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Water chiller using a peltier

post #1 of 17
Thread Starter 
Hey, i've been thinking about using a Peltier in my w/c loop and was wondering if i had 2 loops, one to cool the cpu via the peltier, and the other loop to cool the peltier via a radiator. Will it make a difference if i have the cool side of the peltier on my CPU loop via a waterblock just before the water goes into my CPU? And the hot loop to maintain the heat of the peltier can be managed no problems.

I don't want to put the peltier directly on the CPU, i want the liquid to be chilled down via the peliter. I have an i7 920, when i OC it to 4ghz, my temps are around 45-50c idle. I want to drop this temprature down a bit, it does not need to be sub-zero or even sub -ambient, i'm after something around 25-30c max.

Also, what exacally do i need for the setup? I've got my two watercooling loops, would all i need just be the peltier, 2 copper plates and a power supply? I have an ATX 400w psu allready if that's any use to the peltier. Any help appreciated, thanks.
post #2 of 17
first of all, to get your temps lower, you will need to get the water down below ambient. as long as you're not under-radded, your liquid temp will be close to ambient already (most of the temperature difference is found over the waterblock... in other words, the difference between the CPU itself and the water)
for that, you'll need a lot of "Q" (the wattage of heat a TEC moves)... about 2 times your CPU output i think would give an optimal efficiency and temperature, maybe 3 times. you cant do that with a single TEC, which means you'll be needing dedicated chiller blocks that fit mutliple TECs. these arent widely available, and not available at all in copper (usually theyre made from aluminum, and im sure you already know aluminum in watercooling causes galvanic corrosion which poses a heavy threat to your cooling system) so that means you'll need to have someone make you a custom chiller. someone with acces to a milling machine. then those TECs need power. depending on which model TEC you use you'll need either a 12v or 24v dedicated power supply. ATX power supplies need to be modified to a single rail in order to work, and need to be capable of delivering the necessary amps from that single rail. (only look at the 12v rating)
then you need to insulate your cooling system. even if your CPU wont go below ambient, your tubing and blocks will, and condensation can still drop off those onto your precious hardware. (and as said, if you dont plan to get the coolant below ambient, TECs are not worth it over a big radiator.)

in other words... TEC's are expensive and a lot of work. fi you want to go trough with it...

you'll need to determine the power you'll want to move... the Q... around 2-3 times your CPUs heat output. thats around 600-800W.
all TEC's are rated for a certain Qmax, the Q they move at Vmax, their maximum voltage. but we dont need Qmax, it doesnt tell us very much about the point we're actually going to operate the TEC at... its just an easy way of identifying different models. for example, when people speak of the 437W TEC, than theyre talking about the model with a 437W Qmax rating.
most TECs run at 15.4 Vmax, but the lower voltage you apply, the more efficient the TEC becomes. (for example, the 320W TEC moves 320W at Vmax and consumes about... 450-500W (guesstimate, dont know the exact numbers from the top of my head) or so doing that. while if you turn the voltage down to... say.. 7v, it may move around 150W, and consume about 120W in the process... again, just a guesstimate but it illustrates my point) however, when you turn the voltage down, so goes the maximum temperature difference a TEC can generate. so that means there is a sweet spot... around 10-12v is a nice spot for most people.

so lets say you want to use 4 TEC's, and plan to run them at 12v... that means they need to move 150-200W each. that means 2 nice models are the 226W and the 320W models, depending on whether you take the 600 or 800W total Q figure. i think around that point, the TECs themselves will also consume around 600-800W... maybe a little more... a good single rail 1KW powersupply should run that. (PCP&C, Silverstone..) but make sure you use as many power leads as possible... connecting a TEC to a single molex will melt the cable. just like a high end video card, it needs multiple wires.

now, you see that the TECs move 600-800W, and consume (and therefore produce) another 600-800W... which means your radiator will have to deal with 1200-1600W of heat in a worst case scenario... you'll need a big radiator, maybe 2.

then you need the chiller blocks... a block for the hot side and one for the cold side. those two blocks need to clamp the TECs strongly between them... i think 300PSI was the optimal pressure but i may be confusing units... so dont quote me on that.

then theres the problem that you cant use acetal/delrin on the cold side loop... it turns brittle when it gets cold... not sure at what temperature it does that, but i suggest using a different plastic, or a metal like brass or copper. (duniek for example makes nice brass and copper tops for the swiftech GTZ) im not sure if acryl would work.

tehn insulation... lots of neoprene, kneadable eraser/liquid electrical tape, dielectric grease/vaseline for the motherboard... foam tubing insulation... some foam for the chiller blocks, at least for the cold side, but recommending both sides at once.

gives you about an idea what you'll need to have and do..
post #3 of 17
Don't go rushing off to buy the TEC chielscapes talking about you only need to double up if using carpy ebay TEC's because the ratings the sellers give are the wrong ones.
Knocking 20ºC off your coolant temperature is very feasible and certainly doesn't need the kind of power levels stated.

It is a good job you don't want to put the TEC on the CPU because there isn't really a single TEC powerful enough on the general market for an overclocked i7. Correction there is, maybe just a couple ...but the heatload coming off the thing is horrendous and it needs an expensive power supply.

Swiftech did broach the subject of a direct die cooler for i7 using a custom TEC but they also quoted a lead time of something like 8 weeks and that was up some months ago with nothing appearing on the horizon. It's a tough call... be interesting if they get there but I can be pretty certain it wont please overclockers like you.

So you are pretty much confined to to a chiller if you plan to do this at all.
Don't look at the coolit products....You need a proper chiller.
There isn't much if any around so it's a self-build you will need the experience or will-power to do basic metal work and be prepared to do a bit of research on TEC's. There is a lot to take in far more than can be communicated in a large number of posts on here... a good start would be this guide - http://www.melcor.com/handbook.html

With a chiller for reasons of efficiency it is best to run numerous smaller TEC's undervolted than one or two big ones at normal power.

If you fancy giving TEC a try....and don't be mislead here...It will cost more than you plan...it will take longer than you think...and if you don't do it properly you will fail miserably....stay on here we will help you through it.

EDIT
By the way you got first bit right - two loops - yes you either need two loops in the manner you described or depending on power levels etc it might be possible to use a fan/heatsink straight on the hotside....and no unfortunately the PSU won't do.
Edited by zipdogso - 7/26/09 at 3:25pm
post #4 of 17
Quote:
Originally Posted by zipdogso View Post
Don't go rushing off to buy the TEC chielscapes talking about you only need to double up if using carpy ebay TEC's because the ratings the sellers give are the wrong ones.
Knocking 20ºC off your coolant temperature is very feasible and certainly doesn't need the kind of power levels stated.

It is a good job you don't want to put the TEC on the CPU because there isn't really a single TEC powerful enough on the general market for an overclocked i7. Correction there is, maybe just a couple ...but the heatload coming off the thing is horrendous and it needs an expensive power supply.

Swiftech did broach the subject of a direct die cooler for i7 using a custom TEC but they also quoted a lead time of something like 8 weeks and that was up some months ago with nothing appearing on the horizon. It's a tough call... be interesting if they get there but I can be pretty certain it wont please overclockers like you.

So you are pretty much confined to to a chiller if you plan to do this at all.
Don't look at the coolit products....You need a proper chiller.
There isn't much if any around so it's a self-build you will need the experience or will-power to do basic metal work and be prepared to do a bit of research on TEC's. There is a lot to take in far more than can be communicated in a large number of posts on here... a good start would be this guide - http://www.melcor.com/handbook.html

With a chiller for reasons of efficiency it is best to run numerous smaller TEC's undervolted than one or two big ones at normal power.

If you fancy giving TEC a try....and don't be mislead here...It will cost more than you plan...it will take longer than you think...and if you don't do it properly you will fail miserably....stay on here we will help you through it.

EDIT
By the way you got first bit right - two loops - yes you either need two loops in the manner you described or depending on power levels etc it might be possible to use a fan/heatsink straight on the hotside....and no unfortunately the PSU won't do.
yeah, dont rush off to do anything... i was just giving examples, maybe shouldve been more clear.

and yeah... coolits products are a little underpowered for i7... a boreas has been reported to only barely beating a good radiator, by just a few C or so..that means you'll need a boreas and a freezone or even 2 boreas to properly cool that i7... and those things are expensive as hell.
post #5 of 17
Quote:
Originally Posted by ChielScape View Post
yeah, dont rush off to do anything... i was just giving examples, maybe shouldve been more clear.
Yeah my point was though the power requirement you stated is well over what he would need.
post #6 of 17
im not so sure it is. there's these curves of DTmax versus Qmax... by having more Qmax than you need to play even, temps will lower as the DT increases.
post #7 of 17
actually the best way to have a chiller is to grab some pretty powerful TECs and run them at 30-40%vmax then you don't have the same power requirements or thermal dump from the TECs. But obviously the disadvantage is the cost of each TEC goes up drastically as they get more powerful.
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post #8 of 17
Quote:
Originally Posted by flak-spammer View Post
actually the best way to have a chiller is to grab some pretty powerful TECs and run them at 30-40%vmax then you don't have the same power requirements or thermal dump from the TECs. But obviously the disadvantage is the cost of each TEC goes up drastically as they get more powerful.
even then the actual TECs still arent the largest cost... even the 437W costs 40 bucks if bought from frozen CPU, if they still have it.. ebay is cheaper. they make easy TECs for figures around there using a modified ATX PSU... 12v is around.. 45-50% of vmax? little higher than the 30-40, but still below what 12v is to 15.4vmax TECs. just too bad those units are 62mm squared..
post #9 of 17
I wasn't thinking of the 437 (I don't trust its stats they seem rather false at best) I was thinking this one: http://www.shop.customthermoelectric...&productId=132 It seems like it would be more powerful. And most of the TECs on ebay are garbage.
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post #10 of 17
they arent garbage, they are just called after their cunsumed wattage, at 52 or so C hotside, rather than Qmax. the TECs themselves are still like any other.
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