Numerical simulation of mixing vanes on flow and heat transfer characteristics in 5 × 5 rod bundle

摘要

Single-phase heat transfer characteristics in a pressurised water reactor (PWR) fuel assembly are important. Many investigations have studied flow features in a 5 × 5 rod bundle with a specific mixing vane spacer grid. Three shapes and two arrangements of mixing vane are analysed to compare flow characteristics and heat transfer. No one-to-one correspondence exists between the block ratio and total pressure loss and the heat transfer for different mixing vanes shapes. The cross flow significantly affects the wall heat transfer coefficient of the rods. Cross flow in the channels for the two arrangements in the flow field differs greatly, and the cross flow is more obvious when the mixing vane adopts the second arrangement. Mixing-vane shape mainly affects the magnitude of the cross flow velocity - not the structure - and the Shape2 mixing vane induces maximum cross flow. These influences on cross flow result in a higher heat transfer with the second arrangement or with the second shape than with the first arrangement or the first- and third-shape mixing vanes.