1100 BTU / 12V AC

[lenny flank]

Yeah, evaporation cooling is right up there with unicorns

Oh, and yes--if you are in, say, Florida, it works about as well as unicorn farts.

"Relative humidity" has something to do with it.

 

[velojym]

Yeah, that's a well known fact about evap. If the air won't take enough moisture, little or no cooling. Also well covered in the link I provided.

 

[lenny flank]

Or, as I said in my first post to this thread, "in most areas of the US they are physically incapable of working effectively". Sadly, that gets left out of many discussions about evaporative coolers.

And it also ties in with what Spiff said, about humidity before and after. Any sort of effective swamp cooler is going to be evaporating several gallons of waster a day. Try that in a van and you quickly end up with rainforest conditions (in which a swamp cooler will no longer work anyway). The only way to prevent that is if the humidity at the beginning is sooo low that it can absorb all that water and still not cause condensation--which, again, means in most areas of the US they are physically incapable of working effectively. Sadly, that also gets left out of many discussions about evaporative coolers.

But my original doubt still remains--I've seen no real-world indication that a van-sized swamp cooler (as opposed to the super-sized house units that are common in the Southwest) actually do much effective cooling. All the ones I've seen on YouTube are simp[ly not big enough to do any effective evaporating. Simple physics means they require evaporating several gallons of water a day--and nobody ever seems to be evaporating that much. So, many of the various claims I have heard from people over the year are simply impossible under the laws of physics.

If van-sized swamp coolers were really cheap and effective, every RV manufacturer in the country would be using them. None are. Which tells me something.

 

[dhurtt]

If van-sized swamp coolers were really cheap and effective, every RV manufacturer in the country would be using them. None are. Which tells me something.

Wrong conclusion. Most RV manufacturers in the country are not including them not because they are not effective, but because most units are not destined for very low humidity locations, which as you have pointed out is where they are effective.

Me, I don't care that they don't work in most of the country because I am located where they do work.

If you want to check it out, look the Turbokool, which fits in a standard 14" by 14" RV opening. https://www.turbokool.net/category-s/146.htm to see amp draw, etc. 3 gallons of water a day. I wish I had one the first time I went to Lake Havasu in my 25' class C.

 

[lenny flank]

3 gallons of water a day

Thanks, THIS is what I was looking for. That is roughly equivalent in cooling power to a 3000 BTU AC.

All the DIY thingies you see on YouTube, which use at best a few pints of water a day, are not powerful enough for any effective cooling. They are toys.

 

[Spaceman Spiff]

 . . . 3 gallons of water a day . . .

 . . . That is roughly equivalent in cooling power to a 3000 BTU AC . . .

That doesn't sound right.

A 3000 BTU air conditioner will extract 3000 BTU of heat per hour
= 72,000 BTU per 24 hours  (running at 100% duty cycle).

A swamp cooler evaporating 3 gallons of water per 24 hours
     At 30ºC (86ºF) water temperature, evaporation (enthalpy of vaporization) of water = 1044.6 BTU per pound
     = ~ 8357 BTU per gallon (~8 lbs)
     3 gal/24hrs X 8357 BTU/gal = 25,070 BTU removed in 24 hours.

About the equivalent of a 1000 BTU air conditioner.

 

[lenny flank]

I'm calculating on the basis of 3 gallons of water per eight hours, not 24--assuming there's no need to run the swamp cooler overnight.

So 3 pints water evaporated per hour = 3000 BTU x 8 hours = 24000 BTUs (3 gallons water)

AC: 3000 BTU per hour x 8 hours = 24000 BTUs

Roughly equivalent cooling.

No?

EDIT: Oh, I see my mistake--the figure given for the swamp cooler is 3 gallons per 24 hours, not three gallons per 8-hour day.

So yes, you are right--it is only one-third the cooling power of a 3000 BTU AC, or about 1000 BTU. It's just another toy.

 

[Spaceman Spiff]

My bigger concern is the 3 gallons of water you are dumping into a small space.  If my calculations are correct it should be raining inside:
     At 68ºF, 100% saturated air can hold 17.3g of water per cubic meter.  =~ 1 pint (16 oz) per 770 cubic feet.

 

[lenny flank]

Yep. It'd take a lot of ventilation to remove that moisture.

 

[jimindenver]

The keys to a swamp cooler are dry air going in and ventilation allowing the moist air out. Never run one into a none ventilated space because everything will sweat.