Water vs air cooling? Are pre-filled 'nooby' water cooling systems worth it?

I've heard a ton of talk about how people think that stuff like the H60 or h100i water coolings are a waste of money and that good quality air coolers can be just as good. Is this true? I'm probably going to be getting either a good air or one of these water cooling systems when I upgrade my build and I'm really confused.

I was thinking that water is always just completely better, but I really have no idea. So tell me which do you think is better? Why?


Look at Linus's CPU cooler test, disregard result #12 the fans had an issue


Look at the numbers and decide for yourself

And how would those compare to the stock cooling? What would you recommend? How about the hyper 212


Liquid cooling offers you thermal stability, this is because at the rate that the liquid is being circulated, you have to raise the temperature of the entire mass of the liquid before it begins to pose a problem, with the standard air cooled ones, you can get some really crazy low temperatures, but it is much easier to heat up a smaller area of the cooler due to the way that heat naturally is inclined to flow, and the fact that it has to make it up the heat pipes to reach the cooling fins, where as in a liquid cooler the heat exchange plate is the direct connection to the cooling fluid. Not to mention it takes a lot of energy to raise the temperature of a water based substance. This is why water takes so long to boil. Basically, it has the potential to give you really good, stable temperatures, but it is not for everyone. Hell, it isn't even advisable for most people, because unless you are going for overclocking, you wouldn't see any performance improvement over a Hyper 212 Plus. I do however recommend the smallish 120mm all in one units for those looking for a moderate overclock, or who want to ensure that their system is stable, because you can often pick one of these up for less than $60 and it will work pretty well for keeping things cool.

CPU cooling is a complex thing.

Water is a better coolant than air, but that's not really to the point as far as advanced air coolers are concerned, because of several reasons:

- not all water cooling uses water

- most aftermarket and some stock air coolers use fluid coolants

- both water cooling and air cooling systems are basically air cooling systems

A water cooling system is still air cooled, the heat exchange with the air is just deferred by a water or glycol circuit, whereby, like Mndless says, the fluid acts as a heat energy buffer, which means that the more buffer there is, the more heat is buffered in the fluid.

Most pre-filled water cooling systems use water with additives. This is a good idea, because it enhances the cooling capacity of the fluid. However, the only pre-filled cooling system that uses a high concentration of glycol additive is the Swiftech unit, therefore it will perform much better, because glycol evaporates much quicker than water, therefore dissipating the heat energy much more efficiently, because a CPU in normal operating conditions doesn't emit enough thermal energy anymore these days for pure water to be an efficient coolant. A coolant is most efficient when it is brought to cook, because then the molecules of the coolant will stock the most heat energy, heat energy that is drawn from the baseplate. If the coolant is cooking (that means being in gaseous form in normal atmospheric circumstances), it will also dissipate the heat energy far more rapidly than when it's not cooking (e.g. boiling water put in the freezer freezes over in seconds to a few minutes depending on the volume, while water at 4°C put in the freezer will take a long time to freeze).

Air coolers like the Intel stock cooler don't use fluids, but the Cooler Master made stock AMD cooler and most aftermarket coolers do. This fluid, which is found in the heatpipes, is mostly ammonia or some other fluid that evaporates really quickly. The way this works is that the fluid evaporates at the base plate, then moves towards the cool part of the heatpipe, dissipates it's heat energy there, condensates as a consequence, then is pumped back to the hot part of the heatpipe through some capilar mechanism, either a coating inside the heatpipe, or a wick of some kind.

Water cooling, which uses a coolant that evaporates much more slowly than the fluid in heat pipes, is therefore more efficient if the thermal emission of the CPU is much higher, so basically it's a good solution for highish overclocks, because the water/glycol solution will evaporate faster with higher temperatures, and there will be more volume of coolant, so that it will not reach it's maximum limit as fast as a low volume coolant circuit like a heatpipe. At lower CPU thermal emissions, a water cooling circuit is just simply less efficient than a heatpipe cooler.

Then there is the ability of the non-boiling water to dissipate the stocked heat energy onto the radiator, which is less efficient than of a boiling fluid. Also, copper extracts heat much more efficiently than aluminium, and a lot of pre-filled units do not use a massive copper radiator, while most heatpipes are copper.

But ultimately, the performance of any system will depend on the radiator, the real air cooling part. With water cooling, the radiator often is not bigger than the radiator of an air cooler. A Corsair H80 for instance has about the same radiator as a Noctua NH-U12P, therefore it will basically be able to dissipate about the same amount of heat per minute as the H80, but the Noctua still performs better on most machines, because it uses a more efficient coolant fluid than the H80, and because the coolant only exchanges heat with copper. When the cadded oolant volume and higher boiling point of the H80 comes into play because the thermal energy added to the circuit is more than the specification of the Noctua, the radiator of the H80 will be much too small to dissipate the added thermal energy, and the coolant will actually heat instead of refrigerate. Dual width radiators or more are the only radiators that make any sense on a water/glycol cooling system, and yet, the Corsair H100 for instance has a smaller radiator surface than the Noctua NH-D14 for example, which has a radiator surface that's comparable to the Corsair H110, and if it were used without the resistors on the fans, it would easily outperform the H110 on modern processors because of the more efficiently cycling coolant fluid.

I can understand that water cooling systems look good and sell well because the thermal values of the CPU - like Mndless says - show no extremes because of the higher buffer volume, but most of the time, in consumer grade systems, the CPU's are not operated to specifications that would maximise the efficiency of a water cooler, and even then, most pre-filled systems have radiators that are barely bigger than air coolers.

Custom water cooling circuits though, that's another story, water cooling enthusiasts focus on getting the largest possible radiator surface and efficient air throughput, and only use the water (with a lot of additive) circuit to deliver the heat to those radiators. An average enthusiast gaming rig water cooling loop will have at least two 240x120 mm radiators with 4 to 8 fans on them.

A Noctua NH-C14 is cheaper than a Corsair H90, a Noctua NH-D14 is much cheaper than a Corsair H110, a Noctua NH-U12P is cheaper than a Corsair H80, and exists in an SE14 edition with more surface, etc... and those all have the same radiator surface.

So, in the end they're all air coolers, the differences are type of fluid circuit (copper heat pipe versus plastic tubing), fluid type (high tech pressure optimised low boiling point cooling fluid versus water with or without additives), and pump (capilar pump versus failure-prone electrical pump).

Anyway, that's just my opinion.