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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">True enough.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Ebullient cooling does have some challenges – you can form vapor films, which are good insulators, but if you get the system working right, nothing beats phase
changes for a heat transfer. <o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">I’m aware of high power vacuum tubes using ebullient cooling. I’ve seen demonstrations for electronics cooling using it, but I don’t know of any “production”
applications.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">I’m always skeptical of “first customer” testimonials… (viz ebullientcooling.com)<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">There are some studies out there of experimental systems (NREL did one, Minnesota did one, but I think both of those were full immersion)<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Jim Lux<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">(818)354-2075 (office)<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">(818)395-2714 (cell)<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:windowtext">From:</span></b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:windowtext"> Beowulf [mailto:beowulf-bounces@beowulf.org]
<b>On Behalf Of </b>Prentice Bisbal via Beowulf<br>
<b>Sent:</b> Tuesday, November 06, 2018 8:17 AM<br>
<b>To:</b> beowulf@beowulf.org<br>
<b>Subject:</b> Re: [Beowulf] More about those underwater data centers<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">. 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.<o:p></o:p></p>
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<p>I think everyone on this list already knows I'm no fan of mineral oil immersion (It just seems to messy to me. Sorry, Stu), but immersion cooling with other liquids, such as 3M Novec engineered fluid addresses a lot of your concerns. It as a low boiling
point, not much above room temperature, and it was originally meant to be an electronic parts cleaner (according to a 3M rep at the 3M booth at SC a few years ago, so if you pull a component out of it, it dries very quickly and should be immaculately clean.
<o:p></o:p></p>
<p>The low boiling point is an excellent feature for heat transfer, too, since it boils from the heat of the processor (ebullient cooling). This change of state absorbs a lot of energy, making it very effective at transferring heat away from the processor.
The vapor can then rise and condense on a heat exchanger with a chilled water heat exchanger, where it again transfers a lot of heat through a change of state.
<o:p></o:p></p>
<pre>Prentice <o:p></o:p></pre>
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<p class="MsoNormal">On 11/05/2018 06:30 PM, Stu Midgley wrote:<o:p></o:p></p>
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<p class="MsoNormal">I refute both these claims.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">You DO want to run your boards immersed in coolant. It works wonderfully well, is easy to live with, servicing is easy... and saves you almost 1/2 your power bill.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">People are scared of immersion cooling, but it isn't that difficult to live with. Some things are harder but other things are way easier. In total, it balances out.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Also, given the greater reliability of components you get, you do less servicing.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">If you haven't lived with it, you really have no idea what you are missing.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Serviceability is NOT challenging.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">You really do NOT want to run boards immersed in coolant - yeah, there's folks doing it at HPC scale<br>
<br>
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.<o:p></o:p></p>
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<p class="MsoNormal">-- <o:p></o:p></p>
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<p class="MsoNormal">Dr Stuart Midgley<br>
<a href="mailto:sdm900@gmail.com" target="_blank">sdm900@gmail.com</a><o:p></o:p></p>
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<pre>_______________________________________________<o:p></o:p></pre>
<pre>Beowulf mailing list, <a href="mailto:Beowulf@beowulf.org">Beowulf@beowulf.org</a> sponsored by Penguin Computing<o:p></o:p></pre>
<pre>To change your subscription (digest mode or unsubscribe) visit <a href="http://www.beowulf.org/mailman/listinfo/beowulf">http://www.beowulf.org/mailman/listinfo/beowulf</a><o:p></o:p></pre>
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