Drop breakage

Drop breakage occurs when surrounding fluid stresses exceed the surface resistance of drops. Drops are first elongated as a result of pressure fluctuations and then spHt into small drops with a possibiUty of additional smaller fragments (Fig. 19). Two types of fluid stresses cause dispersions, viscous shear and turbulence. In considering viscous shear effects, it is assumed that the drop size is smaller than the Kohnogoroff microscale, Tj. 

Dronedarone, 5 103, 106 Drop breakage, 16 696-697 Drop breakup, by turbulence, 16 697 Drop diameter, 10 763-764 Drop dispersions, 10 755 nonuniformity of, 10 765... 

The influence of liquid properties is strong. There is clear evidence [Groothius and Zuiderweg, toe. cit. Chem. Eng. Sci., 12, 288 (I960)] that coalescence rates are enhanced by mass transfer from a drop to the surrounding continuum and retarded by transfer in the reverse direction. See also Howarth [Chem. Eng. Set., 19, 33 (1964)]. For a theoretical treatment of drop breakage and coalescence and their effects, see Valentas and Amundsen [Ind. Eng. Chem. Fundam., 5, 271, 533 (1966) 7, 66 (1968)], Gal-Or and Walatka [Am. Inst. Chem. Eng. J., 13,650 (1967)], and Curl [ibid., 9,175 (1963)]. 

Curl and co-workers (R15, R16, VI1) assumed an analogy between drop breakage and molecular decomposition. They assumed a drop forms an activated complex due to imparted kinetic energy, which can be represented schematically ... 

Normal drops "Activated or unstable drops - Breakage products... 

Ross (R15) and Ross and Curl (R16) assumed the /3(u, a) term to be given by the beta function, whereas Shiloh et al. (S21) and Delichatsios and Probstein (D5) assumed that a drop breakage results in two equal daughter drops. 

Conceptually, the framework of the theory permits description of interphase heat and mass transfer with reaction occurring in either or both phases. In theory one can use this approach to study the affects of partial mixing of the dispersed phase on extent of reaction for non-first-order reactions which occur in the droplets. Analyses can be made for mass-transfer-controlled reactions and selectivity for complex reactions. Difficulties in the solution of the resulting integro-diflferential equations have restricted applications at present to partial solutions. For example, the effects of partial droplet mixing on extent of reaction were studied for uniform drops. Mass transfer from nonuniform drops for various reactor geometries was studied for dispersions with drop breakage only or drop coalescence only. 

Analysis of Drop Breakage and Coalescence in Dispersed Phase Systems... 

Podgorska and Bafdyga [Chem. Eng. Sci, 56, pp. 741-746 (2001)] present a model of drop breakage and coalescence and compare four scale-up criteria for agitated liquid-liquid dispersions ... 

For slow-coalescing systems and systems at low holdup, the rate of drop breakage dominates. In this case, according to the analysis of Podgorska... 

Interfacial tension controls the ease of drop breakage. Low interfacial tension (cr < lOdyne/cm or 0.01 N/m) systems require lower power for dispersion than high interfacial tension (cr > 30dyne/cm or 0.03 N/m) systems. 

Legisetty et al. [88] and Calabrese et al. [89] considered the effect of dispersed phase viscosity on drop breakage. In their models, attempts have been made to incorporate the effect of dispersed phase holdup on drop breakage by considering the turbulent velocity fluctuations to be damped by the dispersed phase drops as... 

Ghalehchian, j. S. 2002 Prediction of the hydrodynamics of rotating disc contactors based on a new Monte-Carlo simulation method for drop breakage. Journal of Chemical... 

Hsia, M. a. Tavlarides, L. L. 1983 Simulation analysis of drop breakage coalescence and micromixing in liquid-liquid stirred tanks. Chemical Engineering Journal and the... 

Zaccone, a., Gabler, A., Maass, S., Marchisio, D. Kraume, M. 2007 Drop breakage in liquid-liquid stirred dispersions modelling of single drop breakage. Chemical Engineering Science 62, 6297-6307. 

Figure 9.35 [57] and similar curves from Karam and Belfinger [58] show regions for drop breakage. Conditions must be above the curve for dispersion to occur. The burst energy is a function of the variables shown in Figure 9.35. 

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