Nuclear Engineering and Technology

Korean Nuclear Society (한국원자력학회)
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Spacer Grid Effects on Turbulent Flow in Rod Bundles

지지격자가 봉다발 난류유동에 미치는 영향

  • Published : 1996.02.01
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Abstract

The local hydrulic characteristics in subchannels of 5$\times$5 nuclear fuel bundles with spacer grids were measured at upstream and downstream of the spacer grid for the investigation of the spacer grid effects on turbulent flow structure by using an LDV(Laser Doppler Velocimeter). The measured parameters are axial velocity and turbulent intensity, skewness factor, and flatness factor. Pressure drops were also measured to evaluate the loss coefficient for the spacer grid and the friction factor for rod bundles. From these data, it was found that the turbulent mixing and forced mixing occur up to $x/D^h=10$ and 20 from the spacer grid, respectively. The turbulence decay behind spacer grid behaves in the similar decay rate as turbulent flow through mesh grids or screens. Mixing factors useful in subchannel analysis code were correlated from the data and show the highest value near spacer grid and then have a stable values.

지지격자를 갖는 5$\times$5 핵연료 봉다발부수로내에서 국부 수력특성인자들을 레이저 유속측정장치인 LDV(Laser Doppler Velocimeter)를 이용하여 측정하였다. 이 연구는 지지격자가 봉다발 난류유동구조에 미치는 영향에 관한 연구에 관점을 두었다. 축방향속도, 난류강도, 편이도, 편평도 등의 측정인자들을 측정하였다. 압력강하를 측정하여 지지격자의 손실계수와 봉다발의 마찰계수를 구하였다 실험결과로부터 활발한 난류혼합거리는 지지격자로부터 x/D$_{h}$=10까지이고, 강제 혼합거리는 지지격자로부터 x/D$_{h}$=20까지임이 관찰되었다. 지지격자하류에서의 축방향 난류강도 감쇄거동은 mesh격자나 screen을 통과하는 난류유동과 같은 경향을 보여주었다. 측정된 자료로부터 부수로해석 code에 입력함수로 적용할 수 있는 국부 난류혼합계수상관식을 구하였다. 국부 혼합계수분포 경향을 관찰하여보면 지지격자 근처에서 최대값을 보이고, 하류방향으로 진행하면서 안정된 값을 갖는다.

Keywords

References

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