• Nuclear Engineering and Technology
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• v.54 no.12
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• pp.4776-4797
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• 2022

In the one-dimensional thermal-hydraulic (TH) codes, a subcooled boiling model to predict the void fraction profiles in a vertical channel consists of wall heat flux partitioning, the vapor condensation rate, the bubbly-to-slug flow transition criterion, and drift-flux models. Model performance has been investigated in detail, and necessary refinements have been incorporated into the Safety and Performance Analysis Code (SPACE) developed by the Korean nuclear industry for the safety analysis of pressurized water reactors (PWRs). The necessary refinements to models related to pumping factor, net vapor generation (NVG), vapor condensation, and drift-flux velocity were investigated in this study. In particular, a new NVG empirical correlation was also developed using artificial neural network (ANN) techniques. Simulations of a series of subcooled flow boiling experiments at pressures ranging from 1 to 149.9 bar were performed with the refined SPACE code, and reasonable agreement with the experimental data for the void fraction in the vertical channel was obtained. From the root-mean-square (RMS) error analysis for the predicted void fraction in the subcooled boiling region, the results with the refined SPACE code produce the best predictions for the entire pressure range compared to those using the original SPACE and RELAP5 codes.

• Nuclear Engineering and Technology
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• v.25 no.2
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• pp.233-236
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• 1993

For one-dimensional two-phase flow without phase change and without axially-temporally rapid change of pressure, the interrelationship between the drift-flux model and the two-fluid model is studied. It is derived on the basis of the fact that the vapor conservation equation is related to the momentum equation by the drift flux. Starting from the two-fluid model, we obtain the interfacial friction expressed in terms of drift-flux parameter. Also, by deriving the void propagation equation, the drift-flux is shown to have jnterrelationship with forces in the two-fluid model.

• Korean Journal of Weed Science
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• v.7 no.3
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• pp.337-347
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• 1987

Spary and vapor drift injuries of apple, pear, and peach seedling caused by soil-applied oxyfluorfen were studied in a greenhouse. Bud bursting rate of all fruit trees was reduced by both spray and vapor drifts of oxyfluorfen, but reduction in bud bursting rate of pear and peach was greater than that of apple trees. Reduction in the number of leaves per shoot of apple and peach was greater than that of pear trees. Leaf injury of pear was most severe and occurred earliest, but leaves of peach were least injured, Leaf injuries of pear and apple were caused by both spray and vapor drifts, but leaves of peach was injured largely by vapor drift. Reduction in shoot growth of and pear was greater than that of peach trees. Shoot growth of pear was more rapidly retared compared with apple trees. In the field, oxyfluorfen delayed the time of bud bursting in young apple trees. Oxyfluorfen applied between initiation and completion of bud bursting delayed bud bursting more than earlier application although ultimate number of bursted buds was similar to control. The number of leaves per shoot and total length of shoots were lower than control until 40 days after application of oxyfluorfen, and then were similar to control because of vigorous growth after May.

• Nuclear Engineering and Technology
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• v.51 no.6
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• pp.1487-1503
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• 2019

The methods and performance of a pin-level nuclear reactor core thermal-hydraulics (T/H) code ESCOT employing the drift-flux model are presented. This code aims at providing an accurate yet fast core thermal-hydraulics solution capability to high-fidelity multiphysics core analysis systems targeting massively parallel computing platforms. The four equation drift-flux model is adopted for two-phase calculations, and numerical solutions are obtained by applying the Finite Volume Method (FVM) and the Semi-Implicit Method for Pressure-Linked Equation (SIMPLE)-like algorithm in a staggered grid system. Constitutive models involving turbulent mixing, pressure drop, and vapor generation are employed to simulate key phenomena in subchannel-scale analyses. ESCOT is parallelized by a domain decomposition scheme that involves both radial and axial decomposition to enable highly parallelized execution. The ESCOT solutions are validated through the applications to various experiments which include CNEN $4{\times}4$, Weiss et al. two assemblies, PNNL $2{\times}6$, RPI $2{\times}2$ air-water, and PSBT covering single/two-phase and unheated/heated conditions. The parameters of interest for validation include various flow characteristics such as turbulent mixing, spacer grid pressure drop, cross-flow, reverse flow, buoyancy effect, void drift, and bubble generation. For all the validation tests, ESCOT shows good agreements with measured data in the extent comparable to those of other subchannel-scale codes: COBRA-TF, MATRA and/or CUPID. The execution performance is examined with a mini-sized whole core consisting of 89 fuel assemblies and for an OPR1000 core. It turns out that it is about 1.5 times faster than a subchannel code based on the two-fluid three field model and the axial domain decomposition scheme works as well as the radial one yielding a steady-state solution for the OPR1000 core within 30 s with 104 processors.

• Bulletin of the Korean Chemical Society
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• v.35 no.4
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• pp.1023-1028
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• 2014

Protonated caffeine ($CH^+$) and glucosamine ($GH^+$) overlapped in an analysis with ion mobility spectrometryquadrupole mass spectrometry. Ethyl lactate vapor (L) at different concentrations from 0 to 22 mmol $m^{-3}$ was added as a buffer gas modifier to separate these signals. The drift times of $CH^+$ and $GH^+$ increased with L concentration. The drift time increase was associated to clustering equilibria of $CH^+$ and $GH^+$ with one molecule of L and the equilibrium of $GH^+$ was more displaced to the formation of $GLH^+$ than that of $GLH^+$. $GH^+$ clustered more to L than $CH^+$ because $GLH^+$ formed more stable hydrogen bonds (26.30 kcal/mol) than $GLH^+$ (24.66 kcal/mol) and the positive charge in $GH^+$ was more sterically accessible than in $CH^+$. The aim of this work was to use theoretical calculations to guide the selection of a buffer gas modifier for IMS separations of two compounds that overlap in the mobility spectra and predict this separation, simplifying that empirical process.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2012.05a
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• pp.124-125
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• 2012

Korea institute of materials science (KIMS) use a linear deposition source called as a closed drift linear plasma source (CDLPS) as well as dual magnetron sputtering (DMS) to deposit SiOxCyHz films in $HMDSO/O_2$ plasma. The CDLPS generates linear plasma using closed drifting electrons and can reduce device degradations due to energetic ion bombardments on organic devices such as organic photovoltaic and organic light emission diode by controlling an ion energy. The deposited films are investigated by Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). Optical emission spectroscopy (OES) is used to measure relative radical populations of dissociation and recombination products such as H, CH, and CO in plasma. And SiOx film is applied to a barrier film on organic photovoltaic devices.

• Nuclear Engineering and Technology
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• v.25 no.1
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• pp.91-101
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• 1993

To predict accurately the thermal hydraulic behavior of light water reactors during normal or abnormal operation, the accurate estimation of the void distribution is required. Up to date, many techniques for predicting void fraction of two-phase flow systems have been suggested. Among these techniques, the drift-flux model is widely used because of its exact calculation ability and simplicity. However, to get more accurate prediction of void fraction using drift-flux model, slip and flow regime effects must be considered more properly In the drift-flux method, these two effects are accounted for by two drift-flux parameters ; $C_{o}$ and (equation omitted). At earlier stage, $C_{o}$ is measured in a circular tube. In this study, $C_{o}$ is experimentally determined by measuring local void fraction and vapor velocity distribution in a rectangular subchannel having 4 heating rods which simulates nuclear subchannels. The measurements are peformed with two-electrical conductivity probes which are known to be adequate for measuring local parameters. The experiments are performed at low flow rate and the system pressure less than 3 atmo spheric pressure. In this experiment, (equation omitted), is not measured, but quoted from well-known empirical correlation to formulate $C_{o}$. Finally, $C_{o}$ is expressed as a function of channel averaged void fraction. fraction.

• Nuclear Engineering and Technology
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• v.31 no.1
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• pp.29-48
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• 1999

Local two-phase flow parameters of subcooled flow boiling in inclined annulus were measured to investigate the effect of inclination on the internal flow structure. Two-conductivity probe technique was applied to measure local gas phasic parameters, including void fraction, vapor bubble frequency, chord length, vapor bubble velocity and interfacial area concentration. Local liquid velocity was measured by Pilot tube. Experiments were conducted for three angles of inclination; 0$^{\circ}$(vertical), 30$^{\circ}$, 60$^{\circ}$. The system pressure was maintained at atmospheric pressure. The range of average void fraction was up to 10% and the average liquid superficial velocities were less than 1.3 m/sec. The results of experiments showed that the distributions of two-phase How parameters were influenced by the angle of channel inclination. Especially, the void fraction and chord length distributions were strongly affected by the increase of inclination angle, and flow pattern transition to slug flow was observed depending on the How conditions. The profiles of vapor velocity, liquid velocity and interfacial area concentration were found to be affected by the non-symmetric bubble size distribution in inclined channel. Using the measured distributions of local phasic parameters, an analysis for predicting average void fraction was performed based on the drift flux model and flowing volumetric concentration. And it was demonstrated that the average void fraction can be more appropriately presented in terms of flowing volumetric concentration.

• Korean Journal of Environmental Agriculture
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• v.6 no.2
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• pp.84-93
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• 1987

The water solubilities and vapor pressures of chlorothalonil and Command were measured following the guidelines of the U.S. EPA and OECD. Water solubility of the two compounds is consistent with respective values in the literature. However, the vapor pressures of Chlorothalonil and Command were 5,000 times$(2{\times}10^{-7}\;torr\;at\;25^{\circ}C)$ and 100 times$(<1{\times}10^{-6}\;torr\;at\;45^{\circ}C)$ lower than the literature values, respectively. Courteous use of the vapor pressure values in the handbooks is suggested. With this study, experimental difficulties involved were recognized. Based on the low vapor pressure of Command, the cause of the accidental bleach of non-target plants in the United States might not be attributed to the volatilization of Command, but to the drift during the application of the herbicide. These approaches will be utilized to predict the environmental fate of new chemicals under development, to screen the potential environmental pollutants among chemicals already in use, and to assess measures to minimize the hazards.

• Transactions on Electrical and Electronic Materials
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• v.10 no.4
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• pp.107-110
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• 2009

In this study, the Hall effect has been studied in n-GaAs samples characterized by V/IIl growth ratios of 25, 50 and 100 and prepared by metal organic chemical vapor deposition. For the Hall effect measurements, the grown samples were cut to a size of 1${\times}$1 cm. The measurements were carried out at room temperature, using Indium contact metal at the four corners of the samples. According to the experimental results, the Schottky effect was not ovservation. Also for the n-GaAs sample of V/Ill 100 ratio the electron drift velocity was very high.