Design of capacitance electrodes for concentration measurement of two-phase flow

Abstract

Capacitance electrode systems for the measurement of the volumetric concentration of two-phase flows have inherently non-uniform sensitivity distributions over the pipe cross section and therefore have different responses to different flow regimes (e.g. core, annular and stratified flows). In processes with varying flow regimes, this can lead to significant measurement errors. An electrode system which has a uniform sensitivity distribution and consequently a response independent of flow regime is therefore desirable. The system performance parameters of surface electrode systems used with stray-immune measurement transducers have been characterised quantitatively using a two-dimensional finite-element model. The electrode system design parameters have also been identified and their effects on system performance parameters have been investigated. As a result, optimum electrode designs are proposed, with responses to different flow regimes having a minimum deviation from linearity.