Experimental study of influence of liquid viscosity in horizontal slug flow

Abstract

Slug flow is present in many industrial processes, including the ones related to the petroleum industry. Such flow pattern is characterized by the periodic passage of liquid slugs that may or may not be aerated and elongated bubbles that flow atop a liquid film. Most of the existing models for slug flow have been developed for two-phase water–air flows but, in oil and gas production, the liquid phase is often substantially more viscous than water. The aim of this article is to evaluate the effect of the liquid viscosity increase on slug flow. To achieve this goal, an experimental study on liquid–gas flows in a 26-mm ID, 8.65-m long horizontal pipe was developed. Water and mixtures of water and glycerin (μL≈5.46, 10.27, 15.39, 20.33 and 30.37 cP) made the working liquids. The experimental results from the high-speed camera and resistivity sensors enabled a detailed investigation of elongated bubble characteristics and slug flow parameters. The elongated bubble nose deformation, the appearance of plunging jets and the deformation of the dispersed bubbles are associated to dimensionless numbers. Experimental results show that the dispersed bubble deformation in the slug, the number of fragmented bubbles in the slug and the elongated bubble velocity increase as the mixture velocity and the liquid viscosity increase. The effects on the slug frequency and slug length depend on the superficial velocities of the fluids.