The data reveal that LLHCs can be used up to 10% oil concentrations at the inlet, maintaining high separation efficiency. However, the performance of the LLHC is best for very low oil concentrations at the inlet, below 1%. For low concentrations, no emulsification of the mixture occurs in the LLHC. However, high inlet concentrations, up to 10%, promote emulsification posing a separation problem in the overflow stream.An existing LLHC mechanistic model is modified and refined. The main modifications carried out are improved correlation for the swirl intensity that affects the axial and tangential velocity distributions, the flow reversal radius and the inlet factor.The required inputs for the model are: LLHC geometry, fluid properties, inlet droplet size distribution and operational conditions. The model is capable of predicting the LLHC hydrodynamic flow field, namely, the swirl intensity and the axial, tangential and radial velocity distributions of the continuous-phase. The separation efficiency and migration probability are determined based on droplet trajectory analysis. The flow capacity, namely, the inlet-to-underflow pressure drop, is predicted utilizing an energy balance analysis.The LLHC mechanistic model was tested against the present study data and additional data from the literature, especially from . Very good agreement is observed between the model predictions and the experimental data with respect to the swirl intensity, axial and tangential velocity distributions, migration probability and global separation efficiency. The developed LLHC model can be used for the design of field applications for the industry. v ACKNOWLEDGEMENTS