• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1346-1351
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• 2004

This study is concerned with the thermal analysis during the cool-down period of 135,000 $m^3$ class GT-96 membrane type LNG carrier under IMO design condition. The cool-down is performed to cool the insulation wall and the natural gas in cargo tank for six hours to avoid the thermal shock at the start of loading of $-163^{\circ}C$ LNG. During the cool-down period, the spraying rate for the NG cooling decreases as the temperature of NG falls clown from $-40^{\circ}C$ to $-130^{\circ}C$ and the spraying rate for the insulation wall cooling increases as the temperature gradient of the insulation wall is large. It was confirmed that there existed the largest temperature decrease at the 1 st barrier and 1st insulation, which are among the insulation wall, especially in the top side of the insulation wall. By the 3-D numerical calculation about the cargo tank and the cofferdam during the cool-down period, the temperature variation in hulls and insulations is precisely predicted.

• Fire Science and Engineering
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• v.25 no.4
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• pp.1-7
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• 2011

Recently the interest in disaster prevention on super tall buildings is increasing. Especially in fire, against increasing of evacuation time due to high-rise, It is being tried to minimize the fire spread in building. Fire compartments using the fire-resistant wall and door, typical method to control the fire spread in buildings, delay the fire spread to other compartments and consequently evacuation time increases. But the existing provisions adjure only 2-hour fire resistance with maximum limit regardless of the super tall buildings, so this is a obstacle for research and development of the fire resistance wall in super tall buildings. In this study, we reviewed the fire resistance ratings of the wall, and presented the development directions for the fire resistance wall in super tall buildings considering fire resistance, construction and application of the wall.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.906-911
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• 2008

Because the perimeter of buildings is strongly influenced by solar and the outdoor air temperature, the area has different environmental properties compared to the interior of a building, as in summer heat gain, and in winter heat loss. In particular, if the external wall is glass, the characteristics of the glass material make it pervious to outside conditions, thereby making big changes to the thermal environment. By combining shading device and the efficient exhaust system, an energy saving can be achieved compared to no air barrier systems. The simplified air barrier system is developed with the idea that energy could be conserved by carefully and effectively blowing out the air caught between the glass surface and the roller blind. The way it is configured is therefore by making the roller blind's air-path, and by placing the air output ducts in the most optimum positions. This simplified air barrier system will give improvement in the thermal environment of the parameter area that is strongly affected by solar and the outdoor condition.

• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.6
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• pp.31-37
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• 2010

In proportion to increasing interest in vehicle safety, many country have regulated vehicle safety and performed NCAP(New Car Assessment Program). However vehicles which had good results in these compliance and NCAP frontal crash test have caused problems such as the fork effect and over-riding in real car-to-car accidents. To complement these issues, new frontal crash test modes using new barrier like FWDB and PDB have been developed by EEVC WG15. In this paper, FWDB frontal crash test was performed and the result was compared with the full frontal crash test using the rigid wall in order to comprehend the characteristic of FWDB. The results of FWDB test were compared with one of USNCAP and KNCAP. Using USNCAP data, vehicle performance like deformation and wall force were studied. A comparative study of dummy injuries was made by using KNCAP result. The results showed that vehicle performance of FWDB test like displacement and effective acceleration was similar in spite of absorbing energy of FWDB due to the greater vehicle deformation of rigid wall test. In FWDB test, driver dummy head bottomed out but most of injuries were superior to the injury of rigid wall test.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.11
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• pp.1390-1397
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• 2004

This study is concerned with the thermal analysis during the cool-down period of 135,000㎥ class GT-96 membrane type LNG carrier under IMO and USCG design condition. During the cool-down period, the spraying rate for the NG cooling decreases as the temperature of NG falls down from -4$0^{\circ}C$ to -l3$0^{\circ}C$, and the spraying rate for the cooling of the insulation wall increases as the temperature gradient of the insulation wall is large. It was confirmed that there existed the largest temperature decrease at the first barrier and the first insulation, which are among the insulation wall, especially in the top side of the insulation wall under IMO and USCG design condition. Also, as the NG temperature distribution is fixed, the outer temperature condition under the design condition has influence on the temperature variation at the insulation. By the 3-D numerical calculation about the cargo tank and the cofferdam during the cool-down period, the temperature variation in hulls and insulations is precisely predicted under IMO and USCG design condition. From the comparison between two conditions; IMO design condition shows more severe temperature gradient than USCG design condition, therefore, it provides the conservative estimation of the BOG.

• The KSFM Journal of Fluid Machinery
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• v.15 no.3
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• pp.46-50
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• 2012

Plasma actuator makes parallel flow on the wall surface by the interaction between plasma and neutral air particles. Dielectric barrier discharge (DBD) plasma actuator is widely studied as one type of plasma actuators, which consists of one electrode exposed to the environmental gas and the other encapsulated by a dielectric material. This paper is experimentally focused on the performance of DBD plasma actuator mounted on a flat plate, which depends on kinds of the electrode materials, their thicknesses and the supplied voltage including its frequency. We measured the velocity magnitudes of the induced flow by a stagnation probe as a performance parameter of the plasma actuators. The velocity profiles of the flow induced by the plasma actuators are similar in all measurement cases. The magnitude of the induced velocity is strongly influenced by the thickness of the electrodes and the frequency of the input voltage. The performance of DBD plasma actuators is related to the electric properties of the electrode materials such as the ionization energy and the electrical resistivity.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.1
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• pp.63-69
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• 2004

It is of great interest to enhance mixing performance in a microchannel in which the flow is usually characterized as a low Reynolds number (Re) so that good mixing is quite difficult to be achieved in this laminar flow regime. In this regard, we present a new chaotic passive micromixer, named Barrier Embedded Micromixer (BEM), of which the mixing mechanism is based on chaotic flows. In BEM, chaotic flow is induced by periodic perturbation of the velocity field due to periodically inserted barriers along the channel wall while a helical type of flow is obtained by slanted grooves on the bottom surface of the channel in the pressure driven flow. To experimentally compare the mixing performance, a T-microchannel and a microchannel with only slanted grooves were also fabricated. All microchannels were made of PDMS (Polydimethylsiloxane) from SU-8 masters that were fabricated by conventional photolithography. Mixing performance was experimentally characterized with respect to an average mixing intensity by means of color change of phenolphthalein as pH indicator. It was found that mixing efficiency decreases as Re increases for all three micromixers. Experimental results obviously indicate that BEM has better mixing performance than the other two. Chaotic mixing mechanism, suggested in this study, can be easily applied to integrated microfluidic systems , such as Micro-Total-Analysis-System, Lab-on-a-chip and so on.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.6 s.237
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• pp.904-912
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• 2005

The flow in a microchannel is usually characterized as a low Reynolds number (Re) so that good mixing is quite difficult to be achieved. In this regard, we developed a novel chaotic micromixer, named Barrier Embedded Kenics Micromixer (BEKM). In the BEKM, the higher level of chaotic mixing can be achieved by combining two general chaotic mixing mechanisms: (i) splitting/reorientation by helical elements inside the microchannel and (ii) stretching/folding via periodically located barriers on the channel wall. The fully three-dimensional geometry of BEKM was realized by a micro-stereolithography technology, in this study, along with a Kenics micromixer and a circular T-pipe. Mixing performances of three micromixers were experimentally characterized in terms of an average mixing color intensity of phenolphthalein. Experimental results show that BEKM has better mixing performance than other two micromixers. Chaotic mixing mechanism, proposed in this study, could be integrated as a mixing component with Micro-Total-Analysis-System, Lab-on-a-chip and so on.

• Journal of Aerospace System Engineering
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• v.11 no.6
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• pp.56-63
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• 2017

Thrust force induced by the dielectric barrier discharge inside of cylinder pipes is measured for various conditions. The input peak-to-peak voltage and frequency are varied from 2 to 9 kVpp and from 5 to 15 kHz, respectively. The height of cylinder is varied from 50 to 100 mm. The results of the measurements show that the magnitude of the generated thrusts increases as the voltage and the frequencies increase. It also shows that the generated thrusts are decreased according to the increase in the height of the cylinder. The cause of the thrust decrease is discussed in terms of energy losses due to the frictions on the wall surface.

• Proceedings of the Korean Geotechical Society Conference
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• 2003.03a
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• pp.821-826
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• 2003

Laboratory experiments were peformed to understand physical properties of soil-cement column under the influence of acidic flow including metal contaminants and its retaining capacity against metal migration. The contaminant used in this study was nitric acid with Cu and Cd. The Permeability of soil-cement column decreased when pH of the column began to drop below 12. Decreases in pH led to significant reduction of compressive strength of clayey soil-cement specimen, while relatively marginal reduction for sandy soil-cement specimen. The metal contaminants did not leachate from soil-cement column until pH of soil-cement dropped below 7∼8 for Cu and 9∼10 for Cd. Metal contaminants were precipitated and trapped inside the soil-cement column at pHs higher than those mentioned as verified with metal analysis and visual inspection. This indicated that soil-cement column not only performs well as a cut-off wall, but also helps alleviating the level of contamination of the surrounding environment.