Direct contact watercooling!

[zeroibis]

This was a surprise! I never thought of cooling the chip directly, just imagine if you got a bad mount though and coolant goes shooting out the sides...

The new system – which further increases efficiency by using a system of jet impingement cooling where the water actually makes direct contact with the surface of the chip – will use a sealed-loop system containing around ten [liters] of water, which will be pumped through the system three times every minute.

http://www.bit-tech.net/news/hardwar...upercomputer/1

[Oberon]

There was a fairly recent thread around here from someone direct-to-die cooling a i7, I think. I'll have to see if I can dig it up.

[millertime359]

Yea, there have been a few trys done on this. I think there are a few threads on here of people trying it.

[madmaxx]

hmmm

direct die has been tried before a few time's IIRC maybe this time they will get it right?

[Bradan]

hmmm

direct die has been tried before a few time's IIRC maybe this time they will get it right?

No. They use 60'c water at 30LPM. They are not looking for ideal temps, just stable ones (under 85c). To the people over here, they are doin' it wrong.

[Erasmus354]

Not sure where Bit-tech got that they were using direct die cooling. IBM simply says they have a watercooling block for each chip and are doing "chip-level" water cooling. Read the actual press release and look at the picture of the blade and it doesn't look like anything special. Doesn't look like direct die cooling to me.

http://www-03.ibm.com/press/us/en/pr...ease/27816.wss
http://www.engadget.com/2009/06/25/w...ts-dorm-rooms/

[3Z3VH]

I thought the consensus was that direct-die wasn't as good because water did not absorb heat as quick as copper, so you need to make the water go insanely fast to make up for it.

Bringing the heat from the die to copper is more efficient than die to water, and allows you to add more surface area to the copper. Once you have more surface area, the water will pick up more heat from it at slower speeds.

[SoulsCollective]

I thought the consensus was that direct-die wasn't as good because water did not absorb heat as quick as copper, so you need to make the water go insanely fast to make up for it.

Bringing the heat from the die to copper is more efficient than die to water, and allows you to add more surface area to the copper. Once you have more surface area, the water will pick up more heat from it at slower speeds.

Exactly. This was confirmed in the i7 tests dones here recently.

[NaeKuh]

I thought the consensus was that direct-die wasn't as good because water did not absorb heat as quick as copper, so you need to make the water go insanely fast to make up for it.

Bringing the heat from the die to copper is more efficient than die to water, and allows you to add more surface area to the copper. Once you have more surface area, the water will pick up more heat from it at slower speeds.

so im lost in this statement.

if water cant pick up the heat from the silicon better then copper, which u are right, i think its because silcon might be paritally hydrophobic... How would increasing flow compensate since water can only pick up a set number of molecules anyhow each pass?

[SoulsCollective]

so im lost in this statement.

if water cant pick up the heat from the silicon better then copper, which u are right, i think its because silcon might be paritally hydrophobic... How would increasing flow compensate since water can only pick up a set number of molecules anyhow each pass?

wut?

[NaeKuh]

wut?

1 water molecule can only pick up a limited amount of heat.

The more molecules which have picked up heat collectively represents how hot the water is.

So how is it when your limited on the pick up side, more flow will help you?

do u understand the bottleneck i am pointing out?

[SoulsCollective]

Ah, you meant heat. You originally said water molecules pick up other molecules, which made me go

Assuming each molecule can pick up a certain amount of heat, taking into account inefficiencies, the more molecules you have impacting the die surface in a given period, the more heat can be removed - thermal transfer efficiency for a set silicon/water molecule pair decreases exponentially over time. Even if silicon wafers are hydrophilic, there isn't some set number of molecules that will be "allowed" to contact the surface - you've just got to overcome additional inefficiencies caused by the repulsion of X water molecules.

Although really, any hydrophilic effect will be miniscule in comparison to the surface-area issue.

[3Z3VH]

Souls explained it well. Water is flowing over the die, so effectively, your surface area is calculated by how much water passes over the surface of the die in a given amount of time... where as with a passive cooled copper block, the surface area is static, because your copper isn't flowing over the die.

So the water will get a much larger surface area, but absorbs water MUCH slower than copper... so if you use copper to get the heat away from the die, then flow water over the copper, you can make the surface of the copper as large as you want, giving the water exponentially more surface area to absorb heat from.

In any given amount of time, to get the same volume of water to transfer over the hot surface area, you will have to have the water moving VERY fast over the die to make up for the raw surface area of water flowing over copper.

[madmaxx]

No.

"no" what? there have quite a few attempt's both by regular people and companies to achieve a feasible direct die cooling solution, so far no dice

higher flow + turbulence can improve the cooling capabilitie's IIRC

[MrToad]

Wouldn't you be able to achieve better results creating a larger chamber over the die and spraying the coolant (thus surrounding the die in "mist") rather than letting it flow over it?

[3Z3VH]

I think, then, you have the issue of "how do you now take the warm mist away in an efficient manner to allow more to be sprayed on ?"

Water is nice because it doesn't expand/contract nearly as much as air when it heats up, so you can run a closed loop without worry of high pressures causing leaks, and because its density gives it a higher capacity for carrying heat away from the block than air.

[MrToad]

I think, then, you have the issue of "how do you now take the warm mist away in an efficient manner to allow more to be sprayed on ?"

Water is nice because it doesn't expand/contract nearly as much as air when it heats up, so you can run a closed loop without worry of high pressures causing leaks, and because its density gives it a higher capacity for carrying heat away from the block than air.

I see your point. Perhaps sprays would be better used in combination with chilled and more dense coolants (like fluorinert cooled with a waterchiller for instance) which is, of course, a completely different ballgame...

[3Z3VH]

Phase Change cooling still scares me.

Too much noise, and power hungry... I just can't bring myself to do it, even if it is great cooling !

[Oberon]

Phase Change cooling still scares me.

Too much noise, and power hungry... I just can't bring myself to do it, even if it is great cooling !

Same here, but I really want to try and piece my own system together just for the heck of it.

[MrToad]

Phase Change cooling still scares me.

Too much noise, and power hungry... I just can't bring myself to do it, even if it is great cooling !

Without going to phase change, I had a good "dwell" on the chilled cooling section.

In the end of the day it does offer advantages over liquid cooling, and with the wonga I've spent on the stuff, I could probably have bought half decent kit...

Then I saw the power consumption of the water chillers and... ehm...

Not only because of the consumption of the chiller itself, which is grotesque, also because I like to have good 15-20 mins of UPS run... To keep the rig AND the chiller running for 20 mins, the UPS was worth the price of a small flat

[NaeKuh]

Ah, you meant heat. You originally said water molecules pick up other molecules, which made me go

Assuming each molecule can pick up a certain amount of heat, taking into account inefficiencies, the more molecules you have impacting the die surface in a given period, the more heat can be removed - thermal transfer efficiency for a set silicon/water molecule pair decreases exponentially over time. Even if silicon wafers are hydrophilic, there isn't some set number of molecules that will be "allowed" to contact the surface - you've just got to overcome additional inefficiencies caused by the repulsion of X water molecules.

Although really, any hydrophilic effect will be miniscule in comparison to the surface-area issue.

okey your looking at it from the surface impact point aspect of having more flow.

Assume this, your block is a mini reservoir, which is the case of most direct die/ihs blocks.

You wouldnt have a shortage of water molecules picking up heat. Infact you would have too much water that the flow would dump the water b4 it was even 5% utilized.

In short, i think you wouldnt see any scaling of flow after u hit that critcal point like in d-tek blocks with no nozzles.

If we used your example, then all blocks would scale, however this is not the point we see. And martin also showed us that we get hardly no benifit after we pass the 2gpm mark. :P

[SoulsCollective]

You wouldnt have a shortage of water molecules picking up heat. Infact you would have too much water that the flow would dump the water b4 it was even 5% utilized.

In short, i think you wouldnt see any scaling of flow after u hit that critcal point like in d-tek blocks with no nozzles.

Exactly - you're proving the point Talking about 'utilizing' the heat-carrying capacity of water molecules is starting to sound a lot like the old low-flow arguments - shouldn't the water spend more time in the CPU block/rad so it can pick up more heat? Fact is, as long as that water in the block is actually hitting the die (so we're assuming injector design here, not CPU-block-as-mini-reservoir as you put it), while each molecule may pick up less total heat because it isn't in contact with the die for as long, because thermal efficiency decreases exponentially with time, each molecule has a higher heat-pickup-rate-per-time-unit, because we aren't progressing as far down the heat/time efficiency curve. Given that, and that we effectively have an unlimited supply of water molecules, more flow will give you better temps, as you have a higher total rate of heat pickup from the die surface.

If we used your example, then all blocks would scale, however this is not the point we see. And martin also showed us that we get hardly no benifit after we pass the 2gpm mark. :P

They do, and that's only partially true. I'm glad you said "hardly no benefit", because that's completely true - diminishing returns of course apply. But the principle is sound and continues to apply, it's just that our ability to measure the benefits now starts to come into play. You're still getting better temps with more flow (ignoring for the sake of argument pump heat-dump), you just can't tell becaue your measuring instruments aren't sufficiently precise (or accurate, for that matter).

[rge]

Souls explained it well. Water is flowing over the die, so effectively, your surface area is calculated by how much water passes over the surface of the die in a given amount of time... where as with a passive cooled copper block, the surface area is static, because your copper isn't flowing over the die.

So the water will get a much larger surface area, but absorbs water MUCH slower than copper... so if you use copper to get the heat away from the die, then flow water over the copper, you can make the surface of the copper as large as you want, giving the water exponentially more surface area to absorb heat from.

In any given amount of time, to get the same volume of water to transfer over the hot surface area, you will have to have the water moving VERY fast over the die to make up for the raw surface area of water flowing over copper.

+1...which is why passive direct die cooling wont work on i7, I drew a pic back when arguing with someone else ...there is no getting around the very small surface area of die, and .58 W/M*k heat conductance of water is not going to dissipate 180W. I could see IHS/waterblock combo without thermal paste, ie soldered as doing better, but not direct die.

[NaeKuh]

They do, and that's only partially true. I'm glad you said "hardly no benefit", because that's completely true - diminishing returns of course apply. But the principle is sound and continues to apply, it's just that our ability to measure the benefits now starts to come into play. You're still getting better temps with more flow (ignoring for the sake of argument pump heat-dump), you just can't tell becaue your measuring instruments aren't sufficiently precise (or accurate, for that matter).

actually ud be suprised...

lets see if i can get vapor to shed some light.

[PatRaceTin]

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the pic give clear understanding