Experimental and simulation studies of two-phase flow in a stirred tank.

摘要

Simulation of the air bubble dispersion and calculation of bubble trajectories using the Lagrangian method have been performed. The computational fluid dynamics (CFD) program FLUENT was used in the particle tracking mode to do the simulations of dispersed, transitional, and flooded conditions in Rushton and pitched-blade turbine stirred vessels with an air sparger. A mixing tank of standard dimensional ratios with a ring sparger was used. The method produced gas flow patterns qualitatively similar to those observed in experiments, as shown by comparisons of the simulation graphics and photographs of experimental behavior. Results of simulation showed the thresholds of loaded and flooded conditions to be in very good agreement with experimental data of other investigators and their correlations.; The effects of solid and liquid properties and solids concentrations on the mean particle velocities at various locations in a stirred vessel were studied. The experiments were performed in a standard baffled tank, equipped with a 45° pitched-blade turbine pumping downwards. The mean velocities of dispersed glass particles of refractive index nearly the same as the liquid were measured by laser-Doppler velocimetry (LDV) at just-suspend impeller speed. The mapping of solid particle mean velocities at various particle sizes and solids loadings showed increasing deviation from mean velocity mappings for liquid alone as the solids loadings and particle sizes were increased. These data will be important for the validation of the CFD-based simulation of dispersed solids in stirred vessels.