Here we studied the emulsification process carried out in an extensional-flow unit. By means of rigorous population and momentum balances we captured the phenomenological description of the first principles occurring in such unit. The strong feature of our model approach resides in the fully mechanistic description of the governing phenomena. A population balance equation was formulated and solved to account for the disappearance and appearance of droplets at each size class. Coalescence mechanism was included to account for the instability of newly created droplets. We validated the accuracy of the results obtained from our equation-based model with experimental data obtained at pilot-plant scale. The results obtained by simulation showed that at a given set of operational conditions and pre-emulsion properties the product obtained was within the desired and narrow specifications space. As a concluding remark we suggest further exploring the design and development of extensional-flow units for structured emulsions. (C) 2011 Elsevier Ltd. All rights reserved.