Atomization

Atomization is the process of converting a bulk liquid into a mist or spray of droplets. It is used to increase liquid surface area, promote rapid evaporation, enhance mixing with a surrounding gas, or enable deposition onto a substrate. Atomization is distinct from simple evaporation, as it involves fragmentation of the liquid into smaller units rather than gradual phase change.

In most industrial atomizers, droplets form when liquid is forced through a nozzle or into a moving gas stream, creating instabilities that overcome surface tension. Mechanisms include shear by high-velocity gas (air- or gas-assisted atomization), hydraulic or pneumatic breaking through pressurized nozzles, cavitation, and ultrasonic vibration. The outcome is characterized by the droplet size distribution.

Common atomization technologies include air-assisted or two-fluid nozzles, airless or pressure nozzles, ultrasonic converters, and centrifugal or rotary atomizers. Nozzle choice affects efficiency, droplet size, and how liquids containing solids behave. Industrial processes such as spray coating, spray drying, combustion fuel delivery, and coating deposition rely on appropriate atomization.

Applications span energy, manufacturing, medicine, and agriculture. In combustion, fine droplets improve fuel-air mixing and combustion efficiency. In coatings and thermal spraying, atomization controls coating thickness and appearance. In spray drying, liquids are converted to powders. In inhalation therapies and pesticide applications, droplet size governs delivery and drift.

Characterizing atomization involves measuring droplet size distributions, usually by laser diffraction, phase Doppler, or high-speed imaging. Common metrics include the Sauter mean diameter. Challenges include nozzle wear from abrasive liquids, clogging, and controlling drift of fine aerosols for safety and environmental reasons.