Hydrodynamic behavior modeling of pumps handling fluids with complex rheological behavior

Abstract

The thesis research work addresses the pumping of fluids with complex rheological behavior. The aim of the thesis is to carry out an exhaustive analysis of the performance and internal flow features of a volute centrifugal pump when handling complex non-Newtonian emulsions. The industrial applications in this field are numerous and can include crude oil emulsion pumping, wastewater pumping, and cosmetic and food emulsions. Two elements combine to explain the complexity of this scientific problem: the first involves the pump and its three-dimensional geometry with a strong coupling with the loop. The second concerns the nonlinear and unstable rheological behavior of the pumped fluid, especially when the pump carries a reduced fraction of the continuous phase. These flows concern fluids with non-Newtonian and particularly unstable behavior. The insights needed to achieve their understanding are sometimes at the limit of chemistry with approaches at the molecular scale. In this work, several approaches were used to study the hydrodynamic behavior of the pump under emulsion flow: an analytical approach, a single-phase CFD simulation, and a two-phase CFD simulation. The analytical approach is based on a mechanistic model for the determination of the emulsion viscosity as a function of the pump operating conditions, which is then coupled to a mechanistic model based on the different losses encountered in volute pumps. The single-phase simulation is based on a CFD study in which the rheological behavior of the emulsions has been considered neglecting the two-phase nature of the fluid, and the two-phase study which considers the two fluids and the different interactions between the phases. The approaches adopted belong to two distinct categories; the analytical approach allows for differentiation of the losses within the centrifugal pump, which is not the case for CFD. However, this shortcoming is compensated for by the entropy analysis, which allows for the localization of energy losses. Finally, the ability of the two CFD approaches considered to accurately predict the performance of pumps handling emulsions is evaluated by comparing the numerical results of a multistage pump (ESP) with the corresponding experimental data