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Modeling of collision and coalescence of droplets during microgravity processing of Zn-Bi immiscible alloysA population balance model is presented for the coarsening of the dispersed phase of liquid-liquid two-phase mixtures in microgravity due to gravity sedimentation and Marangoni migration, which lead to the collision and coalescence of droplets. The model is used to predict the evolution of the size distribution of the dispersed phase in a liquid-phase miscibility gap system, Zn-Bi, which has been used in a number of experimental microgravity processing studies in which significant phase segregation has been observed. The analysis shows that increasing the temperature gradient, gravity level, volume fraction of the dispersed phase, initial average drop radius, initial standard deviation of droplet radii, or the temperature coefficient of the interfacial tension leads to an increase in the rate of droplet growth due to collision and coalescence. Comparison of the distribution evolutions for unimodal and bimodal initial distributions shows that the latter yield significantly more rapid droplet growth. Finally, it is shown that droplet growth can be dramatically reduced with antiparallel orientation of the gravity vector and the temperature gradient, provided that the relative magnitude of these two vectors is properly chosen.
Document ID
19900035823
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Davis, R. H.
(Colorado, University Boulder, United States)
Rogers, J. R.
(Colorado Univ. Boulder, CO, United States)
Date Acquired
August 14, 2013
Publication Date
January 1, 1990
Publication Information
Publication: Metallurgical Transactions A - Physical Metallurgy and Materials Science
Volume: 21A
ISSN: 0360-2133
Subject Category
Materials Processing
Accession Number
90A22878
Funding Number(s)
CONTRACT_GRANT: NAGW-951
CONTRACT_GRANT: NGT-50367
CONTRACT_GRANT: NAG3-993
Distribution Limits
Public
Copyright
Other

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