• Proceedings of the Korean Radioactive Waste Society Conference
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• 2005.11a
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• pp.69-78
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• 2005

Appropriate numerical models for the simulation of off-gas flow in hot area of the vitrification plant have been developed in this study. The models have been applied to analyze the effect of design parameters of real plant and numerical analyses have been performed for CCM(Cold Crucible Melter), pipe cooler and HTF(High Temperature Filter) At first, the effect of excess oxygen and the ratio of oxygen distribution on combustion characteristics in the CCM has been studied. Next, solidification behavior of radio nuclide In the pipe tooler has been numerically modeled and scrutinized. Finally, flow pattern In accordance with the location of off-gas entrance of the HTF has been compared.

• Journal of Korea Foundry Society
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• v.15 no.3
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• pp.283-290
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• 1995

Molybdenum ingot of 50mm in diameter were obtained from sintered Mo bars by EB drip melting technique. Macroscopic observation of EB remelted ingot indicates that coarse and columnar grains grow in the direction parallel to ingot pulling direction. This can be explained by slow solidification (3mm/min), large temperature gradient and heat flow to this direction. The orientation of columnar structure was found to be <110>, <200> and <211> by the analysis of X-ray diffraction patterns. The contents of typical metallic impurities in Mo sintered bar are 1.2ppm Cr, 3ppm Fe, 44ppm Zr, 150ppm W. Most of metallic impurities were reduced below the order of ppm except zirconium and tungsten by the selective evaporation. In the removal of nonmetallic impurities, oxygen and carbon impurities were lowered from 120 to 6ppm and from 157 to 106ppm, respectively, after first melting. Although the purification effect was not significant with the number of remelting, Vickers hardness was reduced from 217 to 195 and 184 in sequence with increasing the number of remelting.

• Journal of the Korean institute of surface engineering
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• v.45 no.1
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• pp.1-7
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• 2012

Multi-walled carbon nanotube (MWCNT) aluminum composite powders were deposited to form coatings using a high velocity oxygen fuel (HVOF) spraying process. High thermal energy and contact with atmospheric oxygen were supplied as the MWCNT aluminum composite particles were exposed to a gas flow field at high temperature (${\sim}3.0{\times}10^3$ K) during HVOF spraying. As a result, the particles underwent full or partial melting and rapid solidification due to the high thermal energy, and the exposure to oxygen induced the interfacial reaction of MWCNTs within the particle. The electrical and mechanical properties of MWCNT aluminum composite coatings were evaluated based on microstructure analysis. Electrical resistivity, elastic modulus, and micro-hardness, of the MWCNT aluminum composite coatings were higher than those of pure aluminum coating. The contribution of MWCNTs to the aluminum matrix can be attributed to their high electrical conductivity, dispersion hardening and anchoring effects. The relationship among the properties and the interaction of the MWCNTs with the aluminum matrix is discussed.

• Journal of Korea Foundry Society
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• v.27 no.2
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• pp.88-94
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• 2007

General criteria for the risering design of steel castings and commercial codes for the flow and solidification analysis were used to design the optimized risering in V-process. Three type of specimens were chosen including thin plates and a thick disc. Sided riser installed in the front of a plate casting was effective to prevent the shrinkage defects and to increase the casting yield ratio. Exothennic sleeve and chill were also effective. It was possible to apply the general criteria for the risering design of steel castings to V-process. Temperature of a mold surface was expected to rise over $1,000^{\circ}C$ in the temperature calculation considering radiation effect of molten metal in the mold. Since weakening temperature of the vinyl used in V-process is about $70^{\circ}C$, it should be emphasized that a proper coating of the vinyl film is necessary to prevent the possibility of burning out of the vinyl by the molten metal.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.6
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• pp.136-144
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• 2002

Melting method has long been considered difficult to realize because of problems such as the low foamability of molten metal, the varying size of cellular structures and solidification shrinkage. The parameters to solve the problem in electric furnace were stirring temperature, stirring velocity, heating velocity and foaming temperature It is important to consider the effects of induction heating, because it brings about the inner flow by the temperature gradient. Aspect ratio also depends on the induction heating. Mechanical properties are dependent on cell sizes and aspect rations. Therefore, this paper presents the effects of these parameters on the cell sizes. For the sake of this, combined stirring process was used to fabricate aluminum foam materials by the above mentioned parameters. Image analysis was performed to calculate the cell sizes, distributions, and aspect ratioes at the cross section of feared aluminum in the direction of height.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2005.05a
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• pp.174-179
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• 2005

In the super slow speed die casting process, the casting defects due to melt flow should be controlled in order to obtain sound casting products. The casting defects that are caused by molten metal were cold shut formation, entrapment of air, gas, and inclusion. But the control of casting defects has been based on the experience of the foundry engineers. The calculation of simulation can produce very useful and important results. The calculation data of die casting process condition from the computer simulation by the Z-CAST is made to insure that the liquid metal is injected at the right velocity range and that the filling time is small enough to prevent premature solidification. The parameters of runner shape that affected on the optimized conditions that was calculated with simple equation were investigated. These die casting process control techniques of automobile valve body mid-plate have achieved good agreement with the experimental data of tensile strength, hardness test, and material structure photographies satisfactory results.

• Advances in nano research
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• v.16 no.4
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• pp.325-340
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• 2024

There are several novel uses for dispersing many nanoparticles into a conventional fluid, including dynamic sealing, damping, heat dissipation, microfluidics, and more. Therefore, melting heat and mass transfer characteristics of a 3-D MHD Hybrid Nanofluid flow over a rotating disc with presenting dufour and soret effects are assessed numerically in this study. In this instance, we investigated both ferric sulfate and molybdenum disulfide as nanoparticles suspended within base fluid water. The governing partial differential equations are transformed into linked higher-order non-linear ordinary differential equations by the local similarity transformation. The collection of these deduced equations is then resolved using a Chebyshev spectral collocation-based algorithm built into the Mathematica software. To demonstrate how different instances of hybrid/ nanofluid are impacted by changes in temperature, velocity, and the distribution of nanoparticle concentration, examples of graphical and numerical data are given. For many values of the material parameters, the computational findings are shown. Simulations conducted for different physical parameters in the model show that adding hybrid nanoparticle to the fluid mixture increases heat transfer in comparison to simple nanofluids. It has been identified that hybrid nanoparticles, as opposed to single-type nanoparticles, need to be taken into consideration to create an effective thermal system. Furthermore, porosity lowers the velocities of simple and hybrid nanofluids in both cases. Additionally, results show that the drag force from skin friction causes the nanoparticle fluid to travel more slowly than the hybrid nanoparticle fluid. The findings also demonstrate that suction factors like magnetic and porosity parameters, as well as nanoparticles, raise the skin friction coefficient. Furthermore, It indicates that the outcomes from different flow scenarios correlate and are in strong agreement with the findings from the published literature. Bar chart depictions are altered by changes in flow rates. Moreover, the results confirm doctors' views to prescribe hybrid nanoparticle and particle nanoparticle contents for achalasia patients and also those who suffer from esophageal stricture and tumors. The results of this study can also be applied to the energy generated by the melting disc surface, which has a variety of industrial uses. These include, but are not limited to, the preparation of semiconductor materials, the solidification of magma, the melting of permafrost, and the refreezing of frozen land.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.25 no.1
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• pp.82-88
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• 2015

Objectives: This study is designed to analyze the penetration performance into ceiling materials containing asbestos of scattering prevention agents and investigate the change in penetration depth and viscosity according to the dilution rate of anti-scattering agents diluted with distilled water. Methods: Five different types of scattering prevention agents were spread on plate-type asbestos ceiling materials. The penetration depth of each coated ceiling material was measured by energy dispersive spectroscopy (EDS) analysis, based on X-ray fluorescence (XRF) results of the non-coated ceiling materials. Test equipment installed the ceiling materials and 60 minutes were collected at a flow rate of $10{\ell}/min$ at a filter of 25 mm. Results: An EDS analysis of the cross-section of ceiling materials constructed with a scattering prevention agent revealed that potassium is detected in the process of penetrating hardener solidification and this element could be an indicator for infiltration. When anti-scattering agents with different viscosities were constructed and the penetration depth was analyzed by potassium detection assessment using EDS, the depth results with viscosities of 5.0, 2.5, and 1.9 cP were 98.5, 103, and $147{\mu}m$, respectively. Penetration performance improved with decrease in viscosity. Conclusions: For asbestos ceiling materials, it is concluded that a higher dilution rate of the scattering prevention agent leads to lower viscosity, and hence a deeper penetration depth from $156{\mu}m$ to 3 mm. The asbestos anti-scattering properties according to the penetration depth will be confirmed through further study.

• Korean Journal of Materials Research
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• v.17 no.1
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• pp.11-17
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• 2007

Turbulent in-situ mixing process is a new material process technology to get dispersed phase in nanometer size by controlling reaction of liquid/solid, liquid/gas, flow ana solidification speed simultaneously. In this study, mixing which is the key technology to this synthesis method was studied by computational fluid dynamics. For the simulation of mixing of liquid metal, static mixers investigated. Two inlets for different liquid metal meet ana merge like 'Y' shape tube having various shapes and radios of curve. The performance of mixer was evaluated with quantitative analysis with coefficient of variance of mass fraction. Also, detailed plots of intersection were presented to understand effect of mixer shape on mixing. The simulations show that the Reynolds number (Re) is the important factor to mixing and dispersion of $TiB_2$ particles. Mixer was designed according to the simulation, and $Cu-TiB_2$ nano composites were evaluated. $TiB_2$ nano particles were uniformly dispersed when Re was 1000, and cluster formation and reduction in volume fraction of $TiB_2$ were found at higher Re.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.8
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• pp.1051-1057
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• 2010

This paper proposes a method that involves a combination of FDM and FEM for analyzing casting process. At present, many numerical analysis methods such as FDM, FEM, and BEM are used for solving engineering problems. For a given problem, a specific method that is suited to the problem is adopted; in general, FDM or FVM is favored for problems related to fluid flow or heat transfer, and FEM is adopted in stress analysis. However, there is an increasing need for using a combined method for complex and coupled phenomena analysis. Hence, we proposed a method in which FDM and FEM are coupled in three-dimensional space, and we applied this method to analyze casting process. In the proposed method, solidification and heat transfer was analyzed by using FDM. The field data such as temperature distribution were converted into a format suitable for FEM analysis that was used for calculating thermal stress distribution. Using the proposed method, we efficiently analyzed the analysis process from the viewpoints of work and time.