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Xenocrates · ‎12-15-2014

I've heard/seen some amazing stuff coming out of the forums, while i've been lurking here. I've also been browsing a few other sites, and found 3M's Novec, which says it's pump-able down to -120 C. I realize this is above the boiling point of say, liquid nitrogen. But apparently with plain water as the fluid to dump the heat to, it can manage a density of about 1.3 Kw/liter, just using evaporation and condensing on pipe running tapwater. Could it be used as a working fluid in a cryogenic loop, so that you don't need an LN2 pot directly on the boards, and can instead have something like a bucket with a large radiator in it?

I realize it's probably a terrible idea, because if you accidentally dropped the fluid temp too much it would muck it up, and if you couldn't keep the fluid cool enough it would boil away (some variants run at different boiling temps, such as ~30C, ~70C, and ~80C, and i can't figure out which one 3M has made easiest to get) This is purely an exercise in theory, and I'd appreciate any feedback, as far as problems with it. could you manage to use something like a standard watercooling loop to cool everything, allowing you to have it be a more closed case system, while getting at least some of the benefits of cryogenics?

Note: played with LN2, but never for cooling computers. all freezing banana's and making ice-cream so far. so anyone with experience, feel free to just tell me it's dumb. I have no clue, but an idea.

X-ROG · ‎12-15-2014

If your boiling temp is sub-ambient you'll need a sealed system as it'll be a gas at room temp. I think you need to think along the links of a refrigeration system instead, with compressor and evaporator. It's the act of evaporation on the hot CPU that causes the heat to go with it. Look at the old Vapochill's (although I've no idea what fluid they used). Commercial freezer systems are not designed to run against a constant heat source, so you'll need industrial; something from a small freezer van might be compact enough (food for thought).

X-ROG · ‎12-15-2014

Thanks! For the last 40 minutes I've been looking at refrigeration kits on alibaba.. I have work to do!

Xenocrates · ‎12-16-2014

I've a spare fishtank. I'm planning on putting together something in it, and we'll see how well that works. Biggest issue is, the tank i have is spherical, with a relatively small opening. So i'll have to cut it in half to get a motherboard in. But that can also be turned into an aesthetic feature. If you've seen Steamboy, the balls from that are somewhat of the motif i'm thinking of for it. I will take pictures when i get around to building it. Also, good luck Marshall. I hope it goes well. (and please take pictures of whatever crazy thing you end up building.)

X-ROG · ‎12-16-2014

Fishtank - try mineral oil cooling? Linus has sevearl great videos.

Skunk · ‎12-16-2014

The boiling temperature is above room temperature for the Novec applications. The point being to be able to have a dielectric fluid that is evaporated by the hot components on the computer and condensed by ambient air temperature.

http://www.enterprisetech.com/2013/11/24/3m-allied-control-cool-clusters-novec-bubble-bath/ wrote:
The version of Novec that is used to cool datacenter gear is called Novec 649 and it boils at 49 degrees Celsius (120 degrees Fahrenheit). The Novec 7000 series, which is used in military and aviation equipment for cooling, has boiling points that range between 34 and 128 degrees Celsius, and these can also be used for immersive cooling in the datacenter depending on your needs.

For the military applications a little more detail can be found here:

http://www.parker.com/literature/Gas%20Turbine%20Fuel%20Systems%20Division/TMS%20Microsite%20Literat...

Whereas military must operate in high temperature deserts where the ambient must always be cooler than the boiling temperature of the fluid (this is actually slightly cool for the 85C they prefer as a high temperature), you will be better off using one of the cooler boiling temperature fluids and have a lower steady state temperature operation.

Xenocrates · ‎12-17-2014

I thought about mineral oil, the problem is that it will eventually embrittle components, which prevents me from swapping them with such impunity. Although it's better than a water loop, as far as that goes. Also, thank you very much for the links, Skunk. Besides Marshall, while mineral oil is easily available, and tested to work brilliantly with consumer systems, and thus probably better, it's because Novec is harder to get, and mostly not used outside datacenters that I want to play with it. I mean, immersing 4KWs worth of heaters in a liter of the stuff, and having semi-reasonable temperatures out of it (they also had a liter of heat-exchanger and expansion space, totaling 3 liters of total volume) is pretty impressive from what I can tell. It's no LN2 pot, nor can it likely match a well designed and executed closed loop, but for an almost totally passive system, that because of the peculiarities of my home cooling, is free to run, it's pretty spiffy. Besides, it gives me something new to play with (that's my real reason)

Skunk · ‎12-18-2014

One of the biggest issues I see for build a Novec cooled system would be hermetically seal the system so the boiled Novec doesn't escape. Basically, you'd need to run extensions off of all of your I/O and seal around the extension cable (which I'm not sure will guarantee a complete seal; to be certain, you may need to disassemble the port, encase it in epoxy, and seal that to the volumetric boundary of the system).

Xenocrates · ‎12-18-2014

that's one thing i've heard before, but apparently it's not an issue, at least according to 3M's releases. I'll see how bad it is at leaking like that when i assemble an actual system, and if it does terribly, then i can always seal it further. I like to experiment with stuff like this, so if it turns out that it doesn't need sealing, as 3M says in it's marketing, then that takes a large cost in terms of both time and money off of build like this. That's why the idea of Novec appeals, because sealing it all up means it's much harder to work with swapping components.

I'll be hopeful, but I'm not going to toss any of the boards i care about into it, since I've got a nice pile ****ty components, and am too poor to be willing to buy a recent board to test something that has a reasonable chance of ending horribly.

Skunk · ‎12-18-2014

You may want to read through this thread, if you haven't seen it. Some excellent points are made in it.

3M Novec engineered cooling fluid+ LN2?