• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.6
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• pp.1983-1993
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• 1996

For selected (pure and compound) metallic species effects of saturation ratio, temperature, particle size and number density on condensation mechanisms are first reviewed. The tendencies for vaporization and condensation differ between metallic species because of the significant differences in their saturation pressures. Then particle pressure of a metal vapor species at incineration temperature is calculated by simplifying waste as a compound of methane, chlorine and small amounts of metals and assuming a thermodynamic equilibrium state. Next the condition is assessed for which supersaturation of combustion gases by the species above the critical level for homogeneous condensation may occur, when the gases contain a large number of pre-existing particles such as entrained ashes. Regardless of the presence of chlorine in the waste, the homogeneous condensation of PbO vapors may occur, depending on number density of the pre-existing particles. However, when chlorine exists in the waste, the homogeneous condensation of PbCl$_2$vapors does not occur, which is similar to the case of Cd and Hg vapors. Thus these highly volatile species, PbCl$_2$, Cd, and Hg, may emit to atmosphere as vapor phase. In general, for reducing the emission of hazardous metallic species into the atmosphere, the number density of pre-existing particles has to be increased. For fixed particle number density, the temperature drop rate must be kept in low if the temperature at which a condensable vapor species emits from a incineration system is fixed, while the temperature drop rate must be kept in high if the residence time for which a condensable species stays in the system is fixed.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.392-397
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• 2000

Mono-disperse particles generated by a condensation particle generator are widely used to meet the experimental and industrial needs. The characteristics of particles generated by homogeneous nucleation have been studied experimentally using a laminar flow condensation particle generator. Dry nitrogen gas saturated with oleic acid vapor was cooled well below the saturation temperature causing the highly supersaturated vapor to nucleate. The dependence of GSD(Geometric Standard Deviation), GMD(Geometric Mean Diameter), and the mass concentration of particles on the temperature at the evaporator, flow rate and the temperature condition at condenser was studied. The experimental results show that the mass concentration of particles is affected by the radial temperature profile at condenser. Nucleation at the center of the condenser causes the mass concentration of particles to increase. The experimental results also show that the suppression of additional nucleation by a constant temperature condition at the condenser increases the mean diameter of particle.

• Journal of Mechanical Science and Technology
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• v.18 no.3
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• pp.407-418
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• 2004

Prandtl-Meyer expansion flow with homogeneous condensation is investigated experimentally and by numerical computations. The steady and unsteady periodic behaviors of the diabatic shock wave due to the latent heat released by condensation are considered with a view of technical application to the condensing flow through steam turbine blade passages. A passive control method using a porous wall and cavity underneath is applied to control the diabatic shock wave. Two-dimensional, compressible Navier-Stokes with the nucleation rate equation are numerically solved using a third-order TVD (Total Variation Diminishing) finite difference scheme. The computational results reproduce the measured static pressure distributions in passive and no passive Prandtl-Meyer expansion flows with condensation. From both the experimental and computational results, it is found that the magnitude of steady diabatic shock wave can be considerably reduced by the present passive control method. For no passive control, it is found that the diabatic shock wave due to the heat released by condensation oscillates periodically with a frequency of 2.40㎑. This unsteady periodic motion of the diabatic shock wave can be completely suppressed using the present passive control method.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.3
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• pp.582-589
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• 1988

A rapid expansion of moist air or steam in a supersonic nozzle gives rise to condensation, and the total pressure of the flow is decreased due to this irreversibility of condensation phenomenon. In the present paper, the loss in total pressure during the condensation process has been studied, by numerical analysis and pressure measurement, in the case of moist air expanding in a supersonic nozzle. The effects of the degree of supersaturation at the stagnation condition and expansion rate of the nozzle on the total pressure loss have been studied. The length of the region where the total pressure decreases during the condensation process is longer than that of the nonequilibrium condensation region, and of difference between the length of these two increases with the increase of the degree of supersaturation at the stagnation condition. Furthermore, the larger the expansion rate of the nozzle and the higher the temperature and the degree of supersaturation at the reservoir are, the larger the total pressure loss of the flow becomes. And, it is turned out that the total pressure loss be about 2 to 8 percent in the present study.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.6
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• pp.23-29
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• 2003

Transonic two-phase flow of Saturated humid air, in which relative humidity is 100%, with various condensation processes around thin airfoils is investigated. The study uses an extended transonic small-disturbance(TSD) model of Rusak and Lee [11, 12] which includes effects of heat addition to the flow due to condensation. Two possible limit types of condensation processes are considered. In the nonequilibrium and homogeneous process, the condensate mass fraction is calculated according to classical nucleation and droplet growth rate models. In the equilibrium process, the condensate mass fraction is calculated by assuming an isentropic process. The flow and condensation equations are solved numerical1y by iterative computations. Results under same upstream conditions describe the flow structure, field of condensate, and pressure distribution on airfoil's surfaces. It is found that flow characteristics, such as position and strength of shock waves and airfoil’s pressure distribution, are different for the two condensation processes. Yet, in each case, heat addition as a result of condensation causes significant changes in flow behavior and affects the aerodynamic performance of airfoils.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.2
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• pp.264-274
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• 1997

A numerical analysis on condensation and coagulation of the metallic species with fly ash particles pre-existing in an incinerator was performed. Waste was simplified as a mixture of methane, chlorine, and small amounts of Pb and Sn. Vapor-phase amounts of Pb- and Sn -compounds were first calculated assuming a thermodynamic equilibrium state. Then theories on vapor-to-particle conversion, vapor condensation onto the fly ash particles, and particle-particle interaction were examined and incorporated into equations of aerosol dynamics and vapor continuity. It was assumed that the particles followed a log-normal size distribution and thus a moment model was developed in order to predict the particle concentration and the particle size distribution simultaneously. Distributions of metallic vapor concentration (or vapor pressure) were also obtained. Temperature drop rate of combustion gas, fly ash concentration and its size were selected as parameters influencing the discharged amount of metallic species. In general, the coagulation between the newly formed metal particles and the fly ash particles was much greater than that between the metal particles themselves or between the fly ash particles themselves. It was also found that the amount of metallic species discharged into the atmosphere was increased due to coagulation. While most of PbO vapors produced from the combustion were eliminated due to combined effect of condensation and coagulation, the highly volatile species, PbCl$_{2}$ and SnCl$_{4}$ vapors tended to discharge into the atmosphere without experiencing either the condensation or the coagulation. For Sn vapors the tendency was between that of PbO vapors and that of PbCl$_{2}$ or SnCl$_{4}$. To restrain the discharged amount of hazardous metallic species, the coagulation should be restrained, the number concentration and the size of pre-existing fly ash particles should be increased, and the temperature drop rate of combustion gas should be kept low.

• Bulletin of the Korean Chemical Society
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• v.32 no.1
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• pp.213-218
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• 2011

The scope of homogeneous Lewis acid-catalyzed benzo[N,N]-heterocyclic condensation was expanded to include the use of various metal salts not reported in the literature and $SnCl_2{\cdot}2H_2O$ was finally selected. Among various solid supports activated with $SnCl_2$, heterogeneous $SnCl_2/SiO_2$ proved to be the most effective and significantly higher conversions were achieved compared to $SnCl_2{\cdot}2H_2O$ itself. The results of TG-DTA and BET indicated that dispersed $SnCl_2$ coordinates with surface hydroxyl groups of silica leading to formation of stable Lewis acid sites. Low catalyst loading, operational simplicity, practicability and applicability to various substrates render this eco-friendly approach as an interesting alternative to previously applied procedures.

• Animal cells and systems
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• v.9 no.2
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• pp.65-73
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• 2005

In this study, we found that sperm ball of Urechis unicinctus consisted of a somatic cell and spermatogenic cells. After separation from the sperm ball, individual spermatid floated freely in the coelomic fluid and differentiated into a mature sperm. Because of many nuclear vacuoles, spermatid nucleus was observed to be heterogeneous. Later, the spermatid nucleus condensed into the homogeneous round nucleus of the mature sperm. Perinuclear microtubules could be seen but did not seem to be organized into manchette microtubules. To understand the nature of nuclear condensation during spermiogenesis, the sperm and spermatids (spermiogenic cells) were treated with FITC-phalloidin, or anti-actin-FITC, or labeled with antiactin immunogold particles (AAIP; 10 nm) followed by transmission electron microscopy or confocal laser scanning microscopy. The anti-actin-FITC and FITC-phalloidin reactions occurred distinctly in the nuclei of both spermiogenic cells. FITC-phalloidin reacted more intensely with acrosomes. The AAIP were incorporated mainly into nuclei of both cells sometimes showing local distribution in the nucleus. Nuclear vacuoles of spermatids disappeared progressively with condensation of the nucleus, as the number of incorporated $AAIP/{\mu}m^2$ increased. These results suggest that nuclear actin microfilaments might be closely related to nuclear condensation.

• Particle and aerosol research
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• v.9 no.1
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• pp.7-21
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• 2013

Twelve-hour size-resolved atmospheric aerosols were measured to determine size distributions of water-soluble organic carbon(WSOC) during daytime and nighttime, and to investigate sources and formation pathways of WSOC in individual particle size classes. Mass, WSOC, ${NO_3}^-$, $K^+$, and $Cl^-$ at day and night showed mostly bimodal size distributions, peaking at the size range of $0.32-0.55{\mu}m$(condensation mode) and $3.1-6.2{\mu}m$(coarse mode), respectively, with a predominant condensation mode and a minor coarse mode. While ${NH_4}^+$ and ${SO_4}^{2-}$ showed unimodal size distributions which peaked between 0.32 and $0.55{\mu}m$. WSOC was enriched into nuclei mode particles(< $0.1{\mu}m$) based on the WSOC-to-mass and WSOC-to-water soluble species ratios. The sources and formation mechanisms of WSOC were inferred in reference to the size distribution characteristics of inorganic species(${SO_4}^{2-}$, ${NO_3}^-$, $K^+$, $Ca^{2+}$, $Na^+$, and $Cl^-$) and carbon monoxide. Nuclei mode WSOC was likely associated with primary combustion sources during daytime and nighttime. Among significant sources contributing to the condensation mode WSOC were homogeneous gas-phase oxidation of VOCs, primary combustion emissions, and fresh(or slightly aged) biomass burning aerosols. The droplet mode WSOC could be attributed to aqueous oxidation of VOCs in clouds, cloud-processed biomass burning aerosols, and small contributions from primary combustion sources. From the correlations between WSOC and soil-related particles, and between WSOC and sea-salt particles, it is suggested that the coarse mode WSOC during daytime is likely to condense on the soil-related particles($K^+$ and $Ca^{2+}$), while the WSOC in the coarse fraction during nighttime is likely associated with the sea-salt particles($Na^+$).

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.4
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• pp.1-7
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• 2003

습공기에 포함된 수증기가 상(Phase)변화를 일으킬 때 잠열이 발생하고 이 잠열은 익형 주위의 압축성 유동 상태량들을 변화시키므로, 이러한 열 증가가 유동에 끼치는 영향에 대하여 수치해석을 통하여 연구 수행하였다. 수치해석은 Rusak 과 Lee [1]가 최근에 연구 수행한 미교란 방법(small-disturbance approach)에 근거하여 이루어졌다. 고전적 핵 생성 모델과 작은 물방울 성장(droplet growth)모델을 이용한 이 방법에서는 비평형 균질 응축과정에서 일어나는 열 방출을 묘사한다. 응축에 의한 열전달, 압축성 유동의 운동에너지, 그리고 유동의 열적 상태량들 사이에서 일어나는 비선형 상호영향을 조사하고, 또한 주어진 문제를 지배가호 있는 상사 파라미터들을 제시하였다. 계산 결과들은 Euler 방정식을 사용하여 얻은 선행 수치계산들과 비교하여 잘 일치됨을 보였다. 상사법칙은 유동 동역학과 응축 상태량들이 상당히 비슷하게 거동하는 다양한 유동 형태들을 제안한다. 압축성 습공기 유동은 유체기계에 사용되는 익형들의 공력 성능을 증가시키는데 응용될 수 있다.