Least-maintenance cooling liquid

[squirrelsnatch]

Hi

After building many different systems, primarily air-cooled and sometimes with an AIO, I want to venture into the word of custom loops, mainly for high-density homelab 4U server which should run silently.

One thing I couldn't decide yet is the choice of cooling liquid.

I'm aware that alphacool recommends the Tec Protect 2 in most cases:

Alphacool Tec Protect 2 Clear 1000ml

Jede Wasserkühlung benötigt Kühlflüssigkeit für den Wärmetransport. Mit der Alphacool Tec Protect 2 Clear Kühlflüssigkeit erhält man ein Fertiggemisch, das alle notwendigen Zusätze bereits enthält und direkt aus der Flasche verwendet...

www.alphacool.com

However, there are 2 ES-branded liquids:
"Ultra pure water":

Alphacool ES VE-Wasser (Reinstwasser) 5000ml

Das ES VE-Wasser ist ein von Alphacool speziell entwickeltes Indstrie-Reinstwasser für Server und Workstations. Um frei von organischen und anorganischen Stoffen zu sein, wurde das Wasser mittels mehrfacher Filterungen demineralisiert...

www.alphacool.com

"ES Liquid GL50":

Alphacool ES Liquid GL50 (-40°C) 1000ml

Mit dem ES Liquid GL50 bietet Alphacool eine Industriekühlflüssigkeit für leistungsstarke Kühlung an. Aufgrund der Zusammensetzung schützt sie vor Ablagerungen, kann problemlos durch alle Arten von Gummi sowie Kunststoffteile fließen und...

www.alphacool.com

My main goal is to keep everything as maintenance-free as possible, with Copper/Nickel components, TPV (EPDM / PP) hoses and an Eisbaer Pro ES / (probably) VPP755 combo.

Following is a table of my understanding of the different choices:

Type	Pro	Con	Questions
Ultra pure water	+ Optimal thermal performance	- Does not counter-act contamination, i.e. if something enters the system, it can grow without hinderance	- Maintenance intervals?
Tec Protect 2	+ Similar performance to pure water + With biocides + With lubricant for pumps	- ? - In the forums, some reports of "clouds"(?, "grain of salt")	- Maintenance intervals? - Electrical conductivity (short potential?)
ES Liquid GL50	+ Looks toxic, i.e. extremely low maintenance, no growth(?) + According to description "Very good for components, does not attack rubbers"	- Only ~50% of thermal performance compared to water, i.e. more larger rads and more flow(?) required for equivalent cooling? As corrected by Eddy, performance is slightly lower due to high amounts of additives, but negligble in the real world	- Maintenance intervals? - Electrical conductivity (short potential?)

The liquids have different temperature ranges; I do not plan to operate outside "human" conditions, i.e. 0-60° C, so I do not care about the lower temperature range of GL50 (anyways, all components seem to specify a warranted max temperature of 60° C, so I would prefer not to exceed that).

Given the Homelab environment, I expect comparatively frequent modifications with Quick Disconnects, so the system should be able to cope with some biomass being introduced accidentally.

Can you advise which of the liquids is the "best" for such a use case?

Thanks

 

[Eddy]

Only ~50% of thermal performance compared to water, i.e. more larger rads and more flow(?) required for equivalent cooling?

Where did you read that? That is completely false information. ES Liquid GL50 has a worse performance due to the additives, but we are talking here at the end of a server with 2 CPUs and 2 GPUs so let's say 1500W waste heat of 2-3°k difference in water temperature.
For all B2B customers in the server area and also in most other areas, we use GL50 exclusively. Also because this liquid has by far the longest lifetime. However, this cannot be defined exactly, as it depends heavily on the exact area of application, the components used, and so on. But there are systems that run for over 6 years without maintenance.
Tec Protect 2 and other ready-to-use mixtures commonly used for end-user equipment contain few ingredients. Here it can always happen that flocculation occurs. This depends on how well the system has been rinsed, whether it is in sunlight, which components are used with which material mix. GL50 is pumped so full of substances that it kills virtually everything.
In short, if you want to be safe, have no maintenance if possible, go for GL50.

 

[squirrelsnatch]

Where did you read that? That is completely false information.

Oh, sorry, this must be a mistake by me then - I did not want to spread misinformation.
For what it's worth, I derived this by the safety sheet ( https://www.alphacool.com/download/manual/18671_Alphacool_ES_Liquid_GL50_(-40C)_5000ml_SDS.pdf ), according to which the GL50 is 55-60% ethylene glycol, which according to Wikipedia ( https://en.wikipedia.org/wiki/Ethylene_glycol#Coolant_and_heat-transfer_agent ) has a heat capacity of 2474 J/kgK, which is about half of the roughly 4200 J/kgK of water. This is similar to the thermal conductivity, i.e. 0.256 W/mK for ethylene gycol and 0.6 W/mK for water.

However, I have blatantly disregarded that the safety specifications do only specify the hazardous contents, and the rest (probably) is water, so the thermal properties of the mixture should approach at least 75% of the water characteristics, and that there are other effects influencing the real world examples, such that real-world temperatures are not much worse than the other solutions.

For all B2B customers in the server area and also in most other areas, we use GL50 exclusively. Also because this liquid has by far the longest lifetime. However, this cannot be defined exactly, as it depends heavily on the exact area of application, the components used, and so on. But there are systems that run for over 6 years without maintenance.

So is it safe to say that GL50 is essentially superior in all domains? Is there any downside to it (other than the negligably lower cooling potential)?

Thanks for the quick reply, this clears up a lot to me!

 

[Eddy]

We always have the problem with industrial customers that they know the theory and try to calculate values and are always completely wrong in the end because in practice much more plays into it.
In practice, you only have advantages with GL50, as long as you do not dilute it. DO NOT DILUTE UNDER ANY CIRCUMSTANCES. The only disadvantage is only the 1-3k worse cooling performance in practice. But if it fails, the whole system is already set up incorrectly.