>so you will always fare better (and usually more environment-friendly) with air cooling.
Sorry but this is not true. One of the key drivers of liquid cooling IS efficiency. Liquids are for more effective at heat transfer than air. Additionally, a liquid can carry a lot more heat. Yes, you can run higher density, you can also indirectly free cool servers year-round, even in tropical climates.
You are both right and wrong, because you (and I) are not clearly distinguishing between different kinds of efficiency and effectiveness.
Liquid cooling is, without question, more /effective/. It makes things cooler, it has a far higher capacity for heat transport.
However, with /efficiency/, you do weigh the results against the effort put in: A solution is more efficient if the quotient result/effort is higher. However, in case of cooling, there are two ways to measure effort: energy expended or money expended. In the case of energy efficiency, yes, liquid cooling is better, because of the aforementioned higher effectiveness of heat transport, lesser energy expenses for pumps/fans and easier energy reuse. However, financially, all that liquid handling, custom piping, pumping, coolant, etc. is by far more expensive than a few air ducts and fans. Even with air-air heat pumps, air cooling is still less expensive, so better financial efficiency. That's why everybody is doing it as a default atm.
The problem with liquid cooling, ultimately, is you're still dumping to air. You're actually doing not much more with liquid cooling than just changing where the heat concentration is located.
Unless your radiator is outside of the building itself, you're dumping that waste heat right back into the system over time.
>The problem with liquid cooling, ultimately, is you're still dumping to air.
There's a lot of things you can do outside of a server chassis that you cannot do inside of a chassis. You can have heat exchangers with far more surface area than what you are volume constrained to inside of a chassis. You can run evaporative cooling towers. If you're in the right climate, you can even radiate that heat to space.
>You're actually doing not much more with liquid cooling than just changing where the heat concentration is located.
You're using a more efficient heat transfer medium which does a lot of things for you. You can downsize your chiller tonnage, reduce/eliminate CRAC/CRAH units, and all the UPS required to keep those systems running. All of this translates to CAPEX and OPEX savings.
>Unless your radiator is outside of the building itself, you're dumping that waste heat right back into the system over time.
No one is suggesting that you can plonk some servers into a tank of liquid and the thermal energy magically disappears. Of course, there has to be a thermodynamic "sink" that you are dumping to... the atmosphere, the ocean, the ground, space, etc. Liquid cooling is more efficient means of transferring heat from source to sink.
You use a liquid to transport the heat from denser compute (lowering costs), then run it through a high efficiency radiator (eg, drip/spray towers like with industrial AC). Your compute is denser and your interface with the air is more efficient.
>so you will always fare better (and usually more environment-friendly) with air cooling.
Sorry but this is not true. One of the key drivers of liquid cooling IS efficiency. Liquids are for more effective at heat transfer than air. Additionally, a liquid can carry a lot more heat. Yes, you can run higher density, you can also indirectly free cool servers year-round, even in tropical climates.