• Title/Summary/Keyword: Overheating factor

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In-situ Particle Characterization of Cu Nanopowder using Scanning Mobility Particle Sizer in Pulsed Wire Evaporation Method (전기폭발법에서 SMPS를 이용한 Cu 나노분말의 실시간 입자특성평가)

  • 이창우;맹덕영;박중학;유지훈;이재훈;이창규;김흥회
    • Journal of Powder Materials
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    • v.10 no.4
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    • pp.275-280
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    • 2003
  • Synthesis and characteristics of Cu nanopowder were considered by in-situ characterization method using SMPS in pulsed wire evaporation process. With increasing pressure in chamber, particle size and degree of agglomeration increased by increase of collision frequency. Also, it was found from the XRD analyses and BET measurements that crystallite size and particle size decreased with elevating applied voltage. However, SMPS measurements and TEM observation revealed the increase of particle size and degree of agglomeration with increase of applied voltage. These results suggested that particle growth and agglomeration depend on overheating factor in chamber at the early stage and thermal coagulation in filtering system during powder formation until collection.

Analysis of Volatage and Current Waveform Distortion Characteristics at Office Buildings (사무용 빌딩에서의 전압 및 전류파형 왜곡특성 분석)

  • Yoo, Jae-Geun;Lee, Sang-lck;Jeon, Jeong-Chay;Jeong, Jong-Wook;Lim, Young-Bae
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.19 no.1
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    • pp.155-161
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    • 2005
  • Nonlinear electronic loads used at office buildings distort the voltage and current waveform that cause the overheating of transformer losses, ELB(Electrical Leakage Breaker) tripping, and so on. This paper analyzed waveform distortion characteristics at several once buildings by comparing with magnitude of voltage and current harmonics, crest factor of voltage and current, phase voltage and current unbalance. As a consequence, severe current waveform distortion in phase and neutral line by harmonics and high current unbalance rates by unbalanced using of single loads among the three phases are investigated. The results of the study can be used in making decisions regarding reasonable and economical operating of loads at office buildings.

The expectation effects of a decrease in neutral wires Zero Sequence harmonic currents in 3 phases - 4 wires systems (3상4선식 계통에서 중성선 영상고조파 저감에 따른 기대효과)

  • Kang, Chang-Won;Lee, Sung-Woo;Jung, Yeun-Hea;Kim, Se-Dong;Lee, Won-Goo
    • Proceedings of the KIEE Conference
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    • 2002.07b
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    • pp.715-719
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    • 2002
  • Recently, Dangers due to harmonics emanated from all sorts of machinery have been on the increase with the development in industry. One of them is that Zero Sequence harmonic currents flow from the neutral wires in 3 phases - 4 wire systems. The flowing of harmonic currents in neutral wires brings about the superheating and falloff in output of transformer, the overheating of them, a rise in ground potential and the wrong movement of machinery, so has a bad influence on this system. To develop the machinery to decrease neutral wires Zero sequence harmonic currents and apply it help solve these problems and bring about the effects of a improvement in power factor and energy savings.

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Development of a Novel Passive Harmonic Filter (신개념 수동형 고조파 필터 개발과 성능에 관한 평가)

  • Park, Byoung-Ju;Lee, Han-Sang;Jang, Gil-Soo
    • The Transactions of the Korean Institute of Electrical Engineers A
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    • v.55 no.1
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    • pp.29-36
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    • 2006
  • The interest for harmonic problems has been increasing due to the increment of nonlinear loads. The loads such as DC power system, personal computers, UPS system, inverters and converters operate as harmonic current sources. In this paper, a new type of the passive filter, Hybrid Harmonic Filter (HHF) is suggested to mitigate harmonic problems in power systems. The HHF is developed for reducing harmonic current, especially on the system that includes 6-pulse bridge rectifiers. Also, it is expected to prevent the overheating of transformers and feeders due to overcurrent and to correct the power factor.

A Study on the Safety of Small LPG Storage Tanks at External Fires (외부화재시 LPG 소형저장탱크의 안전성에 관한 연구)

  • Yim, Ji-Pyo;Ma, Byung-Chol;Chung, Chang-Bock
    • Journal of the Korean Society of Safety
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    • v.30 no.4
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    • pp.64-72
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    • 2015
  • The purpose of this study is to study the safety of a small LPG storage tank with a capacity less than 3 ton when it is exposed to an external fire. First, simulation studies were carried out using ASPEN Plus and PHAST to demonstrate that overpressurization in the tank can be relieved by discharging the LPG through an adequately sized safety valve, but the release may lead to the secondary risk of fire and explosion around the tank. Next, the temporal variations of the temperatures of the lading and tank wall were obtained using AFFTAC, which showed that the tank wall adjacent to the vapor space could be overheated in about 11 min to such a point that the weakened strength might cause a rupture of the tank and subsequent BLEVE. The consequences of the BLEVE were estimated using PHAST. Finally, several practical measures for preventing the hazards of overheating were suggested, including an anti-explosion device, sprinkling system, insulation, heat-proof coating, and enhanced safety factor for tank fabrication. The effectiveness of these measures were examined by simulations using AFFTAC and ASPEN Plus.

Cu-Ni-P Alloy Nano Powders Prepared by Electrical Wire Explosion (전기선폭발법에 의한 Cu-Ni-P 합금 나노 분말 제조)

  • Kim, Won-Baek;Park, Je-Shin;Suh, Chang-Youl;Lee, Jae-Chun;Kim, Jung-Hwan;Oh, Yong-Jun
    • Journal of Powder Materials
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    • v.14 no.2 s.61
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    • pp.108-115
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    • 2007
  • Cu-Ni-P alloy nano powders were fabricated by the electrical explosion of electroless Ni plated Cu wires. The effect of applied voltage on the explosion was examined by applying pulse voltage of 6 and 28 kV, The estimated overheating factor, K, were 1.3 for 6 kV and 2.2 for 28 kV. The powders produced with pulse voltage of 6 kV were composed of Cu-rich solid solution, Ni-rich solid solution, and $Ni_3P$ phase. While, those produced with 28 kV were complete Cu-Ni-P solid solution and small amount of $Ni_3P$ phase. The initial P content of 6.5 at.% was reduced to 2-3 at.% during explosion due to its high vapour pressure.

Evaluation of Indoor Thermal Environment according to Type and Color of Blinds Installed in the Classroom (교실에 설치된 블라인드의 유형과 색상에 따른 실내 온열환경 평가)

  • Kwon, Daehyeok;Lee, Jae-Ro;Oh, Juseok;Wi, Seunghwan;Kim, Sumin
    • Journal of the Korea Furniture Society
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    • v.28 no.3
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    • pp.224-232
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    • 2017
  • Building energy saving have been put effort in a long time since buildings consume about 40.6% of total energy use, where heating, cooling and electrical lighting requirement results in energy consumption of building significantly. The window is an important part of building envelope, it usually brings a certain heat load from solar radiation while it allows light passing through, and properly leads to overheating in summer, hence the cooling load increase sand cause of thermal uncomfortable factor. The purpose of this study was to evaluate internal shade performance according to color and materials. There is growing interest in improving the sense of comfort among students who spend most of their time in the classroom. The study examined thermal environment and light environmental performance according to the color and materials of internal blinds to the school classroom. The results of this study were as follows; Among wooden blinds, aluminium blinds, and polyester blinds, the aluminium blinds were most excellent. In addition, among white blinds, light brown blinds, dark brown blinds, the light brown were most excellent.

Safely Improving Method to Zero-Harmonics Current with 4-Pole Low Voltage Circuit Breaker Equipped N-phase Trip Device (4극 저압차단기 N상 Trip장치를 사용한 영상고조파 안전성 개선방안)

  • Ki, Che-Ouk;Kim, Ju-Chul;Choi, Chang-Kyu
    • Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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    • 2009.05a
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    • pp.458-461
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    • 2009
  • In 3-phase 4 wire system, appearance of the $3^{rd}$ harmonic current by increasing non-liner load is the one of causes overheating neutral wire of power line, and apparatus. So it is necessary to protect power-factor decreasing by the $3^{rd}$ harmonic, and electric power apparatus, and line safely, in this study, power system accidents caused by the $3^{rd}$ harmonic were investigated, then harmonic components analysis and unbalanced load analysis got accomplished. As result, we proposed the method to protect the power line and apparatus from over-current of neutral line by using the most economic 4-pole low voltage circuit breaker.

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An analysis of the Liquefied Petroleum Gas Usage and Risk Factor in the Camp Site (야영장 내 액화석유가스 사용실태 및 위험요소 분석)

  • Lee, Duk-Gwon;Lee, Seung-Kuk;Lee, Yeon-Jae;Kim, Hie-Sik
    • Journal of the Korean Institute of Gas
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    • v.20 no.6
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    • pp.89-94
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    • 2016
  • The number of camping population and sites are rapidly increasing with to the expansion of camping culture and the advancement of leisure culture. It is necessary to develop an effective strategy of safety management, as a lot of accidents occur due to the increase of population and sites for camping. Particular attention needs to be paid for accident prevention in the increasing accidents of explosion awing to the overheating of bytane gas, and carbon monoxide poisoning due to the use of non-ventilated areas. In this study, the direction of safety management strategy is analyzed by a survey and analysis of risk factors in campsite about gas facilities and gas appliances in camp site. Accordingly, some directions are suggested. Conclusively, it is expected that the results of this study could help to improve efficiency management for camping.

A study on thermal fluid analysis in X-ray tube for non-fire alarm (비화재보를 위한 X-ray tube 내 열 유동해석에 관한 연구)

  • Yun, Dong-Min;Jeon, Yong-Han
    • Design & Manufacturing
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    • v.16 no.2
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    • pp.33-38
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    • 2022
  • Currently, Korea is an aging society, and it is expected to enter a super-aging society in about 4 years. Accordingly, many X-ray technologies are being developed. In X-rays, 99% of X-rays are converted into heat energy and 1% into light energy (X-rays). 99% of the thermal energy raises the temperature of the anode and its surroundings, and the cooling system is an important factor as overheating can affect the deterioration of X-ray quality and shortened lifespan. There is a method of forced air cooling using natural convection. Therefore, in this study, when X-rays were taken 5 times, Flow analysis was performed on heat removal according to temperature rise and cooling time for the heat generated at the anode of the X-ray tube (input power 60kW, 75kW, 90kW). Based on one-shot, the most rapid temperature rise section increased by more than 57% to 0.03 seconds, A constant temperature rises from 0.03 seconds to 0.1 seconds, It is judged that the temperature rises by about 8.2% or more at one time. After one-shot cooling, the cooling drops sharply from about 60% to 0.03 seconds, It is judged that the temperature has cooled by more than 86% compared to the temperature before shooting. One-shot is cooled by more than 86% with cooling time after 0.1 seconds, As the input power of the anode increases, the cooling temperature gradually increases. Since the tungsten of the anode target inside the X-ray tube may be damaged by thermal shock caused by a rapid temperature rise, an improvement method for removing thermal energy is required when using a high-input power supply.