Flow pattern and pressure drop of foam flow generated from Non-Newtonian fluids: An experimental and modelling study

Abstract

Foam and bubble flow can greatly enhance the mass transfer of gas–liquid-solid systems in reactors and have been successfully applied in water treatment, pharmaceuticals, mineral flotation and other industries. A persistent challenge is the precise prediction of pressure drop of foam flow generated from non-Newtonian fluids across various flow patterns, which is essential for industrial process operational optimal control. A key aspect of achieving this objective involves integrating the nonlinear characteristics of foaming liquid, along with nonlinear and metastable characteristics of foam into the fluid dynamics model. This has not been thoroughly investigated, yet it is vital for the accurate forecasting of pressure drop. This work investigated the effects of non-Newtonian solutions on the flow behavior and pressure loss of foam flow in pipelines. We considered two distinct types of foam flow: full foaming flow (FFO), which encompasses four subflow types, and foam flow containing liquid (FCL), which includes two subflow types. The variations in flow patterns and pressure losses were intricately linked to the characteristics of the foam, such as the viscosity and gas volume fraction, all of which were influenced by factors such as the solution viscosity and gas/liquid flow rate. Building on these insights, a comprehensive foam flow pattern map based on gas and liquid Reynolds numbers was proposed. Furthermore, hydrodynamic models for annular foam flow, along with the governing equations, were formulated. A predictive model for pressure loss in foam flow was finally developed, accounting for non-Newtonian properties of solution and foam, metastable characteristics of foam, and the entrained efficiency of both foam and gas. The developed model in this work had higher prediction accuracy compared with the previous models.