Oil/water flow in a horizontal pipe – dispersed flow regime

Abstract

In multiphase fluid flow, the formation of dispersed patterns, where one of the phases is completely dispersed in the other (continuous medium) is common, for example, in crude oil extraction, during the transport of water/oil mixture.

In this work, experimental and numerical studies were carried out for the flow of an oil/water mixture in a horizontal pipe, the dispersed liquid being a paraffin (oil with density 843 kg m⁻³ and viscosity 0.025 Pa s) and the continuous medium a water solution doped with NaCl (1000 μS. cm⁻¹). The tests were made for oil concentrations of 0.01, 0.13 and 0.22 v/v and velocities between 0.9 and 2.6 ms⁻¹ of the mixture. Experimental work was performed in a pilot rig equipped with an electrical impedance

tomography (EIT) system. Information on pressure drop, EIT maps, volumetric concentrations in the vertical diameter of the pipe and flow images were obtained. Simulations were performed in 2-dimensional geometry using the Eulerian–Eulerian approach and the k-ε model for turbulence modelling. The model was implemented in a computational fluid dynamics platform with the programme COMSOL Multiphysics version 5.3. The simulations were carried out using the Schiller–Neumann correlation for the drag coefficient and two equations for the viscosity calculation: Guth and Simba (1936) and Pal (2000). For the validation of the simulations, the pressure drop was the main control parameter.

The simulations predicted the fully dispersed flow patterns and the pressure drop calculated when using the Pal (2000) equation for the viscosity calculation showed the best fit. The results of the images of the flows obtained by the photographs and simulations were in good agreement.