Very Basic Question

[CaGeRit]

I've been looking at a lot of different water cooled setups and I have a very basic question.

Almost all of the setups I've seen take the heat away from the various sources (namely cpu and gpu) with a liquid carrier. This carrier then runs through a radiator which has air flowing over it to help dissipate the heat.

Ultimately how does this shed more heat than you would from air cooling? The end of the process still has fans flowing over a heatsink/radiator to carry the heat away.
The only room I can see for performance gains is if...

A: The radiator, which isn't confined by the dimensions of the case, can be much larger with much more area than the traditional heatsink.
or
2: You don't use don't use air to take the heat away from the radiator, such as in the geothermal thread (very cool by the way).

P.S. I have read that water can hold more heat than air, but wouldn't that run into the law of diminishing returns. I.E. Your water can old more heat, but now you're running warm water through your block reducing the amount of heat it can absorb and shuttle away.

In essence, aside using a much larger radiator than air cooled heat sink or using an exotic (geothermal cooling) method of shedding heat, why do water cooled systems run at cooler temps? Or at least are reported to run at cooler temps.

Thanks in advance and sorry if this a repeat thread, tried throwing some terms into search, couldn't find anything.

 

[MrLarkins]

Because they transport the heat faster than an air system. This keeps the temps lower.
Also, an air system typically dumps the hot air back into the case only to be exhausted somewhere else. On a water loop the heat is exhausted out of the case by the radiator.

Not everyone goes water for heat dissipation. I have a setup for complete silence. I have a 480mm radiator on mine and a large reservoir. So with the fans on ultra-low or even off, my system never gets hot enough to worry about AND I don't even hear it.

 

[Conumdrum]

Better transfer of heat at the CPU block and better removal due the larger surface area of the rads. Y

 

[KurtBlanken]

This is an interesting question, and although I am not qualified to answer it I will give it a shot:

Let's assume that the radiator and the heatsink have the same fin area, and that the heat dissipation abilities of both are matched. In this case, what is the difference between water and air?

The difference is in how effectively the heat is transferred to the fins in the first place. Air cooling relies mostly on conduction. Metal conducts heat better than water, so this is a good solution, right? However, conduction is a slow process. Imagine dipping a spoon into a hot cup of water, it takes some time for the heat to conduct up the spoon and burn your hand.

Water on the other hand physically transports the heat to the fins, which is much faster. Even though water doesn't conduct heat as well as metal, it can spread the heat to the fins faster by physically moving it instead of relying on conduction.

 

[atclaeys]

Usable surface area, basically. Kurtblanken was pretty much about right with his response, there's only so much surface area on an air cooler that is doing any real heat dissipation because of heat traveling up the fins, while in water you can take advantage of the heat transfer in the block which is highly efficient and then dissipate over a large area.

But as was pointed out to me when I was starting out, WC isn't all about extreme temps. While yes you can put large rads on to dissipate far more heat than you can with only a standard air cooler, you can also have a very quiet system by using quieter fans and taking advantage of the rad's SA. If you really want to go for extreme temps you need something a step beyond standard water cooling (refrigeration, LN2, etc.)