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Scaling of droplet breakup in high-pressure homogenizer orifices. Part I: Comparison of velocity profiles in scaled coaxial orifices

Preiss, Felix Johannes; Mutsch, Benedikt; Kähler, Christian J.; Karbstein, Heike Petra

Abstract:
Properties of emulsions such as stability, viscosity or color can be influenced by the droplet size distribution. High-pressure homogenization (HPH) is the method of choice for emulsions with a low to medium viscosity with a target mean droplet diameter of less than 1 µm. During HPH, the droplets of the emulsion are exposed to shear and extensional stresses, which cause them to break up. Ongoing work is focused on better understanding the mechanisms of droplet breakup and relevant parameters. Since the gap dimensions of the disruption unit (e.g., flat valve or orifice) are small (usually below 500 µm) and the droplet breakup also takes place on small spatial and time scales, the resolution limit of current measuring systems is reached. In addition, the high velocities impede time resolved measurements. Therefore, a five-fold and fifty-fold magnified optically accessible coaxial orifice were used in this study while maintaining the dimensionless numbers characteristic for the droplet breakup (Reynolds and Weber number, viscosity and density ratio). Three matching material systems are presented. In order to verify their similarity, the local velocity profiles of the emerging free jet were measured using both a microparticle image velocimetry (µ-PIV) and a particle image velocimetry (PIV) system. ... mehr

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Verlagsausgabe §
DOI: 10.5445/IR/1000131066
Veröffentlicht am 01.04.2021
Originalveröffentlichung
DOI: 10.3390/chemengineering5010007
Cover der Publikation
Zugehörige Institution(en) am KIT Institut für Bio- und Lebensmitteltechnik (BLT)
Publikationstyp Zeitschriftenaufsatz
Publikationsjahr 2021
Sprache Englisch
Identifikator ISSN: 2305-7084
KITopen-ID: 1000131066
Erschienen in ChemEngineering
Verlag MDPI
Band 5
Heft 1
Seiten 7
Schlagwörter µ-PIV; PIV; scaled disruption unit; free jet; velocity profile; confinement; high-pressure homogenization; orifice
Nachgewiesen in Scopus
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