• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.613-617
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• 2001

The test items like as endurance, air leakage and oil endurance test is requested for reliability evaluation about O-ring which is a kind of core machinery accessories of semi-conduct manufacturing equipment. For verification of these, we design and manufactured a test system for endurance, air leakage and oil endurance of O-ring for semi-conduct manufacturing equipment, and also performed the test for two kinds of O-ring, as it were Viton and Kalretz. The characteristics of this test equipment consist in realization of the test conditions of semi-conduct manufacturing equipment and satisfying the test method. The test conditions are cut gas, vacuum grade, temperature and revolution numbers in the endurance test system, vacuum grade and temperature in the air leakage test system, temperature and time in the oil endurance test system. The separating test results for wearing which is an oil endurance test item, the wearing index of domestic produced Viton O-ring is higher than foreign product by 2%, wearing rate of Kalretz O-ring better than Viton O-ring by 17%, and particles existed in various place. The test result of air leakage which is measured through the RGA sensor used Helium, the vacuum grade was $10^-3$Torr. And the test result of oil endurance, the volume change rate was 7~15%. Hereafter, we intend to analysis the reliability test evaluation and to utilize for domestic manufacturing companies by establishing data base and developing reliability softwares.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.503-506
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• 2001

This paper presents leakage magnetic field and leakage inductance calculations in current transformer by means of 3-D Integral methods. From the distribution diagram of leakage magnetic flux to be analyzed using program called TRACAL3, it confirms a parallel to the winding axis direction of the leakage flux lines in the air gap between the windings. The leakage inductances L$\sub$r1/ and L$\sub$R2/ of the primary and secondary windings were calculated, their values are 4.23 mH and 0.49 mH, respectively. They are also similar to the measured values of the leakage inductances for the experimental verification, 4.06 mH and 0.47 mH.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.6
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• pp.497-504
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• 2001

A study to improve the accuracy of a map-based compressor model with experiment was performed. Corrections on the effects of suction gas superheat and heat leakage from a compressor shell are required to apply the compressor amp model based on the empirical performance data(map) of compressor manufacturers to the actual system. So experiments to assess the effects of superheat and hat leakage were performed and the corrected equations were made. Compressors and refrigerant used in the experiment were the high pressure type rotary compressor and R-22, experiments were performed by compressor calorimeter. From the experiment, a volumetric efficiency correction factor$(F_ν)$ showed the value of 0.77, slightly higher than 0.75 proposed by Dabiri and Rice for low pressure type reciprocating compressor, and the heat leakage from the compressor shell turned out to be a factor that influenced the discharged mass flow rate. The relation between heat leakage of compressor shell and the variation of discharged mass flow rate from compressor was considered in compressor map modeling as an empirical function. With this function, the prediction accuracy of compressor model in system conditions was improved.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.50 no.8
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• pp.365-370
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• 2001

We have proposed and fabricated a new poly-Si TFT employing air-cavities at the edges of gate oxide in order to reduce the vertical electric field induced near the drain due to low dielectric constant of air. Air-cavity has been successfully fabricated by employing the wet etching of gate oxide and APCVD (Atmospheric pressure chemical vapor deposition) oxide deposition. Our experimental results show that the leakage current of the proposed TFT is considerably reduced by the factor of 10 and threshold voltage shift under high gate bias is also reduced because the carrier injection into gate insulator over the drain depletion region is suppressed.

• Tunnel and Underground Space
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• v.28 no.4
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• pp.372-386
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• 2018

The air quality near the backfilled site area is significantly deteriorated during and even after the curing period of the backfill materials. Hazardous gases such as NH3 and CO2 may leak out prolongedly from the mined-out sites backfilled with the composite carbonate-based material; leakage can be observed at the underground working sites as well as on the surface. At operating mines, underground gas leakage will severely aggravate the workplace environment. The ventilation schemes should supply sufficient air to dilute the contaminated air, and control the toxic gas leakage and dispersion. This study shows the applicability of pressurization ventilation system to control gas leakage and dispersion at the backfilled underground mine site.

• Transactions of the Korean hydrogen and new energy society
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• v.23 no.6
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• pp.588-597
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• 2012

In the present study, the dispersion characteristics of hydrogen leakage from a Fuel Cell Vehicle (FCV) were analyzed by numerical simulation in order to assess the risk of a hydrogen leakage incident in a long road tunnel. In order to implement the worst case of hydrogen leakage, the FCV was located at the center of a tunnel, and hydrogen was completely discharged within 63 seconds. The Leakage velocity of hydrogen was adopted sub-sonic speed because that the assumption of the blockage effect of secondary device inside a vehicle. The temporal and spatial evaluation of the hydrogen concentration as well as the flammable region in a road tunnel was reported according to change of ventilation operating conditions. The hydrogen was blended by supply air form a ventilation fan, however, the hydrogen was discharged to outside in the exhaust air. It is observed that the efficiency way to eliminate of hydrogen is supply air operating condition under the hazardous hydrogen leaking incident. The present numerical analysis can be provided useful information of ventilation under the hydrogen leaking situation.

• Cement
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• s.47
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• pp.69-73
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• 1972

본 시험은 현장에서 실시 가능한 간이식 측정 방법에 의하여 실시되었으며 pipe line의 점검, 보수 등의 불철저로 인한 air leakage량은 전체 압기 토출량의 12.42$\%$에 달하고 있다.

• Journal of Climate Change Research
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• v.3 no.2
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• pp.153-159
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• 2012

CFC-12 used in mobile air conditioning(MAC) system has been replaced by R-134a, a type of HFC refrigerant, from 1991 to 1994. R-134a has since been widely used as a refrigerant of a mobile air conditioner. However, it is one of the six main green house gases listed in Kyoto Protocol, which makes it imperative to regulate its emission and develop alternative refrigerants. In this study, the concentration of leaked R-134a was measured using VT(Variable Temperature) shed and Running loss test shed to analyze the level of air conditioner refrigerant leaked in a vehicle. According to the analysis of the concentration of R-134a leaked from a vehicle parked, annual leakage amount of R-134a was in the range of 6.46~13.28 g/yr. The figure was similar with the leakage from the mobile air conditioning system currently used. In a study using the same vehicle model, a vehicle equipped with dual evaporation system had a higher leakage rate of refrigerant than a vehicle with a single evaporation system. It appears that the added fittings and joints of the dual evaporator system led to higher leakage rate. Besides, the analysis of the change in R-134a concentration under various car speed found that more refrigerant leaked under high speed(100km/hr) and but the volume of the wind did not affect to the variation of refrigerant leakage.

• Journal of Korean Tunnelling and Underground Space Association
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• v.24 no.4
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• pp.305-316
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• 2022

Hydrogen energy is emerging as an alternative to the depletion of fossil fuels and environmental problems, and the use of hydrogen vehicles is increasing in the automobile industry as well. However, since hydrogen has a wide flammability limit of 4 to 75%, there is a high concern about safety in case of a hydrogen car accident. In particular, in semi-enclosed spaces such as tunnels and underground parking lots, a fire or explosion accompanied by hydrogen leakage is highly likely to cause a major accident. Therefore, it is necessary to review hydrogen safety through analysis of flammability areas caused by hydrogen leakage. Therefore, in this study, the effect of the air velocity in the tunnel on the flammability area was investigated by analyzing the hydrogen concentration according to the hydrogen leakage conditions of hydrogen vehicles and the air velocity in the tunnel in a road tunnel with standard section. Hydrogen leakage conditions were set as one tank leaking and three tanks leaking through the TPRD at the same time and a condition in which a large crack occurred and leaked. And the air velocity in the tunnel were considered 0, 1, 2.5, and 4.0 m/s. As a result of the analysis of the flammability area, it is shown that when the air velocity of 1 m/s or more exists, it is reduced by up to 25% compared to the case of air velocity of 0 m/s. But there is little effect of reducing the flammability area according to the increase of the wind speed. In particular, when a large crack occurs and completely leaks in about 2.5 seconds, the flammability area slightly increases as the air velocity increases. It was found that in the case of downward ejection, hydrogen gas remains under the vehicle for a considerably long time.

• Journal of the Korean Institute of Gas
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• v.26 no.4
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• pp.27-35
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• 2022

When LPG leaks from the storage tank, the gas try to sink to the ground because LPG is heavier than air. The gas easily creates vapor clouds causing aggressive accidents in no airflow. Therefore, It is important to prevent in advance by analyzing the damaged range caused from LPG leakage and vapor clouds. So, this study analyzed the range of damaged by LPG leakage and vapor clouds with consideration of the cold air flow which is generated by the topographical characteristics and the land use status at night time in the Jeju Hagari. As a result of the cold air flow using KLAM_21, about 2 m/s of cold air was introduced in from the southeast due to the influence of the terrain. The range of damaged by LPG leakage and vapor cloud was analyzed using ALOHA. When the leak hole size is 10 cm at the wind speed of 2 m/s, the range corresponding to LEL 60 % (12,600 ppm) was 61 m which range is expected to influence in nearby residential areas. These results of this study can be used as basic data to prepare preventive measures of accidents caused by vapor cloud. Forward, it is necessary to apply CFD modeling such as FLACS to check the vapor cloud formation due to LPG leakage in a relatively narrow area and to check the cause analysis.