Engulfment model

The evaluation of diazotization reactions [41], which were carried out in Kenics and Sulzer SMXL mixers, provide a possible access to this parameter determination. For small throughputs and high viscosities the yield of the desired product was determined by micro-mixing. The power dissipation of 85-90% in both mixers indicated, that the engulfment model for micro-mixing prevailed. Faster micro- and meso-mixing was achieved in the Sulzer mixers, because larger pressure drops were also present in them, see Fig. 8.11 and 8.12. 

Figure 10.6 Product distribution, X computed for engulfment model...

However, Equations 2.13 and 2.14 do not consider the molecular diffusion and viscous flow effects, which occur in the turbulent flow of small amounts of substance. That is why, if micromixing processes form the limiting stage, other estimating expressions should be used. The engulfment model is often used in this case [21, 22], with the following equation to estimate the characteristic mixing time ... 

Different mixing models such as the lEM (interexchange with the mean) model [67], the droplet erosion and diffusion model [68], the engulfment deformation diffusion model and the engulfment model [69, 70], and the incorporation model [71] have been proposed. 

Figure 13-3 By-product selectivity, Xj, as a function of Damkoehler number based on k2. These data of Bourne in Sharratt (1997) show the increased by-product formation with increasing mixing time based on the engulfment model, Te- As the reaction rate for the second reaction, kiCe, increases, the mixing time must decrease to maintain yield.

This concept was replaced by the engulfment model, which is a more realistic way of treating the breakup of the added reactant. Here the engulfment rate is... 

Table 13-12 summarizes the main simnlation methods that have been or are in use. In the discussion that follows, Enlerian methods based on time-averaged (or Reynolds-averaged) balance equations for the component concentrations and segregation will be emphasized, but the Lagrangian-oriented engulfment model and Monte Carlo coalescence-dispersion models are also presented. 

Lamellar Mixing Simulation Using the Engulfment Model... 

Penney, R. W., H. X. Vo, and G. K. Patterson (1997). Implementation of the Bourne engulfment model using TK-Solver, presented at the AIChE Annual Meeting, Los Angeles. 

There are some alternative models to describe the micromixing eddy breakup model [41], flamelet model [42], and engulfment model [43]. 

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