A Numerical investigation on the heat transfer and turbulence production characteristics induced by a swirl spacer in a single-tube geometry under single-phase flow condition

Abe, Satoshi  ; Okagaki, Yuria  ; Satou, Akira ; Shibamoto, Yasuteru 

Heat transfer in the rod bundle is augmented by the mixing vanes on the spacer grid. We conducted a computational fluid dynamics (CFD) simulation with three isotropic turbulence models - standard -epsilon, realizable -epsilon, and SST -omega models - to investigate the relationship between heat transfer and turbulence behaviors downstream a simulant spacer (with four vanes) in a single tube under single-phase flow conditions. Quantitatively, the predicted heat transfer coefficient (HTC), secondary flow intensity, and turbulence intensity with the SST -omega model displayed a better agreement (than the other isotropic models) with the correlation based on previous studies. Furthermore, the turbulence production was localized in the near-spacer region (z/D 10, where D is the inner diameter), which corresponds with the HTC argumentation region. These results indicate that examining the turbulence production when discussing the HTC augmentation downstream the spacer is essential.