Measuring multiphase flow in a pipe

A system for determining cross-section fractions, as a basis for flow rate determination, for individual phases in a flow of a multiphase mixture at a location in a pipe, velocities of gas and liquid phases respectively in the flow being determined by cross-correlating measurements of one of parameters permittivity and conductivity of the mixture, carried out at a specific position at said relevant location and upstream or downstream thereof the measurements of said one parameter also providing direct information related to the cross-section phase fractions, said system comprising a narrowed flow passage in the pipe with means for measuring differential pressure between a first position upstream or downstream of said narrowed passage and a second position at said passage, said passage having a known cross-section area,

• whereby said narrowed passage being arranged so as to extend some distance along the pipe to each side of said specific position,
• electrodes arranged in said narrowed flow passage for measuring said one parameter, and
• means for calculating, from said differential pressure, from values known beforehand regarding the mass densities of the phases, from respective gas and liquid phase velocities, from said one parameter, and from said cross-section area, the final cross-section fractions of the phases.