Application of Electrical Resistance Tomography (ERT) to Monitor a Flow-Follower in a Stirred Vessel

K. Salem1, K. Kling1 and R Mann2,3

1 Department of Process Engineering, University of Hannover, Callinstrasse 36, Hannover, Germany Karijm.Salem@stud.uni-hannover.de, kling@c36.uni-hannover.de

2 Department of Chemical Engineering, UMIST, Manchester M60 1QD, UK, r.mann@umist.ac.uk

3 Member of the Virtual Centre for Industrial Process Tomography (VCIPT)

ABSTRACT

The flow-follower technique provides a Lagrangian description of fluid flow and mixing in contrast to the more frequently used Eulerian perspective. The technique is thus potentially very useful for capturing the statistics of the unsteady dynamics of turbulent flow which probably plays a dominant mixing role in typical stirred vessels. New results are presented which explore how an existing 8-plane 16 -sensor ring system on a large 2.3m3 stirred vessel can be used to track a neutrally-buoyant flow- follower. By making the flow-follower suitably conducting, a localised conductivity “hot-spot” is created, which can be tracked in 3-D as it circulates around the vessel. Different designs of particle have been evaluated for their detection capability and accuracy as well as their tracking ability. The optimum design was a 15cm copper sphere made neutrally buoyant by partial filling with water. Detection accuracy differs axially and radially, being mostly of the order of 5%, although it is a poor 22% in the higher sensitivity wall region. Some initial results show that the instantaneous velocity is highly variable reflecting the complexity of the turbulent flow field. A visualisation of the 3-D movement using combined front perspective and plan views can be realised using a Kriging positional error minimisation approach which interpolates the “centroid” of conductivity detected by ERT.

Keywords flow-follower, electrical resistance tomography, stirred vessel, Lagrangian fluid mechanics