PIV study of velocity distribution and turbulence statistics in a rod bundle

In reactor fuel assembly in PWR, spacer grids with mixing vanes are used in rod bundles to enhance flow mixing and heat transfer. Thus, the spacer grids have significant influence on the economy and safety of reactors. This paper focuses on visualization research on the single phase flow in rod bundle with spacer grids by Particle Image Velocimetry (Ply), and a measurement of multi-subchannels in the both transverse and longitudinal directions was conducted at the Reynolds number of 10,400. Matching Index of Refraction (MIR) technique was implemented to accurately measure the internal flow field in the rod bundle. The flow statistics of rod bundle were obtained, such as mean velocity, turbulence intensity and Reynolds stress. The velocity distribution and turbulence statistics in the longitudinal flow field are presented downstream the spacer grid. The streamwise development of symmetrical vortex array in the transverse flow field is also evaluated. A comparison of Reynolds stresses in the longitudinal and the transverse flow field is performed to reveal the momentum transfer process in three-dimensional flow field. Experimental results benefit the development and evaluation of spacer grid, and also provide the whole-field validation for numerical simulations. (C) 2018 Published by Elsevier Ltd.