Mechanistic model and experiments of dispersed liquid-liquid pipe flows.*

The transportation and separation of dispersed liquid-liquid pipe flows are significant in the energy and chemical industries. However, accurately predicting their evolution remains challenging due to lack of data and the inherent complexity of the underlying mechanisms. This work aims to improve understanding and to provide a predictive model via experimental studies supported by Model based Design of Experiments (MbDoE) methodologies.

During the separation, four layers form: a continuous phase, a floatation layer (FL) where drops settle towards their homophase, a dense-packed layer (DPL) where drops coalesce with each other and with the evolving dispersed phase interface. When the coalescence rate exceeds the floatation rate, the DPL depletes, and the FL is in contact with the dispersed phase layer. This case has not been studied before.

A novel multi-hole injector was designed to investigate separations  after the depletion of DPL. The flow evolution was studied with high-speed imaging and ultrasound techniques and the oil fraction and droplet size distribution were obtained. The influence of the flowrates and the oil fraction on floatation velocities was also studied.

In the mechanistic model, a number of drop settling correlations were implemented. It was found that flow velocity has a significant impact on drop floatation velocity.  The next step is to develop a regressive correlation for the drop floatation velocity, based on MbDoE, to enhance the predictions of the mechanistic model.