Numerical simulation of hydraulic characteristics of coolant in rod spacer grids

Thermal hydraulic performance analysis of fuel rod bundle with spacer grids takes important role among the pressure water reactor (PWR) design and safety operation. Due to its intrinsic complex geometric configuration, previous studies were almost based on one-dimensional code and many simplifications had to be made to make simulations manageable. In the present paper, the intact and simplified spacer grids were simulated and analyzed by using the Computational Fluid Dynamic (CFD) software, and efforts were emphasized on the influence factors on the flow field including spacer grids with mixing vanes only and spacer grids with mixing vanes springs and dimples, respectively. The results indicate that the springs and dimples have great influences on the flow field and thus cannot be neglected during numerical simulation of coolant flow through subchannels with spacer grids. The transverse flows and pressure drop with springs and dimples show more intense than those without spacer and dimples as expected.