Pressure drop characteristics of gas–liquid flow in a horizontal butterfly valve

Butterfly valves are standard components in pipeline systems for a wide range of industries, including chemical, water conveyance, and petrochemical. Special attention should be paid to the pressure drop caused by the complex two-phase flow through butterfly valves. In this paper, an experimental platform for gas–liquid flow was designed and constructed to investigate the pressure drop characteristics across a horizontal butterfly valve. Focusing on the intermittent flow patterns, including elongated bubble and slug flow, the effects of valve openings and gas–liquid superficial velocities on pressure drop were analyzed through experimental research under different operating conditions. It is found that the two-phase flow exhibited substantial asymmetry within the horizontal butterfly valve, leading to intensified local friction and flow separation, as well as enhanced breakup and merging of the gas–liquid phase interface. The pressure drop caused by gas phase is significant, especially under high valve opening, and the pressure drop multiplier shows a higher growth rate with the increase in gas phase proportion. A parametric model of the two-phase pressure drop multiplier for horizontal butterfly valves is proposed by equivalently describing the flow of gas and liquid phases using a Venturi tube and a thin orifice plate, respectively. The calculated results of the proposed model are consistent with the experimental data, verifying the effectiveness of the model. Compared with existing correlations, the proposed model demonstrates enhanced predictive accuracy of the two-phase flow pressure drop multiplier of horizontal butterfly valves.