WATER-OIL FLOW METER
The main application field are:
- petrochemical industry;
- chemical sector, for example for the transport of polymers in liquid phase.
Currently used systems for the measurement of the flow rates of the non-miscible components of a two-phase liquid-liquid flow involve the use of complex procedures and expensive instruments, such as γ-ray attenuation or offline solutions.
The device has been designed to monitor the flow rates (total and individual phases) in a two-phase liquid-liquid flow (in particular viscous oil – water) in the core-annular or dispersed flow patterns, with the support of experimental measurements and of a specific fluid dynamics model. This device comprises a Venturi tube or a nozzle, to which a pressure transducer is applied between the upstream and the throat section; a second pressure transducer is applied between two sections along the upstream duct. A thermocouple is also installed to measure the temperature of the mixture and to determine its rheological properties (in particular in the presence of an oil phase). The measurement of the flow rates occurs through the determination of an experimental calibration curve that correlates the total volumetric flow rate of the two-phase flow with the difference in pressure between the upstream and the throat section. The liquid-liquid flow behaves as incompressible and the section reduction at the Venturi/nozzle throat causes an increase in the flow velocity and a consequent decrease in pressure. This also leads to a reduction in the slip factor between the phases, so that the total flow of the mixture can be well approximated by a homogeneous model. The determination of the flow rates of the individual phases is at this point obtained by using the fluid-dynamic model and the measurement of the pressure gradient upstream of the device.
The main point of strength of the proposed device and procedure is the possibility to determine the characteristics of two-phase liquid-liquid flows (with viscosity of at least one fluid greater than 0.15 Pa s), in a very wide range of flow regimes, through only measures of pressure drop. The method would avoid the use of combined instruments, and expensive techniques, such as the absorption of γ-rays, electromagnetic measurements and ultrasonic techniques.