A current-sensing electromagnetic flowmeter for two-phase flow and numerical simulation of the three-dimensional virtual potential distribution: I. Fundamentals and annular flow

The theory of the current-sensing electromagnetic flowmeter for a high temporal resolution was developed for two-phase flow measurements. To predict the output of the current-sensing flowmeter, the three-dimensional virtual potential distribution G and the newly introduced flow pattern coefficient f were derived and computed. The output of the flowmeter depends on the liquid conductivity (sensitive to temperature) and flow configurations of the two-phase flow with sinusoidal excitation over 100 Hz. The flow pattern coefficient was specially devised to separate the dependence on the flow configuration of the two-phase flow from that on the liquid conductivity which can be expressed with the calibration of single-phase flow. Using the finite-difference method, the three-dimensional virtual potential distributions were computed for an electrode of finite size. By taking the derivative of the virtual potential, the weight functions were evaluated. In addition, the flow pattern coefficients were evaluated for annular flows with various film thicknesses, and compared with the experimental results obtained by impedance spectroscopy. The numerical results agreed well with the experimental data.