[Beowulf] More about those underwater data centers

[Lux, Jim (337K)]

These things don't actually immerse the computers in sea water.. they use the surrounding water as an "infinite cold sink" to dissipate the heat generated by the computers, which operate in air. 

You really do NOT want to run boards immersed in coolant - yeah, there's folks doing it at HPC scale,  but they're typically doing something in a volume constrained environment (trying to get 100s of servers in a single rack) or some other environment: high altitude aircraft, where the air is thin; or a very dusty/dirty environment, where you need a "sealed box".  I designed a small cluster designed to operate in a dusty environment that was basically a "spray cooling" system in an aluminum case.  There was a small pump that picked up the inert fluid, sprayed it everywhere inside the box, including the boards and box sides, providing a simple(ish) thermal transfer between board and external case.  It wasn't great, but at least it cooled the whole boards.  The typical "liquid CPU cooler" only cools that one chip and depends on airflow for the rest, and you can't move enough heat from board to box shell with air.  Maybe helium or hydrogen would work <grin>

Whatever the coolant, it leaks, it oozes, it gets places you don't want it to go. And serviceability is challenging. You need to pull the "wet" boards out, or you need to connect and disconnect fluid connectors, etc.  If you're in an environment where you can manage that (or are forced into it by necessity), then you can do it.

A good "intermediate" scheme is liquid/air heat exchangers in close proximity to the electronics, and I believe that's what the "subsea datacenter" scheme uses. 



Jim Lux
(818)354-2075 (office)
(818)395-2714 (cell)

-----Original Message-----
From: Beowulf [mailto:beowulf-bounces at beowulf.org] On Behalf Of jaquilina at eagleeyet.net
Sent: Sunday, November 04, 2018 10:27 PM
To: Gerald Henriksen <ghenriks at gmail.com>
Cc: beowulf at beowulf.org
Subject: Re: [Beowulf] More about those underwater data centers

Probably a stupid question here,

What is the advantage of using salty sea water lets say over for example mineral oil? I have seen on you tube these guys showing that a pc will still run in a fish tank and all components submerged in mineral oil? 
Yes it will be messier to change components but would the use of mineral oil be more efficient?