Transient drop size distribution

K.C. Chang, Analysis of Transient Drop Size Distributions in Dilute Agitated Liquid-Liquid Systems, PhD Dissertation, University of Delaware, 1990. P.L. Fondy and R.L. Bates, Agitation of liquid systems requiring a high shear characteristic, AIChE J., 9(3) 338-342 (May 1963). 

Very few studies have been conducted so far to determine the transient drop size distributions used to elucidate the dynamic processes related with breakage and coalescence of the dispersed phase. Bajpai et al. [92] proposed a method for the measurement of the unsteady-state drop size distributions by... 

We begin by considering mechanistic theories that allow correlation of equilibrium mean drop size in dilnte systems. An example of their application is given. Drop size distributions are then discussed. The predictive approach is extended to other contacting devices and to moderately concentrated noncoalescing systems. Some additional factors are considered, followed by a discussion of transient effects and time to achieve equilibrium. 

Core Floods. At present the strong coupling between droplet size and flow has major experimental consequences (1) flow experiments must be performed under steady-state conditions (since otherwise the results may be controlled by long-lived, uninterpretable transients) (2) in situ droplet sizes cannot be obtained from measurements on an injected or produced dispersion (because these can change at core faces and inside the core) and (3) care must be taken that pressure drops measured across porous media are not dominated by end effects. Likewise, since abrupt droplet size changes can occur inside a porous medium, if the flow appears to be independent of the injected droplet-size distribution, it is likely that a new distribution is quickly forming inside the medium (38). 

Reactor configurations other than conventional stirred tanks have been proposed for suspension polymerization. Draft tubes, or internal loops , can be used for suspension polymerization [102], but drop size changes can occur [103] and flow patterns may be complicated [104]. Tanaka et al. [105] used a loop reactor for the suspension polymerization of styrene. They employed a double agitation method to control the transient droplet diameter distribution and the final particle size distribution. Ni et al. [106] developed an oscillatory baffled reactor for batch suspension polymerization of methyl methacrylate. Fluid mixing was achieved by eddies that are generated when a fluid passes through a set of equally spaced, stationary, orifice baffles that are located inside a tube. Periodically formed vortices were con-... 

Special opportunities for the industrial implementation of structured catalysts are offered by the growing interest in millisecond contact time processes, in view of the associated requirements on pressure drop and flow distribution to be matched with strict size constraints. In this case, a better control of the complex interplay between heat and mass transfer and heterogeneous/homogeneous reactions granted by structured catalysts would provide guidelines for the design of reactors and processes with optimized performances in terms of selectivity, yield, fast transient response and operational flexibility. 

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