Liquids' atomization with two different nozzles: Modeling of the effects of some processing and formulation conditions by dimensional analysis

Abstract

Liquid atomization is a largely widespread unit operation. The disintegration of a liquid into droplets depends on the nature of the nozzle, on the process parameters as well as physicochemical characteristics of the fluid. The aim of this work is to study the contribution of the process (liquid outlet speed and air pressure) and physicochemical (viscosity and surface tension) factors on the size distribution of droplets generated by single- and two-fluid flat spray nozzles. The obtained droplet median diameters which range between 77 and 594 mu m for the single-fluid nozzle and between 11 and 599 mu m for the two-fluid nozzle, are discussed in relation with operating conditions of atomization process. Dimensional analysis was performed as a modeling approach. Despite energy input for the droplet formation is known to be influenced by different origins according to single and two-fluid nozzles, it is shown that a unique correlation, with specific values of parameters for each nozzle type, gathers all the parameters affecting droplet size. In the range of process and formulation parameters tested, this correlation is validated and gives satisfactory agreement for the single- and two-fluid nozzles

A dimensional analysis approach for modelling the size of droplets formed by bi-fluid atomisation

“…Several literature studies confirmed this trend (Chigier, 1976;Nguyen and Rhodes, 1998;Nukiyama and Tanasawa, 1939;Lefebvre, 1980); furthermore, it was pointed out that air pressure is a crucial process parameter in the atomisation operation (Chigier, 1976;Ehlers et al, 2010;Hede et al, 2008a;Juslin et al, 1995;Lefebvre, 1980;Mandato et al, 2012;Nguyen and Rhodes, 1998).…”

“…These processes involve the formation of liquid binder droplets by atomisation, which is a critical step, as it directly influences the wetting of fine powder particles and their ability to adhere one to each other and form agglomerates (Iveson et al, 2001;Litster and Ennis, 2004;Mandato et al, 2012;Saad, 2011). Besides, it has been evidenced that the droplet size produced by atomisation is highly correlated to the sizes of final particles in spray-drying and wet agglomeration processes (Cuq et al, 2013;Hede et al, 2008a;Iveson et al, 2001;JimenezMunguia, 2007;Leuenberger et al, 2006;Marmottant, 2001;Parikh, 2006).…”

“…The general mechanism of liquid atomisation by bi-fluid nozzles is outlined below (Beau, 2006;Chigier, 1976;Hede et al, 2008a;Lefebvre, 1980;Mandato et al, 2012;Marmottant, 2001;Nguyen and Rhodes, 1998). Pumping the liquid through the nozzle results in the formation of a liquid jet at the nozzle outlet, which interacts with the surrounding atomising air at higher velocity.…”

“…The geometrical features of the nozzle are also linked to fluid velocities at the nozzle outlet (Cuq et al, 2013;Mandato et al, 2012). At constant liquid and air flow rates, the larger the air orifice area and/or the smaller the liquid orifice area, the lower the airliquid velocity difference at the nozzle outlet, and thus the larger the droplets.…”

“…The main physicochemical properties (viscosity, surface tension, and density), jointly varying when changing the liquid composition, are related to the ability of the liquid phase to resist break-up by frictional forces (Hede et al, 2008a;Lefebvre, 1980;Mandato et al, 2012;Marmottant, 2001).…”