Visualization experiment of gas–liquid flow pattern downstream of single-orifice plates in horizontal pipes under an intermittent upstream flow

Abstract

The flow pattern of gas–liquid mixtures across a single-orifice plate in horizontal pipes, in particular the change in flow patterns downstream of a single-orifice plate (DSOP) when the upstream is in a common intermittent flow, has not been elucidated hitherto. In this study, a visualization experiment was performed using air and water as the gas and liquid phases, respectively. The effects of superficial gas velocity, superficial liquid velocity, and orifice-pipe diameter ratio on the flow pattern transition in DSOPs were experimentally examined in ranges of 0.07–0.51 m/s, 0.35–1.77 m/s, and 0.30–0.61, respectively. Results show that there are two different trends, i.e., stratified and dispersed, in DSOPs for an intermittent upstream flow. It is interesting that in DSOPs, intermittent flows tend to disappear, or, stratified flows can transit to bubble flows directly. In DSOPs, most of the region corresponding to an intermittent flow for a simple horizontal pipe becomes the region of a completely dispersed bubble flow, indicating that the throttling of orifice plates has excellent performance on bubble breakup. Moreover, a novel dimensionless criterion is proposed to predict the transition between stratified and bubble flows in DSOPs.