• 한국추진공학회지
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• 제5권3호
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• pp.33-40
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• 2001

본 연구에서는 초음속 증기 이젝터의 작동특성을 조사하기 위하여 압축성 축대칭 Navier-Stokes 방정식의 수치계산을 행하였다. 2차 유동측의 압력 및 배압을 변화시켜 이들 압력이 혼입유량에 미치는 영향을 조사하였다. 연구의 결과로부터 초음속 증기 이젝터에서 2차 유동측 압력 및 배압은 임계 혼입유량에 상당한 영향을 미치며, 1차구동노즐의 형상과 2차유동의 압력이 주어지는 경우 임계혼입 유량비를 예측할 수 있음을 알았다. 수치계산 결과는 실험에서 얻은 임계혼입유량비를 잘 예측하였다.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2004년도 추계 학술대회논문집
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• pp.127-130
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• 2004

In this study, three-dimensional numerical calculations are peformed to simulate the flow and heat transfer in helically coiled tube steam generator employing a commercial CFD (Computational Fluid Dynamics) code. The problem considered herein includes the boiling phase change flow of tube side fluid and the single-phase counter-current flow of shell side hot fluid transferring heat to the tube side flow thru the tube wall. Detailed investigations are performed for both shell-side and tube-side flow fields in terms of density and volume fractions of each phase of fluids as well as for the tube wall heat transfer field in terms of heat transfer coefficients.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.2612-2615
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• 2008

Diaphragm seals have great effects on the performance of large power-generation steam turbines. Hence, it is important to decrease the leakage flow through the diaphragm seals and understand the flow characteristics within the diaphragm seals. In this study, numerical analysis was carried-out with the seals of large one-body type diaphragms developed by a domestic company. CFX, which is a commercial CFD code, was used to analyze the performance and flow characteristics of the diaphragm seals for three difference clearance cases. The results of numerical analysis show variations in the performance and flow characteristics according to the changes of labyrinth seal clearance.

• 한국전산유체공학회지
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• 제11권2호
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• pp.8-18
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• 2006

A CFD benchmark calculation for a steam blowdown test was performed for 30 seconds to develop the methodology of numerical analysis for the thermal mixing between steam and subcooled water. In the CFD analysis, the grid model simulating the sparger and the IRWST pool were developed by the axisymmetric condition and then the steam condensation phenomena by a direct contact was modelled by the so-called condensation region model. Thermal mixing phenomenon in the subcooled water tank was treated as an incompressible flow, a free surface flow between the air and the water, a turbulent flow, and a buoyancy flow. The comparison of the CFD results with the test data showed a good agreement as a whole, but a small temperature difference was locally found at some locations. The commercial CFD code of CFX4.4 together with the condensation region model can simulate the thermal mixing behavior reasonably well when a sufficient number of mesh distribution and a proper numerical method are adopted.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.1603-1604
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• 2007

The load of power plants changes every from time to time according to which steam flow of boiler changes. the feed water control is very important for the power plant to be operated in its stability conditions. In case of circulation type boiler, the instability of feed water control leads to instability of drum level control. The higher level of drum water can induce bad quality steam to go into turbine which means the possibility of damage. The lower level of drum water can induce the tubes of boiler water wall to be overheated. In case of once through type boiler, the instability of feed water control leads to bad cooling of superheaters. The less the feed water flow is, the more heated the superheater is. It is necessary for the turbine driving feed water pump to be controlled for the optimal feed water flow in the large capacity power plant. The speed of turbine is controled for the feed water flow. By the way, the optimal control of steam valve is necessary for the speed control of turbine. Therefore, the various kinds of the steam valve structures are introduced in this paper

• Nuclear Engineering and Technology
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• 제53권12호
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• pp.3892-3901
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• 2021

The pressure drop of a moisture separator in a steam generator is the important design parameter to ensure the successful performance of a nuclear power plant. The moisture separators have a wide range of operating conditions based on the arrangement of them. The prediction of the pressure drop in a moisture separator is challenging due to the complexity of the multi-dimensional two-phase vortex flow. In this study, the moisture separator test facility using the air/water two-phase flow was used to predict the pressure drop of a moisture separator in a Korean OPR-1000 reactor. The prototypical steam/water two-phase flow conditions in a steam generator were simulated as air/water two-phase flow conditions by preserving the centrifugal force and vapor quality. A series of experiments were carried out to investigate the effect of hydraulic characteristics such as the quality and liquid mass flux on the two-phase pressure drop. A new prediction model based on the scaling law was suggested and validated experimentally using the full and half scale of separators. The suggested prediction model showed good agreement with the steam/water experimental results, and it can be extended to predict the steam/water two-phase pressure drop for moisture separators.

• 에너지공학
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• 제14권2호
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• pp.98-104
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• 2005

Pannier-arrangement condensers are usually adopted in the turbine generator units of combined cycle power plants. Optimization of operating performance and economy is an important goal, which requires accurate understanding of flow and heat transfer effects in the condenser. The tube bundle arrangement and steam flow behaviors of pannier-arrangement condensers are very different from those of common condensers. The physical model for existing numerical simulation program of condenser is refined by constructing the correlations for flow resistance and condensation heat exchange coefficient in which the influences of steam flow direction are considered according to available experimental data. The adaptability of the developed physical model and simulation program of pannier-arrangement condenser is verified with available experimental data.

• 연구논문집
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• 통권25호
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• pp.55-65
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• 1995

Three-dimensional incompressible turbulent flow fields within the passage of the steam turbine nozzle with/without tip clearance have been simulated by solving the Navier-Stokes equations with SIMPLE scheme. The extended k-e model is applied to modeling the Reynolds stresses. Grids in the computational domain are generated by solving the Poisson's equations to improve the smoothness and orthogonality. Flow losses, secondary flow, velocity profiles, and deviation angles are obtained. The computated results without tip clearance show good agreement with the experimental data.

• Korean Chemical Engineering Research
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• 제54권4호
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• pp.479-486
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• 2016

순산소 전로 후드의 일산화탄소와 열회수를 위해서는 고효율의 증기를 발생시키는 증기드럼의 장착이 필요하다. 그러나 제선 제강공정에서 증기발생은 간헐적이거나 주기적인 산소 취입공정기간에 제한적이다. 따라서, 증기드럼은 전로의 주기에 따른 산소의 취련기간 동안 효율적으로 증기를 발생시키도록 최적 설계되어야 한다. 따라서 본 연구에서는 다양한 운전조건 및 기하학적 형상변화가 증기드럼 내의 열유동 특성과 성능에 미치는 효과를 예측할 수 있는 3차원 전산유체역학 모델을 제안하였다. 본 모델은 유체유동 및 열전달 뿐만 아니라 계면유동에서의 증발 및 응축을 유한체적법을 사용하여 고려하였다. 본 모델의 예측성능을 검증하기 위하여 실험에서 구한 증기발생량과 비교하였으며 3.2%의 상대오차를 보였다.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2004년도 유체기계 연구개발 발표회 논문집
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• pp.297-302
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• 2004

CFD analysis has been performed to investigate flow behavior in LP exhaust hood of steam turbines and evaluate exhaust loss, which is directly related to the steam turbine performance, in it. Development of the optimum shape of LP exhaust hood has been done with an improved shape of steam guide, which plays a key role in terms of cost as well as performance. The newly developed LP exhaust hood will be applied for a large USC steam turbine having a capacity of 1,000 MW.