[Beowulf] Servers Too Hot? Intel Recommends a Luxurious Oil Bath

Robert G. Brown rgb at phy.duke.edu
Tue Sep 4 13:50:35 PDT 2012

On Tue, 4 Sep 2012, Lux, Jim (337C) wrote:

> Hydrogen is cheaper than He and works even better.  Just make sure you don't have any air leaks in (i.e. keep a bit of positive pressure).  For the "server farm in a container" model, this would work just fine.. leaks would just float up into the atmosphere.
> @ 300K
> Air 26.2 mW/m*K
> He 156.7
> H2 186.9  !!!
> Ar  17.9
> CH4 34.1

Yeah, and be sure to label the cluster "The Hindenberg", because the day
the power fails, the hydrogen leaks into the server room with the AC
off, the power comes back on and there is an itty-bitty arc in the
server room air as the circuit breakers close or somebody turns on the
lights will be a -- very, very briefly -- memorable one.

It's sort of like gasoline -- might be a great coolant, but I'll never,
ever find out because it is so damn exothermic... which is a good reason
not to use oil (a.k.a. "diesel fuel") as well (depending on the oil).

Arrrgh!  Here I am PARTICIPATING when I'm supposed to be LURKING because
I'm so damn busy... sigh.

> He also is hard to come by..

You mean harder than entering "helium for sale" into Google and choosing
from a gazillion choices at roughly $2/cubic foot full retail in small
quantities (much cheaper in larger quantities)?  It's actually much
more difficult to buy hydrogen gas.  OTOH, you can buy a generator for
H_2 for a few hundred dollars now, thanks to the fuel cell car industry.

Seriously though, I'm not sure I like any of the non-air-cooled
alternatives.  Air has these enormous advantages.  Non-explosive,
non-flammable, non-asphyxiating, not terribly corrosive, very, very
cheap and readily available, easily moved with over the counter fans
designed for the purpose, easily chilled with over the counter AC units
designed for the purpose, through units designed with the express
purpose of channeling the air so that it functions as an adequately
efficient coolant.

Going to ANYTHING else means more money, custom hardware, and a whole
set of headaches.  Who needs headaches?


> Jim Lux
> -----Original Message-----
> From: Robert G. Brown [mailto:rgb at phy.duke.edu]
> Sent: Tuesday, September 04, 2012 6:16 AM
> To: Lux, Jim (337C)
> Cc: Eugen Leitl; beowulf at beowulf.org
> Subject: Re: [Beowulf] Servers Too Hot? Intel Recommends a Luxurious Oil Bath
> 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:rgb at phy.duke.edu

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:rgb at phy.duke.edu

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