• Title/Summary/Keyword: loss of particles

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Aerosol Losses in a 100L $Tedlar^{(R)}$ Bag

  • Oh, Sewon
    • Journal of Korean Society for Atmospheric Environment
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    • v.20 no.E2
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    • pp.61-68
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    • 2004
  • Aerosol losses in a 100L Tedlar$^{(R)}$ bag were investigated for the aerosols with number median diameter of 0.05 ${\mu}{\textrm}{m}$ and number concentration of 6.4 ${\times}$ 10$^4$ cm$^{-3}$ . Over a 1 hr period, loss of particles in the bag is apparent, and the volume decrease with time is significant. The number concentration, surface area, and volume concentration of the aerosols decreased to 34, 50, and 52% of the initial value in 30 min, respectively. This indicates that deposition to the walls was the main loss process for aerosols in the Tedlar$^{(R)}$ bag. Theoretical calculations showed that coagulations and deposition by diffusion and gravitational sedimentation would not change aerosol characteristics significantly, and the electrical force was the dominant loss process for particles in the Tedlar$^{(R)}$ bag over a 1 hr period.eriod.

Experimental and computational study on fluid flow-solid particles interaction associated with entrainment behavior of the particles in the industrial furnaces (산업용 로 내 고체 미립자의 거동 예측을 위한 유동-고체입자 간 비산에 관한 실험과 해석)

  • Lee, Hookyung;Eum, Minje;Choi, Sangmin
    • 한국연소학회:학술대회논문집
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    • 2012.04a
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    • pp.93-96
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    • 2012
  • In the industrial furnaces or reactors, entrainment of the material particles is one of the important issues from the point of view of efficient material-use. The particles of solid phase which has submicron unit are easily entrained with gas phase as a reacting agent or product, and it causes a loss of the material. In this study, wind-tunnel experiment is carried out to interpret the distribution of the particles entrained along the tunnel length. Through CFD-based computational analysis of the experiment, availability of result from the CFD analysis associated with particle size distribution and gaseous velocity to practical system is evaluated.

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Carbon Contained Ammonium Diuranate Gel Particles Preparation in Mid-process of High-temperature Gas-cooled Reactor Fuel Fabrication

  • Jeong, Kyung Chai;Cho, Moon Sung
    • Nuclear Engineering and Technology
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    • v.48 no.1
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    • pp.175-181
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    • 2016
  • This study investigates the dispersibility of carbon in carbon contained ammonium diuranate (C-ADU) gel particles and the characteristics of C-ADU gel liquid droplets produced by the vibrating nozzle and integrated aging-washing-drying equipment. It was noted that the excellent stability of carbon dispersion was only observed in the C-ADU gel particle that contained carbon black named CB 10. ADU gel liquid droplets containing carbon particles with the excellent sphericity of approximately 1,950 mm were then obtained using an 80-100-Hz vibrating nozzle system. Dried C-ADU gel particles obtained by the aging-washing-drying equipment were thermal decomposed until $500^{\circ}C$ at a rate of $1^{\circ}C/min$ in an air or in 4% $H_2$ gas atmosphere. The thermally decomposed C-ADU gel particles showed 24% weight loss and a more complicated profile than that of ADU gel particles.

Powder Characteristics of Fly Ash Beneficiated by Cold Plasma and Heat Treatment

  • Lee, Seung-Heun;Cho, Un-Jin;Kwon, Sung-Ku
    • Journal of the Korean Ceramic Society
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    • v.53 no.1
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    • pp.93-98
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    • 2016
  • Cold plasma and heat treatment were selected as technologies to reduce unburned carbon in fly ash to less than 1.0%. Both cold plasma and heat treatment made it possible to eliminate unburned carbon to less than 1.0%. In the case of fly ash, which almost entirely eliminated unburned carbon with an ignition loss of 0.5%, heat treatment caused adhesion among particles and the BET specific surface area rapidly decreased as the mean particle size increased. On the other hand, with cold plasma, unburned carbon elimination caused the BET specific surface area to decrease and, as no adhesion occurred among particles, the mean particle size became small. Also, cold plasma treatment allowed small spherical particles confined within the unburned carbon particles to be released with the elimination of the unburned carbon frame, so that the quantity of fine particles had a tendency to slightly increase.

Study on the Asymmetric Regional Deposition of Airborne Pollutant Particles in the Human Respiratory Tract (대기오염 입자의 인체 호흡기내 비대칭 국부침전 특성에 관한 연구)

  • 구재학;김종숭
    • Journal of Korean Society for Atmospheric Environment
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    • v.19 no.5
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    • pp.551-560
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    • 2003
  • Particle deposition in human lungs was investigated theoretically by using asymmetric five-lobe lung model. The volumes of each of the five lobes were different, thereby forming an asymmetric lung structure. The tidal volume and flow rate of each lobe were scaled according to lobar volume. The total and regional deposition with various breathing patterns were calculated by means of tracking volume segments and accounting for particle loss during inhalation and exhalation. The deposition fractions were obtained for each airway generation and lung lobe, and dominant deposition mechanisms were investigated for different size particles. Results show that the tidal volume and flow rate have a characteristic influence on particle deposition. The total deposition fraction increases with an increase in tidal volume for all particle sizes. However, flow rate has dichotomous effects: a higher flow rate results in a sharp increase in deposition for large size particles, but decreases deposition for small size particles. Deposition distribution within the lung shifts proximally with higher flow rate whereas deposition peak shifts to the deeper lung region with larger tidal volume. Deposition fraction in each lobe was proportional to its volume. Among the three main deposition mechanisms, diffusion was dominant for particles < 0.5 ${\mu}{\textrm}{m}$ whereas sedimentation and impaction were most influential for larger size particles. Impaction was particularly dominant for particles> 8 ${\mu}{\textrm}{m}$. The results may prove to be useful for estimating deposition dose of inhaled pollutant particles at various breathing conditions.

A Study on the Estimation of Loss Rate of Dredged Fills (준설토의 유실률 평가에 관한 연구)

  • Kim, Hong-Taek;Kim, Seog-Yeol;Kang, In-Kyu;Park, Jae-Eock
    • Journal of the Korean GEO-environmental Society
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    • v.1 no.1
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    • pp.57-63
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    • 2000
  • Volume change of the dredged soils is composed of loss amount of the soil particles flowing over an outflow weir with water and settlements due to both the self-weight consolidation in reclaimed layer and the desiccation at the surface of reclaimed layer. In order to estimate the amount of soil particles flowing over an outflow weir with water, the breakage theory and the results of hydrometer analyses. To verify a validity of the proposed procedure, evaluated loss ratio is compared with various estimates from the other existing methods.

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Effect of Void Formation on Strength of Cemented Material (고결 지반 내에 형성된 공극이 강도에 미치는 영향)

  • Park, Sung-Sik;Choi, Hyun-Seok;Kim, Chang-Woo
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.30 no.2C
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    • pp.109-117
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    • 2010
  • Gas hydrate dissociation can generate large amounts of gas and water in gas hydrate bearing sediments, which may eventually escape from a soil skeleton and form voids within the sediments. The loss of fine particles between coarse particles or collapse of cementation due to water flow during heavy or continuous rainfall may form large voids within soil structure. In this study, the effect of void formation resulting from gas hydrate dissociation or loss of some particles within soil structure on the strength of soil is examined. Glass beads with uniform gradation were used to simulate a gas hydrate bearing or washable soil structure. Glass beads were mixed with 2% cement ratio and 7% water content and then compacted into a cylindrical sample with five equal layers. Empty capsules for medicine are used to mimic large voids, which are bigger than soil particle, and embedded into the middle of five equal layers. The number, direction, and length of capsules embedded into each layer vary. After two days curing, a series of unconfined compression tests is performed on the capsule-embedded cemented glass beads. Unconfined compressive strength of cemented glass beads with capsules depends on the volume, direction and length of capsules. The volume and cross section formed by voids are most important factors in strength. An unconfined compressive strength of a specimen with large voids decreases up to 35% of a specimen without void. The results of this study can be used to predict the strength degradation of gas hydrate bearing sediments in the long term after dissociation and loss of fine particles within soil structure.

Solar Wind Dynamic Pressure during Magnetic Storms and its implications on the Dayside Ring Current Particle Loss

  • Kim, Kyungchan;Lee, Dae-Young
    • Bulletin of the Korean Space Science Society
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    • 2004.04a
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    • pp.39-39
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    • 2004
  • It has been known that ring current particles can be lost through dayside MP(magnetopause). However, details of the loss mechanism of this process has not received much attention. In this study, we show that the solar wind dynamic pressure P$\sub$D/ can play a significant role in the dayside loss. In order to show that, we have first conducted superposed epoch analysis using 95 geomagnetic storm events selected from the period 1997 to 2002. (omitted)

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Fabrication and Characteristics of $Al_2O_{3p}$/AC8A Composites by Pressureless Infiltration Process (무가압함침법에 의한 $Al_2O_{3p}$/AC8A 복합재료의 제조 및 특성)

  • 김재동;고성위;정해용
    • Composites Research
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    • v.13 no.6
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    • pp.1-8
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    • 2000
  • The fabrication Process of $Al_2O_{3p}$/AC8A composites by pressureless infiltration technique and the effects of additive Mg content and volume fraction of particulate reinforcement on mechanical and wear properties were investigated. It was found that the bending strength decreased with increasing volume fraction of $Al_2O_{3p}$ particles. Whereas hardness increased with volume fraction of $Al_2O_{3p}$ particles. The decrement of strength in case of high volume fraction of $Al_2O_{3p}$ particles was attributed to high porosity level. In terms of additive Mg content, $Al_2O_{3p}$/AC8A composites containing around 5~7wt% of additive Mg indicated the highest strength, and hardness values increased with additive Mg contents. Wear resistance of AC8A alloy were improved by reinforcement of $Al_2O_{3p}$ particles especially at high sliding velocity. Wear property of $Al_2O_{3p}$/AC8A composites and AC8A alloy exhibited different aspects. $Al_2O_{3p}$/AC8A composites indicated more wear loss than AC8A alloy at slow velocity region. However a transition point of wear loss was found at middle velocity region which shows the minimum wear loss and wear loss at high velocity region exhibited almost same value as at slow velocity region, whereas wear loss of AC8A alloy almost linearly increased with sliding velocity. It was found that $Al_2O_{3p}$/AC8A composites containing $Al_2O_{3p}$ volume fraction of 20% exhibited abrasive wear surface regardless of sliding velocity and $Al_2O_{3p}$/AC8A composites containing $Al_2O_{3p}$ volume fraction of 40% showed slightly adhesive wear surface at low sliding velocity, and it progressed to severe wear as increasing the sliding velocity.

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Performance Evaluation of Thrust Slide-Bearing of Scroll Compressors under R-22 Environment (R-22 냉매 분위기하에서 스크롤 압축기 스러스트 베어링의 윤활특성 평가)

  • Cho, Sang-Won;Kim, Hong-Seok;Lee, Jae-Keun;Lee, Hyeong-Kook;Lee, Byeong-Chul;Park, Jin-Sung
    • Proceedings of the SAREK Conference
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    • 2006.06a
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    • pp.590-595
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    • 2006
  • This paper presents the friction and anti-wear characteristics of nano-oil with a mixture of a refrigerant oil and carbon nano-particles in the thrust slide-bearing of scroll compressors. Frictional loss in the thrust slide-bearing occupies a large part of total mechanical loss in scroll compressors. The characteristics of friction and anti-wear using nano-oil are evaluated using the thrust bearing tester for measuring friction surface temperature and the coefficient of friction at the thrust slide-bearing as a function of normal loads up to 4,000 N and orbiting speed up to 3,200 rpm. It is found that the coefficient of friction increases with decreasing orbiting speed and normal force. The friction coefficient of carbon nano-oil is 0.015, while that of pure oil is 0.023 under the conditions of refrigerant gas R-22 at the pressure of 5 bars. It is believed that carbon nano-particles can be coated on the friction surfaces and the interaction of nano-particles between surfaces can be improved the lubrication in the friction surfaces. Carbon nano-oil enhances the characteristics of the anti-wear and friction at the thrust slide-bearing of scroll compressors.

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