Teardrops n Tiny Travel Trailers

When I saw this post, the first thing that came to mind was a water feature I assembled for my mother a few months ago. It has 3 small pots with the bottom one having a small pump in it with a small hose running up to the top pot. It is solar powered. A pump that size would be perfect. A bilge pump seems way to large.

Here's what I ended up with for the final model. I solved the flow issue by using drip irrigators to water the pads. Each dripper flows at 1 GPH so the pads stay wet with a minimum amount of water. I kept the baypass since the hoses leak at the joints if I took it out. I think it helps the pump prime too. I used hardware cloth to hold the pads in place as well as screen the inside of the fans (I kept sticking my finger in them). The pump has a hard time priming and I have to unscrew the connection at the pump to let it prime if the lines are dry. Its fine if there's already water in it. I used a dremel tool with a spiral cutting bit to cut the plastic to prevent fractures.

I experimented with the number of pads. I filled the box up with pad material and ran a dripper line over it. It didn't seem to cool the air anymore but it did decrease the amount of air coming out. I settled on just the two pads as shown.

The container I used is a file box from Office Depot. I probably should have made the pads smaller so it could hold more water but it will run at least 4 hours with the 1/2 gallon it holds now. I left out the louvers since they didn't really do anything. I think the louvers were supposed to help with leaks and this one doesn't leak like the mockup did. I can stick it inside the trailer on a pull out shelf. It fits nicely in the sink so I have a place to stow it.

Does it work?

Well, cool air comes out of it and it cools the inside of the trailer when I stick it inside. We'll see how well it works the next time we go camping.

Bruce

bdosborn wrote:
Well, cool air comes out of it and it cools the inside of the trailer when I stick it inside. We'll see how well it works the next time we go camping.

Bruce

Can't ask more than that !
I am still 'sperimenting with an Ice Chest heat exchanger. If it will take the edge off the afternoon heat, then i will be happy

My small pumps came in the other day and I got a chance to test them out tonight and they work great. Here is a picture:



They looked like they were going to be perfect--but wait! DON'T ORDER THEM, they run on 12v AC.

That's right, the two transformers are both AC to AC. Swing and a miss. It's back to the bilge pump for me.

Those pumps probably use a simple diaphram and a pulsing electromagnet rather than a standard 12 volt motor. It wouldn't be difficult to built a circuit with couple MOSFETs and a 555 timer to convert 12VDC to 12Vac. Or of course you could just use a cheap inverter and run it as is.

Q

Hi Q

The idea behind a 12v Swamp cooler is to be as efficient as possible.

Converting 12v to 240v will incur around a 14% loss then converting back to 12v will lose more with a wallwart type transformer, this would be terribly inefficient and drop total running time.

Okay, here's version 2.1. I got another file box and moved the pads and fans around. It works even better with both fans on the same side instead of one on each end.



With pads on both end, it has the same amount of pad area as did before.



It works really well when you drop in some ice but it still works with just water. I'm pretty happy with it. I can just stick it in the cabin but it gets pretty muggy in there unless I turn on the cabin ventilation fan to push some air out the window. That pushes my total amperage up to 2.5A.
Bruce

I got just one question, well 2 actually. But we'll start with the really stupid one first. Which way are the fans blowing? Are they forcing air into the box or are they sucking it out of the box, I think I know which one makes more sense but I just need to make sure. And #2, the things work where? Where there is no humidity or where there is humidity. I think I've seen it so many times that I got myself cornfuuused.

OK, you can go back to intelligent discusion now.

The fans suck air out of the box. That pulls air into the box through the pads. Here's where the swamp coolers work best.

A and B are good regions. C is not so good. I'm in the A region. I wouldn't bother with it if you're in a C region.

Bruce

Thanks, that makes sense. Form the looks of your map I don't suppose there's any point in me putting one together anyway then.
What ever happened to that experimental Pelitier(?) AC unit someone was building? Haven't heard about it in a while and I forgot to put it on the watch list.

GeorgeTelford wrote:Hi Q

The idea behind a 12v Swamp cooler is to be as efficient as possible.

Converting 12v to 240v will incur around a 14% loss then converting back to 12v will lose more with a wallwart type transformer, this would be terribly inefficient and drop total running time.

I don't think it would be that bad. The bildge pump draws 1.5 Amps at 360 GPH. Figure the 50 GPH pump draws 1/3 the current, you'd still have an amp to burn up in the inverter and transformer (assuming the inverter doesn't draw a lot of current just being on) to match the 360 GPH draw. The part I wouldn't like is mixing 120V and water. Well, after thinking about it, I guess you're not. It would just make the wiring a hassle because you'd need 120VAC for the pump xfmr and 12VDC for the fans.
Bruce

Hi Bruce

The best Invertors use .7 Amp Just to stay alive, so if there were no other loses thats a 30% Extra ampage cost.

However a good invertor at peak efficiency costs at least 10% if matched right, unfortunately there is not an invertor small enought to be matched here, an invertors peak efficeincy is usually at Half its continous rating, in this case you would need to find a impossibly tiny invertor, reality is that you would lose about 50% so another .7 Amp.

But it gets worse, wall warts always waste loads of power (hence why they get so warm) .7 Amp is being very generous with a wall wart.

So what have we got 3 X .7 Amp thats 2.1 Amps on top of the 1.5 amps it actually uses to pump, that set up would waste 150% More power than running directly from 12v. a Total (being really generous) of 3.6 AMps to run a 1.5 Amp pump.

There are some low wattage mains air conditioners that use less than that on average.

Say you had 55 Ah of battery power available to use, running directly would allow you to run for 36 Hrs and 40 Mins, running via the invertor you would only get 15 and 1/4 Hrs !!

George,

I see what you mean, but, the 50 gph pump isn't going to use 1.5 amps, its going to use about 1/2 an amp. The 1.5A is for the 360 GPH pump. So if we back an amp out of your (admittedly generous) calculations, we end up at about 2.6 amps, which is where I'm at for my cooler. Add in a fan and we're at 3A. Workable just to see if the cooler worked before spending anymore money on it. Now, will I rush out and rework mine to run off of an inverter? Oh hell no, there's a reason all my devices in my trailer are 12V - inverters kill your efficiency
Bruce

I was looking over this old thread and I know a different source for a small low power 12 volt pump. Check out a car parts store for a Universal replacement Windshield Washer Pump.

Has anyone used a fan on one end that sucks air into the plastic box and through a wet pad, while the fan on the other end blows air into your teardrop? It seems that sucking air through a pad with cold water (with the help of a fan) would get your desired effect sooner.