Characterization of bubble breakup mechanisms in non-coalescing electrolyte solutions

• Experimental BSDs in non-coalescing NaCl solutions at two stirred-tank scales. • Lumped 0D PBE screening of six breakup kernels via quadrature-based moments. • Luo & Svendsen kernel best matched experiments; Liao and Lehr also performed well. • CFD–PBE confirmed 0D trends, system homogeneity, and closer fit to experiments. • Two-step 0D/3D methodology enables efficient screening and kernel discrimination. This work presents an integrated experimental and numerical investigation of bubble breakup mechanisms in non-coalescing electrolyte solutions within two geometrically similar gas–liquid stirred tanks of different scales. Bubble size distributions were measured using optical techniques in complete recirculation gas-liquid regime and varying turbulent dissipation rates. The robustness of the image analysis was validated through manual bubble counting. A lumped parameter population balance equation (PBE) was solved using the quadrature method of moments, with model parameters derived from dedicated CFD simulations. Six breakup kernels, each representing distinct physical mechanisms, were evaluated by comparing predicted and experimental bubble size distributions, moment ratios, and characteristic diameters. The Luo and Svendsen kernel, which models breakup as a function of turbulent eddy energy exceeding surface energy thresholds, showed the best agreement with experimental data. The kernels by Liao et al. and Lehr et al. also performed well, despite being originally validated in coalescing conditions. A full three-dimensional CFD-based PBE solution further validated the lumped parameter approach, confirming its reliability for preliminary kernel screening. These findings support the use of simplified PBE models for efficient evaluation of breakup mechanisms in gas–liquid stirred tanks under non-coalescing conditions.