Electrospray modeling of highly viscous and non‐Newtonian liquids

The electrohydrodynamic spraying of highly viscous and non‐Newtonian aqueous solutions of sodium alginate were experimentally modeled with high direct‐current electric fields. A prototype electrospray setup comprising a nozzle connected to a high‐voltage counter electrode connected to earth and a curing facility to solidify the droplets was used. The main aim was initially set to extend the knowledge of the electrospray to highly viscous liquids, where shear thinning was the main rheological feature of fluid flow through the nozzle of the spray system. To model the process, the effects on the size of beads of the electric field strength, nozzle diameter, flow rate, and the material properties of density, viscosity, surface tension, and electrical conductivity were characterized. The size distribution of the beads was obtained after the droplets were cured in a calcium chloride solution with an image analyzer system. The rheological study, carried out on different concentrations of alginate solution (i.e., 1–3 w/v %), showed a significant reduction in the viscosity as a function of the shear rate. Considering the shear‐thinning behavior of the solutions, in the modeling we applied the viscosity at the operational shear rate in the nozzle. Four dimensionless groups were introduced to obtain the relationship between the dimensionless group representing diameter and the other groups in the dripping and jet modes with statistical analysis of the experimental data. The proposed equations correlated the size of beads within ±10% deviations as compared to the experimental results. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010