Defoaming by Inherent Liquid Spray

Franke and Pahl [49] have made a study of the effect of inherent liquid drop impact on the stability of horizontal liquid films. Their experimental observations 

It is well known that impact of inherent liquid drops can also cause air entrainment (see, e.g., reference [50]), a process that is in fact the basis of the well-known Ross-Miles pour test [51] (see Section 2.2.3). That drop impact can cause both the formation and destruction of foam would seem to be contradictory. It is, however, clearly a real effect that probably concerns the relative magnitude of variables such as the gas phase volume fraction in the foam, foam film thickness, and drop properties such as size, velocity, and frequency. Such a vague statement suggests the need for improved understanding of the phenomena associated with inherent liquid drop impact on foam and foam films. 

FIGURE 7.16 Probability of foam film rupture after impact by drops of inherent liquid as function of film thickness for various surfactant concentrations. Drop velocity 2.74 m s . Surfactant technical grade alkyl sulfonate, (a) 5 x 10 M. (b) 10 M. (c) 5 x 10 M. (Reprinted from Chem. Eng. Process., 36, Franke, D., Pahl, M.H., 175. Copyright 1997, with permission from Elsevier.) 

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