Time resolved particle image velocimetry measurements inside a pebble bed like reactor

The aim of this work is to present the progress of experimental approaches used to investigate the flow pattern towards mass and heat transfer phenomena within a pebble bed. Most of the studies on packed beds consider the porous medium approach to obtain lumped parameters from which bulk characteristics of the flow are determined. This conventional approach neglects the complex flow details within individual pores and constrictions, thus obscuring the physical basis of the model. The experimental approach presented uses Particle Image Velocimetry (PIV) and Matching Refractive Index (MRI) techniques to obtain velocity measurements within a packed bed at the microscopic (pore) level. To completely understand and describe the physical process occurring within the system, local information is required. The main results of velocity measurements for single-phase flow conditions are presented under various flow conditions with Reynolds numbers ranging between 50 and 500, based on particle diameter. The results show evidence of various recirculation zones within the pores. Measurements of flow path within a single pore show considerable changes under various flow conditions. Vortex identification at various pore locations exhibits the need for consideration of additional parameters in the models to accurately describe flow structure in a packed bed. (author)