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Another cooling system

  • #21
I've tried peltier units as well, to no avail. I assume this would be a gentler method of cooling and this condensation would be as drastic.
 
  • #22
I have tried using a glass door peltier wine cooler cabinet as a mini-terrarium, but am having trouble maintaining a reasonable humidity, even when using a fogger inside. I think the problem is that the combination of the fan and the cold surface of the peltier heatsink causes any moisture in the air to condense. I would be interested to know if the above recirculation cooler method has the same issue.

I had the issue you are talking about with my previous setup with a modified AC (see the link in my sig). The problem was that the AC rad would get to below freezing temperatures and all the humidity would condense on it and freeze. One day I came home and the rad was a huge block of ice. I put a plastic covering around the rad and it was much better.

I think with the new setup using the water cooler and having the rad not getting as cold will solve the lowering in humidity issue. However I do expect it to drop a little, but I have a fogger and the tank is usually filled with a bit of water on the bottom which adds to the humidity. Note that I insulated all the tubing and the only thing in the tank that can get condensation on it is the rad. Also the computer rad i have is about half the size of the AC rad.

I got some plexiglass today so I'll be finishing off my tank mod once i borrow a dremel from my dad's place, and then installing the cooling system. I'll be able to give some accurate result once I get it all finished up.

PS. I'm sure you can something like this with a peltier device. Just get a cooler and fill it with water, then seal it and somehow add the peltier into the mix so that it cools the cooler. Then add some circulation rad dillo to it and you got the same setup as me.
 
  • #23
You can get a good sized new transmition cooler from Auto zone for 30 bucks. Nothing but a radiator. Larger than the one shown here in this setup.

Btw. I love the idea!!!

---------- Post added at 09:09 PM ---------- Previous post was at 09:07 PM ----------

Peltiers are terribly inefficient though.

---------- Post added at 09:15 PM ---------- Previous post was at 09:09 PM ----------

You should be able to counter the humidity pulling affect of cooling by using a fogger.
 
  • #25
Why dont you use engine antifreeze like the computer people do?
You mix that 50/50.
 
  • #26
I think the cheapest and easiest by far would be windshield wiper liquid. As long as there is no surfactant in it. But even if there is surfactant, formation of foam could be countered adding a bit of alcohol (I use methanol in the lab to prevent this) to the mix. Not enough to ignite but enough to work.

In addition if your system is closed and there is no air in it surfactant in solution of windshield viper liquid won't make any difference. It wont foam anyway if the pump and tubing are submerged deep enough.
 
  • #27
But car antifreeze would be far better at romoving the heat from the enclosure than windsheild wiper fluid.

There are echofriendly versions if that is the issue.
 
  • #28
But car antifreeze would be far better at romoving the heat from the enclosure than windsheild wiper fluid.

There are echofriendly versions if that is the issue.

As I have mentioned before the wiper fluid I was suggesting is the winter mix type (the one that has -20F on it, the summer version is just diluted crap with soap in it) and is technically the same as engine coolant/anti-freeze

Windshield wiper fluid = 1:1 water:alcohol (http://en.wikipedia.org/wiki/Windshield_washer_fluid#Varieties)
Antifreeze/Engine Coolant = most common 1:1 water:alcohol (http://en.wikipedia.org/wiki/Antifreeze#Corrosion_Inhibitors)


Anti-freeze as engine coolant will range in the concentration of components used with increased % alcohol when the temperatures are extremely cold. Now, since the reasons alcohol is added to the mixture is to keep the coolant liquid, prevent the damage to the cooling system parts due to expansion of volume during liquid->solid phase transition and to inhibit water's corrosive properties, you'd want to lower the percentage of alcohol in solution to increase the coolant's heat capacity and thus increasing system's cooling efficiency (http://homepage.usask.ca/~llr130/physics/HeatCapcityOfAntiFreeze.html the more alcohol the lower the heat capacity of solution).

Thus the windshield wiper fluid is still the cheapest and best choice, and if high efficiency is desired one might want to dilute it with water a bit too :) this will also make it a bit ecofriendlier as well.
 
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  • #30
I am well aware it is poisonous. In a closed system you shouldn't be exposed. Like a vehicles coolant system.

---------- Post added at 10:20 AM ---------- Previous post was at 10:19 AM ----------

Hence the reason I said there were the echofriendly versions too that are non poisonous.
 
  • #31
First of all ---- I'm back from the dead... again!

Second of all --- funny how every time I re-emerge from my cave I see yet another crazy innovative thread about terrarium cooling and/or humidity control. Fantastic stuff.

I'm about to downsize my setup... it's a little crazy, and I've been slowly editing my collection down to a few of my favorite plants, and they should fit in a 24" x 18" x 18" terrarium at this point.

Bonus for me: easier to cool and humidify an enclosed terrarium
Bonus for y'all: a rather large (though modestly curated) plant giveaway is on the horizon!


-------My actual question!---------
I can't find any water coolers near me, and they are a bit large for my tastes. We've talked about using Peltier devices and other random thermoelectric coolers to do the job. General consensus is that they don't work well enough. BUT, check this thing out:
http://www.amazon.com/Thermo-Electronic-Temperature-Dispenser-Countertop/dp/B00076ODTG/ref=sr_1_1?s=appliances&ie=UTF8&qid=1333984276&sr=1-1

It's a thermoelectric cooler, but more importantly, it's nice and compact. Given that robthered' (and others') design for a cooling system involves a relatively small amount of cooling fluid in a closed system, my hypothesis is that the thermoelectric cooler will be plenty to keep the liquid chilly enough to control temperatures in a terrarium.

Anyone care to enlighten me (read: debunk my hypothesis)? If you all think this will work, I'm prepared to pull the trigger on this new setup ASAP!
 
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  • #32
I am a bit worried about all the negative reviews. In addition most OK reviews say that this thing does not cool water down enough. The manual apparently says it would take an hour to re-cool if you only do 1-2 8oz cups.
So it is most likely that you wont reach cold enough temps with this peltier based cooler when you constantly circulate water through a radiator. :( I saw this unit when I was doing my preliminary search and passed it for that same reason.
 
  • #33
Wowza - good catch... 8oz every hour or two before needing a re-cool. So with a pump moving 90 gph through this contraption, it'd probably exceed that capacity by far, no?

I'm interested in two questions:
1) How cold does the water need to be going into the radiator to produce a noticeable temperature drop?
2) Upon exiting the radiator, how much warmer is the water?

If only a little bit of heat is transferred into the fluid upon every pass through the radiator and it doesn't leave a helluvalot warmer than it entered, then this might still work, since this is a closed system. In normal use, this thing would have a reservoir or room-temperature water constantly refilling it after the cold water is depleted; in this application only a small bit of cool water would be drawn and replaced by slightly less cool water... though I agree, the reviews are somewhat off-putting...
 
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  • #35
Wowza - good catch... 8oz every hour or two before needing a re-cool. So with a pump moving 90 gph through this contraption, it'd probably exceed that capacity by far, no?

I'm interested in two questions:
1) How cold does the water need to be going into the radiator to produce a noticeable temperature drop?
2) Upon exiting the radiator, how much warmer is the water?

If only a little bit of heat is transferred into the fluid upon every pass through the radiator and it doesn't leave a helluvalot warmer than it entered, then this might still work, since this is a closed system. In normal use, this thing would have a reservoir or room-temperature water constantly refilling it after the cold water is depleted; in this application only a small bit of cool water would be drawn and replaced by slightly less cool water... though I agree, the reviews are somewhat off-putting...

My guess that to answer both question youd need to take into account size of radiator, flow of air through it, temperature of air in the terrarium, amount of water passing through the radiator and volume of the terrarium. So basically you'd have to play with it and see what works best :)
 
  • #36
temperature differential, heat exchanger efficiency, is the liquid moving through the core in a laminar or turbulent flow pattern, etc etc etc....
 
  • #38
Ha!! OK OK, uncle!! I knew my question was more complicated than it sounded.

I just found this guy: http://newyork.craigslist.org/brk/app/2948100396.html

Sweet. If it's still available I might spring for it...

Looks good man, should be enough to cool your 24x18 terrarium, anything larger though and I think you'll need one of the larger models. Make sure you insulate the circulation tubes.

FYI I'm currently in the progress of fusing two 4 foot aquariums together. Just cutting up the plexi, then i gotta silicone the stuff together. So once that's done I'll have my cooling system installed and will post some of the stats/results.
 
  • #39
Should be enough, methinks - the internet tells me that this thing can cool water down to 42F / 5.5C. Seems to be made of the same guts as the taller units. I'll let you know how it goes, but I think I might have scored a gem!

Looking forward to hearing about that 8-foot "Optimus Prime" terrarium!
 
  • #40
RE: Peltier coolers.

I have a 65W peltier wine cooler, converted into a terrarium. Inside is an 18W PL-L flourescent lamp, with no other heat sources. The lamps ballast is external. The cooler is set to 13°C (55.4°F). When the lamp is on, over the length of the day, which is 13 hours, the temperature in the cooler rises to ~22-25°C (71.6-77°F). The peltier and fans run constantly the whole day whilst trying to achieve the set temperature and only go off at night after the lamp is off and the temperature set point is reached. Basically, the 65W peltier cannot fully dissipate the 18W load of the lamp. This is not to say that the peltier wine cooler is of poor quality, as it can easily reach the set temperature without any additional internal load, thus it makes an excellent wine cooler, but it demonstrates the efficiency of peliter coolers. For my next terrarium setup I will be looking into using a traditional compressor refrigerator.
 
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