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Fluid particle coalescence and breakage phenomena are important for optimal operation of many industrial process units. In particular, in bubble column reactors, the bubble size distribution determines the interfacial momentum, heat, and mass transfer fluxes through the contact area and may thus limit the overall process performance. To elucidate the mechanisms of the coalescence and breakage phenomena, extensive wellplanned model-based experimental investigations are required. In addition, a suitable modeling framework considering the microscopic phenomena is needed to interpret the data achieving extended understanding of the important mechanisms, enabling the formulation of more sophisticated mechanistic kernel functions. This article presents a combined multifluid-population balance model for describing the behavior of vertical bubbledriven flows in bubble columns. In the present modeling approach, the Maxwellian average transport equations for the disperse phase are formulated in terms of a density function. The main advantage of this novel modeling concept is that we obtain a set of transport equations expressed in terms of the set of internal coordinates. All the important moments like the void fraction, contact area, Sauter mean diameter, average disperse phase velocity, mean mass, and momentum fluxes, etc., can then be computed from the predicted density function in a post processing procedure. For model validation, the model predictions are compared to experimental data gathered from the literature. The agreement between the available data and the model predictions ais considered very good. It is concluded that the model is a viable tool for parameter fitting of novel coalescence and breakage kernels provided that sufficient experimental data are made available.

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The breakage frequency and daughter size distribution functions by Coulaloglou and Tavlarides[1] are frequently adopted closures in population balance (PB) modelling. A survey of the extensions and modifications of the Coulaloglou and Tavlarides[1] breakage frequency function is provided. Furthermore, the daughter size distribution functions within the statistical category, herein the model proposed by Coulaloglou and Tavlarides[1], are outlined. Most of the breakage models available in literature commonly assume binary breakage only. Thus, the daughter size distribution function suggested by Diemer and Olson[2] is of interest as higher order breakage can be modelled. The breakage closures are evaluated solving the population balance equation (PBE) for a liquid–liquid emulsification system in a stirred tank. The results obtained from a least‐squares solver are compared with the experimental data when available.