A CURRENT-TYPE ELECTROMAGNETIC FLOWMETER FOR TWO-PHASE FLOW

Yeh-Chan Ahn, Byung Do Oh, Moo Hwan Kim

Abstract

The theory for the current-sensing electromagnetic flowmeter was newly developed. The current-sensing flowmeter has a high temporal resolution so that it can be applied to measure the flows with fast transients like two-phase flow. The signal prediction and the calibration of the current-sensing flowmeter in two-phase flow and the measuring of the characteristics of two-phase flow are the major concerns. <BR />To do this, using a finite difference method, the three-dimensional virtual potential distributions for the electrodes of finite size were calculated for single-phase flow, annular flow and slug flow. With the gradient of the virtual potential, the rectilinear weight functions for the single-phase flow and the annular flow which were the main parameter for the conventional voltage-sensing flowmeter were deduced and compared with existing analytic solutions for the point-electrode. There was a reasonable correspondence between the present and existing results. Particularly the axial weight function and the radial weight function for single-phase flow, annular flow and slug flow were newly defined and computed by taking the gradient of the virtual potential. <BR />The flow pattern coefficient <i>f</i> was introduced to simplify the calibration process for two-phase flow. It was calculated from the solved virtual potential distributions of single-phase and two-phase flow. For annular flow, the coefficient was well-fitted with two decaying exponential functions of the normalized film thickness <i>&delta;</i>*, <i>f</i> = 1 + 1.3 exp(-7 <i>&delta;</i>*) + 7.3 exp(-31 <i>&delta;</i>*). For the slug flow, it was provided as a function of the normalized film thickness <i>&delta;</i>* and the normalized position of a slug bubble tail <i>L</i>*. The coefficient by the numerical simulation was compared with experimental results obtained by Frequency Response Analyzer (FRA) and Potentiostat/Galvanostat. The comparison clearly showed the agreement between the numerical and the experimental results.

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DOI

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IMEKO TC

TC9 - Flow Measurement

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