Role of surfactant in the breakup of liquid jets in food processing operations
Abstract
The spontaneous break up into drops of a liquid jet is a fluid-dynamical process that impacts many important food and agricultural applications from spray drying of liquid foods and atomization of fertilizers and pesticides, to emerging applications such as protein micro-arraying and micro- and nano-encapsulation of flavors and nutrients. While the desired drop sizes differ widely among these applications, the unifying goal is to produce drops having a narrow (mono-disperse) distribution of sizes centered about the targeted size. However, wide (poly-disperse) drop size distributions frequently appear as a consequence of the formation of undesired smaller satellite drops. The formation of satellite drops has a number of disadvantages that are directly related to product quality and stability, and is among the most common causes of inefficiency and environmental pollution in commercial applications involving jet break up. Since surface tension is the driving force causing the jet instability, surfactants play a critical role in the break up processes and are routinely added to facilitate processing (e.g. avoid drop coalescence, reduce energy consumption), or are ubiquitous as contaminants. Although the break up of surfactant-free jets has been extensively studied, for reasons directly related to theoretical and experimental complexity, little is known about the effect of surfactants on the formation of satellite drops. In this work, developments in the field of interfacial fluid dynamics were used to characterize the physical mechanisms that govern the capillary deformation and break-up of liquid jets in the presence of surfactants, with special focus on characterizing the mechanisms leading to formation of satellite drops. Results from these studies showed, for the first time, that the ability of surfactants to develop tangential stresses (Marangoni stresses) on interfaces provides a mechanism that favors the formation of satellite droplets. The rigorous characterization of this novel mechanism provide the foundation for the rational design of improved technological applications, and to reduce the inefficiency and pollutant levels in industrial processes involving jet breakup of complex fluids.
Degree
Ph.D.
Advisors
Corvalan, Purdue University.
Subject Area
Food science
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