Cross-sectional void fraction distribution measurements in a vertical annulus two-phase flow by high speed X-ray computed tomography and real-time neutron radiography techniques

A real-time neutron radiography (RTNR) system and a high speed X-ray computed tomography (X-CT) system are compared for measurement of two-phase flow. Each system is used to determine the flow regime, and the void fraction distribution in a vertical annulus flow channel with particular attention on the temporal resolution of the systems and the time behaviour of the two-phase flow. The annulus flow channel is operated as a bubble column and measurements obtained for gas flow rates from 0.0 to 30.0 l/min. Both the RTNR and the X-CT systems show that the two-dimensional void fraction distribution can be obtained. The X-CT system is shown to have a superior temporal resolution capable of resolving the void fraction distribution in an (r,θ) plane in 4.0 ms. The RTNR system is shown to obtain void fraction distribution in a (r,z) plane in 33.0 ms. Void fraction distribution for bubbly flow and slug flow is determined.