• Journal of computational fluids engineering
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• v.14 no.1
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• pp.78-85
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• 2009

A combined theoretical and numerical study is conducted to design a slit nozzle for large-area liquid coating. The objectives are to guarantee the uniformity in the injected flow and to provide the capability of explicit control of flow rate. The woking fluid is a dilute aqueous solution containing single-walled carbon nanotubes and its low viscosity and the presence of dispersed materials pose technical hurdles. A theoretical analysis leads to a guideline for the geometric design of a slit nozzle. The CFD-based numerical experiment is employed as a verification tool. A new flow passage unit, connected to the nozzle chamber, is proposed to permit the control of flow rate by using the commodity pressurizer. The numerical results confirm the feasibility of this idea. The optimal geometry of internal structure of the nozzle has been searched for numerically and the related issues are discussed.

• Corrosion Science and Technology
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• v.15 no.5
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• pp.245-252
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• 2016

The pipelines and equipments are degraded by flow-accelerated corrosion (FAC), and a large-scale test facility was constructed for simulate the FAC phenomena in secondary coolant environment of PWR type nuclear power plants. Using this facility, FAC test was performed on weld pipe (carbon steel and low alloy steel) at the conditions of high velocity flow (> 10 m/s). Wall thickness was measured by high temperature ultrasonic monitoring systems (four-channel buffer rod type and waveguide type) during test period and room temperature manual ultrasonic method before and after test period. This work deals with the complex effects of flow velocity on the wall thinning in weld pipe and the test results showed that the higher flow velocity induced different increasement of wall thinning rate for the carbon steel and low alloy steel pipe.

• Transactions of the Korean Society of Automotive Engineers
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• v.23 no.6
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• pp.656-662
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• 2015

In the present study, multi-layered Si DLC (Silicon Diamond-Like Carbon) coatings with HMDSO (Hexamethyldisiloxane) buffer layers are applied on SKD 11 substrates by PECVD (Plasma Enhanced Chemical Vapor Deposition) with different HMDSO gas flow rates, while the gas flow rate of $C_2H_2$ is fixed to enhance the electric resistivity of forming dies for electrically assisted forming. The HMDSO buffer layer is introduced to increase adhesion between the base metal and Si-DLC layers. The result of evaluation of electric resistivity and adhesion strength shows that the properties are affected by the flow rate of HMDSO, while the flow rate of 80 sccm results in the coating with the highest electric resistivity and adhesion strength among the selected flow rates.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.24 no.5
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• pp.401-408
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• 2012

Volumetric mass transfer coefficient was measured with carbon dioxide and deionized water for the gas-liquid cocurrent slug flow in 2, 5 and 8 mm tubes. Measurement was repeated with and without a vertical section in an experimental setup and entrance effect was found greater for smaller tubes. Volumetric mass transfer coefficient in the vertical section was found generally a strong function of gas- and liquid-phase superficial velocities. 5 mm- and 8 mm-tube data are highly consistent each other but not with 2 mm tube.

• Transactions of Materials Processing
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• v.3 no.4
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• pp.415-426
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• 1994

Multistage deformation behavior of Nb-microalloyed steel and carbon steel was studied by torsion test with declining temperature T, constant pass strain $\varepsilon_i$, interrupt time $(t_i)$, and varying strain rate $(\.{\varepsilon})$. In the range of $1000^{\circ}C~790^{\circ}C$ and 4.00/sec~0.38/sec, the flow stress at each pass was correlated to the deformation variables. As the finished deformation temperatures are decreased to the range of $790^{\circ}C~900^{\circ}C$, Nb precipitates play an important role on the grain refinement of Nb-microalloyed steel. the flow stress of Nb-microalloyed steel was higher than the carbon steel's while the grain size of Nb-microalloyed steel was smaller than carbon steel below the temperature of $900^{\circ}C$.

• Journal of Powder Materials
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• v.10 no.1
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• pp.1-5
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• 2003

Nano-sized WC powders were synthesized by vapor phase reaction using the precusor of tungsten ethoxide under helium and hydrogen atmosphere. The phases of the powder were varied with reaction Bone and gas flow rate. The powder size was about 30nm in diameter, and the tungsten carbide powder was coated by carbon layer. The synthesis of nano-sized WC powders was promoted as the hydrogen gas flow rate became higher. Inversely, tungsten oxide was formed by increasing the flow rate of helium gas. The synthesized powders were analyzed by XRD, FE-SEM, carbon analyzer etc.

• Journal of the Korean Ceramic Society
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• v.21 no.2
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• pp.156-164
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• 1984

The characteristic of pyrolytic carbon deposited in a fluidized bed as measured by density apparent crystallite size and viewed metallographically under polarized light can be easily controlled by adjusting the deposition parameters such as deposition temperature and propane flow rate or silicon content. The density of isotopic pyrolytic carbons deposited from propane between 120$0^{\circ}C$ and 140$0^{\circ}C$ increases with increasing propane flow rate and decreasing deposition temperature from 1, 73g/cc to 2.08g/cc. The apparent crystallite size Lc parameter appears to depend only on deposition temperature being entirely independent of the propane flow rate. The carbon matrix density of the silicon-alloyed carbonds deposited from propane and methyltrichlorosil-ane from 2.05g/cc for a silicon content around 9wt% to 2.67g/cc for a silicon content of 36.7wt% The Lc parameter of the deposition temperature being entirely independent of the silicon content.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.7
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• pp.645-651
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• 2004

Fin-tube evaporator for carbon dioxide has been investigated both by experiment and simulation. Inside refrigerant heat transfer and outside heat and mass transfer of a wet surface heat exchanger were modeled using appropriate correlations. The results estimated by the calculation were in good agreement with the experimental results. The simulation errors were less than 7.9% for estimating capacity, 0.6$^{\circ}C$ for air exit temperature, 1.2% for air exit humidity and 17% for $CO_2$ exit pressure. The simulation program was used to study the effect of air flow direction, number of rows and refrigerant circuits. For a 2-row evaporator, parallel flow showed better performance for low air velocity but for high air velocity, counter-flow was better. Refrigerant circuits, however, showed insignificant effect on the performance.

• International Journal of Highway Engineering
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• v.19 no.6
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• pp.175-182
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• 2017

PURPOSES : Road sectors contribute approximately 16 % of total GHG emission rates in South Korea. Engineers and experts expend significant efforts to identify countermeasures for the reduction of carbon emission. This study aims to determine how total carbon emission rates change depending on whether or not there is speed limit enforcement. METHODS : In this study, Lamm's travel speed profile theory is first adopted to select the hazard road, which sections are designated as speed limit enforcement. Second, Motor Vehicle Emission Simulator (MOVES) was used to simulate the carbon emission on the road. RESULTS : The total carbon emission rate under speed limit enforcement was 10,773 g higher than the condition without speed limit enforcement in the designated road. This might affect acceleration, which can lead to increased emissions. CONCLUSIONS : There would be no researches about proving the relationship how speed limit enforcement has an effect on carbon emission. The result of our study can provide valuable guidelines regarding road safety and eco-friendly roads.

• Journal of the Korean Vacuum Society
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• v.20 no.5
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• pp.374-380
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• 2011

Carbon coils could be synthesized on nickel catalyst layer-deposited silicon oxide substrate using $C_2H_2$ and $H_2$ as source gases and $SF_6$ as an additive gas under thermal chemical vapor deposition system. The characteristics (formation density and morphology) of as-grown carbon coils according to the injection stage of $SF_6$ gas incorporation were investigated. A continuous injecting of $SF_6$ gas flow could give rise to many types of carbon coils-related geometries, namely linear tub, micro-sized coil, nano-sized coil, and wave-like nano-sized coil. However, the limitation of the geometry as the nano-sized geometries of carbon coils could be achieved by the incorporation of $SF_6$ in a short time (1 min) during the initial deposition stage. A delayed injection of a short time $SF_6$ gas flow can deteriorate the limitation of the geometries. It confirms that the injection time and its starting point of $SF_6$ gas flow would be very important to determine the geometries of carbon coils.