Investigation of a Water Fraction Meter Based on the High Frequency Electromagnetic Field Technique Using an Uninsulated Inside Coil

Abstract

An uninsulated inside coil configuration of the water fraction meter designed by Hammertech AS has been investigated. The general principle behind the water fraction meter is to detect induced eddy currents in conductive water in the presence of a time-varying magnetic field. In the conventional arrangement of the meter an alternating current is sent through a conductive coil wound on the outside of an electrically insulating flow pipe, thereby detecting the water component of multiphase flows. By placing an uninsulated copper coil on the inside of the pipe, a large interface capacitance is formed between the coil metal and the water in the flow, leading to increased sensitivity to the water component of the flow.Static experiments have been conducted with an inside coil configuration and compared to an outside coil configuration with similar dimensions. The measurements were done with the pipe completely filled with water, and with a varying water conductivity. The static experiments show that the inside coil arrangement has far greater sensitivity to water than the outside coil. However, the inside coil used in the experiments can only be applied at conductivities up to 0,3 S/m when the pipe is filled with water.