Local velocity scaling in an impeller discharge flow in T400 vessel agitated by tooth impeller in a fully turbulent region

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

doi:10.1051/epjconf/201818002102

Abstract

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 tooth impeller 133 mm in diameter. The velocity fields were measured in the impeller discharge flow for impeller rotation speeds from 300 rpm to 700 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 68 000 < Re < 221 000. 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 radial turbulence intensity was found to be in the majority in the range from 0.3 to 0.9, which corresponds to the high level of this quantity.

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 aim of this work is to study scaling of the velocity field in the impeller discharge flow in a vessel 400 mm in inner diameter mechanically agitated by a tooth impeller (CVS 691038.1) 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)

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 our previous work [3] the scaling of the velocity field in the zone in upward flow to the impeller for three liquids of different viscosities in a vessel 400 mm in the inner diameter agitated by a Rushton turbine were presented. Agitation of two immiscible liquids or solid-liquid suspension is a frequent operation in chemical and metallurgical industries [4] In this case the tooth impeller has been used usually for dispersion process [5]. The aim of this work is to study scaling of the velocity field in the impeller discharge flow in a vessel 400 mm in inner diameter mechanically agitated by a tooth impeller (CVS 691038.1) 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)

Theoretical background

Mean and fluctuation velocity

Experimental

Experimental data evaluation

Conclusions