Erscheint 6 Ausgaben pro Jahr
ISSN Druckformat: 2152-5102
ISSN Online: 2152-5110
Indexed in
The Effect of a Spacer Grid Mixing Vane on the Critical Heat Flux for a Rod Bundle
ABSTRAKT
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.