• Nuclear Engineering and Technology
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• v.53 no.9
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• pp.3003-3011
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• 2021

A FAC (flow-accelerated corrosion) test was performed for a straight pipe composed of the SA335 Gr P22 and SA106 Gr B (SA106-SA335-SA106) types of steel with welds as a function of the flow rate in the range of 7-12 m/s at 150 ℃ and with DO < 5 ppb at pH levels ranging from 7 to 9.5 up to a cumulative test time of 7200 h using the FAC demonstration test facility. Afterward, the experimental pipe was examined destructively to investigate opposite effects as well as entrance effects. In addition, the FAC rate obtained using a pipe specimen with a 50 mm inner diameter was compared with the rate obtained from a rotating cylindrical electrode. The effects of the complicated fluid flows at the elbow and orifice of the pipeline were also evaluated using another test section designed to examine the independent effects of the orifice and the elbow depending on the distance and the combined effects on orifice and elbow. The tests were performed under the following conditions: 130-150 ℃, DO < 5 ppb, pH 7 and a flow rate of 3 m/s. The FAC rate was determined using the thickness change obtained from commercial room-temperature ultrasonic testing (UT).

• Transactions of the Korean hydrogen and new energy society
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• v.31 no.6
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• pp.614-621
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• 2020

Recently, as the fine dust is increased and the emission regulations of diesel engines are strengthened, interest in diesel soot filtration devices is rapidly increased. In particular, there is a demand for technology development for higher efficiency of diesel exhaust gas after-treatment devices. As part of this, many studies conducted to increase the exhaust gas treatment efficiency by improving the flow uniformity of the exhaust gas in the DPF and reducing the pressure drop between the inlet and outlet of disel particle filter (DPF). In this study, computational fluid dynamics (CFD) simulation was performed when exhaust gas flows into the canning reduction device equipped with a 13" asymmetric DPF in order to maintain the flow uniformity in the diesel exhaust system and reduce the pressure. In particular, a study was conducted to find the geometry with the smallest pressure drop and the highest flow uniformity by simulating the DPF I/O ratio, exhaust gas temperature, inlet-outlet pressure and flow uniformity according to the geometry and hole size of distributor.

• Journal of Ocean Engineering and Technology
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• v.10 no.4
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• pp.118-127
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• 1996

Flow patterns of fluid flow in dividing trbe were visualized, and the energy losses due to dividing were measured in laminar dividing flow of the viscoelastic fluid and its solution in tube junctions with dividing angles of $90^{\circ}$, $60^{\circ}$, $65^{\circ}$ and $15^{\circ}$. Two separation zones were observed. swelling of the streamline to the main tube or to lateral tube was observed. The sizes of the separation zones depend on the Reynolds number, the dividing angle and the dividing flow rate. The energy loss coefficients decrease with increasing Reynolds number, but their decreasing rate decreases with increasing Reynolds number as the sizes of the separation zone increase. The effect of dividing angle on the energy loss coefficients and separation is greater for main tube than for the lateral tube.

• Nuclear Engineering and Technology
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• v.36 no.2
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• pp.153-164
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• 2004

A computational fluid dynamics (CFD) analysis has been performed to investigate the turbulent flow and heat transfer in a triangular rod bundle with pitch-to-diameter ratios (P/D) of 1.06 and 1.12. Anisotropic turbulence models predicted the turbulence-driven secondary flow in a triangular subchannel and the distributions of the time mean velocity and temperature, showing a significantly improved agreement with the measurements from the linear standard $k-{\epsilon}$ model. The anisotropic turbulence models predicted the turbulence structure for a rod bundle with a large P/D fairly well, but could not predict the very high turbulent intensity of the azimuthal velocity observed in the narrow flow region (gap) for a rod bundle with a small P/D.

• Journal of the Korean Mathematical Society
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• v.61 no.4
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• pp.743-760
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• 2024

In this paper, we are devoted to study a forth order curve flow for a smooth closed curve in centro-affine geometry. Firstly, a new evolutionary equation about this curve flow is proposed. Then the related geometric quantities and some meaningful conclusions are obtained through the equation. Next, we obtain finite order differential inequalities for energy by applying interpolation inequalities, Cauchy-Schwartz inequalities, etc. After using a completely new symbolic expression, the n-order differential inequality for energy is considered. Finally, by the means of energy estimation, we prove that the forth order curve flow has a smooth solution all the time for any closed smooth initial curve.

• Transactions of the Korean Society of Automotive Engineers
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• v.1 no.1
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• pp.1-13
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• 1993

The three-dimensional numerical analysis for in-cylinder flow of four-valve engine without intake port has been successfully computed. These computations have been performed using technique of the general coordinate transformation based on the finite-volume method and body-fitted non-orthogenal grids using staggered control volume and covariant variable as dependent one. Computations are started at intake valve opening and are carried through top-dead-center of compression. A k-$\varepsilon$model is used to represent turbulent transport of momentum. The principal study is the evolution of interaction between mean flow and turbulence and of the role of swirl and tumble in generating near TDC turbulence. Results for three different inlet flow configuration are presented. From these results, complex flow pattern may be effective for promoting combustion in spark-ignition engines and kinetic energy of mean flow near TDC is well converted into turbulent kinetic energy.

• The KSFM Journal of Fluid Machinery
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• v.10 no.4
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• pp.47-54
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• 2007

Simultaneous 3-D LDV measurements of the in-cylinder flows of three different engine setups were summarized for the quantification of the flow characteristics in each vertical or horizontal plane, and in entire cylinder volume. The ensemble averaged-velocity, tumble and swirl motions, and turbulent kinetic energy during the intake and compression strokes were examined from the measured velocity data (approximately 2,000 points for each engine setup). The better spatial resolution of the 3-D LDV allows measurements of the instantaneous flow structures, yielding more valuable information about the smaller flow structures and the cycle-to-cycle variation of these flow patterns. Tumble and swirl ratios, and turbulent kinetic energy were quantified as planar and volumetric quantities. The measurements and calculation results were animated for the visualization of the flow, and hence ease to analysis.

• New & Renewable Energy
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• v.5 no.1
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• pp.18-25
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• 2009

PEMFC (Proton Exchange Membrane Fuel Cell) is a low temperature fuel cells which are high efficient and clean energy. But it has many problems like economical efficiency or durability. Because of this reason, many researchers challenge various view points. One of challenge is the flow channel design and many researchers develop new flow channel design. In addition to most of them have the anode and cathode's flow channel overlapped almost perfectly. In this case, the electrochemical reaction is almost done by the inertial force of flow. So we study on the effect of the anode and cathode's flow channel which aren't overlapped perfectly, have more diffusion effect, to PEMFC performance using CFD.

• Proceedings of the Korea Water Resources Association Conference
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• 2004.05b
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• pp.54-61
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• 2004

This paper deals with flow characteristics on the air entrainment and the energy dissipation in nappe flow over the stepped drop structure. Nappe flow occurred at low flow rates and for relatively large step height Dominant flow features include an air pocket, a free-falling nappe impact and a subsequent hydraulic jump on the downstream step. Air entrainment occurred from the step edge, through a free-falling nappe impact and a hydraulic jump. Most energy was dissipated by nappe impact and in the downstream hydraulic jump. It was related with the step height and the overflow depth, but not related with step slope. The stepped drop structure was found to be effcient for water treatment and energy dissipation associated with substantial air entrainment.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.9
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• pp.727-732
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• 2003

In the present study, a PIV measurement and image processing technique were applied in order to investigate the flow characteristics in the gas injected liquid bath. The circulation of liquid was induced by upward bubble flow. Due to the centrifugal force, the flow was well developed near both wall sides than in the center of a bath. The vortex flow irregularly repeated generation and disappearance which helped to accelerate the mixing process. The bubble rise velocity in the bottom region was relatively lower than in the upper region because the energy generated by bubbles' behavior in the region near the nozzle was almost converted into kinetic energy But bubble rise velocity increases with the increase of the axial distance since kinetic energy of rising bubbles is added to buoyancy force. In conclusion, the flow increased bubble rise velocity and the flow of the bottom region became more active.