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Coalescence of rigid droplets in a stirred dispersion-II. Band-limited force fluctuations

Muralidhar, Ramachandran and Ramkrishna, Doraiswami and Das, Parichay K and Kumar, Rajinder (1988) Coalescence of rigid droplets in a stirred dispersion-II. Band-limited force fluctuations. In: Chemical Engineering Science, 43 (7). pp. 1559-1568.

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The coalescence of nearly rigid liquid droplets in a turbulent flow field is viewed as the drainage of a thin film of liquid under the action of a stochastic force representing the effect of turbulence. The force squeezing the drop pair is modelled as a correlated random function of time. The drops are assumed to coalesce once the film thickness becomes smaller than a critical thickness while they are regarded as separated if their distance of separation is larger than a prescribed distance. A semi-analytical solution is derived to determine the coalescence efficiency. The veracity of the solution procedure is established via a Monte-Carlo solution scheme. The model predicts a reversing trend of the dependence of the coalescence efficiency on the drop radii, the film liquid viscosity and the turbulence energy dissipation per unit mass, as the relative fluctuation increases. However, the dependence on physical parameters is weak (especially at high relative fluctuation) so that for the smallest droplets (which are nearly rigid) the coalescence efficiency may be treated as an empirical constant. The predictions of this model are compared with those of a white-noise force model. The results of this paper and those in Muralidhar and Ramkrishna (1986, Ind. Engng Chem. Fundam. 25, 554-56) suggest that dynamic drop deformation is the key factor that influences the coalescence efficiency.

Item Type: Journal Article
Publication: Chemical Engineering Science
Publisher: Elsevier Science
Additional Information: Copy rights of this article belongs to Elsevier Science.
Department/Centre: Division of Mechanical Sciences > Chemical Engineering
Date Deposited: 04 Aug 2009 02:40
Last Modified: 19 Sep 2010 05:39
URI: http://eprints.iisc.ac.in/id/eprint/21969

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