(88d) Experimental Study of the Convective Heat Transfer in Single Phase with 5X5 Rod Bundle in LWR and SMR

In Light Water Reactors (LWRs) and Small Modular Reactors (SMRs), the core is constructed with a square array of nuclear fuel rods arranged vertically by spacer grids (SG) which is considered one of the most important components of a fuel assembly. The purpose of spacer grid (SG) is not only to support the fuel rods, but it also plays a significant role by increasing the coolant turbulent flow, in order to enhance the heat transfer characteristics of the fuel component. Single-phase flow with 5x5 array rod bundle was experimentally conducted at the Multiphase Flows and Reactors Engineering and Applications Laboratory (mFReal). In addition, Sophisticated flush mounted heat transfer probes were used to characterize the heat transfer coefficients by measuring both the local heat flux from the probe to the bulk and the surface temperature of the probe simultaneously, which allows to calculate the convection heat transfer coefficient of the coolant (h). In order to specify the effect of mixing vanes of spacer grid, the measurements were conducted with and without spacer grid in specific locations downstream and upstream of spacer grid (Pitch-to-Diameter ratio P/D =1.33).