Evap air conditioner speed?

[scmhogg]

My experience tells me, that with a refrigeration unit, the air coming out is colder at lower speed.

Now, with an evap unit that drips water through a pad, will the air coming out be cooler at low speed? High speed? Or both the same. [the pump is efficient enough to keep the pad moist at either speed.]

eg. Will the portable evap unit cool an empty room faster a high speed? [The room is empty to take away the cooling factor of the fan on your body.]

[Sawduster]

Evap air conditioners depend a lot on moving a lot of air to cool an area. They don't lower the temperature of the air passing through near as much as refrigerated units do. As well, they pull the dry air from outside rather than recycling the cooler air in side because they depend on evaporation to cool the air. The air inside becomes quite humid so cycling it past the pads again results in less cooling. So you need to have an open window or venitlation system of some sort to let the wet air out as you pull more air in.

We used to keep three or four gallon milk jugs of frozen water in the freezer and on a really hot day would put them into the water pan of the unit. This would cool the water somewhat and the air coming in from the unit would be a bit colder.

[cabinetman]

Steve - Don't know if I can help you, but your question brings to mind my father. During WWII the Army stationed him in Needles, California, for a while, he was a dentist. There was no AC, so he hooked up a bale of hay in the bedroom window, and had a bucket above dripping water on it. Put a fan in front of the thing, and said it cooled the room to a livable temp. I guess what you have is a little more modern than that.

[frumper64]

Anecdotal evidence says faster is better

When I lived in El Paso in the late 60's, the more upscale swamp coolers had two speed fans on them for more cooling at a higher blower speed. As said above, it wasn't like the air was really any cooler, there was just more of the cooled air being blown into the house. They actually really were quite efficient in cooling the house in El Paso where humidity was in the teens.

[maxparot]

There is a velocity effect on the cooling action of an evap cooler. I have a 2 speed unit on the roof of my home. ( in AZ ) Evap cooler work best when the outside air is dry and can cool the air 20-30 degrees. But if you start pulling on the wet pads too hard you'll just pour water into your ducts and into your home.

[rja]

I used to live in New Mexico. First Carlsbad, then Edgewood. At both places we had evaporative coolers which were quite effective. On a 100 degree day, the cooler could cool our 4 bedroom house to the 70s. The very low relative outside humidity made them effective and the humidification effect inside the house was desirable.

[LCHIEN]

I can hazard a guess based upon the physics of how they work.

The refrigeration style (freon based) AC depends upon the amount of freon that can be pumped through the compressor and evaporator so there's only so many BTUs no matter what. Blowing more air through the coil will not increase the BTUs (or thermal energy) only distribute the effect among more air. So, as you noticed, blowing more molecules air only reduced the amount of cold transfered to each molecule.

With an Evap cooler the work is done by absorbing the heat of evaporation. So each additional molecule of air blown by increases the rate of evaporation it would seem you would get more cool air. As long as you didn't run out of water and the air did not become saturated with humidity, blowing more air will aid the evaporation thus absorbing more more heat energy.