EXPERIMENTAL MEASUREMENTS OF FLUID MIXING AT THE SCALED UPPER PLENUM OF HIGH TEMPERATURE GAS COOLED REACTORS

Abstract

The High Temperature Gas-cooled Reactor (HTGR) is one of the promising reactors in the Generation IV nuclear reactors. In this research, experimental measurements were done at 1/16th scaled upper plenum of a HTGR that was scaled, designed and assembled at Texas A&M University. The goal was to investigate the flow mixing, thermal stratification and jet impingement in the upper plenum of HTGR under the Loss of Forced Coolant accident and provide high fidelity experimental database for validating CFD and system codes. Isothermal and non-isothermal cases were the primary investigation cases. Plumes—non-isothermal—will result in the formation of stratified layers with more uniform heat transfer, while jets—isothermal—will impinge on structures and have the potential to lead to more localized hot spots. Time-resolved particle image velocimetry (TR-PIV) and Planar laser-induced fluorescence (P-LIF) measurements were performed in the central plane of the jet/plume flow at the upper plenum. For the isothermal case, various jet Reynolds numbers ranging from 3,413 to 12,819 were performed, and for the non-isothermal case, one case was performed at total power of 0,4kW. From the TR-PIV velocity snapshots, statistical characteristics of the jet/plume flow, such as the mean velocity, root-mean-square fluctuating velocity and Reynolds stress, were presented. Furthermore, two-point velocity cross-correlations, spectral analysis, and squared coherent functions were performed on the TR-PIV velocity vector fields. From the P-LIF temperature snapshots, a convergence of the statistical results was achieved, and the statistical results were calculated and profiles of the mean temperature were plotted.