• Fire Science and Engineering
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• v.25 no.5
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• pp.14-20
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• 2011

As the height of the building increases, the stack effect in stairwell that is main facilities for evacuation becomes stronger. While the pressure rise in stairwell causes difficulties on opening the door for evacuation and has effect on smoke control system, reduction of stack effect will be necessary for providing more safe evacuation environment. The field experiments on pressure field in high-rise building are carried out to present reduction method of stack effect and the numerical analyses using network model are proceeded to design quantitatively the reduction method. As the air flow supplied from outside in lower stair and exhausted to outside in upper stair is formed in stairwell, the stack effect in stairwell is expected to be decreased.

• Fire Science and Engineering
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• v.22 no.2
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• pp.49-56
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• 2008

Smoke propagation for the Daegu Metro fire is reproduced by a reduced-scale model experiment. The three-story station building was modeled with 1/20-scale, and the tunnel connected to the platform was not completely modeled because of its length. To include the flow resistance the tunnel provides the mesh screens were used in the model. The fire scenario was selected based on the fire growth rate of the metro car seat where the fire initiated. The time when smoke arrived at each compartment in the station building was measured by thermocouples and visualization. Regarding fire ventilation, the air supply that has been accepted as conventional design in a subway metro building intensifies smoke spread. The results show that the whole building was filled with smoke in about 10 minutes in case of no ventilation.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.539-543
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• 2009

When the suction pressure of compressor decreases under its limit, the compression ratio is increased causing the malfunctions of compressor. As the method to decrease the compression ratio, hot gas bypass system is usually adopted in heat pump system. In the hot gas bypass system, the discharged gas from the compressor is bypassed into the compressor suction, which causes the increase of suction pressure and the decrease of compression ratio. In this study, the characteristics and performances of the hot gas bypass system in heat pump was investigated experimentally with a variation of the bypass flow rate ratio. With the increase of the bypass rate ratio, the compressor suction pressure was increased, even though the total capacity and COP was decreased. From the analysis of the experimental results, the optimum pressure control algorithm was suggested in this study.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.967-972
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• 2009

A dynamic model has been developed to investigate the operability of a single and double-effect solar energy assisted parallel type absorption chiller. In the study, main components and fluid transport mechanism were modeled. And solar radiation and the solar collector also were also modeled along with its control design. The model was run for the single mode with solar energy supply only and the solar/gas driving double effect mode. From the simulation results, it was found that the present configuration of the chiller is not capable of regulating solution flow rates according to variable solar energy input. And the issues of the excessive circulation flowrate and the mismatch between available solar power and cooling load discourages the use of the single mode, but the dual use of gas and solar power is recommendable in view of controllability and enhanced COP.

• Journal of KSNVE
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• v.9 no.1
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• pp.184-188
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• 1999

Noise regulation of heavy construction machinery is getting stricter： 3 dB per every 4 year in European community. To meet this requirement many engineers have adopted the enclosing structures with thick absorbing materials and small opening, This increases internal temperature of the enclosure which have engine systems such as electric equipment that are vulnerable to heat, and engine block and muffler that can be regarded as heat sources. So noise control engineers have to consider a coupling problem: combining heat balance and noise reduction. This paper describes this approach by introducing simple heat transfer theory and SEA. The enclosing system of the loader whose enclosing structure consists of two rooms is investigated to show the validity of this method. The results represent that the simple heat transfer theory can be useful to estimate cooling performance when it is linked together by the back pressure theory in duct system. and the radiated noise can also be estimated by the SEA. Therefore a designer can use these approaches to define the opening ratio of an enclosure and the mass flow rate of air considering radiating noise.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.12
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• pp.4036-4043
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• 1996

When a high-speed railway train enters a tunnel, a compression wave is generated ahead of the train and propagates along the tunnel, compressing and accelerating the rest air in front of the wave. At the exit of the tunnel, an impulsive wave is emitted outward toward the surrounding, which causes a positive impulsive noise like a kind of sonic boom produced by a supersonic aircraft. With the advent of high-speed train, such an impulsive noise can be large enough to cause the noise problem, unless some attempts are made to alleviate its pressure levels. In the purpose of the impulsive noise reduction, the present study tested the effect of porous walls on the compression wave propagating into a model tunnel. Experimental results were obtained using a shock tube with an open end. The results showed that the cavity/porous wall is very effective for the compression wave with a large nonlinear effect. The porosity of 30% is most effective for attenuation and pressure gradient reduction of the compression wave front. Also the impulsive noise reduction increases with increasing the length and height of the cavity, compared with the tunnel equivalent diameter.

• Journal of Korean Society for Atmospheric Environment
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• v.24 no.5
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• pp.574-583
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• 2008

The results of HAPs emission data using TRI (Toxic Release Inventory), SODAM (Source Data Management system) were investigated and the emissions of 7 heavy metals from their sources and emission processes were also analyzed. Questionnaire for source data analysis as well as the stack sampling were carried out for 17 factories among 6 selected industrial types. The annual amount of emissions was estimated based on the measured concentration and flow rates. All sources were operated with high efficiency control devices and the concentration levels of all heavy metals were shown to be below 0.1 to of regulation standard. The highest emission source of heavy metals was steel manufacturing industry with the annual emission of 342.9 kg/yr and followed by hazardous waste incinerator, paint manufacturing, nonferrous metal manufacturing, rolling & press goods manufacturing and storage battery manufacturing. In the case of Hg, the emissions were quite significant from electric acros of steel manufacturing industry, although the concentration level was below the emission standard, showing the necessity of specific care for its management.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.356-361
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• 2003

The objective of this study is a qualitative comparison between line-integrated OH chemiluminescence ($OH{\ast}$) image and its Abel inversion image at different phase of the oscillating pressure field. PIV(Particle Image Velocimetry) measurements were conducted under non-reacting conditions to see the global flow structure. Also NOx emission was measured to investigate the effect of fuel-air premixing on combustion instability and emission characteristics. Experiments were carried out in an atmospheric pressure, laboratory-scale dump combustor operating on natural gas. Combustion instabilities in present study exhibited a longitudinal mode with a dominant frequency of ${\sim}341.8$ Hz, which corresponded to a quarter wave mode of combustor. Heat release and pressure waves were in-phase when instability occurred. Results gave an insight about the location where the strong coherence of pressure and heat release existed. Also an additional information on active control to suppress the combustion instabilities was obtained. For lean premixed combustion, strong correlation between $OH{\ast}$ and NOx emissions was expected largely due to the exponential dependence of thermal NOx mechanism on flame temperature.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.7 no.1
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• pp.1-8
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• 2011

Advanced SITs of the evolutionary PWRs have the advantage that they can passively control the ECC water discharge flow rate. Thus, the LPSI pumps can be eliminated from the safety injection system owing to the benefit of the advanced SITs. In the present study, a passive sealing plate was designed in order to overcome the shortcoming of the advanced SITs, i.e., the early nitrogen discharge through the stand pipe. The operating principle of the sealing plate depends only on the natural phenomena of buoyancy and gravity. The performance of the sealing plate was evaluated using the VAPER test facility, equipped with a full-scale SIT. It was verified that the passive sealing plate effectively prevented the air discharge during the entire duration of the ECC water discharge. Also, the major performance parameters of the advanced SIT were not changed with the installation of the sealing plate.

• International Journal of Aerospace System Engineering
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• v.3 no.1
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• pp.25-29
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• 2016

This paper highlights the performance of an impulse turbine which is a part of turbopump in a liquid rocket first stage engine. The turbopump, currently under development at Korea Aerospace Research Institute, has an impulse type turbine with 12 nozzles and a single rotor. The impulse turbine can archive high specific power with the low gas flow rates. The supersonic impulse turbine with a single rotor can make a simple structure. High-pressure gases are converted into the dynamic energy with flows through the 12 nozzles and drive the rotor to make the power for the pumps. The turbine test was performed in the high-pressured turbine test facility with air gas instead of burned gas. A hydraulic dynamometer was used to absorb the power from the turbine and control the rotational speed and torque. The test points were at several pressure ratios with 7 different rotational speeds. Results showed the efficiency was highest at the design pressure ratio. The efficiency was insensitive to the pressure ratio variation than the rotational speed. It was a typical characteristic in an impulse turbine.