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Old 26-11-12, 01:52 AM
XionEternum XionEternum is offline
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Question Alternative TEC Cooling?

Hello, I am new here but hardly new to computer tech. I know my way inside and out with basic components and how LCSs and Phase-Change work. I'm a bit lacking on TECs though and how they work. I get and understand the formula, as well as the TDP variance between the CPU and TEC causing significant inefficiency in some cases. What I don't get is why people haven't tried this:

Imagine if you will, your average PC chassis. Has a nicely spaced 120mm exhaust port on the back next to the rear IO, with plenty of room all around it and possibly even mounting for a 140mm fan. Imagine reverse mounting a downward CPU cooler to it like the CM GeminII or the GeminII S and a decent fan, with the CPU block facing into your chassis. Then imagine placing a low TDP TEC, like 80-250watts, with the hot-side against it, then sandwiching them together with a waterblock on the cold-side. Loop your LCS so that the radiator cooled water passes through this block. Would this be an effective solution to the inefficiency of direct contact with the heat generated by the CPU, by acting as a water chiller instead? Since the expected thermal variance between the hot and cold sides won't exceed 70 degrees, and under this application would likely be getting hit on both sides by ambient temp thermal displacement -air on the hot side and water on the cold side- wouldn't we see the waterblock on it get chilled and thus chill the water flowing through rather well before heading straight to the CPU block? I'm curious if anyone has tried this, or genuinely knows the thermal dynamic properties of this application. Will it work? Has it worked?
Thoughts anyone?

Edit after first two responses:
Okay, I should add to the example as having the following loop sequence:
Res> TEC Block> CPU Block> GPU Block(s)> Rads> Repeat. So in theory the rads cool the water to ambient before recirculation to the TEC.
And presume condensation is not an issue, as in wrapped in cloth and sealed.
Also presume that the rads are more than capable of cooling the water to ambient.

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Old 26-11-12, 09:11 AM
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Master&Puppet Master&Puppet is offline
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The major problem with using a chilled system (regardless of how you go about it) is that you can only lower the temperature to ambient before you risk condensation forming. Water has great thermal properties which means that it doesn't actually heat up much at all in a standard loop. Therefore you will only be able to lower the water temperature by 10-20C before hitting ambient and I'm not sure that will transfer into a significant enough core temp drop to warrant it.

Would be interesting to test though.
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Old 26-11-12, 03:38 PM
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Having a rad in the loop will keep the liquid above amibent unless your running a couple of high wattage tecs so condensation isnt to much of an issue other than maybe the metal on the water block on the cold tec side of the heat transfer bit.

The only thing i can think of off the top of my head other than a dedicated external box acting as a full on water chiller that used nothing but tecs to cool the water loop and a 2nd loop to cool the tecs is a guy that used a single 400w tec.

The hot side was cooled by an Antec 625 all in one water thing and the cool side was stuck to a random cheapy cpu water block, iirc it managed to lower a cpu + gpu loop (a heavy OC on an amd quad and GTX 460 i think the guy im referencing was using) by around 7-8c on both the cpu and gpu but it ended up using so much power (more than 16/18 amps on the psu he originaly was using with a 200w tec for testing could give out im pretty sure) he ended up using a 750w 40amp unit....

TLDR a single 400w tec cooling the loop liquid will only lower a cpu + gpu loop by at most around 10c but.
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Old 26-11-12, 09:06 PM
XionEternum XionEternum is offline
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Originally Posted by I Hunta x View Post
The only thing i can think of off the top of my head other than a dedicated external box acting as a full on water chiller that used nothing but tecs to cool the water loop and a 2nd loop to cool the tecs is a guy that used a single 400w tec.

The hot side was cooled by an Antec 625 all in one water thing and the cool side was stuck to a random cheapy cpu water block, iirc it managed to lower a cpu + gpu loop (a heavy OC on an amd quad and GTX 460 i think the guy im referencing was using) by around 7-8c on both the cpu and gpu but it ended up using so much power (more than 16/18 amps on the psu he originaly was using with a 200w tec for testing could give out im pretty sure) he ended up using a 750w 40amp unit.....
Now this puzzles me considering you mention the use of an Antec 625 AIO LCS. I sincerely doubt that cooler is capable of dissipating 400w of heat at an efficiency that balances the delta of the TEC to ambient. Simple fact is, regardless of what wattage a TEC is rated for, it's optimal delta is the same. So why not a lower wattage TEC being cooled by something simpler and more capable of matching the TDP of the TEC? Performance-wise, the Antec 625 isn't effective compared to most similarly priced air coolers. Sure I get that more watts means faster thermal transfer, but if the deltas are the same regardless... Perhaps we can talk someone who can invest in testing this with various wattage TECs? Frankly I'ld be thrilled to test it myself but lack the funds. :3
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Old 26-11-12, 09:21 PM
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Just been doing some google work and i found the thread i was referencing, ill PM you it as i dont like linking to other tech forums openly in threads.
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Old 26-11-12, 09:29 PM
Perturabo Perturabo is offline
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If I am thinking about this right the wattage of the TEC determines the heat flow through it. If a CPU has a TDP of say 75 W then to lower its temperature you need to be extracting more power than this. So if you used a 40 W TEC assuming 100% efficient energy transfer then you have 35 W net power entering the loop, heating the water overall. Just the same as having insufficient rad size in a normal loop. An 80 W TEC would also probably be insufficient in this example due to <100% efficiency of the system.

Thus you need a TEC with a larger power than the CPU's TDP, significantly larger if you want the effect to be noticeable due to the heat capacity of the water in the loop. This is why it is usually done with a second loop to cool the high power TEC/TECs, check out the scan Jellyfish if you havent seen it, they do this in that rig.
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Old 26-11-12, 09:55 PM
XionEternum XionEternum is offline
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Originally Posted by Perturabo View Post
If I am thinking about this right the wattage of the TEC determines the heat flow through it. If a CPU has a TDP of say 75 W then to lower its temperature you need to be extracting more power than this. So if you used a 40 W TEC assuming 100% efficient energy transfer then you have 35 W net power entering the loop, heating the water overall. Just the same as having insufficient rad size in a normal loop. An 80 W TEC would also probably be insufficient in this example due to <100% efficiency of the system.

Thus you need a TEC with a larger power than the CPU's TDP, significantly larger if you want the effect to be noticeable due to the heat capacity of the water in the loop. This is why it is usually done with a second loop to cool the high power TEC/TECs, check out the scan Jellyfish if you havent seen it, they do this in that rig.
This is when the cold side is applied directly to the source of heat. It directly counterbalances the heat transfer rate of the TEC and if generating more heat than it can transfer, it looses and even reverses efficiency. I am talking about air cooling a TEC at a wattage that air cooling can handle, but then chilling the water flow on the cold-side. Big thermal dynamic difference if the air cooler can keep the hot-side cool enough to have a delta balanced to about ambient. Example: Ambient is 20c, hot side is 55c and cold side is -15c under optimal heat transfer rates. Since both sides are being hit with an ambient thermal source, it stands to reason that it would act as a chiller, or this sort of thing wouldn't work in fish tanks, yes? :P
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Old 26-11-12, 09:59 PM
XionEternum XionEternum is offline
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Originally Posted by I Hunta x View Post
Just been doing some google work and i found the thread i was referencing, ill PM you it as i dont like linking to other tech forums openly in threads.
Thanks, at least someone understood what I was getting at. :3
Got the message, I just can't reply since I'm new. Damn spammers making good forums set limits!

Edit: Looked it over and based on this information, I'ld like to consider a lower wattage TEC's potential due to a possible imbalance of the delta in this 400watt application. Moreso, because I have an Antec Lanboy Air Red chassis, and the setup I described above would look slick inside it if it works. Doesn't even look like his waterblock is frosting over or generating condensation, which throws in the wildcard that my application may not need condensation protection. Interesting...
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Old 26-11-12, 10:59 PM
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Keep us updated on what you do GL
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Old 27-11-12, 12:19 AM
XionEternum XionEternum is offline
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Originally Posted by I Hunta x View Post
Keep us updated on what you do GL
Oh it'll be a LONG time before I could dedicate this into a full-scale build. 4.5k in system hardware alone, minimum of 3.5k. Then there's the LCS for another 1.2k. (All USD pricing for parts. Going by Newegg for PC parts and FrozenCPU for LCS parts) I was mostly interested in whether or not the thermal dynamics would actually work. And it looks like they do, but will probably have to test different wattage TECs for the perfect balance between chilling and efficiency.
But if/when I do invest in this, I'll be sure to return with an update and pics. Maybe even a video tour of the setup and benchmarks.
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