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mstavis
27-12-2007, 01:51 PM
I would like to rig a very simple aquarium chiller for an aquatic salamander habitat. Apparetnly this salamander requires water temperatures around 50 F. He recently fell ill because his water was a balmy 65 F. I'm worried about eh summer, and would like to build a chiller for this little guy. The salamander + his home only cost about $100, so i want to make a water chiller at a similarly low price.

I was thinking of simply taking a used cube fridge, and running the output from the salamander's water filter through a hole in the top of the fridge. this water line could then be coiled many times inside the fridge to achieve a large surface area without using a sophisticated heat exchanger or heat conducting fluid. I would use perhaps 100' worth of 1/4" O.D. flexible polyethylene tubing, but actually however much will fit in the cube fridge. The end of this coil of tubing would then run up to the salamander's tank as a water return. the holes in the top of the fridge would be sealed with caulking, and i would likely apply a removable glue like rubber cement around the door, since i won't be opening the fridge unless there's a problem.

The pump/filter will provide the water recirculation, and the cube fridge will provide the cooling. I have a fancy omega temperature control unit, which can use thermocouples to drive a 115 V AC power outlet (this item was salvaged from a decommissioned chemistry lab). I can place the thermocouple in the salamander's tank, and use the controller to drive the fridge. I would probably simply plug the fridge into the omega controller, and tune the fridge to it's lowest temp setting.

Does anyone think this might work? I could just go for it, but I'd prefer not to waste time and money.

Luckiliy, the salamander's tank is only 5 gallons, and total water volume probably would not exceed 7 including the chiller setup. the pump moves 30 gal/hr., according to it's specs, but I imagine this is closer to 3 gal/hr.

I can't use copper tubing (although I could get some for free) for heat exchange in the fridge, because the salamander is very sensitive to copper ions in the water, and for that matter, he is sensitive to most metal salts. However, I could put the coiled tubing (inside the fridge) in a bucket of water to aid in the speed of heat exchange.

The Viking
27-12-2007, 05:19 PM
There will be losses and a high electricity bill but it might work.

BUT.....

If you use the filter's pump to push the water through your "chiller" then 1/4" tubing will stop all water flow.
(Try blowing up a balloon through a straw)
You need something bigger.

Another thing to bear in mind is the temperature fluctuations on the poor guy's environment, if you get a lot of "latent cooling" in your tubing system he might be frozen before the unit stops cooling (as the cooling process will continue after the thermostat stops the refrigerator)

mstavis
28-12-2007, 03:34 AM
Actually, I've changed my plan (if anyone ever looks at these posts). I'm going to use a pelier thermoelectric heat pump. Does anyone know how to translate Qmax for peltier devices into BTU. i will need 1500 btu/hr in the summer, and 750 BTU/hr in the winter.

thanks,
matt

mstavis
28-12-2007, 03:36 AM
also, i will use a heater in combination with the chiller. i have a pretty nice omega controller unit which can handle both. i better read a text on control theory while i'm at it, though. too bad I never took differential equations.