Spacer Grid Effects during a Reflood in an Annulus Flow Channel

Abstract

An experimental study has been performed to investigate the effects of a spacer grid in an annulus flow channel with a uniform power shaped single rod during a bottom-reflood phase. The ranges of the experimental parameters are 2-8 cm/s for the flooding velocity, 20-80°C for the inlet subcooling temperature, and 500-700°C for the initial wall temperature. Two types of spacer grids, i.e., a swirl-vane type grid and a straight egg-crate type spacer grid, have been tested to compare the differences in their thermal hydraulic behavior through the spacer grids. Flow patterns and a rewetting front behavior near a spacer grid are remarkably altered with the types of spacer grids used. In the case of a low flooding rate and a high wall temperature condition, the cooling capacity of the swirl-vane spacer grid is better than that of the straight egg-crate type grid. Rewetting velocities through the swirl-vane spacer grids are faster than those through the other types of grids. The cladding temperature of the heater rod near a spacer grid shows a different pattern with the types of spacer grid used.