fogger

[Johnny Pneumatic]

how do ultra-sonic water foggers work?

[jj]

Originally posted by bewareofdogmas
how do ultra-sonic water foggers work?

By literally shaking the water in a confined space hard enough to cause it to cavitate and break into small droplets that are caught by a fan and blown out into the room.

I've heard a number of concerns about these devices, especially when used with hard water, I do not have any evidence to support or deny such concerns.

[_Q_]

To expand on jj's comments, the following came from a report about ultrasonic humidifiers (http://home.howstuffworks.com/framed.htm?parent=humidifier.htm&url=http://www.pnl.gov/fta/14_ultrahumid/14_ultrahumid.htm) produced by the U.S Department of Energy by the Oak Ridge National Lab. I found it at howstuffworks.com. It's a few years old, but it might address your question.
Ultrasonic humidifiers employ a low power electronic circuit that consists of an oscillator that generates high frequency electrical energy and an electro-acoustic power converter, or transducer (piezo disk), to convert the electric energy to mechanical energy. The oscillator is mounted on a circuit board in the humidifier control unit; the transducers are immersed in the reservoir of mineral-free water.

The transducers contain a metal disk that vibrates or oscillates in response to an electrical signal from the oscillator. At low frequencies, the water in the reservoir follows the oscillations of the transducer. As the frequency increases, the inertial effects of the water keep it from oscillating as fast as the transducer creating areas of momentary vacuum and compression.

The transducer is designed so that this compression is directed at the surface of the water where cavitation occurs, broken capillary waves are formed, and minute droplets break the surface tension of the water and quickly dissipate into the air forming a fog or mist. The droplets in the mist are typically 1 micron in diameter. The mist absorbs heat from the surrounding air, causing the water droplets to evaporate and raising the relative humidity of the air.