[paulmd]

water cooling isn't really that much more efficient than giant air coolers.

at the end of the day, dissipating heat is a function of the radiator fin area and air movement, the water is just a working fluid to move the heat to the radiator fins. Apart from having more thermal mass (takes longer to heat up/cool down) it isn't inherently more efficient than a heatpipe. It's water moving the heat either way, and in some ways the heatpipe is actually more efficient (evaporation moves more heat than raising the temperature of the water a few degrees).

People don't realize it, but a D15 (dual tower cooler, a bit bigger than your U12S) is about on par with a 240mm or 280mm AIO. A 120mm or 140mm AIO is worse than your U12S.

[m463]

I always thought water cooling was about noise.

You could move the heat to a giant radiator, which could have a giant fan. The bigger fan would move exponentially more air with exponentially less noise.

Meanwhile air cooling seems to require a lot more engineering, and you end up with something that looks like an oil refinery in the center of your motherboard.

[paulmd]

It comes down to how much surface area your cooler has (whether that's radiator or a cooler tower) and how much air is moving over it.

There is no magic about a water cooler that reduces noise. It is a thermodynamically determined process. The fin stack has a certain temperature, there is a certain amount of surface area, and a certain amount of air moving over it (at a certain temperature). A radiator really gives you no significant advantage in any of those areas. In fact a lot of radiators actually have less surface area than some of the really big air coolers like NH-D15. They are only maybe a couple centimeters thick, the D15 is about the same size as a 140mm cooler but the fins are four times as thick.

On top of that you have pump noise. An expensive custom loop with a nice quiet pump can reduce that significantly, but AIOs in particular are just never going to be quiet because of the pump. The "pump" on an air cooler is evaporation itself - the working fluid vaporizes on the coldplate (and cools it) and then condenses on the cooler part of the heatplate where the fins are cooling it. This is basically a "silent pump".

The best you can say about a radiator is that (a) by putting it on an intake you can guarantee that the air it's sucking is slightly cooler rather than being warmed by the ambient heat of the case, albeit with the downside that you are now pumping hot air over your other components, and (b) you can put the radiator in a more convenient location than sticking straight out of your motherboard.

(you can of course skip fans entirely! check out the HDPlex H5, it is a cool case where the entire thing is a heatsink, it uses heatpipes to move the heat to the chassis and the chassis itself is finned for dissipation. I have no imminent need for it but I lust for it anyway, it's just so damn cool. https://hdplex.com/hdplex-h5-fanless-computer-case.html )

[cjbprime]

Or for an even prettier one, Streacom DB4!

https://fabiensanglard.net/the_beautiful_machine/index.html

[Retric]

Your working from an overly simplistic model of cooling. The delta between the fin temperature and CPU temperature makes a huge difference in cooling efficiency. Two sets of fins may be moving the same amount of heat, but the CPU’s are at different temperatures due to differences in plumbing. Also, the way your working fluid flows through a radiator is a big deal, ideally you want the coldest part of the radiator on a return loop rather than heating the fluid as it’s passed to the CPU block.

Now, sure under ideal conditions and stock settings it’s not a big deal. But, in practice things get tricky.

[ben-schaaf]

This is only partially true. A larger radiator needs a faster/larger pump, leading to more pump noise.

Interestingly most air cooling solutions are really pump-less liquid cooling, as the liquid in the heat pipes is what transfers most of the heat away from the cpu.

[qes]

> Apart from having more thermal mass (takes longer to heat up/cool down)

_Much_ more thermal mass, and takes much longer to heat up and in most set ups will never reach the same temperature as the heatpipes in an air cooler - the waterblock will be cooler at idle and under load. I would think that larger temp delta allows heat to conduct away from the cpu package more quickly.

My 3960X sees 125MHz higher all core full load, almost 100MHz all core average work load, and 50MHz higher single core boost clocks under a custom loop (280+140 rads & Optimus TR3+ block) than under a Noctua NH-U14S TR4-SP3.

[derefr]

> at the end of the day, dissipating heat is a function of the radiator fin area and air movement, the water is just a working fluid to move the heat to the radiator fin

...in a fluid-recycling system (as all consumer PC cooling is.)

Water cooling is a lot more efficient than air cooling, in a fluid exchange system. Like if your HPC data-center is on the ocean, and you can just pump in cold ocean water, "spend" it by heating it up, and then pump the hot water to an outtake far-enough away that it's not heating up your intake water.

(An even-denser fluid would work even better, but we don't have oceans of even-denser fluids laying about.)

[m3at]

You're right, however one advantage of water cooling your cpu –especially for multi gpu builds that are common in ML setup– is that it moves the heat dissipation away from a crowded area.