• Particle and aerosol research
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• v.8 no.4
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• pp.161-172
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• 2012

Three-dimensional numerical simulation using a computational fluid dynamics (CFD) was carried out in order to investigate the formation and dispersion of the plume discharged from the stack of a thermal power station. The simulation was based on the standard ${\kappa}{\sim}{\varepsilon}$ turbulence model and a finite-volume method. Warm and moist exhaust from a power plant stack forms a visible plume as entering the cold ambient air. In the simulation, moisture content, emission velocity and temperature of the flue gas, air temperature and wind speed were dealt with the main parameters to analyze the properties of the plume composed mainly of water vapor. As a result of the simulation, the plume could be more apparent in cold winter due to a big difference of latent heat capacity. At no wind condition, the white plume rises 120 m upward from the top of the stack, and expands to 40 m around from the stack in cold winter after flue gas heat recovery. The influencing distance of relative humidity will be about 100 m to 400 m downstream from the stack with a cross wind effect. The decrease of flue gas temperature by heat recovery of thermal energy facilitates the formation of the plume and restrains its dispersion. Wind speed with vertical distribution affects the plume dispersion as well as the density.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.523-524
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• 2006

The $TiB_2$ dispersion strengthened copper alloy was attracted as thermal and electrical functional material for the high mechanical strength, high thermal stability and good conductivity of $TiB_2$. In the present study, the focus is on the synthesis of $TiB_2$ dispersed copper alloy by spark plasma sintering process using copper oxide and titanium diboride as raw materials. The mechanical, thermal and electrical properties of sintered bodies were discussed with the sintering parameters, and developed microstructure and phase of sintered bodies.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.425.1-425.1
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• 2014

Thermal transport in nanomaterials is not only scientifically interesting but also technological important for various future electronic, bio, and energy device applications. Among the various computation approaches to investigate lattice thermal transport phenomena in nanoscale, the atomistic nonequilibrium Green's function approach based on first-principles density functional theory calculations appeared as a promising method given the continued miniaturization of devices and the difficulty of developing classical force constants for novel nanoscale interfaces. Among the nanometerials, carbon atomic chains, namely the cumulene (all-doulble bonds, ${\cdots}C=C=C=C{\cdots}$) and polyyne (alternation of single and triple bonds, ${\cdots}C{\equiv}C-C{\equiv}C{\cdots}$) can be considered as the extream cases of interconnction materials for nanodevices. After the discovery and realization of carbon atomic chains, their electronic transport properties have been widely studied. For the thermal transport properties, however, there have been few literatures for this simple linear chain system. In this work, we first report on the development of a non-equilibrium Green's function theory-based computational tool for atomistic thermal transport calculations of nanojunctions. Using the developed tool, we investigated phonon dispersion and transmission properties of polyethylene (${\cdots}CH2-CH2-CH2-CH2{\cdots}$) and polyene (${\cdots}CH-CH-CH-CH{\cdots}$) structures as well as the cumulene and polyyne. The resulting phonon dispersion from polyethylene and polyene showed agreement with previous results. Compared to the cumulene, the gap was found near the ${\Gamma}$ point of the phonon dispersion of polyyne as the prediction of Peierls distortion, and this feature was reflected in the phonon transmission of polyyne. We also investigated the range of interatomic force interactions with increase in the size of the simulation system to check the convergence criteria. Compared to polyethylene and polyene, polyyne and cumulene showed spatially long-ranged force interactions. This is reflected on the differences in phonon transport caused by the delicate differences in electronic structure.

• Textile Coloration and Finishing
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• v.22 no.4
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• pp.362-372
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• 2010

This paper surveys the physical properties of the multiwall carbon nanotube (MWNT) and polyurethane composite film for improvement of mechanical properties and electrical characteristics. The modification of MWNT was carried out by acid treatment with nitric and sulphuric acid mixed solution, and then followed by thermal treatment for enhancing MWNT dispersion with polyurethane. This modified MWNT was mixed with polyurethane by changing the loading content of MWNT and dispersion time under the dimethylformamide solution in the ultrasonic wave apparatus. Various physical characteristics of the modified PU/MWNT films were measured and analyzed in terms of the loading content and dispersion time. The maximum absorbance of the PU/MWNT films were observed with the 2wt% loading at dispersion times of 2 and 24 hour, respectively. The minimum electrical volume resistivity of PU/MWNT film was shown at the loading content of 0.5wt% or more irrespective of dispersion treating time. However the optimum condition was assumed to 2wt% loading at dispersion time of 2 hours by assessing the surface profile of the film using video microscope. The breaking stress and strain of the PU/MWNT film decreased with increasing loading content, but no change of physical properties was shown with increasing in dispersion time.

• 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.

• Polymer(Korea)
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• v.31 no.6
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• pp.543-549
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• 2007

We synthesized various polyurethanes(PU) haying different hard segments with different molecular weights of the soft segment to explore the effect of structure on the dispersion of silver particle in the phase of synthesized polyurethanes matrix. The thermal stability was increased by increasing the number of aromatic compound, while the degree of dispersion for silver particle was decreased. Silver particles showed better dispersion in the PU matrix having aromatic compounds when the soft segments were held constant. On the contrary, when the hard segment was held constant, silver particles on the PU matrix haying low $M_w$ of soft segment showed better dispersion than high $M_w$ of soft segment because poor chain mobility of low $M_w$ of soft segment restricted re-aggregation of silver particle. A sheet resistance of composite materials showed different aspects. In this case, the inter connection between silver particles was more important than its dispersion. In this study, the NDI-PEG 900/silver particle composite film showed the best thermal stability and electro conductivity.

• Journal of Auto-vehicle Safety Association
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• v.13 no.3
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• pp.13-19
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• 2021

Fog is a phenomenon caused by condensation of water vapor in the atmosphere, which is when very fine drops of water float in the atmosphere and the distance of visible is less than 1km. Fog dispersion technology is a technology that removing or weakening fog by using artificial methods to reduce damage caused by fog. It is applied differently depending on the temperature of fog generation rather than the cause of fog. This study conducted an experimental study on the fog dispersion mechanism in order to minimize damage caused by fog on the road, and studied two methods of over-cooling dispersion using solid-carbon-dioxide as a dissipated particle and dissipating fog particles through thermal acoustic waves. As a result the two methods proved experimentally that were capable of dissipating fog.

• Economic and Environmental Geology
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• v.27 no.5
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• pp.451-458
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• 1994

Geochemical studies on gold-bearing quartz veins and granitic wallrocks from the Mugeug mine were carried out in order to investigate primary dispersion patterns of elements and to quantify primary dispersion widths of elements with distance from the gold-bearing quartz veins. The best fitting model of dispersion pattern in altered wallrock around the gold-bearing quartz veins is an exponential function for Au, As, Sb, $Na_2O$ and Sr, and a quadratic function for CaO, $K_2O$, MnO, Ba, Rb and Cs. The primary dispersion widths are 15~343 cm in the hanging wall, and 33~173 cm in the footwall. The width of primary dispersion in the hanging wall is twice as thick as that in the footwall mainly due to the thermal effect and volatile components. The primary dispersion width is increased as the increase of gold-bearing quartz vein width and contents of As and Sb in gold-bearing quartz veins, but is not related to Au content in gold-bearing quartz veins.

• Journal of the Korean Electrochemical Society
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• v.14 no.4
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• pp.245-252
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• 2011

In this study, carbon nanotubes were used as supporter to get high dispersion and high loading of Pt for PEMFC. Thermal oxidation method was applied to carbon nanotubes surface treatment. FT-IR and XPS were used to measure the effect of temperature on functional group. The increased concentration of functional groups was confirmed by XPS analysis, and increased Pt loading and dispersion was also observed by TGA and TEM analysis with increased temperature. Thermal behavior of oxidation is closely related to the manufacture of highly dispersed Pt/MWCNTs. Pt/MWCNTs treatment temperature at $90^{\circ}C$, showed high dispersion and high loading of Pt, and also showed good cell performance.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2177-2181
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• 2007

In this paper, effective thermal conductivities of water-based $Al_2O_3$-nanofluids with low concentration from 0.01 vol. % to 0.3 vol. % are experimentally obtained by transient hot wire method (THWM). The water-based $Al_2O_3$-nanofluids are manufactured by two-step method which is widely used. To examine suspension and dispersion characteristics of the water-based $Al_2O_3$-nanofluids, Zeta potential as well as transmission electron micrograph (TEM) is observed. We confirm the manufactured $Al_2O_3$-nanofluids have good suspension and dispersion. The effective thermal conductivities of the water-based $Al_2O_3$-nanofluids with low concentration are enhanced up to 1.64% compared with that of DI water at $21^{\circ}C$. In addition, experimental results are compared with theoretical results from Jang and Choi model.