• Bulletin of the Korean Chemical Society
• /
• v.32 no.3
• /
• pp.829-835
• /
• 2011

A dispersive liquid-liquid microextraction based on solidification of floating organic droplet (DLLME-SFO) has been developed as a new approach for the extraction of trace copper in water and beverage samples followed by the determination with flame atomic absorption spectrometry. In the DLLME-SFO, 8-hydroxy quinoline, 1-dodecanol, and methanol were used as chelating agent, extraction solvent and dispersive solvent, respectively. The experimental parameters related to the DLLME-SFO such as the type and volume of the extraction and dispersive solvent, extraction time, sample volume, the concentration of chelating agent and salt addition were investigated and optimized. Under the optimum conditions, the enrichment factor for copper was 122. The method was linear in the range from 0.5 to $300\;ng\;mL^{-1}$ of copper in the samples with a correlation coefficient (r) of 0.9996 and a limit of detection of $0.1\;ng\;mL^{-1}$. The method was applied to the determination of copper in water and beverage samples. The recoveries for the spiked water and beverage samples at the copper concentration levels of 5.0 and $10.0\;ng\;mL^{-1}$ were in the range between 92.0% and 108.0%. The relative standard deviations (RSD) varied from 3.0% to 5.6%.

• Journal of computational fluids engineering
• /
• v.12 no.2
• /
• pp.32-36
• /
• 2007

NUFLEX is a general purpose program for the analysis 3D thermo/fluid flow and pre/post processor in a complex geometry. NUFLEX is composed of various physical models, such as phase change(solidification/melting) and spray, MHD(Magneto Hydraulic Dynamics) models. It is possible to simulate continuous cast iron process and spray droplet breakup/collision phenomenon. For the verification of these models, compared with the experimental data and commercial CFD code's results. The results show good agreements with experimental and comercial CFD codes's results.

• 한국전산유체공학회:학술대회논문집
• /
• 2007.04a
• /
• pp.99-102
• /
• 2007

NUFLEX is a general purpose program for the analysis 3D thermo/fluid flow and pre/post processor in a complex geometry. NUFLEX is composed various physical models, such as phase change(solidification/melting) and spray, MHD(Magneto Hydraulic Dynamics) models. It is possible to simulate of continuous cast iron process and spray droplet breakup/collision phenomenon. For the verification of these models, compared with the experimental data and commercial CFD code's results. The results show good agreements with experimental and comercial CFD codes's results.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.5 no.4
• /
• pp.297-308
• /
• 2007

The granulation equipment of concentrated wastes is manufactured for the polymer solidification of concentrated wastes. It uses liquid sodium silicate as a granulating agent for the granulating of dried powder containing boric acid. The granulating agent is sprayed in the form of droplet and mean size of dried granules is $2{\sim}4mm$. The new technology which has been used for the polymer solidification of spent resin in U.S. and certified by Nuclear Regulatory Commission (NRC) is successfully applied to concentrated wastes. This uses in-situ solidification process within drum without mechanical mixing. Maximum loading of waste can be achieved without increasing of waste volume. Polymer waste forms were evaluated with several test such as fire test, compressive strength test, leaching test, immersion test, irradiation test, and thermal cycling test according to standard test procedures.

• Proceedings of the Korean Powder Metallurgy Institute Conference
• /
• 2006.09a
• /
• pp.58-59
• /
• 2006

In Spray Forming, specific enthalpy is a key parameter in the deposition process as it influences the thermal condition of the impinging droplets as well as that of the deposit surface. An empirical model for the distribution of specific enthalpy in the spray cone was developed as an easy to handle alternative to numerical models with which the descriptive partial differential equations are solved numerically. The model results were compared with the experimental data to validate its applicability.

• Journal of Korea Foundry Society
• /
• v.13 no.5
• /
• pp.462-475
• /
• 1993

A numerical analysis on the microstructural evolutions of microcellular and cellular ${\alpha}-aluminum$ phase in the gas-atomized Al-8wt. pct droplets was represented. The 2-dimensional non-Newtonian heat transfer and the dendritic growth theory in the undercooled melt were combined under the assumptions of a point nucleation on droplet surface and the macroscopically smooth solid-liquid interface enveloping the cell tips. It reproduced the main characteristic features of the reported microstructures quite well. It predicted a considerable volume fraction of segregation-free region in a droplet smaller than $l0{\mu}m$ if an initial undercooling larger than 100K is given. The volume fractions of the microcellular region($g_A$) and the sum of the microcellular and cellular region($g_a$) were predicted as functions of the heat transfer coefficient, h and initial undercooling, ${\triangle}T$. It was shown that $g_A$ and $g_a$, in the typical gas-atomization processes with $h=0.1-1.0W/cm^2K$, are dominated by ${\triangle}T$ and h, respectively, but for h larger than $4.0W/cm^2K$, a fully microcellular structure can be obtained irrespective of the initial undercooling.

• Korean Chemical Engineering Research
• /
• v.53 no.5
• /
• pp.627-631
• /
• 2015

Various solid structures were prepared by electrospray technique. In this process, liquid flows out from a capillary nozzle under a high electrical potential and is subjected to an electric field, which causes elongation of the meniscus to form a jet. In our study, by controlling the amount of polyvinyl pyrrolydone in precursor solution, the jet either disrupted into droplets for the formation of spherical particles or was stretched in the electric field for the formation of fibers. During the electrospray process, the ethanol solvent was evaporated and induced the solidification of precursors, forming solid particles. The evaporation of ethanol solvent also enhanced the mass transport of solutes from the inner core to the solid shell, which facilitated fabrication of porous and hollow structure. The network structures were also prepared by heating the collector.

• Nuclear Engineering and Technology
• /
• v.48 no.1
• /
• pp.72-86
• /
• 2016

A steam explosion may occur during a severe accident, when the molten core comes into contact with water. The pressurized water reactor and boiling water reactor ex-vessel steam explosion study, which was carried out with the multicomponent three-dimensional Eulerian fuel-coolant interaction code under the conditions of the Organisation for Economic Co-operation and Development (OECD) Steam Explosion Resolution for Nuclear Applications project reactor exercise, is presented and discussed. In reactor calculations, the largest uncertainties in the prediction of the steam explosion strength are expected to be caused by the large uncertainties related to the jet breakup. To obtain some insight into these uncertainties, premixing simulations were performed with both available jet breakup models, i.e., the global and the local models. The simulations revealed that weaker explosions are predicted by the local model, compared to the global model, due to the predicted smaller melt droplet size, resulting in increased melt solidification and increased void buildup, both reducing the explosion strength. Despite the lower active melt mass predicted for the pressurized water reactor case, pressure loads at the cavity walls are typically higher than that for the boiling water reactor case. This is because of the significantly larger boiling water reactor cavity, where the explosion pressure wave originating from the premixture in the center of the cavity has already been significantly weakened on reaching the distant cavity wall.

• Nuclear Engineering and Technology
• /
• v.54 no.10
• /
• pp.3909-3918
• /
• 2022

In the event of a severe accident, the reactor core may melt due to insufficient cooling. the high-temperature core melt will have a strong interaction (FCI) with the coolant, which may lead to steam explosion. Steam explosion would pose a serious threat to the safety of the reactors. Therefore, the study of steam explosion is of great significance to the assessment of severe accidents in nuclear reactors. This research focuses on the development of a two-dimensional steam explosion integrated analysis code called SEINA. Based on the semi-implicit Euler scheme, the three-phase field was considered in this code. Besides, the influence of evaporation drag of melt and the influence of solidified shell during the process of melt droplet fragmentation were also considered. The code was simulated and validated by FARO L-14 and KROTOS KS-2 experiments. The calculation results of SEINA code are in good agreement with the experimental results, and the results show that if the effects of evaporation drag and melt solidification shell are considered, the FCI process can be described more accurately. Therefore, it is proved that SEINA has the potential to be a powerful and effective tool for the analysis of steam explosions in nuclear reactors.