Experimental study of the evolution of droplet size distribution in water-in-oil emulsions in vertical and horizontal laminar flow
Name: LIGIA GAIGHER FRANCO
Publication date: 24/08/2026
Examining board:
Name |
Role |
|---|---|
| ANA PAULA MENEGUELO | Examinador Interno |
| BRUNO VENTURINI LOUREIRO | Examinador Interno |
| MARCOS AURÉLIO DE SOUZA | Examinador Externo |
| OSCAR MAURÍCIO HERNANDEZ RODRIGUEZ | Examinador Externo |
| RENATO DO NASCIMENTO SIQUEIRA | Presidente |
Pages
Summary: Emulsions are frequently formed during the flow of immiscible liquids in industrial applications due to hydrodynamic stresses that promote the dispersion of one liquid phase into another. Shear and turbulence continuously modify the droplet size distribution (DSD) through droplet deformation and collisions, which may result in droplet breakup or coalescence processes.
Droplet size is a key parameter governing emulsion stability, phase separation efficiency, physicochemical properties, and pressure drop during flow. Despite significant advances in this field, important gaps remain in both numerical and empirical approaches for describing the evolution of the DSD in concentrated emulsions, particularly in predicting droplet size owing
to the complex interplay mechanisms of droplet breakup and coalescence. This thesis experimentally investigates the mechanisms governing the evolution of the DSD in water-in-oil (W/O) emulsions flowing under laminar conditions through vertical upward and horizontal pipelines, representative of flow configurations commonly encountered in the petroleum industry. The study aims to improve the understanding of shear-induced droplet breakup and coalescence in internal flows by investigating W/O emulsions with dispersed-phase volume fractions ranging from 5% to 20 (v/v) of water under operating conditions that remain scarcely explored in the literature. The emulsions were formulated using mineral oil, Triton X-114 surfactant, deionized water, and sodium chloride (NaCl) to obtain metastable emulsions. The experiments were conducted in the emulsion flow loop at the NEMOG laboratory, operating in batch mode. Emulsion samples were collected at the inlet and outlet of the test sections, and the droplet size distribution was determined by laser diffraction. An emulsion recycling procedure was developed based on the reuse of the emulsion after each batch, and its validity was validated through the analysis of the DSD. In the vertical upward flow, droplet breakup was identified as the predominant mechanism, and the evolution of the DSD was found to be primarily associated with the Capillary number and the initial droplet size, demonstrating that the hydrodynamic history of the emulsion affects its flow stability. In contrast, horizontal flow promoted an increase in droplet size, consistent with the predominance of droplet coalescence in long horizontal pipelines, which was also primarily associated with the Capillary number. This thesis
demonstrates that the evolution of the DSD in W/O emulsions flowing under laminar conditions is governed not solely by the hydrodynamic stresses acting on the droplets but also by the initial emulsion structure, which influence the competition between droplet breakup and coalescence.
