Mixing miscible liquids with a large difference in viscosity is a complex process found in many industrial operations such as detergents manufacturing and the food industries. This operation is commonly carried out under turbulent conditions in stirred tanks, and with increasing liquid viscosity, it becomes difficult to maintain a turbulent flow throughout the tank, resulting in long mixing times. An alternative to stirred tanks are in-line mixers which consist of mixing elements inserted into a pipe section. In these devices mixing can be carried out under laminar conditions and the flow is usually a combination of distributive, shear and extensional flows. Although some studies have been presented for mixing liquids with a large viscosity difference under turbulent flow, a lack of quantitative data exists for processes in which the mixing operation is carried out under laminar conditions. This thesis presents a theoretical and experimental study of laminar mixing of miscible liquids with a large viscosity difference in constricted flows where extensional flow is prevalent. The principal objectives of this research are: (i) to develop experimental techniques that will allow quantitative measurements to be carried out when mixing liquids with a large difference in viscosity; (ii) to apply those techniques to improve the understanding of the mixing process; and (iii) to model the flow of a simple mixing device into which two streams with a difference in viscosity are fed. The concepts of interfacial line stretch and interfacial area increase as a measure of mixing were applied to slow viscous flow through an orifice and it was found that the largest line stretch (and area increase) occurred when extensional effects are strongest.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:598240 |
| Date | January 1998 |
| Creators | da Silva, A. J. B. M. |
| Publisher | University of Cambridge |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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