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Thread: [Hexus] JetCool CPU Waterblocks 10x Better at Heat Transfer Reply to Thread
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  Topic Review (Newest First)
07-17-2019 07:58 AM
azanimefan sketchy, first of all something like that will be under pressure. Not sure I like the idea of increasing the pressure in my waterloops.

secondly they have nothing but fancy graphics on their page with no real world products. This makes it look like a kickstarter or venture capital scam.
07-17-2019 05:32 AM
feznz
Quote: Originally Posted by Asmodian View Post
This is simply not true. In the paper you link they suggest the highest thermal transfer using direct Water Jet Impingement.



Because it was unnecessary and too expensive? Using some decently clean DI water should be fine, the jets do not need to be that small. We probably do not need the super small versions that paper talks about.

Also, is your point that it doesn't work due to thermal transfer or that the jets clog? If it doesn't work in the first place, due to poor thermal transfer, I don't see how the jets clogging is an obstacle.
I was referring to direct liquid to die cooling for those that missed that there is a intermediate plate between die and jets

and yes DI water will work for a time but for jets to be effective they ideally would be around 16 jets per mm* squared and the jets will be small a slight piece of soldering flux, hair, dust or corrosion will block those jets eventually.
Just if it were that great it would have been done by now for such a simple piece of engineering.
07-16-2019 05:37 PM
mouacyk I don't want to imagine what a failure (even temporary) would do to the die...

Instant shut off might save it.
07-16-2019 04:56 PM
opt33 That paper is using uniform heat sim dies as does all experimental testing, hence term uniform heat flux. Modern cpus, like 9900k, have hot spots where heat is concentrated on small sections of the die which decrease the effective surface area dramatically. Which is why you can have a 15-25C gradient just through the die. Copper water blocks or copper IHS spread heat at rapid 400 w/mk to a more uniform temp (intel claimed in past white papers to within 1-2C spread vs up to 10X higher temp spread vs bare die hot spots).

Even if there is a multi-jet design (like the one IBM abandoned 15+ yrs ago even though they milled microchannels in die to deal with hot spots) that can cool a uniform heated sim chip 10-15% better than a 15 year old design waterblock (and maybe as well as a modern waterblock), that would not suffice. It would have to perform multiple times better than a cold plate, because without spreading the heat via copper it will have multiple times lower surface area which will will proportionally lower its effectiveness.

Ill believe it when I see it tested independently on an actual intel cpu dissipating 200+W at load. So far its been 15 years, havent seen it yet.
07-16-2019 02:59 PM
Asmodian
Quote: Originally Posted by feznz View Post
direct die cooling will never work unless you start pumping liquid metal.
The is a reason for an IHS (integrated heat spreader)is there, the thermal conductivity simply is not enough for any known liquid feasible to transfer the heat directly off the die.
This is simply not true. In the paper you link they suggest the highest thermal transfer using direct Water Jet Impingement.

Quote: Originally Posted by feznz View Post
But if this was a great idea not too sure why when it was first talked about 15 years ago it isn't mainstream now I think the biggest obstacle was the jets becoming blocked with foreign matter.
http://www.electronics-cooling.com/2...ir-and-beyond/
Because it was unnecessary and too expensive? Using some decently clean DI water should be fine, the jets do not need to be that small. We probably do not need the super small versions that paper talks about.

Also, is your point that it doesn't work due to thermal transfer or that the jets clog? If it doesn't work in the first place, due to poor thermal transfer, I don't see how the jets clogging is an obstacle.
07-16-2019 06:22 AM
feznz https://www.overclock.net/forum/134-...r-cooling.html

direct die cooling will never work unless you start pumping liquid metal.
The is a reason for an IHS (integrated heat spreader)is there, the thermal conductivity simply is not enough for any known liquid feasible to transfer the heat directly off the die.
The solution the put a slab of copper to spread the head over a larger area to transfer the heat to and because excluding silver it ranks higher thermal conductive charts of compounds and elements.

But if this was a great idea not too sure why when it was first talked about 15 years ago it isn't mainstream now I think the biggest obstacle was the jets becoming blocked with foreign matter.
http://www.electronics-cooling.com/2...ir-and-beyond/
07-15-2019 10:01 PM
Lord Xeb I just see marketing ****. Lets see if it is true when someone actually tests it.
07-14-2019 05:56 PM
Andrew LB
Quote: Originally Posted by Asmodian View Post
Air has very little thermal mass to heat up and has a low heat capacity per mass, so it is incapable of absorbing much heat energy. Water is much better at absorbing heat and jetting it into the back of the core allows it to absorb the heat directly, not needing to transfer it. This is why the jets are important in all water blocks.

depends on how much air we're talking about. Ive got a 160psi air compressor in my garage and using the blow gun can cool two freshly welded (with a Mig) pieces of 1/8" steel from a few thousand degrees celcius to cool to the touch in seconds. I can't imagine how noisy air jets would be. Would make Delta or San Ace fans seem quiet.



07-14-2019 04:13 PM
opt33
Quote: Originally Posted by Asmodian View Post
You seem to only be thinking of water and air as static thermal transfer materials. This is wrong.
No. Its called sarcasm. Ive tested different waterblocks for 20 years in some reviews, with and without jet plates, im well aware of the effects of jet plates.

What Im thinking is that even if you maximize flow and turbulence such that any water molecule that has absorbed any heat is instantly replaced with one that has not....water with its low thermal conductance still requires adequate surface area for a given power density.
07-14-2019 02:47 PM
Asmodian
Quote: Originally Posted by opt33 View Post
Im sure air at 0.024 W/mk thermal conductance doesnt need much surface area just like water at 0.6 w/mk doesnt need much surface area when cooling hot spots on die. Traditional thinking of a large copper air cooler spreading heat instantly at 400 w/mk to 1000's times surface area via fins before attempting to transfer heat at a very slow pace of 0.024 W/mk for air... that is all nonsense, just like waterpins/channels doing same for waterblocks is all nonsense.
You seem to only be thinking of water and air as static thermal transfer materials. This is wrong. You are not using the water to transfer heat to something else, you are heating up the water directly. If you tried to simply cool the CPU with a static water bath it would not work very well (convection would allow it to work much better than the 0.6 W/mK would suggest, but still not very good).

Air has very little thermal mass to heat up and has a low heat capacity per mass, so it is incapable of absorbing much heat energy. Water is much better at absorbing heat and jetting it into the back of the core allows it to absorb the heat directly, not needing to transfer it. This is why the jets are important in all water blocks.

Per volume air has about 0.0153% of the ability to absorb heat compared to water. Or stated another way, compared to air the same volume of water will absorb ~6500x as much energy when heating up one degree.

Quote: Originally Posted by prjindigo View Post
The truth is that even jets against the cooling plate don't work well because of turbulence and effect, once the jet leaves the aperture there's no guarantee of laminar flow and it just becomes a mess of cooled water mixing with hot water and all of it flowing sideways out of the system.
This is ideal, turbulence is desired to transfer as much thermal energy to the water as possible. Laminar flow requires a much higher surface area for the same energy transfer due to the boundary effect and the low thermal conductance of water.

Test is some time. If you hold your hand in a stream of cold water and compare how cold it feels when flowing the water along your hand parallel to the stream or with it impacting your hand directly, perpendicular to the stream. Especially significant (and relevant) when cooling a fresh burn.
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