A literature review on mechanisms and models for the coalescence process of fluid particles

Coalescence efficiency model including electrostatic interactions in liquid/liquid dispersions

“…Hence, critical distances are introduced in several models, e.g. the critical film rupture thickness in film drainage models (Liao and Lucas, 2010). As the distance of the characteristic maximum (and minimum) of the resulting DLVO force (Fel + FvdW) varies especially with the electrolyte concentration (Israelachvili, 1991;Pfennig and Schwerin, 1998) (see Figure 4), an assumption of a constant drop distance would be misleading.…”

“…energy dissipation, viscosities and interfacial tension). The modular concept of the population balance equation allows a simple implementation and exchange of sub models which are available in literature for (I) drop breakage (consisting of breakage rate and daughter drop size distribution) (Liao and Lucas, 2009) and for (II) drop coalescence (consisting of collision frequency and coalescence efficiency) (Liao and Lucas, 2010). The collision frequency determines the rate how often droplets in a system collide with each other whereas the coalescence efficiency describes the probability that two interacting drops merge into one.…”

Automated image analysis for trajectory determination of single drop collisions

“…The interfacial tension drives the confluence of the drops by contracting the mutual surface (see Figure 1 at t > 7.00 ms). The steps of drop collision, deformation and film drainage are mechanistic and can be described by several models available in literature [2]. The stochastic phenomenon is the moment at which the draining film ruptures and coalescence occurs.…”

“…Furthermore, the models account for the stochastic film rupture by predicting only coalescence probabilities within a droplet swarm and do not predict single coalescence events. So-called film drainage models regard the drainage and contact times as random variables and put them in relation to each other [2]. In the model representation of film drainage a repulsion of drops after collision can be explained as follows: if the drainage of the thin film takes longer than the contact time of the droplets they repulse each other elastically and do not coalesce.…”

“…State of the art modelling approaches describe the drop size distribution by separate kernels for breakage and coalescence rate. These so called population balance equations allow the separate implementation of * corresponding author Email address: johannes.kamp@tu-berlin.de (Johannes Kamp) URL: www.vt.tu-berlin.de (Johannes Kamp), www.cv.tu-berlin.de (Ronny Hänsch) breakage and coalescence which occur simultaneously in a general dispersion [1,2,3]. Several research groups investigated the breakage [4,5,6,7] and coalescence [8,9,10,11] separately in order to validate and improve these modelling approaches.…”