Local velocity scaling in T400 vessel agitated by Rushton turbine in a fully turbulent region

Radek Šulc,Pavel Ditl,Darina Jašíkova,Bohuš Kysela,Václav Kopecký,Michal Kotek,Ivan Fořt,P Dančová

doi:10.1051/epjconf/201714302120

Abstract

The hydrodynamics and flow field were measured in an agitated vessel using 2-D Time Resolved Particle Image Velocimetry (2-D TR PIV). The experiments were carried out in a fully baffled cylindrical flat bottom vessel 400 mm in inner diameter agitated by a Rushton turbine 133 mm in diameter. The velocity fields were measured in the zone in upward flow to the impeller for impeller rotation speeds from 300 rpm to 850 rpm and three liquids of different viscosities (i.e. (i) distilled water, ii) a 28% vol. aqueous solution of glycol, and iii) a 43% vol. aqueous solution of glycol), corresponding to the impeller Reynolds number in the range 50 000 < Re < 189 000. This Re range secures the fully-developed turbulent flow of agitated liquid. In accordance with the theory of mixing, the dimensionless mean and fluctuation velocities in the measured directions were found to be constant and independent of the impeller Reynolds number. On the basis of the test results the spatial distributions of dimensionless velocities were calculated. The axial turbulence intensity was found to be in the majority in the range from 0.388 to 0.540, which corresponds to the high level of turbulence intensity.

Highlights

It is important to know the flow and the flow pattern in an agitated vessel in order to determine many impeller and turbulence characteristics, e.g. impeller pumping capacity, intensity of turbulence, turbulent kinetic energy, convective velocity, and the turbulent energy dissipation rate
The inspection analysis shows that the validity of the spatial distribution of any dimensionless property for arbitrary process conditions in geometrically similar agitated vessels requires independence of a given dimensionless property from the impeller Reynolds number
In many studies the results are presented only for one impeller speed and, in addition, when a Rushton turbine is used as an impeller, the experiments are often carried out in the transient flow regime

Summary

Introduction

It is important to know the flow and the flow pattern in an agitated vessel in order to determine many impeller and turbulence characteristics, e.g. impeller pumping capacity, intensity of turbulence, turbulent kinetic energy, convective velocity, and the turbulent energy dissipation rate. In PIV studies, the spatial distributions of various properties are often presented. In many studies the results are presented only for one impeller speed and, in addition, when a Rushton turbine is used as an impeller, the experiments are often carried out in the transient flow regime. In our previous work [2] the local velocity profiles in the zone in upward flow to the impeller for three impeller rotation speeds in a vessel 300 mm in the inner diameter filled by a water and agitated by a Rushton turbine were presented. The aim of this work is to study scaling of the velocity field outside the impeller region in a vessel 400 mm in inner diameter mechanically agitated by a Rushton turbine in a fully turbulent region for three liquids of different viscosities. The hydrodynamics and the flow field were measured in an agitated vessel using Time Resolved Particle Image Velocimetry (TR PIV)

Inspection analysis of flow in an agitated vessel

Mean and fluctuation velocity

Experimental

Experimental data evaluation