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<div>Transformer oil isn't all that big a deal.. You buy it in 5 gallon pails, 55 gallon drums, tank truck lots. Runs about $3-4/gallon in large quantities (which is what ALL liquids cost, it seems.. Transportation costs are the dominant component. Sulfuric
acid is pretty much the same price as mineral oil which is pretty much the same price as Jet A, etc.)</div>
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<div>The flash point is well over 100C, as noted, so it's not like you're likely to get that hot in use. It's not like you're running a restaurant kitchen, where they have 10s of liters of similar stuff heated up to 200C or so.</div>
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<div>The problems with oil insulation (aside from messy) is that if you DO get an arc going, it generates hydrogen, which has a peculiarly wide flammability range mixed with air. It also can form a fine mist, which is VERY ignitable. (that's where those nice
spectacular transformer explosion videos come from.. Arc fault, gas pressure builds up, oil sprays, ignites, and fireball 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")</div>
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<div>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.</div>
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<div>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.</div>
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<div>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.</div>
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<span style="font-weight:bold">From: </span>"Peter St. John" <<a href="mailto:peter.st.john@gmail.com">peter.st.john@gmail.com</a>><br>
<span style="font-weight:bold">Date: </span>Tue, 4 Sep 2012 20:35:20 -0400<br>
<span style="font-weight:bold">To: </span>"Robert G. Brown" <<a href="mailto:rgb@phy.duke.edu">rgb@phy.duke.edu</a>><br>
<span style="font-weight:bold">Cc: </span>Jim Lux <<a href="mailto:james.p.lux@jpl.nasa.gov">james.p.lux@jpl.nasa.gov</a>>, "<a href="mailto:beowulf@beowulf.org">beowulf@beowulf.org</a>" <<a href="mailto:beowulf@beowulf.org">beowulf@beowulf.org</a>><br>
<span style="font-weight:bold">Subject: </span>Re: [Beowulf] Servers Too Hot? Intel Recommends a Luxurious Oil Bath<br>
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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 :-)
<div>I just don't feel that power-gamers should be able to get away with anything unavailable to HPC.<br>
<div>Peter<br>
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<div class="gmail_quote">On Tue, Sep 4, 2012 at 9:16 AM, Robert G. Brown <span dir="ltr">
<<a href="mailto:rgb@phy.duke.edu" target="_blank">rgb@phy.duke.edu</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div class="im">On Mon, 3 Sep 2012, Lux, Jim (337C) wrote:<br>
<br>
> I'll bet they have to change it more often than that. This isnt something<br>
> like a pole transformer.<br>
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Absolutely. Think of what you can do with a big vat of hot oil handy in<br>
the workspace. Buffalo Wings. French Fries. Chicken. Fish. The<br>
reason nobody does this is because OSHA prohibits it -- it is a huge<br>
health hazard. Not even Jolt Cola can keep you thin in a sedentary<br>
profession with your own personal deep frier as close as your server<br>
room. Although you do have to change the oil pretty often, as otherwise<br>
shrimp tails and bits of overcooked tempura crust gunk up the memory and<br>
CPU. Systems people were dying like pudgy little flies of advanced<br>
cardiovascular disease before the practice of using computers to heat<br>
deep fat was banned.<br>
<br>
On a more serious note, one wonders why nobody has tried helium instead.<br>
No, silly, not liquid helium, helium gas. The reason they fill windows<br>
with argon is that it has around 2/3 the thermal conductivity of air,<br>
and hence is a better insulator. This, in turn, is because it is more<br>
massive -- conductivity is tightly tied to mass and hence the speed of<br>
the molecules when they have kT sorts of energies.<br>
<br>
Helium, OTOH, has six times the thermal conductivity of air, and is<br>
relatively inexpensive. The biggest downside I can think of is that it<br>
requires a pretty good seal and thick walls to keep the slippery little<br>
atoms from sliding right through to the outside, and of course the fact<br>
that systems techs would always be hitting up the helium tanks so that<br>
they could talk like Donald Duck. And you'd still have to refrigerate<br>
the outside of the systems units. But all of these things are still<br>
orders of magnitude easier than with oil, and even things like cooling<br>
fans work fine in Helium. Maybe there are other problems -- lower heat<br>
capacity to match its higher conductivity -- but it seems like it is<br>
worth an experiment or two...<br>
<br>
rgb<br>
<br>
Robert G. Brown <a href="http://www.phy.duke.edu/~rgb/" target="_blank">http://www.phy.duke.edu/~rgb/</a><br>
Duke University Dept. of Physics, Box 90305<br>
Durham, N.C. 27708-0305<br>
Phone: <a href="tel:1-919-660-2567" value="+19196602567">1-919-660-2567</a> Fax:
<a href="tel:919-660-2525" value="+19196602525">919-660-2525</a> <a href="mailto:email%3Argb@phy.duke.edu">
email:rgb@phy.duke.edu</a><br>
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