Data processing: measuring – calibrating – or testing – Measurement system in a specific environment – Chemical analysis
Reexamination Certificate
1999-05-07
2001-11-06
Hoff, Marc S. (Department: 2857)
Data processing: measuring, calibrating, or testing
Measurement system in a specific environment
Chemical analysis
C702S050000, C073S061440, C073S061520, C324S691000, C324S693000, C324S722000
Reexamination Certificate
active
06314373
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to an arrangement for measuring the conductivity distribution in liquids or multi-phase media with any direction of flow, especially for use in chemical engineering and power plant technology. The electrical conductivity is primarily a measure of other physical or chemical properties (such as the volumetric proportion of gas, the concentration, the type of material, etc.) of the liquid or as an indicator of the phase distribution over the measurement cross section of a multi-phase media.
Measurement of electrical conductivity is used increasingly for detenniniz the properties of liquids and multiphase mixtures, such as the proportion by volume of gas. For this purpose, the medium to be measured is energized by direct-current as well as by alternating-current voltage. The evaluation being made by defining the strictly ohmic or complex resistance. Preferably, for this purpose, wire-shaped or planiform electrodes, which are disposed parallel or concentrically to one another, are put into the medium to be measured in laboratory equipment, as well as for large-scale, initial applications. The conductivity is then measured locally, for example, with needle probes (German patent 3,201,799), or integrally between planiform electrodes (German patent 4,041,160). These methods are less suitable for determining the distribution of the local electrical conductivity over a cross section.
Frequently, therefore, tomographic methods of measuring are used for determining the property distribution of liquids or multi-phase systems over a certain cross section. Aside from the use of light radiation or particle radiation with interferometric or hagographic meffiods of evaluation, particularly the use of electrical tomographic methods, with inclusion of electrical conductivity measurements as well as of capacitive measurements, has proven its value. Aside from contactless methods with electrodes at the edge of the flow channel, methods, for which the electrodes are disposed in grid fashion transversely to the direction of flow of the medium (so-called wire mesh sensors), have become established.
In the case of a method developed at the University of Hannover (M. Boddem, N. Reinecke, D. Mewes: “Measurement of two dimensional phase distributions using a wire-mesh sensor”, Proc. ECAPT, Oporto, Portugal, 1994 pp. 155-162), parallel wires are disposed in the cross section to be measured in three planes perpendicular to the direction of flow of the mediura and the conductivity between two parallel adjacent wires of a plane is always measured sequentially. The wires of adjacent planes are at an angle of 60° to one another. After all measurements between two parallel adjacent wires of all three planes have been carried out, the projections of the conductivity distribution in the three directions specified by the orientation of tem wire grid are known. From these, the conductivity distribution is determined by means of an extensive tomographic reconstruction algoritbm The additional mathematical calculation of the results of the measurements greatly limits the number of wires that can be handled in practice and the attainable frequency for determining conductivity distributions over a particular cross section.
SUMMARY OF THE INVENTION
It is an object of the present invention to measure the distribution of the conductivity of the flowing Ium with the help of grid sensors without the use of tomographic rcconsion algoriins.
Pursuant to the invention, it is possible to measure with high resolution and high measurement succession the distribution of the electrical conductivity of the flowing medium within the cross section bounded by the grid sensor. The measured values obtained represent the local conductivity values directly and do not require any additional calculation by means of tomographic reconstruction algorithms. For this purpose, a grid sensor with at least two electrode planes is required. With an arrangement in three planes, it is possible, in addition, to follow the movement of inhomnogeneities in the flowing medium, which manifests itself in a change of conductivity, in the flow direction. In a case of a two-phase flow, the velocity of gas particles can thus be measured. A volume section to be considered can be expanded at will by connecting several three plane arrangements in series.
REFERENCES:
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patent: 4656427 (1987-04-01), Dauphinee
patent: 4777431 (1988-10-01), Day et al.
patent: 4833413 (1989-05-01), Head
patent: 5210499 (1993-05-01), Walsh
patent: 5641893 (1997-06-01), Penn et al.
patent: 3201799C1 (1983-08-01), None
patent: 4041160C2 (1991-07-01), None
patent: 2614104A (1988-10-01), None
A. V. Ploshinskii: “Primary Sensors With Hydrodynamic Smoothing for Conductometry on Turbulent Flows”, Measurement Techniques, vol. 29, No. 3, 1986, New York US, pp. 250-252, XP002061552.
M. Boden, N. Reinecke, D. Mewes: “Measurement of two-dimensional phase distributions using a wire-mesh sensor”, Proc. ECAPT, Oporto, Portugal, 1994 pp. 155-162.
Boettger Arnd
Prasser Horst-Michael
Zschau Jochen
Bui Bryan
Forschungszentrum Rossendorf E.V.
Hoff Marc S.
Jordan and Hamburg LLP
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