Tomoflow R100* A pdf version of this page can be found on the resources page Tomoflow R100* is a non-intrusive multiphase flow analysis system based on electrical capacitance tomography (ECT). With a Tomoflow R100 package including Flowan* software you can: Image flows of fluid/fluid and fluid/solid mixtures, Measure the velocity at any point or over any zone in the flow-field, Investigate the details of flow structures, Measure the flowrate of a dispersed phase as a function of time and space, Measure the volume of moving structures within the section. The Tomoflow R100 multiphase flow analysis system consists of a capacitance measurement unit, real-time data acquisition and image reconstruction software, and off-line multiphase flow analysis software. Data Acquisition - DAM200e DAM200e is an electrical capacitance tomography measurement unit made for Tomoflow by Process Tomography Ltd***. DAM200e allows measurements on two axially separated planes with up to 12 electrodes on each, with drive for up to 12 sets of guard electrodes. Image capture rates can be set by the user up to the approximate maximum rates given below. Number of sensor electrodes 6, 8 or 12 200 frames per second with 8 electrode twin-plane sensor 100 frames per second with 12 electrode twin-plane sensor Image capture and reconstruction software ECT32 is a comprehensive on-line software suite for controlling and processing data from Tomoflow and PTL ECT systems. The software runs on the Windows operating systems. The images can be shown on the screen in real-time, then recorded and played back at user-defined speeds. Data files can be used for flow analysis using Flowan*. IU2000**. The IU2000 Image Utility software is an extensive set of off-line tools for processing and viewing captured ECT image data. Matect**. Matect software is a set of off-line Matlab utilities for displaying and modifying sensitivity maps and for generating images using these maps and transforms. Makemap**. Makemap software suite calculates accurate sensitivity maps for circular ECT sensors with either internal or external electrodes.

Flowan* off-line Multiphase Flow Analysis Software

Image flows of fluid/fluid and fluid/solid mixtures

	Data from the Tomoflow R100 system may be saved to file for off-line flow structure analysis using Tomoflow’s Flowan multiphase flow analysis software. Example results are given here for several flow conditions in a 50mm diameter pipe. The sensor used is a twin-plane unit with 3cm long electrodes axially separated by 10cm driven guard electrodes. The sensor is shown in the photograph mounted on a 50mm perspex pipe ready to be mounted in the test rig.
	Images of flows are shown as circular maps with a grid of 32x32 pixels using a colour scale from blue (pixel empty) to red (pixel full). The example alongside shows the arrival of a slug front in a horizontal flow of plastic pellets in air. In this case the leading plane is on the right. Flowan automatically establishes the direction of flow .
	Each image plane can be divided into a number of zones – arranged appropriately for the flow conditions. The example alongside shows a typical 13 zone division.
	Flowan can calculate a number of average parameters for each zone, including average concentration and average flowrate. The example shows average concentration (left) over several 10s of seconds, compared with the instantaneous images (middle & right).

For each zone of each image plane the concentration may be plotted against time. The example below shows the area-average concentration in zone 2 (left hand zone highlighted in white) of plane 1 in red, and zone 2 of plane 2 in green. The flow shown is an upward flow of plastic pellets blown by air at about 2 m/s. The average flowrate of plastic beads is 750kg/hr upwards.

The first half of the graph shows upflow - an upward-going slug with concentration going from near 0 to near 1 in a short space of time at plane 1 (red line) slightly before arrival at plane 2 (green line). It can be seen that the rear of the slug is travelling faster than the front. On the second half of the graph the green line shows concentration events at plane 2 (upper) preceding their arrival at plane 1 (lower plane - red line).

Comparison of high speed photography with the image cross-sections shows that the downward going ‘rope’ of solids (left hand side of page) is on one side of the pipe – which is not obvious from the side-on photography. The diagram on the right hand side of page shows the arrival of the slug front.

Measure the velocity at any point or over any zone in the flow-field

The velocity at each point in time within each zone is calculated by correlating the instantaneous concentration of one plane with the same zone in the other plane. The result is plotted as a second graph with axes in cm/second on the right hand side of the graph. The blue line shows positive velocities (in this case upwards) and the mauve line shows downward velocities. It can be seen in this case that the slug front is moving at 100cm/s bur the tail is progressing at 300 cm/s.

Measure the flowrate of a dispersed phase as a function of time and space

The flowrate within the cross section can be found by integrating the product of the velocity and the concentration at each point in time. This gives the flowrate per zone, and all zones can then be summed to give total flowrate. Total flowrate (cm³/second) as a rolling 1 second average is shown as the mauve line in the example above. For an average flowrate in this case of 750 tonnes per hour (about 350cm³/sec) the peak rate is over 3000cm³/sec - almost 10 times the average rate. Such details can be critical in controlling industrial processes.

Comparisons have been made for downward gravity flows through the same 5cm diameter sensor, using plastic beads, small spheres and coffee powder. The results above show the drop of plastic beads from a funnel under gravity. The concentrations at plane 1 and plane 2 are given here for the central zone, together with the velocity (blue line) for that zone. It can be seen that there is an initial plug of beads which pass between the two planes, dispersing slightly as it does so. The velocity is fairly constant since the beads are dropping freely under gravity.

The next figure (above) shows the overall flowrate in mauve (cm³ per second, right hand scale, summed over all zones) for the same case of plastic beads falling under gravity, this time shown with the concentrations in the two planes within the zone at the left hand side of the pipe. It can be seen that the concentration in this zone is greater in the second plane (red) – confirming the results earlier that the initial plug is dispersing towards the edges of the pipe. Integrating the flowrate for the entire record gives a total of 1464 cm³, compared to the actual value of 1490 cm³ – an error of less than 2%.

A summary of test results (above) for a range of flows indicates that Flowan calculates volumetric flow, converted here to mass flow rate, within typically a few percent of the true rate.

Measure the volume of moving structures within the section

In addition to being able to integrate the total flowrate, the volume of individual structures within the flow may be calculated. For example in the slug flow shown above, the volume of the upgoing slug between about 5.5 and 7 seconds is 3392 cm³, equivalent to a 2 metre long plug of solids moving at about 200 cm/s over 1 second. The downward flow, although lasting just as long from about 8 to 9.5 seconds, only contains 252 cm³.

Summary

Tomoflow Flowan* brings a new level of sophistication to multiphase flow structure research. Tomoflow Ltd can either supply Flowan* software for use with existing PTL twin-plane ECT systems or we can provide complete multiphase flow measurement systems.

Please contact us for further information, pricing and delivery:

*Tomoflow and Flowan are marks of Tomoflow Ltd

**ECT32, Makemap, IU2000 and Matect are marks of Process Tomography Ltd

***Process Tomography Ltd (PTL) was established in 1994 to exploit the research and development market for electrical capacitance tomography (ECT) imaging systems and is the world leading supplier of ECT systems. PTL has been leading an EU-supported "CRAFT" research project for the last two years with UMIST and other partners, on the feasibility of using tomographic techniques in multi-phase flow measurement.