Air vs water cooling : what am I missing?

[adidas]

Hi - I've spent quite a while hunting for review of watercooking kits and 'regular' air heatsinks for p4 (socket 775). I was quite surprised to learn that watercooling kits usually don't cool as well as the top-of-the-range air heatsinks. For example:

- results for p4 air heatsinks:
http://www.overclockers.com/articles373/p4sum.asp

- results from waterkits:
http://www.overclockers.com/articles373/waterkit.asp

I chose that example because the reviewer has been using a solid testing platform (the same simulated CPU die) for both systems.

With fans blowing on the radiator, I can't imagine much benefit using watercooled systems in terms of noise emission.

In terms of price, it suffices to say that the best watercooling kits, the asetek l30 costs upward of 180 quids, when the best air solution costs well, erm, less than 40. Yet the difference in performance between the two is minimal.

So now I'm really confused. Obviously there's always the 'cool' factor, I suppose. :D

Steve.

[DaGuv]

Ok, the main thing is you say "kits"... and there is your problem. Very rarely will a pre-built kit perform well, and your right, an XP-90 or 120 etc with a high CFM fan will out perform most if not all w/c "kits". However, you will yield much lower temperatures with a custom/DIY water cooling setup.

Example. My LGA775 was running 38c idle / 55-60c load with stock HSF, i lowered it by adding an after-market HSF, but this only lowered it about 5c and the noise was ridiculous. With my Custom w/c (mainly DangerDen stuff) my temps are 24c idle / 38 load (no OC) this is with my fans spinning at the lowest possible speed (v.quiet). This is 17c Cooler under load and is considerably quieter. This temperature reduction is the reason I could only o/c to 4.1Ghz on air but 4.5Ghz on water.

Granted it is cheaper to get a XP-120 or simillar, and this will give a significant and satisfying temperature reduction to most people, but if like me you want higher O/Cs, more stability or lower noise levels... go custom water cooling :)

[Sgoaty]

Water cooling kits remove heat from the cpu a lot more efficiently but they really come into their own when overclocking with the temperature only jumping a few degrees where as air cooled heatsinks usually allow the temperature to jump more substantially (what he said^)

[adidas]

Thanks for the replies!

DaGuv, I can see you have p4 560 oc'ed to 4.5ghz. According to one of your old posts your cpu temp is 45c under load when oc'ed. That's very impressive, could you give us more details on your cooling rig? And is it stable (as in, able to run prime95 overnight)?

Cheers,

Steve.

[DaGuv]

No probs, i've only got it to be prime stable for a few hours @ 4.5Ghz. I have it at 4.41Ghz for 24/7 use (Prime Stable). The main reason i've managed to keep the temps cool is because i have a 120.3 rad cooled by 3x120mm YS-Techs (125cfm) and the CPU is the only thing in the loop. I originally had a single 120 rad, temps were pretty much the same when Idle, but under load i found this to be way to little cooling and couldn't keep it stable for very long.

[dangel]

Same reason why air-cooled cars aren't popular - air is really very inefficient as a heat conductor and thermal transfer is what it's all about. Air can only carry away so much heat; the more heat you want to dissipate, the more air flow and surface area you need for a heatsink. Eventually you get into the area of diminishing returns, plus you've suddenly got to sort out shifting enourmous CFM of air not just onto the cooler, but in and out of the case too... Not to quote a pun, but water can literally 'soak up' huge wattage of heat compared to air systems and so you often see kits that will cool many items - cpu, gpu, chipset, harddrives - all on one loop. The more heat you need rid of, the better water gets..

Water kits might seem expensive (i'm asetek equipped) but they're worth their weight in gold for overclocking, stability and above all noise (or lack of). I'm never EVER going back to air.

[T00thBru5h]

Water cooling is also fun and somewhat different from the bog standard heatsink and fan combo :D

[pdf27]

Ultimately water cooling is still all about dumping the heat to atmosphere. The main (only) advantage is that using water as a working fluid allows you to use a far bigger and more efficient design of radiator with better airflow through it than you could ever fit onto a CPU. That's why I think it's totally pointless to use anything smaller than a 120mm radiator in a water cooling unit except under really exceptional circumstances - heatsinks like the XP-120 will get better airflow than the smaller radiators...