[zer00eyz]

> cooling is moving the heat completely outside of the building while it’s still liquid.

We have been doing this for decades, it's how refrigerants work.

The part that is new is not having an air-interface in the middle of the cycle.

Water isn't the only material being looked at, mostly because high pressure PtC (Push to Connect) fittings, and monitoring/sensor hardware has evolved. If a coolant is more expensive but leaks don't destroy equipment, and can be quickly isolated then it becomes a cost/accounting question.

[liquidgecka]

> The part that is new is not having an air-interface in the middle of the cycle.

I wasn’t clear when I was writing but this was the point I was trying to make. Heat from the chip is transferred in the same medium all the way from the chip to the exterior chiller without intermediate transfers to a new medium.

[marcosdumay]

The claim is that Google has larger pipes that go all the way out of the building. While mainframes have short pipes that go only to a heat exchanger on the end of the hack.

IMO, it's not a big difference. There are probably many details more noteworthy than this. And yeah, mainframes are that way because the vendor only creates them up to the hack-level, while Google has the "vendor" design the entire datacenter. Supercomputers have had single-vendor datacenters for decades too, and have been using large pipes for a while too.

[cyberax]

Glycol is cheap and safe, but it has lower specific heat capacity and higher viscosity. So that's why water is still being used.

The next step is probably evaporative cooling, with liquid coolant ("freon") pumped to individual racks.

[jabl]

Not sure what Google specifically is using here, but PG25 (25% propylene glycol, 75% water) is somewhat common in data center applications. The glycol takes care of avoiding microbial growth.