Measurement of Two-Phase Flow: Static CT System Based on Carbon Nanotubes

Abstract

Two-phase flow measurement with high precision plays a significant role in safe and efficient operation of nuclear reactor. This paper focuses on the void fraction of gas-liquid flow in a non-transparent tube with the inner diameter of 13mm. X-ray computer tomography (CT) is considered to be effective for two-phase flow measurement because of its good qualities of non-invasion. However, due to the mechanical limitation of rotating speed, solutions for fast CT system to reduce the scanning time have been suggested relied on multiple sources and detectors. Recently, carbon nanotube (CNT) based X-ray source has been applied to CT imaging, significantly improves the temporal resolution by increasing the number of sources and avoid the gantry rotation. This paper proposes a potential static CT system design for the imaging of two-phase flow in straight steel tube. The setup of this system employed 90 couples of CNT X-ray sources and detector arrays arranged in a circle. Gas-liquid flow was simulated with different sizes of spheroidic bubbles randomly placed in the water inside the tube. To substitute for the flow moving, the z-axis of the simulator was added according to the flow velocity and exposure duration. Iterative image reconstruction was applied for the inverse problem of density distribution, and the reconstruction result of the experiment indicates the static CT system is useful to distinguish the flow pattern and measure the void faction distribution of gas-liquid flow.