peltier air cooling

[CzarDestructo]

is such a setup really worth it? i see everyone doing just water cooling,but what about for air cooling? what kind of PSU could i use for this,something external? what do most use,just a really beefed up ATX PSU? would a low power 100watt TEC under my SP-97 be worth bothering with? i don't want water cooling,and i don't want loud fans so i'm trying to find a better way to get my temps further down.

also, would i need to do as much prep work with a low power peliter? could i just foam around the base of the socket or should i still prep the back of the mobo?

 

[Tigerbiten]

A 100 watt peltier wont cut it.
Most pelts have a Vmax of around 15-16 volt.
Thats the voltage needed for maximun cooling.
Running it a 12 volts means your looseing 20-25% cooling power.
So your 100 watt pelt is only going to be removeing 75-80 watts of heat.
You cpu will be probably putting out this amount of heat if not more so there will be no cooling effect.

Plus putting more heat into the heatsink-case will mean you will need bigger-faster fans to remove it.
So more noise.

Luck.........

 

[CzarDestructo]

well i think when calculated my cpu is pushing out roughly 120watts. is that really how to calculate,is it really spot on watt for watt? so i'd need a 150watt+ TEC?

also my 12V rail has a pretty hefty load,i was hoping to use the 5V rail and lots of amps. i was asuming so long as the wattage was the same it would be fine? i wanted to use 5v and more amps instead of volts to make up the wattage, or do TECs not work this way?

the extra heat doesn't phase me, the heatsink is sandwitched between a 140mm and 120mm fan on two sides, so the heat will get draw out instantly.

also,i can't put the TEC directly on the die, correct? if so then i doubt a copper plate+TEC will fit between the SP-97s mounting system.

 

[HeThatKnows]

Genrally you want cooling capacity of 2 or 3 times the heat produced. The 226 W TECs are the smallest I'd use on a 120 W CPU.

No, you can't make up for lower voltage with extra amps. If you give the TEC x% of it rated voltage, it'll draw x% of the rated current.

Can't put the TEC directly on the CPU, you have to use a cold-plate (usually 6 to 10 mm thick). And the coldplate has to be bolted to the heatsink (with around 200 pounds of clamping force). You won't get good heat transfer if you rely on the mounting clips to press everything together.

 

[CzarDestructo]

you shot my dreams in the foot!

thank you for the very informative post!

 

[Ice Czar]

and building on HeThatKnows post


the trick (like most thermal transfer chains) is to increase the interface to something that will handle the load at the normal ambient you have to work with

thus the coldplate which goes from the core to the TEC
(instead of the tec only contacting a part of the core) and the TEC to the heatsink
thus increasing the transfer interface to the air

(the clamping force increases the actual contact inbetween two surfaces, flattening micro moutains on both)

The heat transfer through the wall follows a simple equation:
Q=k/L(T1-T2)

We can draw some interesting conclusions from this equation. First, heat transfer is proportional to the temperature difference on the object. If the temperature differential doubles, the heat transferred doubles. Second, the conduction coefficient "k" is proportional to heat transfer. If the conduction coefficient doubles, the heat transfer doubles Alternatively, for the same differential temperature, twice as much heat may be transferred. The final observation is "L". As thickness (or distance) increases, heat transfer decreases. Alternatively, to maintain the same heat transfer through a material twice as thick requires twice the temperature differential.

General Heat Transfer Guide

the thickness of the coldplate forstalls heat transfer but ensures that the heat is actually distributed to the whole TEC, and because of its delta that works out better than directly on the core

of course the colder the air cooling the heatsink (or the more air) the lower the actual temperature will be, heat transfer is all about differential temperatures, but that effects the whole chain, actually you need to make sure that the heatsink interface is large enough, or the air cooling it is cold enough, or that the volume of air is high enough to actually meet the total heat load

with any basic thermal solution there are 3 main areas to address:

the transfer interface(s) the larger the interface the more heat can be transfered which is why heatsinks have fins, from a massive passively cooled radiator that could be twice as small with a fan assist or a bigger heatsink, to a waterblock with a pelt employed not only as an assist to the transfer but also increasing the heat transfer size from the CPU core through a heatspreader to a much larger interface, which is possible because of the delta a pelt has)

the transfer medium whatever that fluid happens to be, air, water, or phase change refrigerant how well the heat is transfered to it (turbulence being a great assist generally stripping off superheated boundary layers) to the flowrate be it a less restrictive water circuit or a larger fan
more flowrate in and of itself is always better, but its never in and of itself, there is always a penalty in pumpheat (something that is a real concern in a water circuit) TNSTAAFL otherwise known as the 2nd law of thermodynamics

the temperature differential the lower the ambient at the end of whatever set of processes your employing the lower the temperature your able to maintain all the way up the line, in the case of say a phase change setup, the condenser (rad) being cooled by a lower ytemperature air, means the compresser has to do less work to maintain a set temperature (like a room AC) or simply is able to run at a lower temperature over all in a constant on situation like a computer, same applies to an air cooled heatsink or rad in a water cooled system, its able to remove more heat to the air, and thus the water is cooler going through the pump and picking up energy in the form of momentum, and thus able to absorb more heat from the waterblock for a given flowrate and design

design of components is how you address these three issues

 

[Napalm_Fire]

I air cooled my P4C 2.4Ghz @ stock with an SP-94 and an 80 watt peltier, it ran 11c, and started condensing, luckily, I shut the system off before the drop of condensation got to move anywhere

of course, the CPU was putting out 66w of heat then, now its putting out 130w @ 3.63GHz and 1.675V, but my SP-94 handles that very nicely, im running 37c at the moment with 127w heat out put

 

[K2Rage101]

is such a setup really worth it? i see everyone doing just water cooling,but what about for air cooling? what kind of PSU could i use for this,something external? what do most use,just a really beefed up ATX PSU? would a low power 100watt TEC under my SP-97 be worth bothering with? i don't want water cooling,and i don't want loud fans so i'm trying to find a better way to get my temps further down.

also, would i need to do as much prep work with a low power peliter? could i just foam around the base of the socket or should i still prep the back of the mobo?

I already tried building a pelt air cooler. Looks nice, doesn't work.

Here is my work log if you are interested:
http://members.accesstoledo.com/k2rage101/AC/

 

[BallerX]

LOL it wont work?!!! why? because you tried with a 50w pelt and it did nothing?

basically it will work and you would need at least 2 226w TECs and 2*18volt...24amp power supplies or 1 18 volt 50 amp power supply. and all of that together would cost you 4 times more than a 5000 btu a/c unit from wally_world, cool less, and use way more energy...
so it is a case of diminishing returns....buy the 100 dollar a/c unit from walmart and use it to make a water chiller and you will be way closer to your goal of cooler and quiter for a lot less money

 

[K2Rage101]

Maybe you don't quite understand TECs...

The problem is not the wattage. It is the efficiency, and the fact that I chose two small fans to do the heat removal work. I have no doubt it would work fine with a little insulation and some beefier fans.