The influence of four-wire structure on the flow and heat transfer process in supercritical water-cooled reactor fuel assembly

Abstract

Based on the supercritical water-cooled reactor fuel assembly, a 19-rod bundle physical model with a hexagonal outer casing is established, and the four-wire structure is added to the bare bundle. To analyze the influence of wire spacers on the flow and heat transfer process, numerical investigations of supercritical water in the reactor under design conditions are performed by using the Reynolds stress model with enhanced wall treatment. The results show that the mass redistribution is the main factor affecting the distribution of thermal–hydraulic parameters regardless of the existence of wires. The wire plays a role in weakening the mass redistribution by reducing the cross-flow between the adjacent sub-channels. However, due to the large local hydraulic diameter of the side sub-channels and the sharp change of the supercritical water physical properties, the fluid gradually gathers in the external sub-channels. In addition, the four-wire structure drives the fluid to spiral upwards around the fuel rod, which significantly enhances the convective heat transfer between the fluid and the fuel rod. At the same time, the influence of the local hydraulic diameter on the circumferential non-uniformity is weakened by the wires, and the circumferential wall temperature gradient of the external fuel rod is significantly reduced.