Development of a novel flexible printed circuit sensor and post-processing algorithm for two-phase flow measurement in narrow rectangular channels

•A novel flexible printed circuit sensor is developed based on the wire-mesh sensor system for the measurement of two-phase flow in narrow rectangular channels.•Dedicated algorithms are developed to characterize bubbly flow and slug flow.•The accuracy of the sensor and post-processing algorithm is validated based on comparison with high-speed camera images. Experimental measurement of two-phase flow in narrow rectangular channels is of great interest for various industrial applications. As it is almost prohibitive to apply the conventional two-phase flow measurement technology in narrow rectangular channels, the novel flexible printed circuit (FPC) sensor has been developed based on the wire-mesh sensor system. The FPC sensor avoids the stretching device which significantly disturbs the flow and achieves the spatial resolution of 1.35 mm and the sampling rate up to 3150 Hz in a narrow channel. The dedicated post-processing algorithms, including that for noise elimination, resolution refinement, interface sharpening and parameter derivation, were developed for bubbly and slug flows. The reliability of the FPC sensor and the accuracy of post-processing algorithms are assessed based on comparison with high-speed camera images. According to the validation, for bubbly flow with the bubble diameter larger than 4 mm, the bubble diameter can be underestimated by −5.2% with the relative standard deviation below 7.8%. When recommended criterion is followed in postprocessing, the bubble velocity is underestimated by 2.0% with the relative standard deviation below 3.74%. For slug flow, Taylor bubble velocity and length can be underestimated by −1.03% and −2.22% with the relative standard deviation of 5.37% and 7.11%.