Structural Effect of a Staggered-Blade-type Grid Spacer on the Flow and Heat Transfer Characteristics of Supercritical Water in a Triangular Core Channel.

Abstract

The flow and heat transfer characteristics of supercritical water within a triangular subchannel of a supercritical water-cooled reactor (SCWR) were numerically studied using the SSG turbulence model. The structural effect of staggered-blade-type grid spacers on the flow and heat transfer characteristics of supercritical water was analyzed. The results show that the wall temperatures calculated by the SSG model are consistent with the experimental data. The structure of the staggered-blade-type grid spacers has a significant effect on the supercritical heat transfer in the large specific heat region. The change in the inner-wall temperature and local heat transfer coefficient caused by the blocking rate at different leaf deflection angles has the same trend in the flow direction. The heat transfer coefficient peak gradually increases with an increase in deflection angle. A clear vortex is generated downstream of the grid spacer, and when the blade angle increases from 0 to 90°, the secondary flow is more obvious, and the velocity near the wall is the largest, which is about 1.99 times the center velocity. As the structure-blocking effect increases, the pressure drop in the subchannel gradually increases and the performance evaluation criteria first increase and then decrease. When using the staggered-blade-type grid spacer to improve the supercritical heat transfer effect, the spacing between adjacent grids should be ensured as far as possible, and avoid using it at the end of the channel.