Liquid cooling baseline testing

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I have a piece of thin aluminum plate (one side of a type of extruded  
aluminum enclosure really, but the edges are not thermally well-coupled  
to the other sides of the box) about 25 cm long by 5 cm wide by 1 mm  
thick, and a 40 mm by 40 mm copper water block thermal epoxied to it.  
The lone cooling block looks rather like this:

<https://imgur.com/a/woLmWnZ

Connected to a copper processor water block thermal pasted to the CPU  
that looks rather like this:

<https://imgur.com/a/7CwLe4t

About 18" total of 3/8" PVC tubing connects everything up to a small  
off-the-shelf water/coolant pump of dimensions about 4" x 3" x 3".

With the CPU idling at around 75 watts dissipation the loop reaches  
thermal equilibrium in a couple minutes, with the pump flailing away at  
2500 RPM, and the CPU temp reported at around 50-51 degrees C/125 F, too  
hot, but better than I was expecting for not much coolant block contact  
area at all, and not hot enough that the processor enters thermal  
shutdown immediately so hey that's something!

There's probably enough data available from this simple setup, along  
with measuring the plate and block temp, to construct a thermal  
resistance model of a somewhat more elaborate system good enough for  
rock and roll.

I think three or four of them distributed strategically around the  
enclosure surface might be enough to keep it cool enough under moderate  
workload to not have to resort to TECs or fancy techniques. Maybe just a  
lil bitty BLDC fan mounted to one side of the final cooling block.

I'm using the "long cure" variant of this brand thermal epoxy:

<https://www.amazon.com/MG-Chemicals-Conductive-Adhesive-Dispeners/dp/B06XDL1NRQ/ref=sr_1_4?ie=UTF8&qid15%38753747&sr=8-4&keywords=thermal+epoxy>

it's pricey, takes about 2-3 days to fully cure but seems to transfer  
heat across an interface amazingly well.

Re: Liquid cooling baseline testing
On 10/05/2018 11:47 AM, bitrex wrote:
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10mm, not 1mm, rather.

Re: Liquid cooling baseline testing
On Friday, October 5, 2018 at 11:47:09 AM UTC-4, bitrex wrote:
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1.4 W/m*K is not all that great, but a thin layer, it won't matter
much.
https://en.wikipedia.org/wiki/Thermal_conductivity#Experimental_values

George H.  
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Re: Liquid cooling baseline testing
On 10/05/2018 01:49 PM, George Herold wrote:
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Another design challenge is where I'm going to find a miniature "No  
Fishing" sign with the right geometry to fit thru the fill port opening  
of the coolant reservoir...


Re: Liquid cooling baseline testing
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Why thermal epoxy and not solder?

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seems unlikely that it would unlikely to outperform metal.

--  
  Notsodium is mined on the banks of denial.

Re: Liquid cooling baseline testing
On 10/05/2018 06:03 PM, Jasen Betts wrote:
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I've hand-soldered a couple small brass parts together with 60/40 to  
make some custom plumbing fittings for this project (regular electronics  
solder and a ~50 watt iron works great for small brass pieces.)

I've brazed some copper pipe before but...basically I don't have any  
experience soldering (welding?) large parts of dissimilar metals like  
that together. The enclosure itself is small, a bit delicate and awkward  
to fit a clamp or clamps into.

Essentially I feel it will probably be a pain in the ass for me to do it  
well on the first try as compared to the epoxy, most likely result is a  
moderately costly screwup. :(

Re: Liquid cooling baseline testing
On 10/05/2018 07:11 PM, bitrex wrote:
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This box is kind of a "labor of love" at this point anyway I'm not  
turning a big profit on it as is sometimes the case when you have  
clients who work in "the arts."

Those copper heatsinks are kinda expensive - copper is expensive!

Re: Liquid cooling baseline testing

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d
  
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soldering aluminium is not quite impossible but close nough

Re: Liquid cooling baseline testing
On Friday, October 5, 2018 at 7:35:40 PM UTC-4, Lasse Langwadt Christensen  
wrote:

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t  
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With the right flux it's easy...  

George H.  

Re: Liquid cooling baseline testing
On 10/05/2018 07:35 PM, Lasse Langwadt Christensen wrote:

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If it matters the chassis is anodized and brushed finished, the interior  
of it as well, it's a very slick surface

Re: Liquid cooling baseline testing
On Friday, October 5, 2018 at 9:14:55 PM UTC-4, bitrex wrote:
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Yes. if you wanted to try solder and Al ya gotta sand off the  
anodization.  Otherwise some thermal grease and squeeze hard.
I've never used thermal epoxy.

George H.

Re: Liquid cooling baseline testing
On 10/5/18 9:23 PM, George Herold wrote:
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Arctic Silver epoxy is pretty good.  Several W/m/K.

Cheers

Phil Hobbs

--  
Dr Philip C D Hobbs
Principal Consultant
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Re: Liquid cooling baseline testing
On Friday, October 5, 2018 at 7:11:35 PM UTC-4, bitrex wrote:
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Huh, well I'm no expert either, but it's mostly a matter of getting  
everything to the right temperature.  For your type of things  
it looks like a hot plate would be a great help.  
Tin both sides, heat and squish together, scrap off excess solder  
that runs out the edges, and let cool.  

As far as screwing up, you've got to get some other pieces to  
practice with first.  A hot plate and propane blow torch.  
If one side breaks it's easier to take apart than epoxy.  
  
George H.  

Re: Liquid cooling baseline testing
On 10/5/18 6:03 PM, Jasen Betts wrote:
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It'll turn into a pretzel due to differential thermal expansion as it cools.

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It doesn't, except from a dimensional stability and residual stress  
point of view.

Cheers

Phil Hobbs


--  
Dr Philip C D Hobbs
Principal Consultant
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Re: Liquid cooling baseline testing
On Saturday, October 6, 2018 at 2:57:33 PM UTC-4, Phil Hobbs wrote:
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Hmm a relatively thick layer of the 'right' TCE alloy.  
I have no idea if such solders exist.  

George H.  
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Re: Liquid cooling baseline testing
On 10/6/18 3:28 PM, George Herold wrote:
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You can indium-solder to anodized aluminum.  Indium is soft enough to  
relieve the thermal stress in many cases.

Some pals of mine made a pretty big splash a decade or so back with  
liquid-metal thermal interface materials (TIMs).  They started out with  
indium-gallium alloy, but due to corrosion problems they eventually  
wound up with thin indium foil with a quilted pattern on it, made with a  
hand-powered rolling mill from India (quite appropriately). ;)

A lot of Apple and IBM servers had their TIMs in them.

Cheers

Phil Hobbs


--  
Dr Philip C D Hobbs
Principal Consultant
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Re: Liquid cooling baseline testing
On 10/08/2018 09:28 AM, Phil Hobbs wrote:
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...and osmium and astatine and radium, And gold and protactinium and  
indium and gallium, And iodine and thorium and thulium and thallium.

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Re: Liquid cooling baseline testing
On 10/8/18 11:53 AM, bitrex wrote:
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"These are the only ones of which the news has come to Hahvahd....And  
there may be many others but they haven't been discavahd."

Tom Lehrer.  One of the greats.

Cheers

Phil Hobbs

--  
Dr Philip C D Hobbs
Principal Consultant
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Re: Liquid cooling baseline testing
"Phil Hobbs"  wrote in message  
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My personal favorite, the great mathematician Lobachevsky:

Plagiarize!  Let nothing evade your eyes!  But please, to call it research  
...

--
Regards,
Carl Ijames  


Re: Liquid cooling baseline testing
On Monday, October 8, 2018 at 6:03:02 PM UTC-4, Carl wrote:
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We need more good comedians these days.  
(Is Joe Rogan any good? I've only watched his podcasts.)

George H.  

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