Experimental study on the effect of surfactants on the characteristics of gas carrying liquid in vertical churn and annular flows

Abstract

In this paper, air-water and air-SDBS solution vertical pipe flow experiments were carried out at room temperature and pressure. The purpose of this work is to study the effect of surfactants on the characteristics of gas carrying liquid in churn and annular flows by a high-speed camera. The results show that surfactants significantly affect the gas-liquid distribution characteristics in churn and annular flows. The process and degree of momentum transfer between the gas phase and liquid phase also change. With the introduction of surfactants, the bubble entrainment is enhanced while the droplet entrainment is inhibited. In churn flow, surfactants make the way of gas carrying liquid change from the accelerated migration of entrained liquid blocks to the one-way migration of stable waves. In annular flow, surfactants make the way of gas carrying liquid change from the accelerated migration of entrained liquid droplets and wave unidirectional migration to the migration of waves with uniform circumferential and axial distribution. The change of the way of gas carrying liquid caused by surfactants increases the momentum transfer between the gas phase and liquid phase, leading to a significant increase in the pressure drop gradient. The foaming of the liquid film is due to the fact that the wave growing from the liquid inlet can more easily satisfy the conditions of bubble entrainment than droplet entrainment. The gas and liquid flow rates determine the growth characteristics of the wave at the liquid inlet, thus determine the degree of change in the way of gas carrying liquid by surfactants.