Design, Construction, and Evaluation of Low-Cost Electrical Impedance-Based Multiphase Flow Meter with Two-Phase Flow in Large Diameter Pipes
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Because of the high cost of many of industry’s current multiphase flow meters, there is a desire to develop low-cost solutions to the multiphase flow measurement problem. One such potential solution is an electrical impedance based device placed downstream of a slotted orifice plate.The electrical impedance based part allows one to measure the density, while the slotted orifice plate measures the total volumetric flow rate. This type of device has been proven effective for NPS 2” piping, but not for larger piping with higher flow rates and pressures. This thesis describes the design, testing, and evaluation of one such multiphase flow meter (MPFM) designed for an NPS 6” pipeline carrying an air/water mixture. The MPFM was tested in a closed loop test facility capable of operating at various flow rates, pressures, and gas volume fractions (GVFs). The test set-up also included a venturi tube flow meter downstream of the MPFM for additional flow rate verification. The electrical impedance portion passes a multi-frequency signal through the fluid between two electrodes diametrically opposed on the pipe. The signal gain across them was measured and shown via analysis of variance (ANOVA) techniques to be correlated to total flow rate and pressure as well as the GVF of the fluid. The flow rate correlation had not been seen in smaller diameter pipes using this MPFM concept. A multi-variable regression was applied accordingly, resulting in a calibrated equation that predicted the fluid GVF with an uncertainty of ±5.85% GVF with 95% confidence. The slotted plate flow rate data is believed to have been affected partially by the presence of large plastic pieces in its upstream piping, but removing the anomalous data showed an average measurement uncertainty of ±8.80% with 95% confidence. The venturi was capable of predicting the flow rate with an uncertainty of ±4.53%. Because of the interdependence of GVF and flow rate predictions, an iterative technique was used to achieve the accuracies described above. The technique assumes an initial guess for flow rate and uses that guess in the GVF prediction equation. The GVF prediction is then used in the flow rate equation to obtain a better flow rate estimate. This improved flow rate estimate is then used in the GVF equation, and the process repeats itself until flow rate and GVF converge on a solution. This technique resulted in total mass flow rate predictions with an uncertainty of ±6.14%, and GVF predictions with an uncertainty of ±5.85% GVF. These results imply that the electrical impedance-based MPFM concept is applicable to pipes as large as 6”.
Nolen, Craig R (2015). Design, Construction, and Evaluation of Low-Cost Electrical Impedance-Based Multiphase Flow Meter with Two-Phase Flow in Large Diameter Pipes. Master's thesis, Texas A & M University. Available electronically from