Coalescence Behaviour of Liquid Drops at Solid Surfaces

Abstract

The literature on droplet hydrodynamics and coalescence mechanisms in packed beds has been reviewed. The fundamentals of liquid-liquid and solid-liquid coalescence, and characterisation of 'wetting' or 'non-wetting' behaviour in liquid-vapour-solid systems by contact angles are summarised. Contact angle measurements have been extended to liquid-liquid- solid systems. Five organic liquids and water were investigated using both high and low surface energy solid surfaces. The contact angle varied with the size of the drop and with surface characteristics of the solid. The mechanisms by which a contact angle is subtended are explained with respect to the nature of a surface. The true contact angle was that measured with a ‘wetted’ surface; with a 'non-wetted' surface the drop actually 'rested' on adsorbed immiscible liquid...