CFD modeling of pump‐mix action in continuous flow stirred tank

Abstract

The present work involves Computational Fluid Dynamics (CFD) modeling and validation of head and power characteristics of a Top Shrouded Turbine with Nonradial Rectangular Blades (TSTNRB) operated in backswept mode. Following the successful validation reported here and in two previous studies by the authors. CFD has been used to simulate the performance of different kinds of impellers viz. Straight Blade Paddle (SBP), Rushton Turbine (RT), Top Shrouded Turbine with Radial Rectangular Blades (TSTRRB), Top Shrouded Turbine with Radial Trapezoidal Blades (TSTRTB), Top Shrouded Turbine with Non‐radial Rectangular Blades (TSTNRB), Top Shrouded Turbine with Curved Blades (TSTCB), and Both side Shrouded Turbine with Radial Trapezoidal Blades (BSTRTB), to compare them for pump‐mix action. Baffle‐impeller interaction has been modeled using the sliding mesh approach. Standard k‐ε model has been used for turbulence modeling. The power number, head number, and flow number have been computed for each impeller. The impellers have been rated on the basis of head generated by them for equal specific power input. An attempt has been made to explain why different impellers operating at the same speed and handling the same inlet flow rate should give different heads. How this insight can be used to conceptualize better designs of pump‐mix impeller is illustrated. © 2007 American Institute of Chemical Engineers AIChE J, 2008

Influence of Dispersed-Phase Viscosity on Droplet Breakup in a Continuous Pump-Mixer

“…However, it is hard to intuitively evince the influence of dispersed-phase viscosity on the DSDs, as there are several variables with different systems. In such a scenario, the drop diameter d was substituted with d / We –0.6 in the x coordinate to isolate the effect of the dispersed-phase viscosity, where We is the impeller Weber number, We = ρ c N 2 D 3 /σ. This conversion was based on the general conclusion that the mean drop size depends on the −0.6 power of Weber number in stirred vessels. − Moreover, it is also valid for low viscous systems in this study (as shown in Figure ).…”

Numerical simulations to evaluate basic geometrical shapes as headers for equal liquid flow distribution

“…The computational approach adopted in the simulations involves numerical solution of the Reynolds‐averaged Navier–Stokes equations and equations of standard k–ε model of turbulence for incompressible fluid . A commercial solver FLUENT 6.3.26 is used for carrying out numerical simulations.…”

CFD–PBM Simulation of Liquid–Liquid Dispersions in a Pump-Mixer

“…A mixer containing the pump-mix impeller is named pump-mixer. 5 During the operation, the liquid−liquid phases are aspirated into the mixer for mixing, and a well-controlled drop size distribution (DSD) is desired to enhance the hydrodynamics and masstransfer performance of the two-phase flow. Due to the inhomogeneous distribution of the turbulence intensity in space and energy dissipation rate in the mixer, the phases are often not uniformly distributed throughout the mixer.…”

“…Over the years, various types of equipment were adopted in the industry, for example, centrifugal extractors, extraction columns, , and mixer-settlers . Among them, mixer-settlers are one of the most widely used ones because of their inherent advantages such as high efficiency of the stage, strong adaptability, simple operation, and large processing capacity. − Generally, mixer-settlers adopted in industry have a multi-stage structure. A cascade of mixer-settlers requires inter-stage fluid transportation of two phases.…”

“…Instead of introducing additional pumps for this, a pump-mix impeller which can realize the pumping and mixing actions simultaneously is often adopted in industry. A mixer containing the pump-mix impeller is named pump-mixer . During the operation, the liquid–liquid phases are aspirated into the mixer for mixing, and a well-controlled drop size distribution (DSD) is desired to enhance the hydrodynamics and mass-transfer performance of the two-phase flow.…”