In many industrial application areas so-called multiphase flows determine efficiency and safety issues relating to processes and plants.

In industry, multiphase flows occur, for instance, in chemical reactors, power plants and turbo machinery.

The Forschungszentrum Dresden-Rossendorf has developed a new sensor that enables complex flows of arbitrary substance mixtures with high spatial and temporal resolution to be measured and visualised – for the first time, it is claimed.

One of the tasks of the Institute of Safety Research at the Forschungszentrum Dresden-Rossendorf (FZD) is to analyse and model industrial processes using experimental methods and thermal fluid dynamics.

It was within the context of this work, that the new capacitance wire-mesh sensor was developed. It is a successor of the well known conductivity wire-mesh sensor, which was also developed at FZD and is currently employed all around the world.

The conductivity wire mesh-sensor is based on the measurement of electrical conductivity in a flow cross-section and is therefore only suitable for investigating the flow of mixtures with an electrically conductive component – for example, water-steam flows.

However, the new capacitance wire-mesh sensor is able to measure arbitrary substances, such as oil or other organic fluids.

In this way, this sensor is applicable in a number of new industrial fields, for example in process engineering and oil industry.

As with the conductivity wire-mesh sensor, the capacitance wire-mesh sensor consists of a set of wire electrodes stretched across a vessel or pipe in two slightly separated planes.

Within one plane, electrodes run in parallel, whereas electrodes of different planes are perpendicular to each other.

A grid of electrodes is therefore formed in the cross-section.

Associated electronics measure the electrical capacitance in all crossing points, which, in turn, gives a measure of the dielectric constant of the substance surrounding each crossing point.

The electronics are optimised to measure the tiny electrical capacitances of the crossing points that are in the range of only few femtofarads.

This can be done at a very high time resolution of up to 10000 frames per second.

Since different substances have different dielectric constant values, the sensor can discriminate phases or components.

The capacitance wire-mesh sensor from the Forschungszentrum Dresden-Rossendorf can be employed in industrial applications where complex flow conditions are to be investigated.

It does not require optical access to the flow as other measurement techniques do.

The results of this work were recently published in the journal Measurement Science and Technology.

The Forschungszentrum

Dresden-Rossendorf is a member of the Leibniz Association and is engaged in basic and application-orientated research.

The main topics are: structure of matter; life sciences; environment and safety. Six major research facilities are operated at the Forschungszentrum Dresden-Rossendorf, which are also available to external users.

For more information, visit www.fzd.de