• 한국지열·수열에너지학회논문집
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• 제13권4호
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• pp.8-13
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• 2017

The effects of operational conditions of cooling water system on energy consumption for central cooling system are researched by using TRNSYS program. Cooling tower water pump flow rate, cooling tower fan flow rate, and condenser water temperature with various dry-bulb and wet-bulb temperatures are varied and their effects on total and component power consumption are studied. If the fan maximum flow rates of cooling tower is decreased, cooling tower fan and total power consumptions are increased. If the cooling tower water pump maximum flow rates is decreased, chiller and total power consumptions are increased. If condenser water set-point temperature is increased, chiller power consumption is increased and cooling tower fan power consumption is decreased, respectively.

• Nuclear Engineering and Technology
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• 제38권2호
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• pp.119-128
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• 2006

We start to develop a predictable technology for thermal-hydraulic performance of the RMWR core using an advanced numerical simulation technology. As a part of this technology development, we are developing the advanced interface tracking method to improve the conservation of volume of fluid. The present paper describes a part of the development of the twophase flow simulation code TPFIT with the advanced interface tracking method. The numerical results applied to large-scale water-vapor two-phase flow in tight lattice rod bundles are shown and compared with experimental results. In the results of numerical simulation, a tendency of the predicted void fraction distribution in horizontal plane agreed with the measured values obtained by the advanced neutron radiography technique including the bridge formation of the liquid at the position of adjacent fuel rods where an interval is the narrowest.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1998년도 춘계학술발표회논문집(1)
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• pp.532-537
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• 1998

Friction factor and two-phase flow frictional multiplier for a CANFLEX bundle are newly developed and presented in this paper. CANFLEX as a 43-element fuel bundle has been developed jointly by AECL/KAERI to provide greater operational flexibility for CANDU reactor operators and designers. Friction factor and two-phase flow frictional multiplier have been developed by using the experimental data of pressure drops obtained from two series of Freon-l34a (R-134a) CHF tests with a string of simulated CANFLEX bundles in a single phase and a two-phase flow conditions. The friction factor for a CANFLRX bundle is found to be about 20 % higher than that of Blasius for a smooth circular pipe. The pressure drop predicted by using the new correlations of friction factor and two-phase frictional multiplier are well agreed with the experimental pressure drop data of CANFLEX bundle within ${\pm}\;5\;%$ error.

• Nuclear Engineering and Technology
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• 제36권2호
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• pp.165-174
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• 2004

The distributed resistance model has been recently implemented into the MATRA-LMR code in order to improve its prediction capability over the wire-wrap model for a flow blockage analysis in the LMR. The code capability has been investigated using experimental data observed in the FFM (Fuel Failure Mock-up)-2A and 5B for two typical flow conditions in a blocked channel. The predicted results by the MATRA-LMR with a distributed resistance model agreed well with the experimental data for wire-wrapped subchannels. However, it is suggested that the parameter n in the distributed resistance model needs to be calibrated accurately for a reasonable prediction of the temperature field under a low flow condition. Finally, the analyses of a blockage for the assembly of the KALIMER design are performed. Satisfactory results by the MATRA-LMR code were obtained through and rerified a comparison with results of the SABRE code.

• Nuclear Engineering and Technology
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• 제52권1호
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• pp.170-177
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• 2020

A mixer with a new concept design has been adapted into water treatment plants. It reportedly cuts down the energy consumption of the mixer by the new mixer, which moves vertically and creates internal flows toward its bottom. However, no experimental observations have been made on the internal flow caused by a vertical impeller. In this study, a radiotracer experiment, radioactive particle tracking (RPT) technique, and particle image velocimetry (PIV) were carried out to visualize the flow in the mixer, and compared to each other. The results show that the flow patterns from these techniques are very similar to each other, and the performance of the mixer was good enough to mix the inner materials.

• 한국정밀공학회지
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• 제21권11호
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• pp.46-52
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• 2004

CMP (Chemical-Mechanical Polishing) is a process in which both chemical and mechanical mechanisms act simultaneously to produce the planarized wafer. CMP process is an extensive usage and continuing high growth rates in the semiconductor industry. The understanding of the process, however, is much slower. The nature of material removal from the wafer is still undefined and ambiguous. Material removal rate according to the slurry flow rate is also undefined and ambiguous. Thus, in this study, the basic mechanism of material removal rate as slurry flow rate is defined in terms of energy supply and energy loss.

• Structural Engineering and Mechanics
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• 제43권3호
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• pp.395-410
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• 2012

The visualizing energy flow and control in vibrating stiffened plates with a cutout are studied using finite element method. The vibration intensity, vibration energy and strain energy distribution of stiffened plates with cutout at different excitation frequencies are calculated respectively and visualized for the various cases. The cases of different size and boundaries conditions of cutouts are also investigated. It is found that the cutout or opening completely changes the paths and distributions of the energy flow in stiffened plate. The magnitude of energy flow is significantly larger at the edges near the cutout boundary. The position of maximum strain energy distribution is not corresponding to the position of maximum vibrational energy. Furthermore, the energy-based control using constrained damping layer (CDL) for vibration suppression is also analyzed. According to the energy distribution maps, the CDL patches are applied to the locations that have higher energy distribution at the targeted mode of vibration. The energy-based CDL treatments have produced significant attenuation of the vibration energy and strain energy. The present energy visualization technique and energy-based CDL treatments can be extended to the vibration control of vehicles structures.

• 에너지공학
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• 제24권3호
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• pp.48-54
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• 2015

중앙집중식 냉방 시스템을 적용하고 있는 대형 빌딩이나 플랜트 설비들의 경우 부하 증설 및 피크부하에 대응하기 위한 여유율을 반영한 설비 설계 및 시공이 이루어지고 있다. 이는 부분부하가 걸리는 기간 동안에는 설비의 저부하 운전으로 인한 장비의 효율 저하와 에너지 과소비의 원인이 된다. 본 연구는 부분부하에 효율적으로 대응할 수 있도록 냉방플랜트 최적 유량제어를 통한 에너지 절감 방안에 대한 연구로서 냉방플랜트 에너지 성능 분석 프로그램을 이용하여 냉방 부하를 분석하고, 최적 유량제어 시스템을 제안하여 그 에너지 성능을 비교 평가하는 것을 목적으로 한다. 성능 분석 결과 냉방플랜트 최적 유량제어 시스템 적용 시 기존 에너지 사용량 대비 약 17%의 전기에너지 절감이 가능하였다.

• Nuclear Engineering and Technology
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• 제56권4호
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• pp.1244-1249
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• 2024

A combination of flow-accelerated corrosion (FAC) tests and corresponding computational fluid dynamics (CFD) tests were performed to determine the hydrodynamic parameters that could help predict the highly susceptible location to FAC in the elbow section. The accelerated FAC tests were performed on a specimen containing elbow sections fabricated using commercial 2-inch carbon steel pipe. The tests were conducted at flow rates of 9 m/s under the following conditions: water temperature of 150 ℃, dissolved oxygen <5 ppb, and pH 7. Thickness reduction of the specimen pipe due to FAC was measured using ultrasonic testing. CFD was conducted on the FAC test specimen, and the turbulence intensity, and shear stress were analyzed. Notably, the location of the maximum hydrodynamic parameters, that is, the wall shear stress and turbulent intensity, is also the same location with maximum FAC rate. Therefore, the shear stress and turbulence intensity can be used as hydrodynamic parameters that help predict the FAC-induced wall-thinning rate. The results provide a method to identify locations susceptible to FAC and can be useful for determining inspection priority in piping systems.

• 한국수소및신에너지학회논문집
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• 제33권1호
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• pp.47-54
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• 2022

In this study, we performed numerical analysis for 1 kWe SOFC stack of internal manifold types according to the different manifold sizes to verify the influence of the flow uniformity into each cell. To simulate the flow phenomena in the stack, the continuity and momentum conservation equations including the standard k-𝜺 turbulent model for the steady-state conditions were applied. From the calculation results, we verified that the pressure drop from inlet pipes to outlet pipes decreased to a log scale as the manifold size increased in the internal manifold types. Also, we found that the flow uniformity increased on an exponential scale as the manifold size increased. In addition, the calculation results showed that the flow uniformity gradually improved as the fuel and oxygen utilization increased.