Comparison of ultrafast x-ray electron beam tomography and capacitance wire-mesh sensor imaging applied to multiphase flow measurement

In this paper we compare ultrafast electron beam x-ray tomography and wire-mesh sensor imaging for a gas-water two phase flow in a vertical Perspex pipe. A 16 x 16 wire-mesh sensor was applied to measure the flow under controlled conditions in an experimental two-phase flow loop. Part of the flow loop is a two metre tall round pipe of XX mm inner diameter operated with water and air under controlled conditions. A special injector device at the bottom of teh vertical test section provides controlled gasification of the water. This way, different flow patterns and a broad range of void fraction value values can be generated. The ROFEX scanner was installed to visualize the flow just underneath the wire-mesh sensor which is located at a sufficient distance upward the injector to secure a well developed flow.

Experiments were run with flow patterns of bubbly, slug and churn turbulent flow at different liquid and gas superficial velocities. Both sensors produced synchronized data sequences of 10 s at 2,500 frames per second rate. Measured and reconstructed image data was analyzed and compared with respect to cross-sectionally averaged gas fractions, radial as fraction profiles and bubble size distributions. Fairly good agreement between ROFEX scanner and wire-mesh outputs was found for higher mixture superficial velocity while in the lower range some discrepancies were found. Detailed description will be given in the full paper.