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Radeon 7990 Custom super cooler

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ZytheEKS

Registered
Joined
Dec 30, 2012
I'm posting this thread because I want suggestions/recommendations on my design.

So I'm going to be getting a 7990, and so far all the waterblocks I've seen are complete crap. I have found some that work really well, but I HATE how they look and seeing as how I have a mostly clear DIY chassis I don't want it looking like scat so I'm going to be making a custom waterblock and I figure if I'm going to be putting in the effort to make a custom full coverage block why not go overkill with a super cooler.


So here's the idea I'll get something like this with peltiers mounted on both sides
http://www.shop.customthermoelectri...87D55D979F715B024CF89EAF114B16C7.qscstrfrnt06

Have it configured so that one peltier sits with the cold side on the GPU and the other peltier sits with the cold side pulling heat from the fluid in the waterblock

Then mount that on both GPU's, then use a vacuum bag and seal it flush with the card. Then cast the mold in a ceramic, then use basic casting stuffs to reverse the mold. Then run copper tubing along all the rest of the card. Then put that tubing in the mold and smelt some copper so I have a full coverage block.

Then a chamber outside the full coverage pipes and outside the GPU blocks that would be encased in a clear acrylic chamber for visual effects.

I would have the entire block with only 1 in barb and 1 out barb. The water would flow in the following sequence

in barb -> full coverage copper tubing -> GPU #1 block -> GPU #2 block -> freeflow acrylic chamber -> out barb

I'm have various ideas for heatsinks for the second peltier set that pulls heat from the liquid, so don't assume I have overlooked that. I have not, I just haven't decided if I want to use a second set of liquid cooling for that, or if I don't to use fans, or most likely I will have a passive heatsink for it




ANY IDEA ;D
 
Wait, so you have a GPU cooled by a pelt cooled by a waterblock cooled by another pelt?

I get the first pelt, gives you awesome GPU temps. But I don't get the purpose of the 2nd pelt, that would give you better water temps, but do those even matter given that you have good GPU temps from the first set? They seem to provide no benefit and just increase the inefficiency/total heat you have to disperse. Why not just have a pelt on each GPU, and make a custom block out copper/acrylic to cool those and be done with it?
 
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don't forget the 2nd water chamber/waterloop cooling the 2nd peltier... he's got a 7990... which has 2 7970 cores on the card itself.

So he's planning on making a custom water loop which is really just system for cooling the peltiers he'll slap onto the two cpus... (2 blocks & 2 peltiers -> 2 cpus on one loop)... then he's building a custom water-chamber on the back of the gpu... he'll stick a 2nd peltier on the other side of the block to counteract the heat from the 1st peltier and submerge that side in the custom water-chamber, which i assume will then be part of it's own loop, separate from the water in the loop cooling the gpus...

several technical issues come to mind.

1) full copper tubing for the ingress would expose the incomeing water to the heated peltier cooling loop water. which would result in warming that loop prior to hitting the gpu.
2) peltiers put out something silly like 2 to 3 times the heat on their backside then one's frontside can cool. which means IF your backside peltiers CAN cool the water in the block enough to counter the extreme heat from the chipside peltier, the backside peltier will likely be putting out 4 to 6 times the heat energy the CHIPSIDE peltier is "cooling"...

sounds like you'll need a boatload of rad to cool that backside acrylic water loop
 
I just don't get the point of the peltier on the back side. Two pelts and two blocks for two GPUs...that just seems simpler, same performance, and less overall heat to cool. He could even just stick a custom giant single block to cool both pelts (one on each GPU). Why more than two pelts are advantageous, I don't understand.
 
Knufire you make a good point, but the point of having that second peltier is so that the waterblock won't put out immense amounts of heat for my rads. The second peltier would not be submerged as azanimefan thought, it would have a passive cooler. Maybe an aircooler, not sure on that yet.

After reviewing your posts I think it would make more sense to put

in barb -> GPU #1 block -> GPU #2 block ->f ull coverage copper tubing -> freeflow acrylic chamber -> out barb


The freeflow acrylic chamber serves absolutely no significant purpose. It is for aesthetic purposes only ( I will probably add a temp probe and a flow rate sensor too, but it still doesn't serve any cooling purposes)

Basically after the cooling block has done it's job the fluid exits into a chamber, then the chamber has the fluid exit the system at the other end of the acrylic chamber.

Again, the acrylic part is mainly just for show.



The second peltier is crucial to this setup otherwise I will need probably another radiator to let this block work properly. Peltiers put out a LOT of heat, that second peltier is so that the heat from the first peltier is mostly removed from the water BEFORE it exists the waterblock and goes to the rest of my system
 
The physics just doesn't make sense here.

Say one GPU on the thing is 175W. Assuming the peltier is 50% efficient, that's 350W the 2nd peltier has to remove from the liquid. That means the hot side on the 2nd pelt is like 700W. You're going to passively cool 700W?

Those are nice numbers too, because a 7970 is like a 230-250W chip and pelts are potentially less efficient than 50%. You have an outright massive amount of heat off the 2nd pelt that needs some serious cooling.
 
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Knufire you make a good point, but the point of having that second peltier is so that the waterblock won't put out immense amounts of heat for my rads. The second peltier would not be submerged as azanimefan thought, it would have a passive cooler. Maybe an aircooler, not sure on that yet.

After reviewing your posts I think it would make more sense to put

in barb -> GPU #1 block -> GPU #2 block ->f ull coverage copper tubing -> freeflow acrylic chamber -> out barb


The freeflow acrylic chamber serves absolutely no significant purpose. It is for aesthetic purposes only ( I will probably add a temp probe and a flow rate sensor too, but it still doesn't serve any cooling purposes)

Basically after the cooling block has done it's job the fluid exits into a chamber, then the chamber has the fluid exit the system at the other end of the acrylic chamber.

Again, the acrylic part is mainly just for show.



The second peltier is crucial to this setup otherwise I will need probably another radiator to let this block work properly. Peltiers put out a LOT of heat, that second peltier is so that the heat from the first peltier is mostly removed from the water BEFORE it exists the waterblock and goes to the rest of my system
 
mmm... no... knufire's point is valid. its what i was saying. there is gonna be way too much heat energy to deal with passively or otherwise.
 
Water will be flowing through the block in-between the two TEC blocks.

My fear here is that if I remove the second TEC the GPUs and TEC will put out to much heat for a single loop, and I'll end up having to run in an additional loop. And the second additional peltier won't have the full load of the GPU and peltier, there will be liquid flowing through it. So the passive heatsink wouldn't be cooling anywhere near the roughly 500watts of a peltier+GPU

It cools the liquid flowing through the block so I can keep this all in a single contained device, instead of running in multiple loops.
As you said, 400-500watts is a lot of heat and having a single loop cooling 2 of these, not gunna happen.

As whether a passive heatsink can hand a single peltier cooling the water while it's flowing I guess that will have to be a trail and error process, if not I'll make a fan based heatsink for it/them.
 
Each TEC needs be about 2x the wattage of the heat you want to transfer.
So at stock with your 250w GPU core you're going to need a 400-500w TEC.
That means that the hot side of the TEC needs 650-750w of cooling, the wattage spec of a TEC is how much power it draws.
TEC's don't destroy heat, they only move it, and add their own to it.

Between the two cores and the TEC for each core you're looking at 1400w-1500w of heat your poor loop is going to need to get rid of.

That, of course, assumes that you can find a 400+ watt TEC. You'll need a special 24 V PSU for them, too.

TECs cooling water typically slowly freeze the water and plug the waterblock up.


Bottom line: TECs really don't work for high wattage chips.
 
=.= Damn, didn't think about the possibility of water freezing over the second TEC block. Damn, that would definitely cause immediate issues.

Will have to rethink the rig I guess
 
I don't think you understand how much heat would be coming off the 2nd TEC in this scenario. A trial and error process is almost certainly going to cause you to fry the chip. You would need a heatsink the size of your entire case, and that was with my nice numbers. With the numbers Bobnova posted (which I would trust to be more accurate), that's the amount of heat a small portable room heater would put out.
 
You're assuming the second peltier would be pulling anywhere near the amount of even the chip. I have a pretty wicked rad setup on my cooling loop.
Again, that second peltier + passive heatsink is meant to cool the liquid... just the liquid, not the chip.


In reality if I just rigged my loop in with 3 separate inputs/outputs on that rig with only 2 peltiers (one per GPU) I would be able to easily run it... But again, having 3 cables going in and 3 coming out would look pretty gnarr

Going to have to rethink this all, hopefully I'll be able to get some idea together for it =/
 
The second TEC will be dissipating its heat plus as much as it can of the water's heat. Remember that "heat" is all relative to absolute zero, not to room temperature. There is plenty of heat for a TEC to transfer even if the cold side is already well below freezing.
 
You're assuming the second peltier would be pulling anywhere near the amount of even the chip. I have a pretty wicked rad setup on my cooling loop.
Again, that second peltier + passive heatsink is meant to cool the liquid... just the liquid, not the chip.


In reality if I just rigged my loop in with 3 separate inputs/outputs on that rig with only 2 peltiers (one per GPU) I would be able to easily run it... But again, having 3 cables going in and 3 coming out would look pretty gnarr

Going to have to rethink this all, hopefully I'll be able to get some idea together for it =/


Hmm, so if I understand this right you're going to use the 2nd Pelt to just cool the liquid ONLY?

What about the heat left from the 2nd pelt cooling that water? Where is it going to go? You're going to use a passive heatsink to cool that? Nope, not possible. I've done TEC/Pelt cooling and there's noway in hell a passive sink is going to remove that much heat. If there was a way, trust me I would know about it.

If you do find a method, let me in on it. Good luck with that. Just be sure to have a fire extinguisher handy.
 
Either a passive heatsink or fan based heatsink. I don't plan to use a super powerful peltier for the second one, it's just to pull enough of the heat out so that I can keep it all in a single loop.
www.shop.customthermoelectric.com/Water-Block-Assembly-162-x-162-x-055-WBA-162-055-CU-01.htm;jsessionid=87D55D979F715B024CF89EAF114B16C7.qscstrfrnt06
Again, 1 peltier has it's cold side lay on the GPU and the hot side on that block, the other peltier has the cold side on the liquid so that the heat from the other peltier is dissipated enough so I can keep the liquid loop in a single loop, instead of having it run in multiple loops for that single device.
Again, after reading all this I know my design is a dud and I'll have to rethink the design.

Going to try and rethink my design so I can keep the peltiers on the GPUs, will get back with a new design when I do.
 
You'll still have 1500w to get rid of if you're sizing the GPU TECs correctly.
A 150w TEC isn't going to make much of a dent in that.

What you need for TEC cooling GPUs is GPUs that draw less than 100w.
 
Bobnova is spot on...
TEC's don't work for more modern gpu's cause of the massive heatloads.
They are nowhere near efficient and introduce a lot of heat to dissipate added to the gpu cores own.
If you want subzero, get a phase change unit or build one. Or get massive peltiers place them over the gpu cores and cool the hot sides with your uber loop. Only way it would work, and it would require a second psu just for the tecs.
 
You know what? **** it, I'm just gunna get an extension plug for the PCI-E and submerge the ****in' card in liquid nitrogen, problem solved (Is joking obviously)
 
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