In the experiment, the interfacial velocities which were measured by the high-speed CCD camera were about $26{\sim}33$ cm/s and the velocities increased as the inclination angle did. In the numerical experiment, CFD-ACE+, a commercial program, was used, the velocities had similar values with experimental results. As the inclination angle and the contact angle increased, the interfacial velocities did because of the surface tension which causes to move the interface. The effect of inclination angle was larger in the converging channels than in straight channels.

• The KSFM Journal of Fluid Machinery
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• v.6 no.4 s.21
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• pp.29-37
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• 2003

This study was undertaken to verify the effect of flow coefficient when a globe control valve was attached by different type of fitting. The valve flow coefficient is usually determined by measuring the flow rate and the pressure drop with the connection of straight pipe through the valve. The effect of different fitting that is mounted on the downstream of the valve is studied. Four types of fittings and three distances between the valve and a downstream fitting are compared parametrically to investigate the effect on the flow coefficient of it. Measured flow coefficient and numerically predicted value by using computational fluid dynamics were compared in detail. It is concluded that the flow coefficient is reduced if the fitting is attached after a valve, but the effect of different type of fitting is not crucial.

• 유체기계공업학회:학술대회논문집
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• 2000.12a
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• pp.65-74
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• 2000

A five path ultrasonic and/or magnetic flowmeter were installed after valve. Five path ultrasonic flowmeter were tested to obtain it's performance in a water flow standard system and magnetic flowmeter. It's varied with straight pipe length(nD), install direction and valve position. All the results are summerized. The multi-path flowmeters(MUF) showed up to $\pm0.5{\%}$ at a 2, 4, 8, 15D spacing : the MUF was significantly better than magnetic flowmeter at disturbed flow conditions.

• Journal of Advanced Marine Engineering and Technology
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• v.27 no.2
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• pp.299-304
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• 2003

Static mixer consists of a straight pipe of circular cross section into which individual elements are inserted to cut, fold, twist and re-combine the mixing fluid. The number of elements and their shape required in any application depend on the complexity of the mixing process. The objectives of this study are to develop a new static mixer and to perform the experimental investigation of pressure drop in order to evaluate the performance of the new one. The mixing fluid used is Glycerin. The pressure drop is measured using a hydraulic manometer and the correlation of Z-factor is suggested as a function of Re. The Z-factors of SSC and YNU mixer are about 40% lower than and 4% higher than that of the Sulzer one.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1955-1960
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• 2003

Static mixers have found a large range of applications, including blending, reaction, dispersion, heat transfer and mass transfer. All static mixers have in common a straight pipe or transfer tube into which individual elements are inserted to cut, fold, twist and re-combine the mixing fluid. The operations virtually ensure uniformity in composition, concentration, viscosity and temperature. The objective of this study is to perform the experimental investigations of mixing characteristics for three mixing element types. The resulting mixing patterns were recorded with a digital camera. OPTIMAS was used to analysis the visualized images. The results clearly indicated that the mixing characteristics was highly influenced by the mixer types or mixing mode.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.8
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• pp.726-732
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• 2011

Straight absorptive silencers have been designed to reduce the noise level of a centrifugal blower. Three-dimensional boundary element method is used for the design of absorptive silencers which consist of a perforated main pipe and a outer chamber filled with fibrous material. The experimental results show that the absorptive silencer reduces up to 8 dB(A) in the overall sound pressure level of the blower and up to 15 dB at the blade passing frequency. It is also found that the gap between the silencer and the impeller may substantially alter the acoustic performance of the silencers. The transmission loss predicted by the boundary element method follows overall trends of the measured insertion loss. The experiments also show that the impact of the silencers on the aerodynamic performance of the blower is minimum.

• Journal of Mechanical Science and Technology
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• v.18 no.3
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• pp.526-532
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• 2004

A motionless mixer consists of a straight pipe or transfer tube containing the mixing elements that are used to cut, fold, twist, and re-combine the mixing fluid. The number of elements and their shape required in any application depend on the complexity of the mixing process. The objectives of this study are to develop new motionless mixers and to perform the experimental investigation of pressure drop in order to evaluate the performance of the new ones. Glycerin is used as a mixing fluid. Pressure drop is measured using a hydraulic manometer and correlations of friction factor are proposed as a function of Re. The friction factors of Sulzer SMX mixer are in qualitative good agreement with the published data. On the average, the friction factors of SSC and YNU mixers are about 36% lower than and 6% higher than that of the Sulzer one.