On Wed, 5 Sep 2012, Lux, Jim (337C) wrote:
ensues.. (I used to make my living doing fireballs.. A bit of explosive (PETN) to disperse the flammable liquid, a bit of something that burns well (black powder) to ignite it is the usual recipe for the "car falling over a cliff and exploding")
Gawd, some people have all the luck! What a career! Why in the world would you quit doing that to go to work in a boring, plodgy organization like NASA? Oh, wait, they do like to blow things up, don't they...;-)
WW II prompted the development and adoption of Gas Insulated Switchgear in Europe (using SF6). Nothing like dropping an incendiary bomb on an electrical substation full of thousands of liters of oil to get a good fire going. In the US, we still use mostly oil insulation: it's cheaper, and our switchgear tends to be in places where fire isn't as big a deal AND we didn't have to replace it all in the late 40s. Cheap oil and expensive SF6 doesn't hurt either. But when talking cooling substances.. There's an interesting trade between conductivity and viscosity (He and H2 are clear winners.. High conductivity AND low viscosity) and density SF6 is really dense, so on a temperature rise per unit volume basis, it actually does pretty well. BTW, high power turbomachinery (power plant generator driven by steam turbines and such) are often insulated with H2, because the low viscosity reduces windage losses.
Yeah, like that. It is a MIX of considering conductivity, heat capacity, viscosity and related turbulence/reynolds number. Prototyping justified, instant adoption not so much until after the prototype and perhaps a bit of -- dare I say it -- engineering and CBA? rgb
From: "Peter St. John" <[email protected]> Date: Tue, 4 Sep 2012 20:35:20 -0400 To: "Robert G. Brown" <[email protected]> Cc: Jim Lux <[email protected]>, "[email protected]" <[email protected]> Subject: Re: [Beowulf] Servers Too Hot? Intel Recommends a Luxurious Oil Bath Wiki tells me that the flash point of Transformer Oil (a type of mineral oil) is 140 C; does that sound safe in a server room? I'm a worse chemist than I am a physicist so I can't tell if you're serious about OSHA not liking mineral oil in server rooms (I'm **pretty** sure you're not serious about frying chicken in the cpu box :-) I just don't feel that power-gamers should be able to get away with anything unavailable to HPC. Peter On Tue, Sep 4, 2012 at 9:16 AM, Robert G. Brown <[email protected]> wrote: On Mon, 3 Sep 2012, Lux, Jim (337C) wrote: > I'll bet they have to change it more often than that. This isnt something > like a pole transformer. Absolutely. Think of what you can do with a big vat of hot oil handy in the workspace. Buffalo Wings. French Fries. Chicken. Fish. The reason nobody does this is because OSHA prohibits it -- it is a huge health hazard. Not even Jolt Cola can keep you thin in a sedentary profession with your own personal deep frier as close as your server room. Although you do have to change the oil pretty often, as otherwise shrimp tails and bits of overcooked tempura crust gunk up the memory and CPU. Systems people were dying like pudgy little flies of advanced cardiovascular disease before the practice of using computers to heat deep fat was banned. On a more serious note, one wonders why nobody has tried helium instead. No, silly, not liquid helium, helium gas. The reason they fill windows with argon is that it has around 2/3 the thermal conductivity of air, and hence is a better insulator. This, in turn, is because it is more massive -- conductivity is tightly tied to mass and hence the speed of the molecules when they have kT sorts of energies. Helium, OTOH, has six times the thermal conductivity of air, and is relatively inexpensive. The biggest downside I can think of is that it requires a pretty good seal and thick walls to keep the slippery little atoms from sliding right through to the outside, and of course the fact that systems techs would always be hitting up the helium tanks so that they could talk like Donald Duck. And you'd still have to refrigerate the outside of the systems units. But all of these things are still orders of magnitude easier than with oil, and even things like cooling fans work fine in Helium. Maybe there are other problems -- lower heat capacity to match its higher conductivity -- but it seems like it is worth an experiment or two... rgb Robert G. Brown http://www.phy.duke.edu/~rgb/ Duke University Dept. of Physics, Box 90305 Durham, N.C. 27708-0305 Phone: 1-919-660-2567 Fax: 919-660-2525 email:[email protected] _______________________________________________ Beowulf mailing list, [email protected] sponsored by Penguin Computing To change your subscription (digest mode or unsubscribe) visit http://www.beowulf.org/mailman/listinfo/beowulf
Robert G. Brown http://www.phy.duke.edu/~rgb/ Duke University Dept. of Physics, Box 90305 Durham, N.C. 27708-0305 Phone: 1-919-660-2567 Fax: 919-660-2525 email:[email protected]
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