A New Proof Of Concept

A project log for The Swampless Cooler

A very low power (P.O.C. is less than 10W) cooler that delivers cool dry air, and is driven by evaporation of water.

DustinDustin 07/29/2021 at 22:360 Comments

Wow, time sure flies, no fun required... When I put this project up last year I had intended to get right to adding updates with more explanation, better pictures, etc. Thanks to what I believe was long covid-19, followed immediately by having to evacuate from the oncoming creek fire (for those that don't know, the biggest single fire in California of 2020) which was stopped a couple miles away from here, and quite a few other difficulties since then, it's taken a while... In spite of all that, there's finally an update!

An explanation of the concept and how it differs from typical evaporative coolers is on my website here As far as I can tell, the idea is similar to an old fashioned cooling tower, but the concept is largely misunderstood and unexploited. I was able to find a patent, from a Korean inventor if I recall correctly, for a similar process. I don't remember what device I saved that info to though, so I'll post it in another update when I can locate it again (do note how long this update took, it may be a bit).

So this is the new P.O.C. made from rubbing alcohol bottles, some scrap square(ish) tubing, pot scrubbers, two fans (1 blower using 2W, and a pc fan using 2.2W), and a small water pump (using 4.8W).

There are three alcohol bottles, for the sake of description lets call them like this: There's a bottle that makes the corner, this bottle has the tubes running through it. There is another bottle taped to the front, this bottle encloses the ends of the tubes at one end so air can be pulled through them. There is also a bottle taped to the top of the corner bottle, to which the blower fan and monster exhaust tube are attached. The top bottle is basically just for mounting and ducting (there's also part of a hydrogen peroxide bottle used here for a mounting bracket of a sort). All the magic happens in the corner bottle. Packed around the tubing are (cheap stainless?) pot scrubbers I picked up at the dollar store (not ideal, they started to rust in days, but after more than a week of heavy use, they're holding up okay). Water is pumped over the top of the scrubbers and tubing, while air is pulled in from the bottom and exhausted out the top (note the humidity leaving with the exhaust). This cools the tubes, and air drawn through the tubes is cooled while still being kept dry.

Now if you know something about evaporative coolers, and this looks like an inconsequential design tweak, I'd highly recommend reading the explanation of this cooling process on my website. That little design tweak is VERY consequential, it's not just a simplified two-stage cooler meant to keep the air dry. While the pot scrubbers are less than ideal, the fact that I'm using metal ribbons instead of the typical wood ribbons of a typical swamp cooler, also has purpose (though I'm not sure how consequential this choice is...still testing).

I have little time/ability to thoroughly test the output, but initial testing shows some impressive numbers. First let's address the output air temperature. The front bottle leaks a lot of heat, compounded by the fact that the fan is putting suction on the front bottle apparently leaking outside air in from somewhere. Because of these things, the output air doesn't get as cold as it should, it's being re-warmed as it exits the cooler....ugh prototypes..... That little problem, combined with the fact that I don't have a thermometer that I can measure the output air with (the one I have is far too big physically to put in the right spot), means I don't know the actual output air temp. The output air sure does feel nice compared to the environment its in. That little wisp of cool air is practically arctic chill compared to the 110-115 I've been dealing with. As an alternative, I've used my cheap Harbor Freight infrared thermometer to get temperatures for different points on the cooler, as well as the bricks under the cooler tray. The bricks were measured through the water at the point directly under the cooler. Column 1 is the temperature before start up, and column 2 is the temperature after just over twenty minutes of runtime. These may not look like much, but do keep in mind that this is off of 9W of power use, and that it's also producing a constant whiff of cool air into the surrounding environment, not just getting itself cold. I'd be fascinated to see anyone achieve anything like this with typical evap cooling. My attempts with typical evap cooling only produced the little whiff of cool air at best, and that came with the expected humidity.

    1       2
    80f     76f     bricks
    88f     73f     air cooling tubes
    92f     77f     monster exhaust tube (measured at the fan end)
    94f     95f     surrounding air temperature

As far as I can tell there's also another design tweak that can take the output down to below freezing, but we'll get to that bit later.

Hopefully another update wont be too far off. I have another P.O.C. started already (started as in, figuring out what materials to build the thing out of), and if it works like I think it will, it'll be the best design yet! Stay tuned...