Thesis (M.Eng.)--Chulalongkorn University, 2013

A mixing tank in the critical stage of production process of shellac-carnauba wax fruit coating solution has been simulated using Computational Fluid Dynamics (CFD) technique. The laboratory system consisted of carnauba solution prepared in a lab-scale tank with 220 mm diameter (T). A 6-blade impeller with 29 mm diameter (D) was equipped at 44 mm clearance from the tank wall (off-center) and 11.4 mm from the bottom. The first objective of the research was to develop a suitable CFD model to analyze fluid dynamic of carnauba solution inside the mixing tank. Power measurement was performed and the power curve (power number versus impeller speed) was generated for model validation. The laminar mixing was simulated using three-dimensional, Moving Reference Frame (MRF) model. The model was applied based on single phase and multiphase assumptions. The result of the single phase simulation provided reasonable agreement with the experimental data; however, it required less computational time compared to the multiphase simulation. To accomplish the second objective, the single phase model was applied to study the flow behavior and the parameters influencing the fluid dynamics such as rotational velocity, viscosity and shear stress inside the mixing tank. For the third objective, the kinematic, dynamic, and geometric similarities were analyzed for scale-up criteria predicted by the CFD model.