How does an ultrasonic humidifier / atomizer affect temperature?

Question

Evaporative cooling is a technique used to cool air by using the evaporation of a liquid.

My google research on evaporative cooling shows a ubiquitous concept of forcing air through a pad/membrane/foam/sponge that holds water, and the air exiting the pad is colder to a degree that depends on the ambient humidity. Apparently the output can be 10C or more colder than the input.

(Image from wikipedia.org)

As I understand, it's the evaporation of the water that causes the air to be cooled. And, as I take it, it's the heat from air at the input being absorbed by the water and causing a phase change that cools it.

What if the water is atomized by something such as an ultrasonic humidifier? Ultrasonic humidifiers use a "speaker" of sorts to vibrate water into a vapor. I can't find any mention of ultrasonic humidifiers being used to cool a room. At first it seemed to me that they would not cool the air, as water was simply atomized (instead of the heat from the air going in to a phase change).
But thinking about this another way: The atomized water particles would mostly evaporate in the air, which should thus cool it, right?

Do ultrasonic humidifiers cool air to the same degree that pad-based evaporative coolers do? (Assuming similar water volume used). If not, can ultrasonic humidifiers be used in a more elaborate system to cool the air?

Answer 1

What you propose has been in use for many years. It is called an air washer, which uses a pump to spray water through nozzles into a fine mist which is mixed with the incoming air stream and then passed through a trap that catches any unevaporated water droplets before the cooled air is distributed.

Answer 2

Ultrasonic humidifiers cool the air only to the same degree as the volume of water that they consume. Note that swamp/evaporative coolers for whole-home cooling are generally fed with many gallons of water per day via a directly piped water line connected to the main water line.

Ultrasonic humidifiers by contrast usually only consume a small fraction of one gallon of water per day, and are often fed by a small tank (1-2 liters). This difference in scale of water consumption is the same proportional difference in the cooling effect produced, because the process of cooling itself is directly proportional to the number of water molecules which absorb enough heat to become liberated from liquid form.

Although you might find a way to atomize the same volume of water in a single day by ultrasonic means as an evaporative cooler with pads and a fan, your next challenge would be to find a way to remove that humid air from the environment and replace it with dry air, so that you can continue to evaporate (atomize) water into the air. This is why swamp/evaporative coolers always require an exhaust port (open windows, doors, or special vents) to allow the same volume of air to exit the home as that which is pulled in from the outdoors. The rule of thumb for sizing is that for every 1,000 CFM (cubic feet per minute) of airflow generated by the swamp/evaporative cooler, you need between 1-2 square feet of open window or venting for air to leave the space.

If an ultrasonic transducer with water feed could generate a sufficient rate of water transfer into the indoor atmosphere to continuously cool a home as much as that home acquires heat from the outdoor environment (think ambient heat transfer), then you'd need a method for continuously removing that same volume of water from the indoor air in order to maintain a steady level of humidity.

If you then suppose using a peltier _de_humidifier to remove the moisture, then you're actually adding a little more heat back into the air as was removed, unless you have some method of dumping that heat to the outdoors efficiently.

It's possible that ultrasonic humidification may work well to increase the efficiency of a standard swamp/evaporative cooler, but there is a big difference in water consumption rates with typical household devices. Maybe someone with more experience with the math can offer more guidance.