I have a question regarding my ducted roof top evaporative cooler that has been bugging me for some time. Some sources say that the air is drawn over the filter pads and some say through the filter pads. Personally I can't see how such a large breeze which I am getting can possibly be drawn through the filter pads. And if it was why isn't water also being sprayed in with the air.
Then there is the alternative. My cooler is a square with filter pads on 4 sides. How can air be drawn over the pads when the pads take up the entire vertical space on each 4 sides. If one side was open I could see this happening or if the square box was open at the top, but it is not. Is there a large gap somewhere where the air is being drawn in? There doesn't seem to be such a gap anywhere.
I also see one source saying that these coolers can use 1500 watts of power. My agent told me mine was using 400 watts. And I run mine in economy mode which is half the normal speed, then say 200 watts. I am using much less power than my heating bills in the winter even when the cooler is on all day, every day.
Can anyone provide a definitive answer? This is a science or physics question so is a valid question for this forum. I have recently designed a microcontroller thermostat for an evaporative cooler. While this has no relevance to the questions I am asking it would just be satisfying to know the answers.

 

Hi All, evaporative air conditioners. Denison here. I can now answer my own question. The answer is both over and through the pads. I have had a close look at at the pads in a mobile evaporative cooler I bought recently. I can see a lot of gaps in the material of the pads. The fan draws the air through these gaps which is then cooled by the water soaked pad. There must be no droplets of water in the gaps or otherwise these would also be dragged through with the air. Bit hard to see how this is accomplished as water is flowing down from the reservoir at the top. The pad must be fully absorbing this water.

 

Yes, the air is drawn through the pads, but any drops drawn into the air are small and evaporate rapidly so no water gets into the room.
The air into the room has, of course, a much higher humidity from the evaporated water (which provides the cooling) than the outside air.

 

Hence the colloquial name “swamp cooler.”