[Beowulf] bring back 2012?

Prentice Bisbal pbisbal at pppl.gov
Mon Aug 22 07:56:15 PDT 2016

On 08/20/2016 09:52 AM, Stu Midgley wrote:
>>      * try and get a permit to hold large volumes of it in a computer
>>     room
>>      * try and find a computer room that will allow it in
>>      * the above two are mostly due to the low boiling point of the fluid
>     I understand that. That's why they are usually closed systems.  I
>     would like to point out at SC, several booths had open tanks of
>     the stuff on the exhibitors floor. I believe IBM says it's safe,
>     but I wouldn't want to take my chances breathing it in every day.
> Closed systems are almost worst... their is the possibility of 
> explosion (not due to fire, but more the compressed gas explosion).  
> Go and read your local juristrictions's requirements for hazardous 
> materials (which ALL these fluids are classified as).  Being closed 
> doesn't really count for much and may work against you (ie. you may 
> have to prove to the local fire department - people who have NO IDEA 
> what you are doing - that your closed system can handle the pressure 
> of the vapour it is containing).

While the risk of an explosion is a certainly a theoretical possibility, 
In practice, the risk of this is virtually non-existent for a variety of 

With water, the processors and other heat-generating components would 
fail from the heat before the boiling point of water is reached, so 
there would be little to no generation of water vapor that could lead to 
an explosion. Also, any heating/cooling system with water would be 
designed to included an expansion tank to account for the thermal 
expansion and contraction of water. There are millions, if not billions, 
of homes and businesses in existence with hot water heating systems, 
yet, I've never heard of any of them ever exploding.

With Novec and other two-phase systems, the gas phase is compressible, 
meaning it can store energy like a spring, preventing or minimizing the 
case risk of an overpressure situation rupturing the vessel. All that is 
required for this to be used safely is an adequate volume for the gas, 
so that is has excess 'capacity' to be compressed. This simple design is 
what allows 20-pound propane tanks to be used all over America (and 
probably other countries) to fuel gas grills and be left out in direct 
sunlight all summer long, and be stored directly under the 
heat-producing burners.  If those tanks were filled to the top, they 
would explode in those conditions, but but leaving about 1/3 of the tank 
empty, the risk has been virtually eliminated. This was actually a top 
we spent a lot of time discussing in my Chemical Engineering Safety 
class in college.

This also applies to the tanks storing liquid nitrogen, liquid oxygen, 
and other gases/liquid stored well below their boiling point. Tanks of 
these substances can be found throughout the world in industrial and 
laboratory environments, yet explosions caused by them are quite rare. 
When they explode, it's usually because someone who didn't know what 
they were doing overfilled the tank, or the ambient temperature exceeded 
the designed safety margins through some other catastrophic event. 
(structure file, etc).

Finally, all systems where this is a risk would have plenty of safety 
features to prevent this. My gas water heater at home has a simple 
temperature/pressure switch to safely discharge excess 
pressure/temperature event. These are cheap, readily available items 
that you can buy at any local hardware store. I also have a steam heat 
system in my house. In the early days of steam heat, it was not unheard 
for a steam boiler to explode with devastating results, but just to some 
simple design elements (Hartford Loop) and basic mechanisms (low water 
cut-off valve, pressure relief valves) have virtually eliminated this risk.

Before I got in to HPC as a profession, I was a process control systems 
engineer. My companies specialty was control systems for boilers for 
power generation. The pressures of these systems were much higher than 
what we're talking about here. Our systems had plenty of pressure 
sensors, release valves and failsafes. Incorporating any of these safety 
elements into a cooling system like this is trivial, and I'm sure the 
vendors who sell such solutions have already done that where appropriate
> Novec is a common fluid used in fire suppression systems in computer 
> rooms... so you shouldn't have too much of an issue with the 
> flammability of the fluid, but it is an entirely different issue to 
> get them to warrant the solution.
If it's already used in fire suppressions systems, where it's going to 
deliberately be sprayed into the atmosphere, I don't see how a system 
where it's designed to be completely contained would more of a safety 
issue, but this could be a local practice issue (USA vs. Australia laws, 
etc.) In the event of an emergency venting, as stated above, the vents 
are hooked up to exhaust piping so that that gases released are piped 
away to a location to where it can be safely released to the 
environment, so a venting event would pose no risk to the occupants of 
the data center. This is done all the time at chemical plants. In fact, 
venting like this happens quite regularly in those environments, but I 
honestly don't even see this type of venting being needed in a system 
like this.
> Perhaps the final nail in the coffin of the Novec solutions... it has 
> been on many different booths at SC for many years... now go and try 
> to find a vendor that will actually sell you a solution...

I guess you never stopped by the Icetope booth at SC, then. They've had 
solutions on the market for several years now, and have had booths at SC 
for several years now, too.

> -- 
> Dr Stuart Midgley
> sdm900 at sdm900.com <mailto:sdm900 at sdm900.com>

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