peltier drinks cooler?

[FightTheFuture]

Hello everyone!

I'm a bit new at this, so please bear with me. This is the first time I've ever used the oc-forums.

I am a final-year IGCSE student (grade 10, for those people under the American system), studying for an IG in Design Technology: Design & Realisation in Bangkok, Thailand. I have decided to create a peltier-based drinks cooler as my project.

So this doesn't actually doesn't really have anything to do with computers, per se, so I hope I'm in the right place.

I intend to use a second-hand PSU, probably around 220 wats or less. It will power only the Peltier and a single fan for the heat sink. The casing I will make myself, probably using metal for the base (where the PSU and the Peltier will be), and plastic piping for the drinks-holder on top. This will be insulated with bubble-rap (don't know what its called in the US - its the packaging stuff that people always pop) (probably), and metal - possibly copper, to retain heat and insure that any spillage does not damage the Peltier or PSU. The casing will be coated with black wood for aesthetics.

What type of Peltier should I use? Will 220wats be enough? Is there anything I need to know about Peltiers before I start? What type of heatsink/fan should I use? Do I need a fan, or can I simply let the exhaust from the PSU cool the heatsink? Should I use thermal grease or thermal expoxy? I dont want any condensation ruining my Peltier and PSU, so is covering the PSU with a plastic bag (with holes cut to enable airflow) a good idea? Would covering the edges of the Peltier with thermal grease or epoxy stop condensation from destroying it (Thailand is very humid)?

Would I be able to simply flip a switch to reverse the currant and start heating my tea? I know that cooling of the hot side (the side not touching the cold drink) enables better cooling (of the drink), but how about for heating hot drinks? Would the fact of the heatsink on the (now cold side) impeed or accelerate the heat on the (now hot side) - the side now touching the (hot) tea? (Umm... I hope that made sense.)

I once read about a guy who did a similar thing, but his drinks cooler was actually built into his system. Stupidly, I lost the URL.

Thanks in advance for any help you can give me!

Daniel

 

[Penguin4x4]

http://overclockers.com/tips1045/

 

[Paxmax]

I intend to use a second-hand PSU, probably around 220 wats or less. It will power only the Peltier and a single fan for the heat sink.

Ok, if the powersupply gives a TOTAL of 220W, you are not going to be able to shove enough amps at 12 volts for a 226 watt TEC.
Possibly a 120W TEC could be powered from that PSU.
In the article mentioned by Pengiun4x4, he used a 72 W TEC. It took a long time to cool that beercan. If you are permitted to add some water inside the copper "cup" where the can is being cooled, then you might speed up the cooling process due to better heat transfer.

What type of Peltier should I use? Will 220wats be enough? Is there anything I need to know about Peltiers before I start? What type of heatsink/fan should I use? Do I need a fan, or can I simply let the exhaust from the PSU cool the heatsink? Should I use thermal grease or thermal expoxy?

The peltiers size is only limited of the powersupply.
Yes you need a big heatsink, look at overclockers.com in their heatsink ranking, go for the best one you can afford. You also need a separate fan, if you go with 120W TEC a 25-36 CFM fan will do (with a good heatsink) if you end up with 226W TEC you must go for like 50+ cfm + very good heatsink. Basicly it boils down to "How fast must it cool down that beer?"
A good choice would also be 226W tec powered at 5 volts, then the 220W PSU will do. The TEC will be in a more efficient mode at 5 volts, you'll get away with a cheaper heatsink(but think BIG) and slower fan, like 25 CFM.
Use thermal grease, cheaper, easier and you can dissasemble it afterwards.

I dont want any condensation ruining my Peltier and PSU, so is covering the PSU with a plastic bag (with holes cut to enable airflow) a good idea? Would covering the edges of the Peltier with thermal grease or epoxy stop condensation from destroying it (Thailand is very humid)?

Try to enclose the peltier assembly with "closed cell type" foam or neoprene. also add vaseline/petroleum jelly to ensure airtight assembly around peltier. Make sure that your "cold beverage" compartment is sealed off/insulated so that condensation won't dribble down the sides and possible reach the electronics.

Would I be able to simply flip a switch to reverse the currant and start heating my tea? I know that cooling of the hot side (the side not touching the cold drink) enables better cooling (of the drink), but how about for heating hot drinks? Would the fact of the heatsink on the (now cold side) impeed or accelerate the heat on the (now hot side) - the side now touching the (hot) tea? (Umm... I hope that made sense.) )

Yes it would work, but: The heating of the beverage holder is much more efficient than the cooling it. Therefore you need to have a regulator to make sure that the TEC never gets above 80 C or what the manufacturer suggest, or it might be destroyed. Besides that, the beverage holder is isolated, meaning it will get hot very fast, and may get too hot if precaution isn't taken. You might wanna switch down the power to 3.3 volts or lower if it gets too hot. Cycling the power on/off to regulate the heat is very stressful on the TEC and it could be damaged in the long run. Also consider the cold side. I don't think it will come to this point, but, if the heatsink outside gets too cold, condensation will form on it, and may drop into the fan or pour over somewhere it shouldn't be.