Visualization and holdup measurement of viscous oil-water dispersed pipe flow by capacitance wire-mesh sensor

Experiments were performed in a test facility at NETeF (Thermal-Fluids Engineering Laboratory) of the Engineering School of São Carlos. The facility consists basically of a horizontal glass pipe of 26 mm of inner diameter and 12 m length. Mineral oil (860 kg/m3 density and 100 mPa∙s viscosity) and tap water stored in separated tanks are circulated under controlled conditions through the test pipe. The flow rates of each liquid are individually controlled and measured. After passing the horizontal test section, the mixture flows to a coalescent-plate separator tank. The liquids once separated are returned to their respective storage tanks by gravity. A wire-mesh sensor with 8 x 8 wire configuration was installed close to end of the horizontal pipe at 10.3 m from the entrance. To assemble the wire-mesh sensor in the test pipe, a flange of transparent Perspex was manufactured which allows for optical observations (Fig 1a). A high-speed camera (Optronis, Camrecord 600) was applied to monitor the flow patterns and investigate the influence of wire-mesh sensor in the flow.
Experiments were performed at oil superficial velocity between 0.2 m/s to 1 m/s and water superficial velocity between 1 m/s to 3 m/s. The recording speed was 2000 fps for the high-speed camera and 500 fps for the wire-mesh sensor, whereby data acquisition of both systems was synchronized by a common trigger signal. Figure 1b and 1c show exemplary images of the flow obtained by the both imaging devices. Note that the high-speed camera depicts a lateral view of the flow, while the wire-mesh sensor images show holdup distributions over the cross section of the pipe. From the two-dimensional holdup distribution measured by the wire-mesh sensor we have further determined liquid holdup integrated over different domains thus obtaining time and/or spatially averaged holdup values, e.g. radial profiles or mean holdup. Furthermore, for comparison purposes of holdup measurements, the quick-closing valves (QCV) technique was employed. Good agreement was found between QCV and WMS techniques. In the full paper, a complete description of the measurements will be presented along with a discussion of the accuracy in the measurements.