• Journal of computational fluids engineering
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• v.16 no.2
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• pp.30-48
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• 2011

A three-dimensional thermal-hydraulic code, CUPID, has been developed for the analysis of transient two-phase flows at component scale. The CUPID code adopts a two-fluid three-field model for two-phase flows. A semi-implicit two-step numerical method was developed to obtain numerical solutions on unstructured grids. This paper presents an overview of the CUPID code development and assessment strategy. The governing equations, physical models, numerical methods and their improvements, and the systematic verification and validation processes are discussed. The code couplings with a system code, MARS, and, a three-dimensional reactor kinetics code, MASTER, are also presented.

• Proceedings of the KSME Conference
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• 2001.06b
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• pp.121-126
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• 2001

In this study, the 4-way spool valve characteristics are clearly defined and proposed new type of spool valve. This paper presents governing equations of the flow through clearances between sleeve and spool as a model of orifice flow for null characteristic analysis, and programmed analysis software of it. This software is possible to basically analysis that not only which case of open center, closed center or critical center but +,- displacement of spool, lab position, boundary region and spool opening of the valve, and to estimate the pressure variation in the spool and external leak flow variation. We are convinced that the scale of load pressure difference is changed as lab condition of spool valve, and this scale is changed with boundary point on the annular clearance. It is vary useful to designer and user of spool valve with this design data and analysis software.

• Journal of Korean Society of Water and Wastewater
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• v.26 no.6
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• pp.861-869
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• 2012

The chlorine's residual concentration prevents the regrowth of microorganism in water transport along the pipeline system. Precise prediction of chlorine concentration is important in determining disinfectant injection for the water distribution system. In this study, a pilot scale water distribution system was designed and fabricated to measure the temporal variation of chlorine concentration for three flow conditions (V = 0.88, 1.33, 1.95 m/s). Various kinetic models were applied to identify the relationship between hydraulic condition and chlorine decay. Genetic Algorithm (GA) was integrated into five kinetic models and time series of chlorine were used to calibrate parameters. Model fitness was compared by Root Mean Square Error (RMSE) between measurement and prediction. Limited first order model and Parallel first order showed good fitness for prediction of chlorine concentration.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.05b
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• pp.474-477
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• 2005

The Industrial development and the Increase in population have brought out a rapid increase of wastewater discharge. To deal with this matter, much estimate has been spend on construction and management of a large scale sewage treatment plant. Although every effort has been carried out, river water quality has no significantly improved. Especially. the aggravation of the water quality in dry season is brought out a serious social problem. The purpose of this study Is the development of an optimal water quality management technique considering the efficient control of the multiple pollutant load associated with the total pollutant load control. A GUI(Graphical User Interface) system named 'QL2-XP' model is developed by object-oriencted language for the user convenience and practical usage. Suggested GUI system consist of hydraulic analysis. water quality analysis, optimized model calibration processes, and postprocessing the simulation results.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.8
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• pp.886-892
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• 2013

Hydraulic hose assemblies are used as piping components for construction machinery, automobile, aircraft, industrial machinery, machine tools, and machinery for ships. Then the reliability of hose assemblies is important because total hydraulic system, which used to deliver the fluid power ($P^*Q$) needed to flexibility in the piping system, is not operated if the hose assembly failed in the system. The data of the accelerated life test estimated through the shape parameter(${\beta}$) resulting of the Weibull distribution analysis. This study has tried to reduce the test time resulting from varying impulse pressure range and the flexing diameter. Accelerated life test model for the test results was adopted the GLL(generalized log linear) and the accelerated indexes are identified as 6.64 for the pressure and 4.46 for flexing radius. Also, it found that shape parameter is 6.19, scale parameter(${\eta}$) is $1.035{\times}108$, which were adopted the pressure 35 MPa and the flexing diameter R100 mm in the used condition.

• Nuclear Engineering and Technology
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• v.48 no.5
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• pp.1083-1095
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• 2016

The design of Prototype Gen-IV Sodium-Cooled Fast Reactor (PGSFR) has been developed and the validation and verification (V&V) activities to demonstrate the system performance and safety are in progress. In this paper, the current status of test activities is described briefly and significant results are discussed. The large-scale sodium thermal-hydraulic test program, Sodium Test Loop for Safety Simulation and Assessment-1 (STELLA-1), produced satisfactory results, which were used for the computer codes V&V, and the performance test results of the model pump in sodiumshowed good agreement with those in water. The second phase of the STELLA program with the integral effect tests facility, STELLA-2, is in the detailed design stage of the design process. The sodium thermal-hydraulic experiment loop for finned-tube sodium-to-air heat exchanger performance test, the intermediate heat exchanger test facility, and the test facility for the reactor flow distribution are underway. Flow characteristics test in subchannels of a wire-wrapped rod bundle has been carried out for safety analysis in the core and the dynamic characteristic test of upper internal structure has been performed for the seismic analysis model for the PGSFR. The performance tests for control rod assemblies (CRAs) have been conducted for control rod drive mechanism driving parts and drop tests of the CRA under scram condition were performed. Finally, three types of inspection sensors under development for the safe operation of the PGSFR were explained with significant results.

• Nuclear Engineering and Technology
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• v.46 no.5
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• pp.655-666
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• 2014

The CUPID code has been developed at KAERI for a transient, three-dimensional analysis of a two-phase flow in light water nuclear reactor components. It can provide both a component-scale and a CFD-scale simulation by using a porous media or an open media model for a two-phase flow. In this paper, recent advances in the CUPID code are presented in three sections. First, the domain decomposition parallel method implemented in the CUPID code is described with the parallel efficiency test for multiple processors. Then, the coupling of CUPID-MARS via heat structure is introduced, where CUPID has been coupled with a system-scale thermal-hydraulics code, MARS, through the heat structure. The coupled code has been applied to a multi-scale thermal-hydraulic analysis of a pool mixing test. Finally, CUPID-SG is developed for analyzing two-phase flows in PWR steam generators. Physical models and validation results of CUPID-SG are discussed.

• Journal of Korea Water Resources Association
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• v.33 no.4
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• pp.407-417
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• 2000

To estimate the longitudinal dispersion coefficient at the downstream of Jungrang-River, the undistorted 1/20 scale hydraulic model was used in this study. Experiments were conducted for dry season discharge, and Rhodamine B was used as a tracer. The relationship curve between concentration and conductivity of Rhodamine B was otained by laboratory test, and the conductivity which was measured in hydraulic model was converted to concentration using this curve. The longitudinal dispersion coefficient was calculated using the relationship between the peak concentration and the time to peak concentration. The results of this study were compared with the calculated values by the empirical equations for the longitudinal dispersion coefficient and with the field data. The results of comparison show that Parker's equation underestimates, and Liu'g equation and Iwasa and Aya's one overestimate, and McQuivey and Keefer's equations, Fischer's one, Magazine's one, and Seo and Cheong's one predict relatively well. The measured data sets were relatively close to the observed ones in natural river. The longitudinal dispersion coefficient at the downstream of Jungrang-River was estimated $10\textrm{m}^2/s$.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.08a
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• pp.277-284
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• 2004

Low carbon steels containing Si of up to $1.2\;wt\%$ were oxidized in air at 1373 K and 1523 K, i.e. below and above the eutectic temperature of FeO and $Fe_2SiO_4$. The influence of a impurity element, S on behavior of scale formation during oxidation was investigated by using $M\"{o}chssbauer$ spectroscopy and EDS. This allowed establishment of an interface oxidation model of Si-added steel depending on temperature and an impurity element. A compound of FeO and FeS was formed in the scale/matrix interface of low carbon steels containing S of up to $0.03\;wt\%$ oxidized above 1213 K of the eutectic temperature. This was flat formed between $Fe_2SiO_4$ nodules along the scale/matrix interface without selective oxidation. It is due to low viscosity and high wettability of the compound of FeO and FeS in liquid. Conventional metallographic examinations revealed that roughness of the scale/matrix interface in Si-added steels became flat as the content of S increased. It was independent of oxidizing temperature and Si content. Effects of oxidizing temperature and an impurity element content on descaling characteristics in Si-added steels were evaluated by using a hydraulic descaling simulator. Good descaling characteristics was attributable to this flatness of the scale/matrix interface.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.159-159
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• 2022

Soil represents a substantial component within the global carbon cycle and small changes in the SOC stock may result in large changes of atmospheric CO₂ particularly over tens to hundreds of years. In this study, we aim to (i) evaluate the SOC stock in the topsoil 0 - 15 cm from soil physical and chemical characteristics and (ii) find the correlation of SOC and soil organic matter (SOM) for national-scale in South Korea. First of all, based on the characteristics of the soil to calculate the soil hydraulic properties, SOC stock is the SOC mass per unit area for a given depth. It depends on bulk density (BD-g/cm³), SOC content (%), the depth of topsoil (cm), and gravel content (%). Due to insufficient data on BD observation, we establish a correlation between BD and SOC content, sand content, clay content parameter. Next, we present linear and non-linear regression models of BD and the interrelationship between SOC and SOM using a linear regression model and determine the conversion factor for them, comparing with Van Bemmelen 1890's factor value for the country scale. The results obtained, helps managers come up with suitable solutions to conserve land resources.