• Nuclear Engineering and Technology
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• v.52 no.12
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• pp.2821-2835
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• 2020

The phenomenon identification and ranking table (PIRT) is an important basis in the nuclear power plant (NPP) thermal-hydraulic analysis. This study focuses on the importance ranking of the input parameters when lacking the PIRT, and the target scenario is the small break loss of coolant accident (SBLOCA) in a pressurized water reactor (PWR) CPR1000. A total of 54 input parameters which might have influence on the figure of merit (FOM) were identified, and the sensitivity measure of each input on the FOM was calculated through an optimized moment-independent global sensitivity analysis method. The importance ranking orders of the parameters were transformed into the Savage scores, and the parameters were categorized based on the Savage scores. A parameter importance ranking table for the SBLOCA scenario of the CPR1000 reactor was obtained, and the influences of some important parameters at different break sizes and different accident stages were analyzed.

• Proceedings of the KIEE Conference
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• 2001.07a
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• pp.155-157
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• 2001

This paper presents an comparative study on the effect of SSSC and UPFC to the power system static analysis. SSSC is used to control active power flow in transmission lines by controlling the phase angle of the injected voltage source which is in rectangular to the line current. UPFC is used to control the magnitude and phase of the injected voltage sources which are connected both in series and in parallel with the transmission line to control power flow and bus voltage. To compare the effect of SSSC and UPFC in power system static analysis, the PSS/E simulation program is used. As the FACTS device model such as SSSC and UPFC is not provided in PSS/E yet, an equivalent load model is used. This procedure is implemented by IPLAN which is an external macro program of PSS/E. The simulation results show that UPFC is more effective to improve bus voltage than SSSC in power system static analysis.

• Journal of Power System Engineering
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• v.13 no.3
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• pp.27-32
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• 2009

Numerical analysis information of a complex discharge-passage will be very useful to improve hydrogen compression system. General information about an internal gas flow is presented by numerical analysis approach. Relating with hydrogen compressing system, which have an important role in hydrogen energy utilization, this should be a useful tool to observe the flow quickly and clearly. Flow characteristic analysis, including pressure and turbulence kinetic energy distribution of hydrogen gas from cylinder going to the chamber of a reciprocating compressor are presented in this paper. Discharge-passage model is designed based on real model of hydrogen compressor. Pressure boundary conditions are applied considering the real condition of operating system. The result shows pressure and turbulence kinetic energy are not distributed uniformly along the passage of the hydrogen compressing system. Path line or particles tracks help to demonstrate flow characteristics inside the passage. The existence of vortices and flow direction can be precisely predicted. Based on this result, the design improvement should be done. Consequently, development of the better hydrogen compressing system will be achieved.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.05a
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• pp.461-464
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• 2003

A new control volume finite element method is proposed for three dimensional analysis of polymer flow. Tetrahedral finite element is employed and co-located interpolation procedure for pressure and velocity is implemented. Inclusion of pressure gradient term in the velocity shape functions prevents the checkerboard pressure field from being developed. Vectorial nature of pressure gradient is considered in the velocity shape function so that velocity profile in the limit of very small Reynolds number becomes physically meaningful. The proposed method was verified through three dimensional simulation of pipe flow problem for Newtonian and power-law fluid. Calculated pressure and velocity field showed an excellent agreement with analytic solutions for pressure and velocity. Driven-cavity problem, which is reported to yield checkerboard pressure filed when conventional finite element method is applied, could be solved without yielding checkerboard pressure field when the proposed control volume finite element method was applied. The proposed method could be successfully applied to the three dimensional mold filling problem.

• Transactions of The Korea Fluid Power Systems Society
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• v.5 no.1
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• pp.20-26
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• 2008

Various types of hydraulic shock absorbers are widely used in many fields because of its numerous advantages. However, in order to design adequate damping characteristics, accurate flow data near the orifices are required essentially. In this paper, a commercial computational fluid dynamics(CFD) code, FLUENT is adopted to investigate the flow characteristics near orifices of a shock absorber. Static pressure and velocity vector distributions, fluid path lines are presented for compression/tension strokes and various piston speeds. In order to validate the result of analysis, the numerically obtained damping forces are compared with those of analytical estimations obtained by modified Bernoulli equation. The results reported herein will provide better understanding of the detailed flow fields within shock absorber, and the CFD analysis method proposed in this paper can be used in the design of other types of hydraulic shock absorber.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.19 no.2
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• pp.100-106
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• 2005

This paper addressed the issue of the three-phase load flow program for electric power distribution systems that include distributed generations. The equipment models were selected in order to consider imbalances among phases for the load flow analysis of distribution systems. Also, power equations and measurement functions are newly derived. The load flow analysis program developed in this paper was tested for the propriety of algorithm and convergence characteristics by case studies on test systems in various scales and types.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.6
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• pp.805-810
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• 2011

Recently, Use of Auxiliary power unit(APU) is increasing by growing demand for improvement of insufficient electric power and installation of emergency generation devices in military tracked vehicles and civil markets. And the trend is that the units are demanded for smaller size, lighter weight and higher output power, etc to suit consumer demands. To achieve these, it is essential to develop high performance system. Therefore, in this study, it was conducted in numerical analysis to investigate flow characteristics of rotor in APU generator. Also output performance of APU applied on the rotor is analyzed by experimental method. As the result, higher rotating speed of rotor caused high air flow rate at suction and it leads to linear increase of discharging flow rate. The maximum theoretical power was achieved at 12 $m^3$/min of flow rate and, at that time, output power of generator was about 7.825 kW. Also, it can be confirmed the stabilization of output performance is achieved in about 2 seconds by experiment.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.5 no.1
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• pp.65-72
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• 1993

An experiment has been carried out to identify flow patterns in a horizontal condensing flow with R-113. Characteristics of flow patterns were determined based upon a statistical analysis of differential pressure fluctuations at an orifice. The probability density function and power spectral density function of instantaneous pressure drop curves for various flow conditions were obtained. In comparison to the results of air-water flows, the flow patterns in a condensing flow such as annular, wavy, slug and plug could be identified. The experimental data determined by this technique were compared with the flow pattern maps suggested by other investigators. The result indicates that the statistical characteristics of differential pressure fluctuations at an orifice may be a useful tool for identifying flow patterns both in condensing flows and in adiabatic two-phase flows.

• The KSFM Journal of Fluid Machinery
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• v.12 no.5
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• pp.7-12
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• 2009

A nuclear fuel test loop(after below, FTL) is installed in the IRI of an irradiation hole in HANARO for testing the neutron irradiation characteristics and thermo hydraulic characteristics of a fuel loaded in a light water power reactor or a heavy water power reactor. There is an in-pile section(IPS) and an out-pile section(OPS) in this test loop. When HANARO is operated normally, the fuel loaded into the IPS has a nuclear reaction heat generated by a neutron irradiation. To remove the generated heat and to maintain the operation conditions of the test fuel, a main cooling water system(MCWS) is installed in the OPS of the FTL. The MCWS is composed of a main cooler, a pressurizer, two circulation pumps, a main heater, an interconnection pipe line and instruments. The interconnection pipeline is a closed loop which is connected to an inlet and an outlet of the IPS respectively. The MCWS is under a cold function test during a start-up period. This paper describes the system flow network analysis results of the flow control of a main cooling water system in the HANARO fuel test loop. It was confirmed through the results that the flow was met the system design requirements.

• Journal of Drive and Control
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• v.11 no.2
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• pp.22-29
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• 2014

This paper presents simulation-based analysis of energy flow of a wheel loader. The objective of this study is to analyze the energy flow of a wheel loader during driving and working. Because the wheel loader powertrain consists of a mechanical and hydraulic powertrain, the generated power from the engine is divided into 2 powertrains. Further, a virtual prediction of energy flow in the powertrains is a key factor in terms of optimal design. Accordingly, the simulation model that is able to predict the virtual energy flow is developed and analyzed in this study. The proposed wheel loader simulation model has been constructed in the Matlab/Simulink environment. It is expected that the developed simulation model will analyze the energy flow and efficiency in the design stage.