cooling your tent or van

[Pootzen]

Then I would go heavier with the epoxy, as those other things may not bond to what you already put on there.

Heavy enough so that its more of a liner than a paint job.

The label says to wait a week if you've already applied it before applying any more to the surface. Definitely seems like more of a paint job than a liner at this point (since it sprays on pretty thin) so maybe I can get away with it...

Oh, and it's going to be a little humid this year, so expect about 20 degrees cooling effect instead of 30.

Might just call the whole thing off

[FIGJAM]

I don't read labels.

I just spray it till the can runs out.

I will be fine.

As backup, I bring a tube of GOOP, in case I have to seal seams.

Happened ONCE, because the cooler sat all year and I didn't check it before the trip.

GOOPed the seams and was good to go.

[Canoe]

Then I would go heavier with the epoxy, as those other things may not bond to what you already put on there.
Heavy enough so that its more of a liner than a paint job.

The label says to wait a week if you've already applied it before applying any more to the surface. Definitely seems like more of a paint job than a liner at this point (since it sprays on pretty thin) so maybe I can get away with it...

Remember, you're not trying to make a pretty looking appliance surface.
Nuke that puppy.
But do give it a quick wipe down with acetone - and let it fully dry - before spraying.

[Foxwalker]

Here's my version:

IMG_2608.JPG

IMG_2609.JPG

IMG_2610.JPG

Parts:
8 gal trash can
12v DC water pump - http://tinyurl.com/hdpx4sk
6" USB fan - http://tinyurl.com/z2yykbm (they raised the price, I only paid $15)
1/4" ID vinyl tubing
nut, bolt and washers to seal end of tube (it's what I had on hand)
pad
2" chicken wire
duct tape
connectors and wire for the water pump

I already had a solar panel/battery system

The pad is held securely between the chicken wire. About 3" of chicken wire extend beyond the sides of the pad. I duct taped this to the sides of the can. It makes a good seal as when I put my hand over the vent hole, the fan noticeably drags.

First I tried piercing the tubing which didn't work. Then I melted holes with a pointed soldering iron which worked but was inconsistent. Then I drilled holes using a 1/16" bit which worked great. The holes are 1/2" apart.

I'll just use a thin flat board to cover the top. A cutting board worked for testing.

I plan to keep it inside my hexayurt and run a vent to it from the outside.

Thanks Figjam for the inspiration. I realized while doing it that I should've just followed your instructions instead of trying to reinvent the wheel, but after re-working a few parts, it works. Hoping for a cool burn!

Jason

[Canoe]

... I plan to keep it inside my hexayurt and run a vent to it from the outside.
... I realized while doing it that I should've just followed your instructions instead of trying to reinvent the wheel, but after re-working a few parts, it works.

yup
While it 'works', will it work well on the playa?
Read these and consider solutions if you discover they're an issue on the playa. Possible issues:

• The 'on the inside' and 'run a vent' means you're drawing hot air past your insulated yurt wall. This will introduce some heat to the swamp cooler (it's walls aren't insulated) and hence the hot intake side will be providing some heat to your interior. This will affect efficiency. Worse if you run an uninsulated duct from the wall to the swamp cooler.
• The vents on figjam's designs, including the holes on the bucket cooler, mean that air can flow freely at the CFM they work at, but a heavy wind is limited in trying to overpower the vents and force air through to the interior.
• Therefore: I hope 'run a vent' means it will be against the wall against a matching hole and you can have an appropriate vent cover on the outside.
• Another key part of figjam's designs is ensuring that the pad is wet to its top, so there are no dry areas through which hot dusty outside air can get by the wetted pad and passed through to the interior. I'm not seeing a hose-to-pad layout that makes me comfortable that the entire pad will be wet.
• The properties of the fan, beyond CFM and being relatively quiet, may limit how well the swamp cooler runs.

So only things that can affect efficiency, except for a vent grill on the outside to limit the effect of a big blow.

In case you have an issue with the tape you used holding for the week, I'd suggest you take a roll of aluminum foil tape, but you'll already have some for sealing the edges of the yurt's wall panels and those of any holes cut in any panels.

[Foxwalker]

Thanks for your observations!

My original plan for the 4' duct from the yurt wall to the cooler was about a 20" duct (it was a duct I had on the outside on previous years just so there was air flow. I have a similar duct on the other side of my yurt so the air can move through.) I don't think it would affect the efficiency of the cooler, in fact, it should improve it, as it would make the incoming air hotter. But at the same time, you're right, it would be introducing a hot element into my yurt. Having the cooler as close to the wall as possible makes sense though and I should be able to make that adjustment. As for a vent cover, I have a hard time seeing the wind blowing air into my vent, through the cooler, into my yurt. I think it could do that a little, but considering the last two years I had open vents, it couldn't be worse.

The hose is very close to the top of the cooler (the pad is actually a little higher than the top and is pushed over and down by a flat lid), but I get your point about having no dry areas of the pad. When I tested it, the pad was uniformly wet below the hose. I can revise it so the hose is on the very top.

I'm up late reading through the many pages of this thread (up to page 37 so far), and was surprised FIgjam kept saying the cooler couldn't be inside the structure but never said you could have it inside pulling outside air into it, except when he talked about putting his bigger box cooler right up against an interior wall.

The fan runs pretty good. I've have a 120mm CPU fan and I think the one I'm using puts out more air.

I haven't tested it in the heat yet but it brought cool 73 degree air down to 66 degrees.

BTW, I don't have a full-size yurt. It's the 6' stretch.

Thanks again for your input, I really appreciate it!

[FIGJAM]

"The Bucket" model has to be outside because of all those holes.

Any single intake cooler can be easily adapted for inside the space.

I can think of many ways to make the bucket work inside the space, but it would add so much to the build that it would no longer be small and portable.

Which was the whole point.

"The Unicooler" took care of all that for people that had a little extra room for transporting to the playa.

[Foxwalker]

Thanks Figjam.

Because I got the fan I did, which has a switch on the back of it, I wanted mine inside so that I can easily turn it on/off. I keep my battery inside to power my lights, etc. If I put the cooler outside, I'd have to run a wire inside.

[FIGJAM]

I couldn't find CFM stats for your fan, which is the key to a happy cooler.

Looks like you could easily double or triple the pad for more evap surface, but your design looks fine to me.

[Foxwalker]

Thanks! I actually first made it with two pads parallel to each other, but that seemed to strain the fan a little, so I reduced it to one.

[Foxwalker]

Fan description says "airflow up to 3.7m/s." Not sure if that is measuring just speed of airflow or volume of air.

Did the math. 3.7 m/s of airflow over the area of a 6" circle = 146 cfm. Actual number lower since there's no flow in the center. I got what I paid for. Went for the $15 fan instead of the $30 fan.

[EGAZ]

Seeing as how you are having air flow issues, cut the inlet hole to at least the dia of the fan.

[Canoe]

Should be a good match for the stretch.

But you lost me a bit.

... I have a similar duct on the other side of my yurt so the air can move through.)...

By 'similar duct on the other side' do you mean hole?

But you can put that hole to work as the required structure exhaust for a swamp cooler.
And as you have ducting, consider running ducting from your exhaust hole up to the top of the inside of your yurt. That way when you turn your swamp-cooler on, as it pushes air into your yurt the air exhausted is the hottest air up near the peak of your yurt. (shows a bucket cooler, but that's not relevant)

viewtopic.php?t=33842&p=965260#p965260
Duct to collect from the top to the exhaust is NOT required, but just a tweak to improve the cooling inside.

...I don't think it would affect the efficiency of the cooler, in fact, it should improve it, as it would make the incoming air hotter...

I don't see how making incoming air hotter helps you get the coolest air possible into your interior, nor how it would be made hotter.

Anyway, here's some images illustrating what I mean by having a duct bring air from a hole in your yurt to your swamp cooler would introduce heat to the interior. This a crude marking of your photo, but the blue shows the surfaces that would be cool, and the red those surfaces that would be hot (conducting and radiating heat to the interior), while pretending there's a duct going to your box intake hole. So technically it doesn't affect the efficiency of the swamp cooler, but it does affect the efficiency of your interior cooling, as you're are introducing heat at the same time you're blowing in cooled air.

hot-cool-zones, duct.jpg

You can insulate the duct going from the hole in the wall to your box, or simply place the box against the wall and skip the duct. Then no need for an insulated duct and the intake side of the box is against your insulated wall, reducing the heated surface area putting heat into your interior to part of two sides.

Also, if you have time and like to play: you noticed how going to a single thickness pad from a double thickness pad allowed your fan to move more air, as it reduced the resistance to the airflow. Going for a greater pad area (by longer pad path) will also further reduce the air flow resistance.
If a longer/larger pad is routed as shown, then it has more area for reduced air resistance and the surface area of the box that is heated is reduced! If it's against the wall, then there's only a tiny bit of heated surface along the edge, and against the lid (you can insulate that if you'd like, but you've reduced the hot surface area by so much already (80% or more?)).

reduced-hot-zone.jpg

To test if the size of your air intake on the box is limiting the air flow that the fan & pad are capable of, compare the output airflow you're getting with the top completely covered, vs if you cover only the top from the pad to the side with the fan. If the second way has more fan flow and you want that, then your intake hole needs to be larger. (If you make your intake hole larger, then your structure exhaust hole may need to be larger to, so that's not the limiting factor, although you do get air leakage with a yurt.)

And you can use the chicken wire to devise support for pad that gives you even more pad area, playing with different configurations: for reduced air resistance allowing for a potential higher CFM, or lower velocity through the pad at a given CFM for greater air dwell time within the pad (if CFM is so high it's not having time to have it's full cooling potential).

greater pad area, reduced velocity for CFM, greater dwell.jpg

[Foxwalker]

Wow Canoe, the time, diagrams and thought you put into responding to my post is impressive!

Last night I tested it after work and it brought 81 degree air in and put out 74 degree air.

I've used my yurt the last two years. When I first constructed it, I put one 4" hole about a foot high on one end and another 4" hole near the top of the roof on the other end. I taped into those holes 4" x 2' long flexible metal elbows on the outside,, both bending downward. My thought was the hot air at the top would kinda be drawn out and would suck in cooler air at the bottom. I also used the lower one to run wires between my battery inside the yurt and my solar panel outside the yurt. I also had two years of failed DIY cooling devices that I won't go into haha. I should've read this thread!

I was a little concerned with the power of my fan, so these will be delivered tomorrow:

They're not as powerful as the recommended one, but I plan to just add them to the sides, so between the three I'm feeling good. At this late stage, I needed to utilize the Prime shipping.

I actually pulled the pad out last night and was playing with different configurations, exactly as you show. One way or another, I'm going to make it work!

Are you going this year? It'd be fun to meet and show you what I end up with.

[Canoe]

I was a little concerned with the power of my fan, so these will be delivered tomorrow:
They're not as powerful as the recommended one, but I plan to just add them to the sides, so between the three I'm feeling good. ...

oh oh
Fan Wars

two years of failed DIY cooling devices that I won't go into haha. I should've read this thread!

Should I be saying, here you go again?
Big hint: do you see any playa-tested recommended multi-fan designs?
Don't do it.
(Ignoring the issues with mutiple fan types) if you're drawing more air through the box, you're going to need more intake capacity. There are flow limits for given diameters (noise goes up too).
And if your pump flow can't keep up with keeping the pad wet with the increased airflow, then you get dry spots (passing hot dusty air to the interior).

There's a reason to stick with playa-tested designs, like figjam's. You've currently got a non-standard fan, but you're getting cooling.

You're only trying to fill a stretched six with cooled air, and it's insulated and has a radiant barrier. I'd be using the design you showed photos for, with:

• ensuring the hose is high enough to keep all of the pad wet (this one is important, the rest below are enhancements),
• putting it against the wall,
• enlarging the intake (hole through the yurt and box; tape the edges) to the same size as figjam's unicooler, with an intake grill on the outside of the yurt; if you like using elbows, then up the size for the same flow capability as the unicooler,
• consider new pad size/shape/orientation, for the reasons previously stated.

You could take the extra fans with you, so you can replace the current with with one of the new (or a pair of the new - don't mix types), spending your Burn time adjusting things if you don't like what you're getting in cooling on the playa. If you decide that going to Burning Man is for playing/fighting with your swamp cooler vs. for Burning.

[Foxwalker]

I reconfigured the pad into a U shape like your second picture, but in the opposite direction (the top of the U faces the fan). That made the most sense space wise since the fan sticks out toward the inside (and it is more like box designs with three sides of pad and one output). The hose is now completely on top of the pad. I'm quite happy with the pad and hose now as they are nicely secure with chicken wire. I do plan to have the unit against or at least very close to the wall. I am gathering that you want the intake size to be larger than the output size, because if the intake is smaller, the fan has to work harder to pull the air in. That makes sense. I will look at enlarging the intake.

If I have time and inclination I'll test it with the other fans. Testing can't hurt, right? I was planning to put them on the lid blowing upward. That's the only place they could go since the pad is the other way around now. Or, what if I put one on the intake side and the other on the output side? Does it matter if they're on the same end or opposite ends? I saw a post that said putting two fans side by side should increase CFM and putting them inline should increase pressure, and it's pressure that you want, to pull air through the resistance of the wet pad. The two CPU fans I got are supposed to be for high pressure applications. Specs are 3.1 mm/H2O static pressure and 63 CFM each.

[Foxwalker]

I will say this: if I had followed Figjam's proven design exactly, I would not have the understanding of the principles invovled--WHY it works--that I now do.

[Canoe]

The hose is now completely on top of the pad.

• As long as it keeps it the entire pad wet, great!!!

> ...I would not have the understanding of the principles invovled--WHY it works--that I now do.

• But, your posts show that while you have an improving understanding of some of the basics, but don't yet understand the swamp cooler nor how that works in a system that includes the hexayurt.

> I reconfigured the pad into a U shape like your second picture, but in the opposite direction (the top of the U faces the fan). That made the most sense space wise since the fan sticks out toward the inside (and it is more like box designs with three sides of pad and one output).

• More area for the pad > always good.
• Wrong direction for the U to resist the vacuum created by the fan, that draws the air into the box. BUT, you've got it secured with chicken wire so that shouldn't be a problem.
• But, both box sides will be heated by incoming hot air, providing conducted and radiated heat to your interior space. If the U was the opposite direction, then those sides wouldn't be heated.

> plan to have the unit against or at least very close to the wall.

• The closer to the wall, the less duct length between the wall and the box, so the less surface area of duct that is providing heat to your interior space.
• Better if it's against the wall, then the intake side (heated by the hot air) only has it's edges providing heat to your interior.

> I am gathering that you want the intake size to be larger than the output size, because if the intake is smaller, the fan has to work harder to pull the air in. That makes sense. I will look at enlarging the intake.

• Your output size is smaller than you think, due to the fan motor being in the middle of that opening. It would be a shame to have your airflow limited by the size of the intake.

> I'll test it with the other fans. ... I was planning to put them on the lid blowing upward.

• Which will screw up having your swamp cooler "filling the space with cooled air", as fans blowing upwards will mix (read as dilute) the cooled air with the hotter air above, so your space will take a lot longer to have cool air down low where you lay or sit in the yurt.

> Or, what if I put one on the intake side and the other on the output side? Does it matter if they're on the same end or opposite ends?

• No. Just no. It can have push-pull fans, but the engineering to have it benefit instead of impede is a nightmare. Do you have independent fine speed control of each fan and pressure sensors and circuitry to decide and drive those speeds?

This is why there are playa tested designs with specific components, sizes, specs. They work, without having to work through the engineering. There is a lot more to why/how the designs work than is published, as it just confuses the issue and 99% of the various technically demanding "improvements" (the rare ones that actually improve performance and not degrade it) provide such minor enhancements over the proven design, while consuming more power and adding more points for failure. What's the point.
You end up leaving the realm of practical benefit way behind, and blow right through the realm of any potential meaningful material benefit and heat off into engineering intellectual masturbation.

> Specs are 3.1 mm/H2O static pressure and 63 CFM each.
That's worth knowing. Google this thread to find the fan specs of the fans figjam recommends for the bucket cooler. That will give you an idea of what those fans may be able to do for you.

[Foxwalker]

Thanks again Canoe! I appreciate your thoughts. It makes me curious how much Figjam played with his design before posting it. We don't see much evolution or experimentation,, just bam here it is based on that earlier big one and it works great. Or maybe he already had enough construction and design experience to design it well from the get go.

[Foxwalker]

P.S. Don't take this shit too seriously! It's an adventure. If you're not having fun, you're not doing it right!

[Canoe]

He did TONS!

His resulting designs are easy to build, reliable, effective, low power consumption, low maintenance, etc., all deceptively simple.
So deceptively simple, that people assume they can play/adjust with anything and have it work as well.
The whole is not equal to the sum of the parts.

Such simple details, like the slope of the bucket sides vs the pad being vertical and not touching the sides: keeps the water flowing on the pad in the bucket and not out the holes, while letting air in the holes with airflow going up and down on the inside of the bucket before getting sucked through the pad, for better use of the area of the pad above the water providing a reduced air velocity through the pad for an increased dwell time. So many don't believe the necessity of that simple detail, some coming up with all sorts of "solutions" when all they need is to have it properly spaced.
Or substituting a different pad material "that's just as good", and it does have that space when first built, but with use it swells, decreasing or closing that space, or creating an air gap at the top seal, and sometimes clogging with playa dust.

[Canoe]

P.S. Don't take this shit too seriously! It's an adventure. If you're not having fun, you're not doing it right!

Ah, but we have to be careful that explorations away from the proven designs don't distract those that simply want, or need, to have reliable effective low maintenance cooling for their shelter on the playa. Or unintentionally mislead them into thinking that the proven design details don't matter, or can be played with without risking negatively affecting the end result, as so commonly happens.

[FIGJAM]

Not really tons.

The first bucket had more holes and I just lined it with the pad, so it leaked.

Fixed that by adding a shade cloth liner, but that restricted the air flow.

Had a 100cfm fan that used .52amps and a harbor freight solar pump.

It worked in principle, but wasn't practical as it wouldn't cool any significant space.

This all lead to the second design which uses almost 4x as much power, but it works very effectively and doesn't depend on any solar!!!

And here we are 700,000 views later still talking about it!!!!!!!!!!

[Foxwalker]

80.5 > 73.4 (tilt head left). See you in the dust!

IMG_2612.JPG

[Dr Fish]

It was 72*f in Gerlach an hour ago, can't that hot there today... Dusty it always is after a couple days... You get a whole new appreciation for water trucks after a few days....

[Ano]

Years later, my figjam bucket is possibly one of the best things I've ever built for playa. I had a particularly trying early-week lanes shift that went all morning that knocked me right the fuck out - six hours of dust and sun and running out of water and not drinking enough cerasport and etc meant I got back to camp, ate, and needed to sleep. But it was 1pm.... but I was freezing cold underneath sleeping bags in my shaded kodiak.

Thinking about building a FIGJAM bucket for next year? Yeah, it's a good idea. Don't skimp on the fan and you'll be so happy.

[Leap]

My buckets worked great! Didn’t use it much because I was too excited to sleep in most mornings, but it was there when I needed it. The camp-mate and his girlfriend I gifted a bucket to LOVED theirs. Thank you FIGJAM and everyone else to helped out!

[cassiepea]

Our box cooler ended up working fantastically, with a few adjustments right before we left/on playa. Wanted to share, in case my tweaks/mistakes can help someone in the future.

I ended up building a box from plywood. The box was about 25"x25"x9.75" - I used poplar 1x10s for the sides and bottom and a piece of a 1x12 for the top. I cut the holes for the intakes and the fan and taped off about 1/2" on each edge (so that the wood glue would not be hindered by the waterproofing) and coated each piece with 3 coats of spray appliance epoxy paint and then 3 coats of outdoor poly. Once the pieces were dry, I applied wood glue and clamped the pieces together one at a time, added 3-4 screws along each side, to create the box. I sealed all the inside edges with a construction adhesive/sealant and then tested for water tightness. The box held water so I moved onto installing the filters and the fan.


I took the rear cover panel off of the fan and drilled four holes into it and the box around the circular hole I had cut. By doing this I was able to use 4 bolts/washers to attach the fan to the box (and later sealed with more construction adhesive) so that it was removable while I tweaked it. Originally I had planned to use a different material but ended up going with some landscape fencing I had on hand to create the "holes" for the intake. I wish I had attached this while the box was still in pieces because it was difficult to get it taught, and this created an issue for me later. I attached the sections of cooler pad directly to the black landscape fencing with 22ga wire, but because the fencing wasn't tight, it bowed out a bit and water leaked out of the box (not a lot, but enough) once I turned it on. I used some 10ga flexible wire I had on hand, and bent it into a C shape with two little flanges that went into small holes I drilled on each side of the intake. This held the pad back far enough from the opening to stop it from leaking. I ended up using a staple gun to attach the pad directly to the box around the intake openings to prevent air from being pulled in around the pad. If I had had more time I would have come up with a more elegant solution, but it worked. Added weather stripping to the top of the box, and cut a 1x12 to overhang slightly to use as a top. I also added some cheap drawer pulls to each short side in order to lift and move the thing more easily. You can't see them in any of the pics.



The original pump I purchased was not powerful enough to push water all the way around the box to the third side/pad, the tubing was only 1/4" and the pads were not getting wet enough. I switched it out for this sump pump, which was a beast and had no problem pumping water through 1/2" tubing with holes approx 3/4" apart. Next year I'll add more holes in the tubing. This pump pulls considerably more amps than the smaller ones Fig recommends and we were prepared to charge our battery every day if need be (we were also using it to power LED strip lights inside the box truck), but our camp ended up having tons of power and a 24/7 genny so we just hooked the battery up to a charger that remained plugged in and it wasn't an issue. I found that if I sprayed down (or used my hands) to wet the entire pad when I started it each day the entire pad was more likely to stay wet than if I just started the pump and walked away.

The main reason I'm posting is to share how we were able to use the box cooler on a box truck without a plywood back wall; we flew in and did not have the time or tools to build a wall for the truck we rented in Reno. I used 6mil plastic sheeting, a zip wall zipper, and stucco tape to construct a back wall with a zippered entrance to our truck. I taped to the outside of the truck so that the back door could still be rolled down for shade/warmth at night/privacy. I cut a hole in the sheeting and put the fan directly against it and then taped the sheeting to the box. I started with one vent (covered with extra evap pad to act as a dust filter), but the sheeting was billowing outward as there was not enough air flow, so I added a second one.


The zipper held well all week (Mon-Mon), the tape removed without any residue (in cool temperatures on Monday at sunrise), and we slept like babies inside the box truck. Originally I had the bed closest to the door with a sheet hung across the back, in order to minimize the amount of space the cooler had to cool, but it was kind of inconvenient and we realized it was cooling the whole tuck w no problem so we rearranged the space mid week.






TL;DR - Box cooler worked great, THANK YOU FIG! Stucco Tape worked great, THANK YOU RATTY! Cassie earns nickname Dexter for plastic sheeting back wall and kills her first burn, THANK YOU UNIVERSE!

[FIGJAM]

This baffled me, so I'm reposting this for some group think.

I need your help in designing a two-stage evaporative cooler. I asked on this forum and didn't get much help. http://www.doityourself.com/forum/evapo ... ooler.html

"
I want to build a two-stage evaporative cooler that can cool a 20x20x8' room. I want it to be super effective for Las-Vegas-in-July type climate, and have a footprint no larger than 1x2'.

1) I need help designing the heat exchanger that cools the incoming dry air for the second stage. I have two 4" aluminum dryer ducts I can use for this, and would like to maximize the heat transfer.
2) Would having two separate resivoirs help in cooling? My theory is the first stage water will be warmer than the second stage water, and if both stages draw from one resivoir there will be less end-cooling vs seperate resivoirs for each of the two stages.

I am looking at the diagrams in these two articles for this project:
Source 1:
Evaporative Cooling: Direct, Indirect & Two-Stage Evaporative Cooling Systems
http://www.drenergysaver.com/cooling-sy ... oling.html
Source 2:
Home Energy Magazine :: Two-Stage Evaporative Cooling"
http://homeenergy.org/show/article/nav/ ... /6/id/1301

I didn't say the real application which will be for the van (and not just for burning man!), as this forum is about conventional house diy.
Could you help in the design? I am modeling it after your Unicooler, and perhaps we can collaborate?

Just a thought; The two-stage Unicooler can help cool people at the Las Vegas regional burn, which is a hotter and lower elevation climate than BRC.

[Popeye]

This baffled me, so I'm reposting this for some group think.

I need your help in designing a two-stage evaporative cooler. I asked on this forum and didn't get much help. http://www.doityourself.com/forum/evapo ... ooler.html

"
I want to build a two-stage evaporative cooler that can cool a 20x20x8' room. I want it to be super effective for Las-Vegas-in-July type climate, and have a footprint no larger than 1x2'.

1) I need help designing the heat exchanger that cools the incoming dry air for the second stage. I have two 4" aluminum dryer ducts I can use for this, and would like to maximize the heat transfer.
2) Would having two separate resivoirs help in cooling? My theory is the first stage water will be warmer than the second stage water, and if both stages draw from one resivoir there will be less end-cooling vs seperate resivoirs for each of the two stages.

I am looking at the diagrams in these two articles for this project:
Source 1:
Evaporative Cooling: Direct, Indirect & Two-Stage Evaporative Cooling Systems
http://www.drenergysaver.com/cooling-sy ... oling.html
Source 2:
Home Energy Magazine :: Two-Stage Evaporative Cooling"
http://homeenergy.org/show/article/nav/ ... /6/id/1301

I didn't say the real application which will be for the van (and not just for burning man!), as this forum is about conventional house diy.
Could you help in the design? I am modeling it after your Unicooler, and perhaps we can collaborate?

Just a thought; The two-stage Unicooler can help cool people at the Las Vegas regional burn, which is a hotter and lower elevation climate than BRC.

The links above seem to be broken, so it's hard to know exactly what he is talking about. My first thought was that a two stage unit would not work, but, it seems I am wrong. My old 1999 ASHRAE Handbook of HVAC Applications says that a two stage evap. cooler using mechanical refrigeration to cool the water as the first stage will improve cost (efficiency) by 25 to 40 percent from mechanical airconditioning only.
Also: "Indirect evaporative cooling applied as a first stage upstream of a second, direct evaporative stage reduces both the entering dry and wetbulb temperatures before the air enters the direct evaporative cooler." Think of cooling the air entering the cooler with a heat exchanger. They show a 60 to 70 percent reduction in cost compared with mechanical refrig.
Yes, I know that we are not talking about using mechanical refrigeration but the two comparisons give us a look at how much more efficient two stage is over single stage.
There is a lot more including diagrams and psycometric charts but I won't copy it here. ASHRAE Handbooks are not available on line but most large librarys have copies, They run in 4 year cycles and articles sometimes repeat with updated versions.