Large-Eddy Simulation of Single-Phase Flow Dynamics and Mixing in an Industrial Crystallizer

The design of industrial crystallizers requires detailed information about the fine structure of turbulence in vessels of complex geometry. The currently available methods (e.g., empirical correlations, experimentation, simple theories, computations based on the Reynolds-averaged Navier–Stokes equations) cannot provide the required information at an adequate level of accuracy for crystallizers of non-standard design. This paper assesses the feasibility of using a computationally efficient large-eddy simulation (LES) technique to quantify the fine scale turbulent structure in an industrial crystallizer. LESs of the single-phase flow in a baffled, industrial crystallizer with a draft tube were performed at three values of the Reynolds number ( Re = 14 000, Re = 82 000 and Re = 350 000). The flow was driven by a standard Rushton turbine. A much weaker secondary flow was generated by a throughput stream that entered through a nozzle at the bottom and exited through the sidewall. The effects of the spatial resolution and the sub-grid scale model were investigated. The mixing performance of the tank was evaluated by means of particle tracking. It was found that the simulations adequately resolved the highly anisotropic fine-scale turbulence generated by the strong interaction between the impeller, the various other internals and the vessel wall at least at the low Reynolds number. The potential significance of the computed flow structures for crystallization performance is briefly noted.