2012 Volume 45 Issue 5 Pages 337-342
A method is proposed to determine the ratio of liquid droplets and vapor in the product of an ultrasonically-atomized aqueous ethanol solution. A salt which only enters into droplets is used as a tracer. Since no selective partitioning of salts has been reported between droplets and bulk solution, the amount of liquid turned into droplets is obtained from the change in the amount of salt. Knowing the ratio of the amount of droplets and vapor provides a clue for understanding the separation mechanism of ethanol enrichment in the fog. The ratio varied with the change in ethanol concentration in the feed solution. The ethanol concentration in the fog has been measured to discuss the relation between ethanol enrichment and the ratio. A multiphase model is proposed, where the source of the fog is regarded as shell-bearing bubbles and/or droplets. The basic mechanism of the enrichment is regarded as the surface excess of ethanol at the shell. By combining the amount of those droplets and bubbles, the predicted values of the ratio are obtained, and are compared with the observed values.