Abstract
Computational fluid dynamics simulations (CFD) were used to evaluate mixing in baffled and unbaffled vessels. The Reynolds-averaged Navier−Stokes k–ε model was implemented in OpenFOAM for obtaining the fluid flow field. The 95% homogenization times were determined by tracer tests. Experimental tests were conducted by injecting sodium chloride into the vessel and measuring the conductivity with two conductivity probes, while the simulations replicated the experimental conditions with the calculation of the transport of species. It was found that the geometry of the system had a great effect on the mixing time, since the irregular flow distribution, which can be obtained with baffles, can lead to local stagnation zones, which will increase the time needed to achieve the homogenization of the solute. It was also found that measuring local, pointwise concentrations can lead to a high underestimation of the global mixing time required for the homogenization of the entire vessel. Dissolution of sucrose was also studied experimentally and by mathematical modeling. The dissolution of sucrose was found to be kinetically limited and a very good agreement was found between the experiments and the modeling approach. The extent of the applicability of CFD simulations was evaluated for enabling rapid process design via simulations.
Highlights
Stirred tanks are widely used in various fields, such as chemical, biotechnological, pharmaceutical and mineral industries
Local fluid dynamics and associated phenomena such as chemical reactions and mass transfer have been successfully predicted by means of computational fluid dynamics (CFD)
The first part represents the time until the suspended sucrose the dissolution process was divided into two parts
Summary
Stirred tanks are widely used in various fields, such as chemical, biotechnological, pharmaceutical and mineral industries. Local fluid dynamics and associated phenomena such as chemical reactions and mass transfer have been successfully predicted by means of computational fluid dynamics (CFD). Mixing and dissolution are important industrial processes and are the focus of this article [1]. Inhomogeneity of a fluid is reduced by the elimination of concentration, temperature and residual system gradients by the process of mixing, which is a composite process, consisting of distribution, dispersion and diffusion. Distribution is the process where the fluid circulates in the order of magnitude of the mixing vessel. Dispersion is the process of breaking up a stream into gradually smaller vortices
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