peltier devices

[donkey]

ok there is alot of people that say these are good alotsaying they are not. but anyway I have a grand scheme of making a very small air con. I have some of the parts required and some on order. but I will try to get to the questions soon.
first of all I got me a stock standard 80watts peltier, its 40mm x 40mm. I got a 50mm x 100mm heatsink. and last but not least I got 1 (my final design uses 2) compuuter fans rated at 12volts.
the only things I need to know is the read up I have done says that the cool side will be "x" amount cooler than the hot side. so a fan blowing across it makes it cooler... is there anything else that would do this?
also I know its rated at 80watts, what formula do I use to calculate how much heat will be transfered?so if the hot side isat say 30celcius what temp should the cold side beif running well?

 

[Raven Luni]

I havent got a scooby about formulas but I've actually managed to get some good results with one of these. I would have to say low power is the key to getting good results. I recently used one of these 80W ones with an old AMD heat sink and fan. At 5V it draws about 2A (so thats 10W) and the cold side will stay below freezing all day long without even warming the heat sink (I sat it in water and made ice). The initial 12V I fed it wasnt much use at all and all it did was fuse the hot side to the heat sink (there was still a thin layer of adhesive from the old CPU).

I'm hoping to make a fursuit cooling system for furries

 

[donkey]

hey ty raven. run into an issue. I borrowed a heatsink from a old computer. it included a fan which I was impressed with. anyway I can't get the cold side to freezing temperature as I had hoped.
the ambient temp is 30+celcius here at the moment so that could be a factor.
I was considering making my own heatsink of sort using metal and tubing to let water go through to aid in cooling. all copper if I can source some at a decent price. then run the water through a radiator (homemade too) to aid in cooling. what do you think?
the heatsink will consist of a copper plate soldered (or welded if I can loan one) to 4 pieces of 2-3 inch copper pipe then connect hoses up to it to pass water through it

 

[Raven Luni]

What are you powering it with (it will take a fistful of amps depending on the voltage)? I'd say as long as the heat sink is good enough it should work fine. Thermal contact might also be an issue

 

[donkey]

I am using a 12v 7ah sla battery which I think is half the cause as the voltage may be causing too much heat. the heatsink is bigger than the device and about 50mm deep with a fan on top.

 

[Raven Luni]

Definitely the voltage I'd say. I used a PC supply. 12V is just insanely hot but using the 5V rail is how I got the freezing result. You could try putting a couple in series - nothing wasted that way.

 

[donkey]

today I got the freezing using the 12volt battery but the heatsink side was submerged in water, we actually put icein the water to keep it low temp.
I am thinking of taking a transmission radiator some piping and a small pump and fan now to make this thing. and rather than actual water I might try coolant. but if i try coolant I have to get the right pump.

 

[donkey]

just a stupid question but why would the voltage be an issue? it is rated for 13+ volts

 

[Raven Luni]

The more volts you give it the more power it uses and the more off the scale the hot side gets

 

[donkey]

I am trying to locate a variable power supply to try and make this work. I am trying to figure out a few things to make it work of the parts i have.
for starters using 2 peltier devices in series from a 12volt battery may lower the heat as each should hypothetically receive lower voltage.
also I have a design for cooling sidebut its a question of money to get it to work. once I figure out what is needed I can solar the sucker

 

[GonzoEngineer]

I remember years ago when I got one of those for the first time.

Being a young and anxious Engineer, I immediately hooked it up to a bench power supply and turned it on.

I was amazed at how fast it got cold, and how fast it melted and fell apart in pieces because I didn't mount it on a heat sink!

 

[donkey]

lol gonzo. I am hoping to avoid that. going to try a few things to cool it, water cooling is one of them. I am also thinking of piggybacking 2 of them apparently this makes it colder. all this for a small ice cold fan lmao.

 

[donkey]

this is my garnd scheme as it stands now. I hope to get a trial run soon. I doubt it will revolutionise the world but I hope it coolsme down in summer lol. if all goes well I will be back on here with pics... if it fails lets never speak of it again lmao