RT Journal Article ID 280c945f61f64d77 A1 Lee, Joon Sik A1 Park, J. H. A1 d'Aillon, M. Gros T1 The Effect of a Spacer Grid Mixing Vane on the Critical Heat Flux for a Rod Bundle JF International Journal of Fluid Mechanics Research JO FMR YR 1998 FD 1998-06-01 VO 25 IS 1-3 SP 230 OP 242 AB The present study experimentally investigates the critical heat flux for a 5 × 5 rod bundle as a simple model for an actual PWR fuel assembly. Tests were performed for the 25 rod bundle with and without mixing vanes of spacer grids to evaluate the effect of mixing vanes on the critical heat flux. The enthalpy distribution among the subchannels and turbulent mixing coefficient were obtained by single-phase flow tests, and the effect of the mixing vanes on the critical heat flux was examined by two-phase flow tests for various inlet subcooling, mass flux and pressure conditions. The results show that the effect of the mixing vanes on the critical heat flux is more dominant in the subcooled or bubbly flow regime than in the slug or annular flow regime. The mixing vane gives the positive effect by generating the swirling flow and turbulent inter-channel mixing, and by agitating bubbles from the wall for all the flow conditions, on the other hand, it also incurs the negative effect by thinning and destroying the liquid film as a result of increasing the entrainment at the annual flow condition and by the blockage-like behavior at the high mass flux condition. PB Begell House LK https://www.dl.begellhouse.com/journals/71cb29ca5b40f8f8,6b7c8043191c60e1,280c945f61f64d77.html