Possible optimisation of pastes and the according apparatus in process engineering by MRI flow experiments

In this paper, the spatially resolved determination of velocities in suspensions by means of nuclear magnetic resonance (NMR) imaging (MRI) techniques is described and applied to steady tube flows (with regard to the total flow rate) in different geometries. Three types of suspensions with different solid volume concentrations are examined in order to demonstrate the influence of the material-specific flow-behaviour and of the geometry of the experimental set-up on the observed flow-pattern. MRI offers the possibility to study the flow of multiphase materials with various forms of contrast (e.g. spin density, relaxation and spectroscopic data, diffusive and convective transport) spatially resolved. Thus even optically opaque suspensions can be studied in the interior of the material and the studied device. In this work the local probability distribution of single velocity components is determined. From this probability distribution both the local mean value and the according standard deviation can be derived. The standard deviation can be interpreted as the local dispersion coefficient of the according velocity component.