The role of rheology in the flow and mixing of complex fluids

[摘要] Mixing of fluids with complex rheology is encountered more and more frequently in industries. Nonetheless, mixing behaviour of such fluids is still poorly understood due to the complexity of their rheological behaviour. This study aims to enhance fundamental understanding of the flow and mixing of rheologically complex fluids such as thixotropic, shear-thinning and viscoelastic fluids. The objectives of this study were to investigate within stirred vessels the effects of thixotropy and viscoelasticity, separately, in the absence of other rheological behaviours for the fluids examined. To achieve these aims the rheological behaviour of the fluid examined is isolated by using a fluid that exhibits only one of these behaviours of interest at a time. The Particle Image Velocimetry (PIV) technique was employed to characterize the flow fields of fluids. The flow pattern, normalized mean velocity and cavern growth in the vessel were characterized during the mixing for both thixotropic and viscoelastic fluids. The results were compared to the reference fluids under laminar and transition regimes. Three different types of impeller were investigated: Rushton turbine (RTD), and Pitch Blade Turbine (PBT) in up pumping mode (PBTU) and in down pumping mode (PBTD). Additional work was conducted using th Planar Laser Induced Fluorescence (PLIF) visualization technique to investigate in more detail the evolution of mixing in a cavern with time for a thixotropic fluid. The mixing efficiency of the impellers was analyzed in terms of impeller pumping efficiency and size and growth of a cavern.

[发布机构] University:University of Birmingham;Department:School of Chemical Engineering

[关键词] Q Science;QD Chemistry