Numerical Analysis of the Thermohydraulic Effects of Swirl-type Mixing Vanes in Pressurized Water Small Modular Reactor Core in Single-Phase Condition

Small Modular Reactors (SMRs) produce power in the range of 100 to 300 megawatts, which is less compared to power reactors. Typically, the cores of these reactors are smaller in size than power reactors, and power generation equipment are placed inside the reactor vessel. SMRs have several types, the most common being the pressurized water SMRs. Basically, in a pressurized water reactor, the most important constraint for heat generation is the heat disposal from the reactor core fuel rods. The mixing vanes attached to the spacer grids of the fuel assemblies enhance heat disposal from the reactor core. In this numerical study, Computational Fluid Dynamics (CFD) and sub-channel approach are used to simulate fluid flow and investigate the effect of swirl-type mixing vanes in the reactor core. Single-phase fluid flow equations are solved using the k-? turbulence model by ANSYS CFX 18. The model is validated using available experimental data in a 2 × 2 rod bundle array and there is an acceptable 9% difference between numerical results and experimental data. Simulations are analyzed with and without the presence of swirl-type mixing vanes in the computational domain in different Reynolds numbers, which correspond to different mass flow inlets. Results reveal that swirl-type mixing vanes increase turbulence by making secondary flows in the lateral direction. These vanes can be used to decrease the average temperature of fuel rods surfaces by 1.75°C and raise the generated power level by 19.8%. However, the core pressure drop and pumping costs rises reasonably.