In the right climate they do work - up to a point.

LiK's mom used one in her house up to the day she died, and she was "satisifed" with the cooling, but that was in North Texas where the outdoor humidity was generally fairly low during hot weather.

Hers was about a 3.5 foot "cube" that hung in a window, connected to a water tap with a float valve so that the bottom automatically was kept filled, and a small pump flowed water to the top of the three "excelsior" air filters (the three outside vertical sides of the cube).

In dry weather, the air coming into the house might be 15 - 20 F (8 - 11 C) cooler than outside. I never got a humidistat in, but it felt like the humidity indoors didn't rise more than perhaps 10 - 15 percent with her unit.

The temperature drop for the incoming air is pretty much fixed by the humidity, and a too small unit won't bring in enough cool air to do much good. An excessively large unit may add enough indoor humidity to defeat the effect of the air being a little cooler, but "up until the moss grows" on the walls there's probably some positive effect. A unit that just recirculates the air in the room may "bootstrap" the humidity up faster than it cools anything, so this kind of cooler usually works better if it brings in outside air continuously.

In a "hot muggy" climate, like in most big eastern US cities I'd expect it to be pretty much useless due to the humidity that settles in between all the tall buildings, and maybe in southern coastal areas, although I've heard of some use in Florida(?).

For a little more ($150 - $200?) you can probably get a "real" 6,000 Btu "window" air conditioner to "spot cool" a room, without messing with the water leaks and mildew. That's about as big as you can go on a (US) 120V - 20A outlet although you might stretch it to 8 - 10 KBtu on a "dedicated" outlet(?). Of course it will eat a little on your electric bill, but even in Kansas I'd generally go with the compressor.

John