Drop break-up in turbulent pipe flow downstream of a restriction

This work addresses the drop fragmentation process induced by a cross-sectional restriction in a pipe. An experimental device of an upward co-current oil-in-water dispersed flow (viscosity ratio λ ≈ 0.5 ) in a vertical column equipped with a concentric orifice has been designed. Drop break-up downst...

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Bibliographic Details
Published in:	Chemical engineering science Vol. 60; no. 23; pp. 6511 - 6528
Main Authors:	Galinat, S., Masbernat, O., Guiraud, P., Dalmazzone, C., Noı¨k, C.
Format:	Journal Article
Language:	English
Published:	Oxford Elsevier Ltd 01-12-2005 Elsevier
Subjects:	Applied sciences Break-up probability Chemical engineering Drop break-up Drop size distributions Exact sciences and technology Hydrodynamics of contact apparatus Orifice flow Weber number Break-up probability Drop size distributions Weber number Orifice flow Drop break-up Viscosity Statistical analysis Pipe flow Interface tension Reynolds number Hydrodynamics Experimental device Cocurrent flow Modeling Dispersion Population balance Operating conditions Fragmentation Drop Design Particle size distribution Pressure drop High speed Daughter product
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Summary:	This work addresses the drop fragmentation process induced by a cross-sectional restriction in a pipe. An experimental device of an upward co-current oil-in-water dispersed flow (viscosity ratio λ ≈ 0.5 ) in a vertical column equipped with a concentric orifice has been designed. Drop break-up downstream of the restriction has been studied using a high-speed trajectography. The first objective of this work deals with a global analysis of the fragmentation process for a dilute dispersion. In this context, the operating parameters of the study are the orifice restriction ratio β , the flow Reynolds number, Re and the interfacial tension, σ . The break-up domain has been first mapped on a β ( Re ) graph and drop size distributions have been measured for different flow Reynolds numbers. It was observed that the mean drop diameter downstream of the restriction linearly increases as a function of the inverse of the square root of the pressure drop. This behaviour is in agreement with the observations previously made by Percy and Sleicher [A.I.Ch.E. Journal, 1983, 29(1), 161–164]. In addition, experiments based on the observation of single drop break-up downstream of the orifice have allowed the identification of different break-up mechanisms, and the determination of statistical quantities such as the break-up probability, the mean number of fragments and the daughter drop distribution. The drop break-up probability was found to be a monotonous increasing function of the Weber number based on the maximal pressure drop through the orifice. The mean number of fragments is also an increasing function of the Weber number and the reduced mean daughter drop diameter decreases as the Weber number increases. The daughter drop distributions are multimodal at low and moderate Weber numbers as a result of asymmetrical fragmentation processes. The statistical analysis of single drop break-up experiments was implemented in a simple global population balance model in order to predict the evolution of the size distribution across the restriction at different Reynolds numbers, in the limit of dilute dispersions.
Bibliography:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23
ISSN:	0009-2509 1873-4405
DOI:	10.1016/j.ces.2005.05.012