Stella Posted February 3, 2006 Report Share Posted February 3, 2006 We are looking into building a chiller using peltiers. Something along the lines of this: http://www.overclockers.co.nz/ocnz/revi ... atsink0103 It is the same basic idea as the iceprobe chillers. The ideas keep getting caught on a couple of crucial points: Is aluminium a problem for freshwater aquariums? The heatsinks are aluminium. If not, what could we coat it with to protect the water from direct contact, without losing toooo much efficiency? And is thermal epoxy glue bad for fishies? (it is a special glue for transfering heat) SO the plans are based on the outcomes to those questions... Has anyone explored using peltiers before? (We have an 80 litre native tank, with galaxids, bullies, crayfish and a shrimp) Thanks Stella Quote Link to comment Share on other sites More sharing options...
Ira Posted February 5, 2006 Report Share Posted February 5, 2006 I don't think aluminum should be a problem. But, maybe if you can find a stainless steel heatsink, that would be better. Otherwise maybe just a thin sheet of plastic seperating the water from the cold side of the petier will work with a good current across it? Quote Link to comment Share on other sites More sharing options...
monaro1 Posted February 5, 2006 Report Share Posted February 5, 2006 if the aluminum becomes problem you could try HPC coatings Quote Link to comment Share on other sites More sharing options...
Warren Posted February 6, 2006 Report Share Posted February 6, 2006 I looked at making a heater chiller using peltier's. I was going to cast stainless 316 tube into an aluminium block for one side and use a standard fan-cooled aluminium heatsink for the other. In summer it would need to only take about 4-5'C off the temperature and in winter, add 15-17'C. You can reverse the polarity on a peltier to make it work in either direction. The advantage of heating is you get approx 2:1 transfer ratio. I was going to use about 500W of peltiers to get about 500W of colling in summer and about 1kW of heating in winter. The only reason I haven't done it is time. It would take a while to design and build a controller, especially by the time the software is debugged and all the design stuff-ups are sorted. Part of the big problem is peltiers do not like thermal cycling or AC ripple in their power supply. The junctions fatigue and break and bye bye peltier. A control system is required to put only contant DC current into the peltier and to cycle it as little as possible so it's life is maximised. It is all relatively easy to do but time consuming... This year summer is not as hot so the tank is not overheating much. Next time we get a heat wave it may motivate me to start the project... Quote Link to comment Share on other sites More sharing options...
Stella Posted February 13, 2006 Author Report Share Posted February 13, 2006 Warren, Interesting to read about your plans! Sadly we lost half our fish a few weeks back due to heat while we were out of twon, so we HAVE to get this sorted. Dont want to get any new fish until we do. Major motivation!! So you were going to have aluminium in the aquarium water? Did you find out if it was safe? I still havent found anything concrete. I know it is bad in saltwater aquaria, but I dont know if that is the result of it reacting with somehting else in that sort of setup that I wouldn't have. It appears the salt is particularly corrosive, not a problem in my tank. I have found that it can be toxic where the water is higher than pH 8.0, and more so if the temperature is high. I dont know what pH my tank should be, but last test it was 8.8. We have a big peltier on its way Stella Quote Link to comment Share on other sites More sharing options...
Warren Posted February 13, 2006 Report Share Posted February 13, 2006 I was going to cast stainless 316 tube into an aluminium block for one side and use a standard fan-cooled aluminium heatsink for the other. No, stainless steel tube cast into an aluminium block. The water goes through the tube and the peltier mounts to the block. Quote Link to comment Share on other sites More sharing options...
Tanksman Posted February 13, 2006 Report Share Posted February 13, 2006 I dont know what pH my tank should be, but last test it was 8.8. Stella Do you know what ph the water comes out of your tap? Seems quite high ph8.8 Be interested to hear your progress as you build this peltier chiller. Quote Link to comment Share on other sites More sharing options...
Grizzly Posted February 16, 2006 Report Share Posted February 16, 2006 from a strictly engineering point of veiw they are pretty inefficent. what are you trying to cool hacking up an old bar fridge mould be better IMO but maybe its a bit large for an 80L tank. Quote Link to comment Share on other sites More sharing options...
Warren Posted February 16, 2006 Report Share Posted February 16, 2006 It may not be the most efficient way but it's relatively cheap, silent and very easy to set up. During winter you get a 2:1 heating ratio so more efficient than heaters. Much less efficient than a good heat exchanger though... Quote Link to comment Share on other sites More sharing options...
Robert Smith Posted March 7, 2006 Report Share Posted March 7, 2006 Stella, pH 8.8 would not be good for Al. That's pretty high, what's the special fish? Also, if you use tank salts, they could be a problem. SS is a very poor thermal conductor Since this is going to be in the water, why would you even need a heat exchanger? The water in direct contact with the peltier surface would do the job nicely (especially if there is flow). I assume that your filter is internal? I live in Oz and have a similar problem. We survived this summer, but things got a bit warm last summer. I have an external cannister filter (400L/m) for an 80L tank (vroom, vroom) and was going to try connecting a peltier cooler straight to the glass (on the outside). It's horribly inefficient, but it's only to take the edge off on those really hot days. Then I thought about buying one of those peltier car coolers and dropping the output tube from the filter through a heat exchanger in the 'fridge'. Quote Link to comment Share on other sites More sharing options...
Feelers Posted March 7, 2006 Report Share Posted March 7, 2006 Can galvanised steel be used? If it can you could just chuck the heat sink into it. I know it stops it corroding, but I'm geussing zinc isnt reef safe. You can buy titanium piping at about $30 US a meter apparantly. Quote Link to comment Share on other sites More sharing options...
Pies Posted March 7, 2006 Report Share Posted March 7, 2006 Check reefcentral.com for heaps of info on people who have tried using TECs for DIY chillers for tanks. The bottom line is that it doesn't work (well it does, but its so inefficient its not worth the time). You also need to despense with all that hot air on the TEC as well. There is on comercial unit for sale that has been used in PICO/NANO reefs, but from i've read its not worth the hastle. Pie Quote Link to comment Share on other sites More sharing options...
Shilo Posted March 31, 2006 Report Share Posted March 31, 2006 Stella, When researching chillers for my native tank I found that the Peltier method to be less cost efficient then converting a dehumidifier. The number of peltiers and the size of them made it 3 times the cost, a 2nd hand commerically made chiller could be brought for the same price. Its doable but beware that the heat from the opposite side of the peltier must be removed efficiently for it to work. Blowing a fan on some fins attached to them with thermal grease will help, but then you have the problems of waterproofing (glass is not a very good heat conductor). The dehumidifier method has worked well keeping the tank 10deg below air tempature. Its on 12hrs a day (switching on and off every hr) but it is quieter then a fridge and I have not noticed any increase in the electricity bill. Keep us informed on how it goes. Cheers Grant Quote Link to comment Share on other sites More sharing options...
Warren Posted April 1, 2006 Report Share Posted April 1, 2006 Hmm, I expect a peltier chiller could cost about the same. I can easily make one very cheaply but then I have access to really cheap electronic parts through work (including the peltiers). I'm so used to getting the bits for really low prices I tend to forget most other people probably can't... Just quickly worked out the cost to make a peltier cooler for 300W cooling and 600W heating. For anyone who has to use parts available from the likes of Electronic Retailers, forget it and modify a dehumidifier. To make one properly will cost about 1.5 times the dehumidifier. Quote Link to comment Share on other sites More sharing options...
WEKA Posted April 1, 2006 Report Share Posted April 1, 2006 Anodizing the aluminium parts will stop corrosion even with saltwater. It changes the surface composition of the aluminium and makes it very hard. It is not expensive to have done. Quote Link to comment Share on other sites More sharing options...
suphew Posted April 2, 2006 Report Share Posted April 2, 2006 Anodizing the aluminium parts will stop corrosion even with saltwater. It changes the surface composition of the aluminium and makes it very hard. It is not expensive to have done. be intresting to know if this works, but im putting my $ on it not working, but would be really good if it did. i haven't ever seen it used even in cheap marine gear. even high grade stainless rusts in marine tanks. Quote Link to comment Share on other sites More sharing options...
supersecretshinto Posted May 6, 2006 Report Share Posted May 6, 2006 Consider this DIY chiller idea. Could use any help I can get. Being an American, the only advice my countrymen can usually muster is "throw money at it". http://www.nano-reef.com/forums/index.p ... opic=86712 http://www.nano-reef.com/forums/index.p ... id=792641& Quote Link to comment Share on other sites More sharing options...
slappers Posted May 6, 2006 Report Share Posted May 6, 2006 Quote Link to comment Share on other sites More sharing options...
Robert Smith Posted May 25, 2006 Report Share Posted May 25, 2006 Shinto, Thermal conductivities: http://www.engineeringtoolbox.com/therm ... d_429.html Aluminium 250 W m-1 K-1 (Watts per metre per degree Kelvin) Steel 50 Stainless steel 16 Pyrex 1.1 Plastic 0.1 to 1 Polypropylene 0.5 Wood 0.15 Air 0.024 Why not use something with poor thermal conductivity but easy to work with like plastic and overcome the thermal conductivity with an increase in the contact area. Glass is only twice as good as PP, so double the contact area (more windings) will do the same job. PP tubing tends to be thicker than glass, so you may have to more than double, but PP is very easy to work with, glass is a bitch! Chemists only use Pyrex because it can take the high temperatures and caustic environment. If you can drill holes in floors, why not get really tricky and tap a heat exchanger into/onto/around the water main! That way you don't waste any water. You use a closed-loop heat exchanger from your tank to the main and the main is always cool. The temperature differential is small, but the thermal mass of the main is huge. So instead of wasting lots of water, you just pump your closed-loop exchanger as fast as you can. Also, insted of using water in the heat exchange loop you could use oils, or refridgerants. There were a few comments about water not being a wasteable natural resource. That's not true. Yes, you can always get more fresh water (by distilling the sea, for example). But the amount of 'naturally available water' is often limited. I live in Sydney and haven't washed my car in four years due to water shortages. Bob Quote Link to comment Share on other sites More sharing options...
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