What distinguishes an external mix atomizer from an internal mix atomizer?

The correct choice relates to the fundamental operation of external mix atomizers, where the mixing of liquid and air happens after the discharge. In these types of atomizers, the liquid and air are introduced separately and come together only at the nozzle or discharge point. This means that the atomization process begins after both components exit the nozzle, allowing for better control over the mixing ratio and potentially resulting in larger droplet sizes.

This contrasts with internal mix atomizers, where the liquid and air are combined within the body of the atomizer before being expelled, leading to finer mist production and a more uniform spray. The understanding of this principle is crucial for applications ranging from combustion systems to spray painting, where the characteristics of the mist or spray can significantly vary based on the design of the atomizer.