Chapter 36 - Numerical simulation of flow of Newtonian fluids in an agitated vessel equipped with a non standard helical ribbon impeller

Abstract

Mixing operation involving highly viscous Newtonian fluids are commonly encountered in the food and chemical industries. For such complex liquids, helical ribbon impellers are considered to be among the most efficient systems and therefore are frequently used in process industries (polymerization reactors). This chapter describes the use of a commercially available fluid dynamic (CFD) software package (FLUENT) to conduct numerical simulation for the flow field of Newtonian viscous fluids in a rounded bottom vessel equipped with an atypical helical ribbon impeller. First for eight different Newtonian fluids, measured and numerically calculated power consumption are reported. Then, for different Newtonian fluids, measurements of axial circulation time data obtained by flow follower and conductivity method are compared to the predictions calculated by CFD approaches. Close agreement between the numerical computed CFD values and the experimental measurements were obtained. Finally, the flow velocity field computed under laminar regime for Newtonian liquids in the vessel are analyzed and discussed. The reliability of the numerical procedure is demonstrated on the basis of a comparison of the numerical results with experimental data in several ways. The analysis of numerical results for the flow of Newtonian fluids indicates that the impeller generates an important axial flow. The presence of vertical arms which support the blades produced a significant shift in the flow pattern, generating local radial flow in the vessel.