An investigation of transition processes from transient gas–liquid plug to slug flow in horizontal pipe: Experiment and Cost-based recurrence analysis

Abstract

Transient gas–liquid two-phase flows are often encountered in nuclear industries. Investigating the dynamics of the transient gas–liquid flows is of significance for optimizing the reaction processes and predicting the thermal–hydraulic phenomena relevant to the performance of nuclear reactors. In this study, a multi-nozzle gas inlet was designed to mimic the transient gas–liquid flows in a horizontal pipe. A conductance wire-mesh sensor (WMS) was used to visualize the phase distribution at the pipe cross-section. Based on the WMS data, a cost-based recurrence analysis (CBRP) was developed to reveal the dynamics of transient gas–liquid flows. Different transition processes from plug flow to slug flow were observed in the experiment and explored by the determinism (DET) of the CBRP. Note that special flow structures, i.e., wave bridge and pseudo slug, were encountered during the flow pattern transition, and their generation mechanisms were uncovered. The processes of the flow pattern transition were also characterized by the slug frequency and the probability density function of the water holdup, which presented a good agreement with the CBRP results.