• 한국유체기계학회 논문집
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• 제12권4호
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• pp.7-13
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• 2009

The purposes of present work are to analyze the convective heat transfer with three-dimensional Reynolds-averaged Navier-Stokes analysis, and to optimize shape of the mixing vane using the analysis results. Response surface method is employed as an optimization technique. The objective function is defined as a combination of inverse of heat transfer rate and friction loss. Two bend angles of mixing vane are selected as design variables. Thermal-hydraulic performances have been discussed and optimum shape has been obtained as a function of weighting factor in the objective function. The results show that the optimized geometry improves the heat transfer performance far downstream of the mixing vane.

• 한국전산유체공학회지
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• 제14권2호
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• pp.1-8
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• 2009

The purposes of present work are to analyze the convective heat transfer with three-dimensional Reynolds-averaged Navier-Stokes analysis, and to optimize shape of the mixing vane taken tolerance into consideration by using the analysis results. Response surface method is employed as an optimization technique. The objective function is defined as a combination of heat transfer rate and inverse of pressure drop. Two bend angles of mixing vane are selected as design variables. Thermal-hydraulic performances have been discussed and optimum shape has been obtained as a function of weighting factor in the objective function. The results show that the optimized geometry improves the heat transfer performance far downstream of the mixing vane.

• 설비공학논문집
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• 제28권5호
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• pp.186-194
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• 2016

As a turbulence-enhancing device, a mixing vane installed at a spacer grid of the fuel assembly plays a role in improving the convective heat transfer by generating either swirl flow in the subchannels or cross flow between fuel rod gaps. Therefore, both configuration and arrangement pattern of a mixing vane are important factors that determine the performance of a mixing vane. In this study, in order to examine the flow distribution features inside $5{\times}5$ fuel assembly with swirl-type mixing vanes used in benchmark calculation of OECD/NEA, simulations were conducted with commercial CFD software ANSYS CFX R.14. Predicted results were compared to data measured from MATiS-H (Measurement and Analysis of Turbulent Mixing in Subchannels-Horizontal) test facility. In addition, the effect of swirl-type mixing vanes on flow pattern inside the fuel assembly was described.

• 대한기계학회논문집B
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• 제30권1호
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• pp.24-31
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• 2006

Mixing vanes have been installed in the space grid of nuclear fuel rod bundle to improve turbulent heat transfer. Split mixing vanes induce the vortex flow in the cooling water to swirl in sub-channel of fuel assembly. But, The swirling flow decays rapidly so that the heat transfer enhancing effect limited to short length after the mixing vane. In thi present study, the large scale vortex flow(LSVF) is generated by rearranging the mixing vanes to the coordinated directions. This LSVF mixing vanes generate the most strong secondary flow vortices which maintain about 35 $D_H$ after the spacer grid. The streamwise vorticity generated by LSVF sustain two times more than that split mixing vane. Heat transfer in the rod bundle occurs greatly at the same direction to cross flow, and maximum temperature at the surface of bundle drops about 1.5K

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.1819-1824
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• 2004

The common method to improve heat transfer in Nuclear fuel rod bundle is install a mixing vane in space grid. The previous split mixing vane is guides cooling water to swirl flow in sub-channel of fuel assembly. But, this swirl flow decade rapidly after mixing vane and the effect of enhancing the heat transfer vanish behind this short region. The large scale secondary vortex flow was generated by rearranging the inclined angle direction of mixing vanes to the coordinated directions. This LSVF mixing vanes generate the most strong secondary flow vortices which maintain about 35 $D_H$ after the spacer grid and the streamwise vorticity in subchannel with LSVF mixing vane sustain two times more than that in subchannel with split mixing vane. The turbulent kinetic energy and the Reynolds stresses generated by the mixing vanes have nearly same scales but maintain twice more than previous type.

• 설비공학논문집
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• 제18권10호
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• pp.811-818
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• 2006

Mixing vanes have been installed in the space grid of nuclear fuel rod bundle to improve turbulent heat transfer. Split mixing vanes induce the vortex flow in the cooling water to swirl in sub-channel of fuel assembly. But, The swirling flow decays rapidly so that the heat transfer enhancing effect limited to short length after the mixing vane. In the present study, the large scale vortex flow (LSVF) is generated by rearranging the mixing vanes to the coordinated directions. This LSVF mixing vanes generate the most strong secondary flow vortices which maintain about $35D_h$ after the spacer grid. The streamwise vorticity generated by LSVF sustain two times more than that split mixing vane.

• 한국방사성폐기물학회:학술대회논문집
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• 한국방사성폐기물학회 2003년도 가을 학술논문집
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• pp.590-595
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• 2003

An Exponential experiment system which is composed of a neutron detector, a signal analysis system and a neutron source, Cf-252 has been installed in order to experimentally determine the neutron effective multiplication factor for a PWR spent fuel assembly. The axial background neutron flux is measured in a preliminary performance test. From the results, the spacer grid position is determined to be consistent with the design specifications within a 2.3% relative error. The induced fission neutron for four of the assemblies is also measured by scanning the neutron source, Cf-252 or the neutron detector. The exponential decay constants have been evaluated by the application of the Poisson regression to the net induced fission neutron counts. The measured keffs determined on the basis of the exponential decay constants of Cl5 appeared to be 0.541, 0.540, 0.597 and 0.556, respectively, which are comparable with 0.55195$\pm$0.00232 of the MCNP calculation.

• 대한기계학회논문집B
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• 제27권3호
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• pp.311-318
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• 2003

The present work evaluates the effects of mixing vane shape on the flow structure and heat transfer downstream of mixing vane in a subchannel of fuel assembly. by obtaining velocity and pressure fields. turbulent intensity. flow-mixing factors. heat transfer coefficient and friction factor using three-dimensional RANS analysis. Four different shapes of mixing vane. which were designed by the authors were tested to evaluate the performances in enhancing the heat transfer. Standard k-$\varepsilon$ model is used as a turbulence closure model. and. periodic and symmetry conditions are set as boundary conditions. The flow blockage ratio is kept constant. but the twist angle of mixing vane is changed. The results with three turbulence models were compared with experimental data.

• 대한기계학회논문집B
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• 제40권5호
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• pp.329-337
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• 2016

연료집합체의 지지격자에 설치된 혼합날개는 난류 강화 기구로서 부수로 내부에서 선회류 또는 연료봉 간극사이에서 횡류를 발생시켜 대류열전달을 증진시키는 역할을 한다. 따라서 혼합날개의 기하학적인 형상 및 배열 형태는 혼합날개의 성능을 결정하는 중요한 인자이다. 본 연구에서는 OECD/NEA의 벤치마크 계산에서 활용된 분할 형태의 혼합날개가 장착된 $5{\times}5$ 연료집합체 내부에서의 유동분포 특성을 파악하기 위해 상용 전산유체역학 소프트웨어인 ANSYS CFX R.14를 사용하여 계산을 수행하였고, 계산결과를 MATiS-H 시험장치의 측정값과 비교하였다. 또한 분할 형태의 혼합날개 형상이 연료집합체 내부유동 형태에 미치는 영향에 대해 설명하였다.

• Nuclear Engineering and Technology
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• 제25권4호
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• pp.552-560
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• 1993

지진 및 냉각재상시사고시 핵연료집합체의 건전성 확인은 원자로심모델의 핵연료집합체 집중질량모델을 이용하여 지지격자에 발생한 충격 해석치와 동적좌굴시험치와의 비교를 통해 사고시의 핵연료집합체 건전성을 평가하여 왔다. 그러나 이 방법은 사고시 핵연료집합체 부품별 설계 요구사항 만족여부를 평가하는데 미흡하여 본 연구에서는 지진 및 냉각재상실사고시 핵연료집합체 구조적건전성 평가를 위한 수평방향 핵연료집합체 응력해석모델을 개발하였다. 이를 위해 첫번째 단계로써 원자로심모델의 해석 결과인 각 절점에서의 변위와 회전각으로부터 응력을 계산하고 가장 큰 응력을 갖는 핵연료를 찾아내는 MAIN이라는 전산프로그램을 개발하였다. 그리고 다음단계로써 이 .프로그램에서 구한 핵연료집합체 변위와 회전각을 이용하여 핵연료집합체의 주요부품에 가해지는 응력을 계산하기 위한 핵연료집합체 응력해석모델을 개발하였다. 이 모델은 집합체주요부품인 안내관과 연료봉을 3차원보요소로, 지지격자스프링을 선형 및 회전스프링으로 각각 모델링 하였으며, MAIN 프로그램의 출력인 집합체의 변위를 구속조건으로 사용하였다. 또한, 개발된 프로그램과 응력해석모델을 이용하여 하나의 적용 예로써 임의의 지진하중하에서 16$\times$16형 핵연료집합체에 대한 응력해석을 수행하였다. 이 모델을 개발하므로써 지진 및 냉각재상실사고시 핵연료집합체 설계용구사항 만족여부를 평가할 수 있는 기틀을 마련하였다.