20. Novel Applications of Power Ultrasonic Spray

Atomization is a process where a liquid is dispersed into droplets in a gas. Ultrasonic atomization was discovered in the 1920s (Loomis and Woods, 1927). Since then, atomization has seen diversified applications in devices such as drug nebulizers, room humidifiers, and air refreshers, as well as in industrial processes such as combustion, prilling, and web coating. In contrast to conventional liquid atomizers, ultrasound atomizers generally handle lower flow rates, and atomization of the liquid is achieved not by pressure, but by the vibration of ultrasonic waves (Morgan, 1993). This latter feature decouples the requirement of orifice geometry and pressure from the flow rate, allowing the flow to be controlled independently. Typically, ultrasonic atomizers excel in accurately processing low flow rates and slurry without clogging issues.