The present experimental study investigates single-phase heat transfer coefficients downstream of support grid in 6×6 rod bundles. Support grid with Split mixing vanes enhance heat transfer in rod bundles by generating turbulence but this turbulence is confined to a short distance. Support grid with large scale vortex flow(LSVF) mixing vanes enhanced heat transfer to a longer distance. In this study, the experiments were performed at reynolds numbers of 50,000. The characteristics of the heat transfer enhancement of the Split mixing vane and those of the LSVF mixing vane were compared. The results showed that the characteristics of the heat transfer enhancement of rods by the Split mixing vane were limited to 10 Dh after the spacer grid, but those by the LSVF mixing vane were maintained until 15 Dh after the spacer grid. For the reynolds number of 50,000, the heat transfer enhancement effect was 3.0% greater when using the LSVF mixing vane than when using the Split mixing vane between the 1 ∼ 15 Dh interval after the spacer grid.

1. 서 론
 2. 실험 장치 및 방법
  2.1 실험 장치
  2.2 국부열전달계수 계산방법
  2.3 국부열전달계수의 측정
 3. 실험 결과 및 고찰
 4. 결 론
 후 기
 References

• 변선준(Member, Korea atomic energy research institute) | S.J. Byun Corresponding author
• 신용철(korea atomic energy research institute) | Y.C . Shin
• 민경호(korea atomic energy research institute) | K .H . M in
• 방윤곤(korea atomic energy research institute) | Y.K . Bang
• 채영종(korea atomic energy research institute) | Y.J. C hae