Demisting using an ultrasonic standing wave field.

Removing drops from an air flow can be challenging, particularly, for small drops. Herein a method for demisting is presented that employs ultrasonics to force small drops to combine. Specifically, a cylindrical ultrasonic standing wave field is established in a tube, forming pressure nodes that take the form of cylinders located within the tube and having the same axis as the tube. Droplets are driven toward these pressure nodes by the acoustic radiation force, forcing smaller drops to combine to form larger drops, which eventually fall due to gravity, thereby demisting the flow. Experiments presented herein show that, for the setup employed, this method can remove a fraction of drops that approaches 0.8 and that the improvement due to ultrasonics, compared to the case without ultrasonics, is as large as 2.8. The effect of air flow rate and power is investigated.