Homemade evap cooler for small vehicle

[JennyJ]

While cruising through a link on 30 Ways to Recycle Styrofoam, I saw a suggestion for making a very simple evaporative cooler:

Which led me to this version that's even better since it can run off solar, with suggestions below saying that just water or even a soaked towel works nearly as well:

Seems like a great idea for small vehicles in a dry climate... any downsides?

 

[MrNoodly]

Evaporative coolers (a.k.a. swamp coolers) really only work in places with low humidity. If the air is already saturated then the air from the cooler won't evaporate. Then you're just making things damper, inviting mold and mildew.

A friend in very dry Arizona experimented with several versions of these homemade coolers. The best he got was a 2° difference after running it for hours in a small travel trailer in the shade. Then he ran out of ice.

 

[highdesertranger]

a mister fan blowing right on you works the best and is simple to make. highdesertranger

 

[JennyJ]

Ahh, I knew it was a good idea to ask if it had any downsides!

Did anyone see Idea #3 on 30 uses of styrofoam?

3. Alternative to Ice
You can use packing peanuts as an alternative to ice in a cooler to keep the contents cold, or in conjunction with ice to make the ice colder and last longer without melting.

Warning: Do NOT put packing peanuts into a beverage as an alternative to ice. It should be common sense, but I’ll put it out there just in case somebody has the idea of dropping styrofoam into lemonade.

I might have to try this, having a cooler and not a fridge.

 

[user 423]

A swamp cooler will also use up a lot of water and toting that around in a smaller vehicle is a problem.

 

[MrAlvinDude]

One down side is, that both these coolers depend on ice, to lower the temperature of the air.
Once the ice has melted, then it no longer cools.

If you have access to an unlimited amount of ice, then it is a portable way to get the cooling effect right there where you want it.


An other method to create cooling, is by using evaporation methods.
If you take a liquid, and blow air over it, to make some of it evaporate then the remaining liquid will become colder. 

I think that one gram of evaporated water, will make the remaining liquid about 1-1.5 BTU colder (I am not quite sure about the math here, but I think it is about that amount).

Small electric Air Conditioners, is typically able to cool an equivalent of a number of 1000's of BTU's.  So you will need to evaporate quite a bit of water in order to cool something similar to 1000 BTU's


But one way, to get a more direct way of benefiting from the evaporation, is to mist ones clothes - and stand in the wind (natural or fan). Then the evaporation effect will cool down ones skin, much more directly.
This method work better in a dry climate, and not quite as well in an already fully saturated humid climate.  The more humid the climate, the more one needs to use ice (or an AC compressor) in order to create the cooling effect.

 

[jonyjoe303]

swampcoolers do work, I been using them for 9 years. Right now we are going through another heatwave and just have a small 2 amp swampcooler keeping me cool. I don't use any ice, I just use water.
The simple ice coolers (shown on the videos) don't qualify as evap coolers, The evap coolers need some evaporator pad (I use the cardboard based celdek material) . The water flowing over the celdek while having a fan blow through it gives you the cooling effect. Even in hot conditions it works better then just having a fan.
You have to try a swampcooler before you decide against using one. Even in your area you might find it works. Even a few degrees of temp drop is better then nothing.
If you build one, make sure and keep the water seperated from the fan section so when your driving around water doesnt slosh out of the unit into your carpet. This also makes it easier since you don't have to drain the water out of it, everytime you have to drive.

Picture of a small 2 amp evap swampcooler I built. The brown material is the celdek evaporator pad. Its a simple design, all you need is a 120mm 12 volt fan, a 6 dollar 12 volt submersible water pump, some tubing, and evaporator pad. Putting it together is the hard part, but nothing that requires complex skills.


The smallest swampcooler 1.5 amp I built, I actually used it to keep me cool during an entire summer. I build this one to see how small I could build one that actually works. It worked good enough that I kept it going until winter. The only drawback with small swampcooler is you have to fill with water more often.

 

[MrAlvinDude]

Did anyone see Idea #3 on 30 uses of styrofoam?

I might have to try this, having a cooler and not a fridge.

Either method uses a method to 'store up the cold', and this 'cold' can then be used elsewhere, to cool the air.

Ice cubes are most likely to be able to store more energy (store more cold) than a similar size of water filled styrofoam is. 

But the styrofoam may make for an  easy and convenient sizes of 'block' to move around. And water soaked (and cooled) styrofoam may separate easier, than picking at a large ice-cube. 



But heat/cold is part of a physical constant, so heat (or cold) can only be moved. it can not be made into nothing. There is a constant relation between: temperature x pressure x volume = constant.

At the change of a substance, right there, the constant is however different.
So to transform a solid to liquid, and then again from a liquid to a gases-form, right there, there is a need for extra energy to do the transformation.


So the three only ways to change temperature, is to either a) change pressure or volume or b) transform between solid, liquid and gas - or to use heat transfer, and move the heat to somewhere else.

One (or all) of these methods are being used in cooling mechanisms.


The core method for the swamp cooler is to utilize  the liquid to mist transformation method.

The core method for the ice-box fan cooler, is to utilize the extra energy stored in the ice, and being released as the transformation from solid to liquid happens.


It takes about twice as much energy to transform from a liquid to mist, as it does to transform from a solid to a liquid.


Water can transform from a liquid to mist at any (normal human) temperature, but it happens very much faster at boiling point.
But it also happens at body temperature, just much slower.

At body temperature, one way to speed up the transformation from liquid to mist, is to move more air past the water surface.

Another way to speed up the transformation from liquid to mist, is to increase the surface area of the water.
This happens when you wet/mist a piece of clothing.
Or when you run the water in a swamp cooler over the straw-wall.


So the simpler method is to use a damp/misted piece of clothing and stand in the wind (natural wind or fan wind).



An easy method is to do the ice-fan-box, but you need a steady supply of ice. 


The advanced method is to change volume and pressure. This is the method that happens in the compressor of an AC, a refrigerator or freezer. 

The method of change in volume, is what happens when you cool a fridge using bottled propane. 


The method of using increased evaporation is what is typically used in a 'swamp-cooler'.



I hope these words makes sense.  And can help you find simple and easy ways to stay cool   ?

 

[bagabum]

JennyJ, you stated the magic word , "dry" climate. (They get a bad rap from people that try to use them in high humid areas in which they are not effective)  They work great  in dry climates and can drop the temp 15 degrees, that's a big difference on a 95 degree day, they do use a lot of water though. I use to love ours when I was a kid, around July we would commission it , clean reservoir and and put new straw pads in it, always smelt like a fresh rainstorm. You do not have to use  Styrofoam for your build, it can be anything that holds water, try to find straw pads if possible for the tremendous surface area they offer. .   Good luck

 

[JennyJ]

Thanks for all the advice, lots to think about!

I first time heard of swamp coolers when I moved to Boulder CO some 35 years ago. Lived there 15 years and almost never used the AC, even when it reached 110. The dry heat was a huge blessing after a lifetime of lower Michigan's sucky hot humidity, lol.

I've spent the last five years in FL's Space Coast, and this year has been unusually hot and humid, so I'm really looking forward to heading west towards dry heat again.  But I suspect living in a small RAV4 is going to be rather hotter than living in a house, reason I wondered about that small swamp cooler.