Thermal-hydraulic analysis of PWR fuel assemblies based on the MSM

Transient CFD simulations play a crucial role in ensuring the safe operation of pressurized water reactors (PWR). This study aims to investigate the applicability and accuracy of the momentum source model (MSM) in transient thermal-hydraulic analysis of PWR fuel assemblies using computational fluid dynamics (CFD) simulation. Due to the presence of intricate components such as springs, mixing vanes, and steel protrusions, the classical model (CM) requires a finer mesh. In contrast, the MSM does not involve such complex structures and can utilize a coarser mesh. To avoid errors in data exchange caused by grid splitting, the MSM does not divide the grid. The momentum source expressions related to local velocities are corrected and applied as momentum source terms in the momentum equation by employing a 3 × 3 multi-span model and conducting CFD simulations. The applicability and accuracy of the MSM in transient simulations are being verified, and the computational time and convergence characteristics of the two models are being compared through a three-pump idle rotation accident scenario. The results demonstrate that the MSM can accurately simulate the flow field and temperature field during transient simulations, exhibiting high applicability and accuracy. Additionally, it is observed that the MSM converges faster and requires less computational time compared with the CM. This study provides a new method and technique for the transient thermal-hydraulic analysis of PWRs, which is of significant importance for optimizing reactor design and operation.