Mechanistic Scale-Up of Gas-Solid Fluidized Beds via Local Hydrodynamic Similarity

This study presents a detailed experimental evaluation of a newly developed mechanistic scale-up methodology for gas-solid fluidized beds. Traditional scale-up approaches typically rely on matching global dimensionless groups, which often fail to ensure local hydrodynamic similarity. In contrast, the new mechanistic method aims to achieve scale-up by matching the radial profiles of gas holdup between geometrically similar beds at corresponding dimensionless axial positions (z/Dc). This approach is based on the premise that when gas holdup profiles align, other key hydrodynamic parameters—such as solids holdup and particle velocity—also become similar. To validate this methodology, experiments were conducted in two fluidized beds with inner diameters of 14 cm and 44 cm. Optical probes and gamma ray densitometry (GRD) were used to measure local gas holdup, solids holdup, and particle velocity at multiple axial and radial positions. The results show that matched gas holdup profiles led to mean absolute deviations (MAD) below 3% in solids holdup and particle velocity, confirming hydrodynamic similarity. In contrast, unmatched profiles resulted in significant deviations across all parameters.