• Title/Summary/Keyword: Pressure Dispersion

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A Study on the Characteristics of Pressure Distribution for Heat Exchanger Types of Domestic Gas Boiler (가정용 가스보일러 열교환기 유형에 따른 압력분포특성에 관한 연구)

  • 최경석;오율권;차경옥
    • Journal of the Korean Society of Safety
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    • v.16 no.4
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    • pp.22-28
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    • 2001
  • Heat transfer and pressure distribution for heat exchanger type of domestic gas boiler are different from shape, pitch, thickness of fin and array of pipe respectively. In order to measure the pressure distribution across the heat exchanger, a suction type wind tunnel was constructed and velocity distribution was measured for pilot tube(4 point) of rack type. The experiments were performed for 5 different air flow mass, rpm=3,6,9,12,15 and transverse axis of heat exchanger(x-length) is 5cm respectively. Results showed that above 9.5m/s, pressure distribution dispersion for wet type of heat exchanger is on the increase and above 5.5m/s, pressure distribution dispersion for dry type of heat exchanger is on the increase. Also, pressure distribution dispersion by comparing two different types heat exchanger, dry type of heat exchanger showed a higher augmentation than wet type of heat exchanger.

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MOLTEN CORIUM DISPERSION DURING HYPOTHETICAL HIGH-PRESSURE ACCIDENTS IN A NUCLEAR POWER PLANT (원자로 노심 용융물의 고압분출 및 비산 현상에 대한 수치해석적 연구)

  • Kim, Jong-Tae;Kim, Sang-Baik;Kim, Hee-Dong;Jeong, Jae-Sik
    • 한국전산유체공학회:학술대회논문집
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    • 2009.11a
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    • pp.121-128
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    • 2009
  • During a hypothetical high-pressure accident in a nuclear power plant (NPP), molten corium can be ejected through a breach of a reactor pressure vessel (RPV) and dispersed by a following jet of a high-pressure steam in the RPV. The dispersed corium is fragmented into smaller droplets in a reactor cavity of the NPP by the steam jet and released into other compartments of the NPP by a overpressure in the cavity. The fragments of the corium transfer thermal energy to the ambient air in the containment or interact chemically with steam and generate hydrogen which may be burnt in the containment. The thermal loads from the ejected molten corium on the containment which is called direct containment heating (DCH) can threaten the integrity of the containment. DCH in a NPP containment is related to many physical phenomena such as multi-phase hydrodynamics, thermodynamics and chemical process. In the evaluation of the DCH load, the melt dispersion rates depending on the RPV pressure are the most important parameter. Mostly, DCH was evaluated by using lumped-analysis codes with some correlations obtained from experiments for the dispersion rates. In this study, MC3D code was used to evaluate the dispersion rates in the APR1400 NPP during the high-pressure accidents. MC3D is a two-phase analysis code based on Eulerian four-fields for melt jet, melt droplets, gas and water. The dispersion rates of the corium melt depending on the RPV pressure were obtained from the MC3D analyses and the values specific to the APR1400 cavity geometry were compared to a currently available correlation.

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Filtration Characteristics according to Hollow Fiber Dispersion in Submerged Membrane Module (침지형 막모듈에서 중공사 분산에 따른 여과특성)

  • 이재인;신춘환
    • Journal of Environmental Science International
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    • v.9 no.2
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    • pp.173-176
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    • 2000
  • This study was carried out to investigate the filtration characteristics of membrane modules according to hollow fiber dispersion for direct solid-liquid separation of activated sludge. 2 bundle, 4 bundle, and 10 bundle, and 10 bundle module used in this experiment according to hollow fiber dispersion was manufactured at laboratory and permeate flux and transmembrane pressure(TMP) of each module were observed under a suction pressure of 0.5kgf/c$m^2$. As the hollow fibers were dispersed, permeate flux was increased and TMP was decreased. Permeate flux and TMP of each module was 15.0 $\ell$/$m^2$.h and 31.8 cmHg for 2 bundle, 16.0 $\ell$/$m^2$ .h and 17.4 cmHg for 4 bundle, and 20.4 $\ell$/m2 .h and 31.8 cmHg for 10 bundle. In conclusion, the membrane fouling is expected to be decrease by maintaining lower TMP with hollow fiber dispersion.

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Recent Topics on Cavitation Research

  • Kato Hiroharu
    • Proceedings of the KSME Conference
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    • 2002.08a
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    • pp.1-4
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    • 2002
  • This article presents the unique characteristics of cavitation, those are very high pressure and very high temperature even in a very short time. Such the high-pressure causes the destruction of material, which sometimes brings a severe problem to fluid machinery. However, if we look the cavitation from the different direction, such the high pressure can be used to various applications. The author presents two examples of the utilization of cavitation recently done at the Toyo University. Those are 'dispersion of spilled oil' and 'killing planktons'.

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Fabrication of Silica-Containing Breathable Waterproof Polyurethane Dispersion Film (Silica를 함유하는 Polyurethane dispersion 투습방수 Film의 제조)

  • Shin, Hyun-Ki;Huh, Man-Woo;Yoon, Nam-Sik
    • Textile Coloration and Finishing
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    • v.27 no.2
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    • pp.126-131
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    • 2015
  • Silica-polyurethane hybrid breathable films were prepared and their breathabilities were assessed. Appropriately aggregated silica was prepared through sol-gel reaction of water glass and its particle size ranged 360~500nm. The polyurethane dispersion was prepared by the reaction of isophorone diisocyanate(IPDI) as diisocyanate and polytetramethylene glycol(PTMG) and dimethylol propionic acid(DMPA) as polyol, particle size ranging 30~120nm. The reaction between isocyanate and hydroxyl group to form urethane bonding was checked by the intensity of the stretch peak of isocyanate at $2270cm^{-1}$ in the FT-IR. The silica was incorporated into polyurethane dispersion and casted into film. It was shown that the incorporated silica(1~5wt.%) increased water vapour permeability of the films by 30~100%, and decreased the hydrostatic pressure by 10~40%. From the results, it could be concluded that the appropriate hybridization of silica can increase the breathability of polyurethane dispersion film, while minimizing the loss of hydrostatic pressure.

Performance Dispersion Analysis and Applications of Gas Generator Cycle Liquid Rocket Engine (가스발생기 사이클 액체 로켓 엔진의 성능 분산 해석 및 활용)

  • Nam, Chang-Ho;Cho, Won-Kook;Seol, Woo-Seok
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2006.11a
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    • pp.191-195
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    • 2006
  • It is definitely required to control dispersion of the rocket engine performance in order to accomplish the mission of a launch vehicle successfully. A performance dispersion analysis was conducted for a gas generator cycle liquid rocket engine and the required pressure drops were estimated for engine tunning. As a result, the vacuum thrust dispersion of the engine was from +9.1% to -8.7% and the mixture ratio deviated from +9.7% to -9.6% from the nominal value due to the errors of components and the engine inlet condition of propellants. The required pressure drop in the LOx line to the combustor is higher than in the fuel line for same mixture ratio change.

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Development of a Dispersion Analysis Program for the Liquid Rocket Engine and its Application (액체로켓 엔진 성능 분산해석 프로그램의 개발 및 응용)

  • Park, Soon-Young;Nam, Chang-Ho;Seol, Woo-Seok
    • Aerospace Engineering and Technology
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    • v.10 no.1
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    • pp.63-69
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    • 2011
  • In this study, we developed a dispersion analysis program of the gas-generator cycle liquid propellant rocket engine by expanding the mode analysis software(GEMAT). The performance dispersions of an engine that are arisen from the internal dispersion factors of engine's sub-components were formulated and solved to find the effects of each dispersion factor. We were also able to present the calculation method to find the required pressure margin for the compensation of those dispersion to satisfy the required performances of engine. Using this method, we could propose a novel procedure of compensating during the ground firing test which would induce the performance improvement by lessening the pumps discharge pressures or augmenting the combustion chamber pressure.

A Study on Dispersion Analysis and Calibration of Gas Generator Cycle Liquid Rocket Engine (가스발생기 사이클 액체로켓엔진의 성능분산해석과 엔진성능보정)

  • Nam, Chang-Ho;Kim, Seung-Han;Kim, Cheul-Woong;Seol, Woo-Seok
    • Aerospace Engineering and Technology
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    • v.6 no.1
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    • pp.120-127
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    • 2007
  • Performance dispersion in the engine should be considered to predict the flight accuracy of a launch vehicle. A dispersion estimation method was presented with a LOx/Kerosene gas generator cycle engine. The orifices in the propellant supply lines in the engine were assumed to be used for calibration of the performance and the required pressure drops were acquired. The dispersions after calibration were quantified also.

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Measurement and Analysis of Indoor Environment in Emergency Switching Type Temporary Negative Pressure Isolation Ward that Use Portable Negative Pressure Units (이동형 음압기를 적용한 긴급 전환형 임시음압격리병실의 실내 환경 측정 분석)

  • Lee, Wonseok;Lee, Sejin;Kim, Heegang;Yeo, Myoungsouk
    • Journal of The Korea Institute of Healthcare Architecture
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    • v.28 no.4
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    • pp.89-97
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    • 2022
  • Purpose: Because of the recent COVID-19 pandemic, there have been many cases of using portable negative pressure unit to convert general wards into temporary negative pressure isolation wards. The purpose of this study is to analyze the indoor environment of the switching type wards. Methods: Field measurements and experiments were conducted in a medical facility. Air volume, wind speed and pressure difference were measured in non-occupant state. Dispersion tests were performed with gas and particle matter. Results: The pressure difference between the wards and the corridor was higher than -2.5 Pa in normal situation. However, in the gas and particle dispersion tests, it was found that there were concerns about the spread through leakages in low-airtight walls or ceilings. In addition, it was confirmed that the pressure imbalance in ducts through the non-sealed diffusers could cause back flow during portable unit operation. Furthermore, when there was a pressure difference between adjacent wards planned to be at same pressure level, the possibility of the spread through the leakages was found. Implications: When using portable units for making switching type wards, it is necessary to create airtight space and seal the non-operation diffusers. In case of operating the air handling unit, T.A.B must be performed to adjust the duct balancing.

BEHAVIOR OF LIQUID LPG SPRAY INJECTING FROM A SINGLE HOLE NOZZLE

  • PARK K.
    • International Journal of Automotive Technology
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    • v.6 no.3
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    • pp.215-219
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    • 2005
  • Liquefied petroleum gas (LPG) has been used as motor fuel due to its low emissions and low cost. A liquid direct injection system into a cylinder was suggested as a next generation system to maximize a fuel economy as well as a power. This study addresses the analysis of the LPG spray injecting from single hole injector. Two different test conditions are given, which are a fully developed spray case with various injection pressures and a developing spray case with ambient pressure variation. The LPG spray photographs are compared with the sprays of gasoline and diesel fuel at the same conditions, and the spray angles and penetration lengths are also compared, and then the spray behavior is analyzed. The LPG spray photos show that the dispersion characteristic depends very sensitively on the ambient pressure soon after injection. The spray angle is very wide in a low ambient pressure condition until the saturated pressure, but the angle is quickly reduced at the condition over the pressure. However, the down stream of the LPG spray shows much wider dispersion and less penetration than those of gasoline and diesel sprays regardless ambient pressure condition.