• Title/Summary/Keyword: Particle Residence Time

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Ignition Temperature and Residence Time of Suspended Magnesium Particles (마그네슘 부유 분진의 입자 체류시간과 발화온도)

  • Han, Ou-Sup
    • Journal of the Korean Institute of Gas
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    • v.19 no.3
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    • pp.25-31
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    • 2015
  • Effects of residence time on the MIT(Minimum Ignition Temperature) in suspended Mg particles are examined by using MIT experimental data and calculation results of terminal velocity. With increasing of the average particle diameter, we were able to identify that MIT of Mg dusts increased and the calculated residence time of particle decreased exponentially. Also, the influence on terminal velocity due to temperature increase increased slightly with increasing of average particle diameter.

Modeling Variation in Residence Time Response to Freshwater Discharge in Gangjin Bay, Korea (남해 강진만 담수유입에 따른 체류시간 변화 모델링)

  • Kim, Jin Ho;Park, Sung-Eun;Lee, Won-Chan
    • Korean Journal of Fisheries and Aquatic Sciences
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    • v.54 no.4
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    • pp.480-488
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    • 2021
  • The term residence time is defined as the time taken for substances in a system to leave the system and is a useful concept to explain the physical environment characteristics of a coastal area. It is important to know the spatial characteristics of the residence time to understand the behavioral properties of pollutants generated in a marine system. In this study, the spatial distribution of average residence time was calculated for Gangjin Bay, Korea, using a hydrodynamic model including a particle tracking module. The results showed that the average residence time was about 10 days at the surface layer and about 20 days at the bottom layer. Spatially, this was the longest residence time in the southwestern sea. There was no significant difference in average residence time at the surface layer due to freshwater discharge, but spatial variation at the bottom layer was larger. The average residence time at the bottom layer decreased in the southwestern area due to freshwater discharge and increased in the northern area. This result suggests that the residence time of anthropogenic pollutants may have a large spatial difference depending on the freshwater discharge, and thus the time taken to influence cultured organisms may also vary.

The Effect of Residence Time on the Generation of Silica Nanoparticles in a Turbulent Diffusion Flame (난류 확산화염에서 체류시간이 실리카 나노입자의 생성에 미치는 영향)

  • Kwak, In-Jae;Bae, Soo-Ho;Shin, Hyun-Dong
    • 한국연소학회:학술대회논문집
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    • 2006.10a
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    • pp.196-201
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    • 2006
  • Silica(SiO2) nanoparticles are used as additives in plastics and rubbers to improve mechanical, electrical, magnetic properties and optical material. Silica nanoparticles were synthesized by the gas phase thermal oxidation of several kinds of precursors in many types of reactor. Diffusion flame reactor has some advantages compared with other types of reactors. In this study, we investigated the generation of silica nanoparticles on the effect of residence time by tetraethylothosilicate(TEOS) in a turbulent diffusion flame reactor controlled by providing reactant flowrate and reactor geometry affect particle morphology, particle size and particle size distribution. To determine the flame residence time, flame length should be determined which was examined by ICCD image. Particle size, distribution and morphology were performed with TEM.

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A Study of Residence Time Calculation Methods in Decay Tank Design (감쇠탱크 설계를 위한 체류시간 계산 방법에 관한 연구)

  • Jung, Minkyu;Seo, Kyoungwoo;Kim, Seonghoon
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.29 no.5
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    • pp.220-230
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    • 2017
  • In this study we apply and compare a variety of numerical methods for calculating residence time distribution in decay tanks, a major design component in the for reducing N-16 radioactivity. Our research group has used a streamlined method using user-defined particle numbers. However, this streamlined method has several problems, including low exiting particle ratios, particle diminishing, and unphysical time distribution, among others. We utilize three numerical methods to establish residence time and time distribution (streamlined, discrete phase method [DPM], and user defined scalar [UDS]) and subsequently compare the averaged results of each. The three tests demonstrate the flow features within the decay tanks, which are then numerically simulated to enable comparison. We conclude that although each simulation predicts similar time averages, the UDS methodology provides a smoother time distribution and tracer contour plots at specific times.

Analysis on NOX Removal Efficiencies and Particle Growth Using Pulsed Corona Discharge Reactor (펄스 코로나 방전 반응기를 이용한 NOX 제거 효율 및 입자 성장 분석)

  • Park, Jung-Hwan;Kim, Dong-Joo;Kim, Kyo-Seon
    • Journal of Industrial Technology
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    • v.21 no.B
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    • pp.155-161
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    • 2001
  • In this study, we analyzed the $NO_X$ removal efficiency and particle size distribution by the pulsed corona discharge process and investigated the effect of several process variables. The NO removal efficiencies and the particle characteristics were measured and analyzed as the function of initial concentrations of NO, $H_2O$, and $NH_3$, applied voltage, pulse frequency and residence time. As the frequency of applied voltage increases, or as the applied voltage increases or as the residence time increases, the NO removal efficiency increases. The change of initial $NH_3$ and $H_2O$ concentrations do not affect the NO removal efficiency significantly. The particle concentration and size increases with the increases of initial NO concentration, residence time and applied voltage.

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Numerical Studies of Flow Characteristics and Particle Residence Time in a Taylor Reactor (테일러 반응기의 유동특성과 입자 체류시간에 관한 수치적 연구)

  • Lee, Hyeon Kwon;Lee, Sang Gun;Jeon, Dong Hyup
    • Applied Chemistry for Engineering
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    • v.26 no.1
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    • pp.67-73
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    • 2015
  • Using a computational fluid dynamics technique, the flow characteristics and particle residence time in a Taylor reactor were studied. Since flow characteristics in a Taylor reactor are dependent on the operating conditions, effects of the inlet flow velocity and reactor rotational speed were investigated. In addition, the particle residence time of $LiNiMnCoO_2$ (NMC), which is a cathode material in lithium-ion battery, is estimated in the Taylor vortex flow (TVF) region. Without considering the complex chemical reaction at the inlet, the effect of Taylor flow was studied. The results show that the particle residence time increases as the rotating speed increased and the flow rate decreased.

Flow Characteristics and Residence Time of Activated Carbon in the Cyclone for Optimized Design of an Adsorption/Catalysis Reactor (흡착/촉매 공정개선을 위한 사이클론 내 유동특성 및 활성탄 체류시간 산정)

  • Choi, Choeng-Ryul
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.31 no.5
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    • pp.416-424
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    • 2007
  • In adsorption/catalytic process, numerical analysis has been performed to identify the flow characteristics of flue gas in the cyclone and to estimate the residence time of activated carbon using Computational Fluid Dynamics (CFD) technique. To consider flue gas and activated carbon particles simultaneously, Euler-Lagrangian model was employed so that residence time could be obtained from the numerical analysis directly. The numerical analysis has been performed with different three particle sizes and compared each flow characteristics with particle’ size. Fundamental flow patterns of flue gas and activated carbon particles, pressure distribution, residence time of flue gas, and activated carbon particles and distribution of activated carbon have been obtained from the numerical analysis.

Numerical Analysis on Flow Characteristics in the Reactor of an Integrated Adsorption/Catalysis Process with Bag Filters (백필터를 활용한 흡착/촉매 통합공정 시스템의 반응기 내 유동특성 및 체류시간에 대한 수치해석적 연구)

  • Choi, Choeng-Ryul;Koo, Yoon-Seo
    • Journal of Korean Society for Atmospheric Environment
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    • v.23 no.2
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    • pp.203-213
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    • 2007
  • Numerical analysis has been performed to understand flow characteristics in the reactor with bag filters in an integrated adsorption/catalytic process which can treat dioxin and $NO_{x}$ together. Computational fluid dynamics technique was employed with Euler-Lagrangian model to consider flue gas and activated carbon particles simultaneously, so that residence time of flue gas and activated carbon particle could be obtained from the numerical analysis directly. The numerical analysis has been performed with different three particle sizes and compared each flow characteristics with particle's size. Fundamental flow patterns of flue gas and activated carbon particles, pressure distribution, residence time of flue gas and activated carbon particles, and distribution of activated carbon have been obtained from the numerical analysis. Flow patterns of flue gas and activated carbon particles in the reactor were very complicated and they moved along very various paths. Therefore, their residence time in the reactor was also various. The results obtained would be effectively used to estimate the removal efficiency in the reactor once the residence time is combined with the reaction equation.

Calculating Average Residence Time Distribution Using a Particle Tracking Model (Particle Tracking Model을 이용한 평균체류시간의 공간분포 계산)

  • Park, Sung-Eun;Hong, Sok-Jin;Lee, Won-Chan
    • Journal of Ocean Engineering and Technology
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    • v.23 no.2
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    • pp.47-52
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    • 2009
  • A Lagrangian particle tracking model coupled with the Princeton Ocean Model were used to estimate the average residence time of coastal water in Masan Bay, Korea. Our interest in quantifying the transport time scales in Masan Bay was stimulated by the search for a mechanistic understanding of this spatial variability, which is consistent with the concept of spatially variable transport time scales. Tidal simulation was calibrated through a comparison with the results of semi-diurnal current and water elevation measured at the tidal stations of Masan, Gadeokdo. In the model simulations, particles were released in eight cases, including slack before ebb, peak ebb, slack before flood, and peak flood, during both spring and neap tides. The averaged values obtained from the particle release simulations were used for the average residence times of the coastal water in Masan Bay. The average residence times for the southeastern parts of Somodo and the Samho River, Masan Bay were estimated to be about 20~50days and 70~80days, respectively. The spatial difference for the average residence time was controlled by the tidal currents and distance from the mouth of the bay. Our results might provide useful for understanding the transport and behavior of coastal water in a bay and might be used to estimate the dissimilative capacity for environmental assessment.

Assessing Average Residence Time as a Physical Descriptor for Shellfish Farming Areas in Jaran Bay, Korea (자란만 패류양식해역의 물리환경 설명을 위한 평균체류시간 산정)

  • Kim, Jin Ho;Park, Sung-Eun;Kim, Youngmin;Kim, Chung Sook;Kang, Sungchan;Jung, Woo-Sung;Sim, Bo-Ram;Eom, Ki-Hyuk
    • Journal of Environmental Science International
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    • v.29 no.3
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    • pp.273-282
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    • 2020
  • Residence time is defined as the time taken for a material in a system to leave the system. The residence time characteristics in shellfish aquaculture determine the dispersion of excretion from aquaculture farms, along with the supply of food by seawater exchange. In this study, we estimated the spatial distribution of average residence time in the shellfish farming area using a particle tracking model. As a result, a relatively short average residence time of about 20 days or less was calculated in most areas, but an average residence time of more than 40 days was calculated in the inner areas. Relatively long average residence times were calculated along the west coast compared to the east coast, with the longest average residence time of more than 50 days in the northwestern areas. It can be inferred that the disturbance of the benthic ecosystem caused by shellfish farms is likely to be large because of the relatively weak dispersion of excrement from shellfish farms located on the west coast, especially in the northwest region. This distribution of average residence time is important for understanding the potential effects of seawater exchange on the environmental sustainability of shellfish farms, along with the seawater circulation characteristics of Jaran Bay.