Numerical investigation on hydraulic performance of spacer grid with cross weld

As an important structural parameter of spacer grid, the shape of the cross weld between inner straps is closely related to the strength and hydraulic characteristics of the spacer grid. In order to deeply study the influence of the shape of the cross weld on the hydraulic characteristics of the spacer grid, numerical investigation on the flow field of the rod bundle using ANSYS CFX12.1 is conducted taking the 5 × 5 spacer grid as research object. The numerical result show that increasing the diameter of the cross weld can reduce swirling strength in the subchannels and the coolant exchange strength between subchannels nearby the grid in the grid downstream area, and enhance them far away from grid in the grid downstream area; Increasing the diameter of the cross weld only has a slight effect on the mixing strength in subchannels in the grid downstream area. Local resistance coefficient of the spacer grid increases as the diameter of the cross weld increases. It can be concluded that heat transfer performance in the downstream region of the spacer grid tend to be balanced by using larger diameter cross weld, thus the temperature distribution of the core is more uniform; At the same time, greater pressure loss will be produced. (author)