Numerical analysis of dimple structure effect on grids performance under subcooled boiling condition

As the most important structure to enhance the thermal-hydraulic performance of fuel assembly, the mixing vane spacer grids has great effects on the safety and economic efficiency of reactors. As one of the key components of the spacer grids, the dimple can play an important role in the stability maintenance of the rod bundle and the distribution of the flow in spacer grids. In this paper, ANSYS CFX 14.5 was used to analyze the flow condition and heat transfer effect of a series of 5 × 5 spacer grids. Three different dimple structure spacer grids were modeled to obtain the effects of the dimple structures. After a basic verification of the CFD model and demonstration of the fully developed calculation domain length, the dimple structure effect on the thermal-hydraulic performance of the spacer grid were evaluated from the pressure drop, lateral velocity and void fraction distribution along the axial or radial direction. (authors)