A Eulerian-Lagrangian Hybrid model for the simulation of the drop size distribution of liquid-liquid emulsions in stirred tank reactors

Description

Emulsions are widely used in the several industries such as food, pharmaceutical, cosmetic, chemical and petroleum. Drop size distribution (DSD) plays the key role as it controls mass transfer and heat transfer in the Emulsions. In the current work, we developed a new idea for droplet breakup, where the droplet breaks locally under the specific condition depending on an in-house correlation for the local Sauter mean diameter. This correlation is based on the local shear rate and fluid properties such as viscosity, density and interfacial tension. Commonly, a population balance equation (PBE) is employed to describe the breakup and coalescence of the droplets; however, such an approach does commonly not distinguish between different slip velocities of the smaller and larger droplets. Therefore, we propose a hybrid modelling strategy, which combines an Eulerian-Eulerian two-fluid model (TFM) and a Lagrangian discrete particle model (DPM), which is referred to as the Hybrid TFM-DPM model. This method enables the efficient evaluation of the poly-disperse liquid-liquid drag form the local distribution of the different droplet diameters. The latter can be obtained by tracking statistically representative droplet trajectories for each droplet diameter class (Schneiderbauer et al. 2015) .Furthermore, the breakup of the droplets can be evaluated based on those tracer trajectories. In addition, a novel model for the droplet coalescence was proposed, where we do not require to resolve the individual collisions between the droplets. In contrast, the local droplet size distribution is discretized and the collisions of each droplets are evaluated based on the volume fraction of those droplet size fractions. Both the breakup and coalescence model are implemented into ANSYS Fluent by employing user defined functions (UDF).

Period	05 Oct 2017
Event title	10th World Congress of Chemical Engineering
Event type	Conference
Location	SpainShow on map