|
|
Post by av8tor1 on Dec 10, 2007 17:37:51 GMT
Been pondering building a small chamber using a pelteir chip, so Ive been doing my homework and came across this excellent article on the subject, thought i would pass it along... should be easy enough to visualize the possibilities btw the chips are only 10$-ish on ebay, shipping included  www.electronickits.com/kit/complete/peltier/ck500.pdfCheers' Av |
|
kby
Full Member
Posts: 162
|
Post by kby on Dec 10, 2007 19:09:45 GMT
Been pondering building a small chamber using a pelteir chip, so Ive been doing my homework and came across this excellent article on the subject, thought i would pass it along... should be easy enough to visualize the possibilities btw the chips are only 10$-ish on ebay, shipping included www.electronickits.com/kit/complete/peltier/ck500.pdfCheers' Av My experience (with the ready-made versions--the various car/travel heater/cooler chests) is that they don't have a whole lot of capacity. The typical "car seat" one will only go down to 45 F or so in the reasonably well [thermally] insulated tiny chamber (enough to hold at most 6 soda cans). It's fairly hopless in any larger and less well insulated environment. I have found such a thing useful for pumping cool water over Darlingtonia roots, though, as I mentioned in the Darlingtonia thread. For a 40gal or so terrarium I needed to use the cooler unit from a bar fridge for nighttime cooling (and even it isn't as good as I'd like but appears to be adeuate).-kby |
|
|
|
Post by av8tor1 on Dec 10, 2007 21:03:32 GMT
thanks for the feedback Kby, I have also considered the same issues, and it may very well be pointless... but there are some definite advantages to rolling your own over the prefab units
firstly you can get the chips all the way up to 500watts (ebay), secondly I am hoping the insulation will not be such an issue since i will have the chamber in a relatively constant 70f home environment instead of trying to keep my Budweiser cool in 90f heat/summer sun or a 140f parked car
but realistically I'm hoping the higher wattage and better heat sinking will be the key... and if nothing else it will be a fun to try
Av
|
|
|
|
Post by av8tor1 on Dec 11, 2007 3:52:53 GMT
FWIW, I did the math... a 350w peltier is equal to approx 1100-1200 BTU which should be more then enough for my project..
Ive got one ordered, ill keep pics as I go...
now to find an old power supply that can deliver 30amps @12vdc :-)
|
|
kby
Full Member
Posts: 162
|
Post by kby on Dec 11, 2007 8:02:54 GMT
I'll be interested to see. My experiments were on a room-temp thing, although it gets to the 80s. I actually didn't try it directly in the tank since it was in fact pre-fabed into the container. I did try using a cooling bath to cool circulating water and that was pretty hopeless. So, I can't remember looking but how much more efficient are these than a motor? 350W seems like a lot of oomph, figuring power consumption's at least x2 (just a guess...if you've seen better numbers feel free to put them up)?-kby
|
|
|
|
Post by av8tor1 on Dec 11, 2007 13:33:55 GMT
the 350w is the power consumption... since there are no moving parts efficiency should be extremely high... (assumption) much higher then most pumps which can run from a low of 60% for an external gear to a high of 90%+ for a variable displacement axial flow piston pump... so compared to a typical gas cycle cooling system there should be no real comparison... instead of using the aluminum plate as in the article (they had to for clearance purposes) Ill use another cpu heat sink and fan... this should make the "footprint" much smaller, improve heat exchanger effciency and providing air circulation sounds good on paper anyways  Av |
|
|
|
Post by Not a Number on Dec 11, 2007 16:00:45 GMT
en.wikipedia.org/wiki/Thermoelectric_cooling#PerformanceThermoelectric junctions are generally only around 5–10% as efficient as the ideal refrigerator (Carnot cycle), compared with 40–60% achieved by conventional compression cycle systems (reverse Rankine systems like a compressor). Due to the relatively low efficiency, thermoelectric cooling is generally only used in environments where the solid state nature (no moving parts, maintenance-free) outweighs pure efficiency.
Peltier (thermoelectric) cooler performance is a function of ambient temperature, hot and cold side heat exchanger (heat sink) performance, thermal load, Peltier module (thermopile) geometry, and Peltier electrical parameters.
|
|
Clint
Full Member
Posts: 808
|
Post by Clint on Dec 11, 2007 16:53:20 GMT
I'd just go out and buy a chest freezer. A 'small' chest freezer isn't more than a couple of hundred bucks (save some cash if you get it used), get a thermostat or two (for safety), a fan or two, or a light. It would be nice to get the kind with sliding glass doors but you could get a regular one and replace the lid with acrylic or glass. It would take forever for something like N. villosa to outgrow it. I totally intend to do this once I get my own stable residence.
|
|
|
|
Post by av8tor1 on Dec 11, 2007 17:31:22 GMT
warren, now dangit here you go raining on my parade  chit 5-10% wont be worth anything... Clint, Ive already got medium sized chest freezer that I am not using... but heck eveyone does that oh well... |
|
|
|
Post by Not a Number on Dec 11, 2007 22:46:47 GMT
chit 5-10% wont be worth anything... Yeah, pretty poor, I was stunned when I saw that myself. However you could cobble together a Darlingtonia solar powered drip cooler I was thinking about. Basically attach a solar powered Peltier to a small sealed metal box. Water drips into the box from the top, gets chilled, drips out the bottom into the Darlingtonia pots. You can even add a solar powered submersible pump and make it recirculating if you work out the flow rates or a cutoff so the pump won't run dry. Well enough species drift... |
|
kby
Full Member
Posts: 162
|
Post by kby on Dec 12, 2007 2:49:02 GMT
I probably read the efficiency figure when I tried (obviously unsuccessfully) before & just forgot.
the darlingtonia thing you describe is what i have set up described in the darlingtonia thread, sans the solsr power.-kby
|
|
