High-frame rate, fast neutron imaging of two-phase flow in a thin rectangular channel

TL;DR

This study demonstrates high-frame-rate fast neutron radiography for visualizing and measuring parameters of two-phase air-water flows in a thin rectangular channel, showing promising initial results and potential for future improvements.

Contribution

It introduces a novel application of high-frame-rate fast neutron imaging to study two-phase flows with detailed flow parameter measurements.

Findings

Successful imaging at 10 ms exposure times.

Measured flow parameters like gas fraction and bubble velocities.

Initial results show promise for further development.

Abstract

We have demonstrated the feasibility of performing high-frame-rate, fast neutron radiography of air-water two-phase flows in a thin channel with rectangular cross section. The experiments have been carried out at the accelerator facility of the Physikalisch-Technische Bundesanstalt. A polychromatic, high-intensity fast neutron beam with average energy of 6 MeV was produced by 11.5 MeV deuterons hitting a thick Be target. Image sequences down to 10 millisecond exposure times were obtained using a fast-neutron imaging detector developed in the context of fast-neutron resonance imaging. Different two-phase flow regimes such as bubbly slug and churn flows have been examined. Two phase flow parameters like the volumetric gas fraction, bubble size and bubble velocities have been measured. The first results are promising, improvements for future experiments are also discussed.