Water atomization droplet size distribution

Some quantitative studies1498115011 on droplet size distribution in water atomization of melts showed that the mean droplet size increases with metal flow rate and reduces with water flow rate, water velocity, or water pressure. From detailed experimental studies on the water atomization of steel, Grandzol and Tallmadge15011 observed that water velocity is a fundamental variable influencing the mean droplet size, and further, it is the velocity component normal to the molten metal stream Uw sin , rather than parallel to the metal stream, that governs the mean droplet size. This may be attributed to the hypothesis that water atomization is an impact and shattering process, while gas atomization is predominantly an aerodynamic shear process. 

Most water-atomized metal particles (powders) have been observed to follow the log-normal size distribution pattern. Relatively narrow size distributions of both fine and coarse particles may be generated by water atomization. A review of published data for droplet size distributions generated by gas and water atomization of a variety of liquid metals and alloys has been made by Lawley,[4] along with presentations of micrographs of surface morphology and internal microstructure of solidified particles. 

Schroder J, Kleinhans A, Serfert Y et al. (2012) V iscosity ratio A key factor for control of oil droplet size distribution in effervescent atomization of oil-in-water emulsions. Journal of Food Engineering 111 265-271. 

The figure 12 shows droplet size distribution for water and hydrogel suspension. The atomizing speed is 80 m.s and the feed flowrate 3 kg.hr (curves 1 and 2). Curve 3 represents the particle size distribution of a xerogcl, which is produced from the hydrogel of curve 1 dried in the labmatory spray dryer using the atomizing device described here. 

Droplet size distribution of atomized water and hydrogel are quite similar. These two-fluids (a newtonian one and a non-newtonian one) have same surface tension and, om our results, we think that their apparent viscosities are veiy similar at the high yiel stress existing at the atomizing wheel periphery-... 

In most research studies on SP and SD in the lab scale, ultrasonic atomization has been used to generate droplets/sprays. To increase the powder production rate, other atomization methods should be examined without affecting the particle size, size distribution and quahty. For instance, a twin-fiuid atomization technique was used to produce lead zirconate titanate (PZT) powder using a starting soluticm composed of lead acetate, zirconium acetate, and titanium propoxide (stabilized by acetylacetone) dissolved in water by Nimmo et al. [19]. Commercialization of SP technique is closely interrelated to its throughput and strong evidence that SP is a suitable method for the production of some particular advanced powders. 

The sample is converted into an aerosol in an atomizer. It then passes through an expansion chamber to allow a fall in the gas pressure and the larger droplets to settle out before passing to the burner, where the solvent evaporates instantly, the atoms remaining as a finely distributed gas. Atoms in the sample that are bound in molecules should be decomposed at the flame temperature so rapidly that the same effect is achieved. In practice only a small proportion of the sample (approximately 5%) is effectively atomized because the drop size of the remaining 95% is so large that the water is never effectively stripped away. In low temperature flames, for instance, only one sodium atom in about 60000 is excited but despite this apparently low efficiency the technique is very sensitive. 

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