Fans on rad, blow air to the rad or suck air out of it?

[Makubex_GB]

What's the most efficient way to cool a rad, to set the fans so they would blow air through it or so they would suck air out of it?

I thought blowing would be more efficient, but someone told me that sucking can bring the temps down about 2C. Is this true? And Why?

[bobkoure]

I believe which (push or pull) is more effective depends on a number of all factors.
I've had slightly better luck with "pull" - but with undervolted fans pulling/pushing through 2" thick heater cores (low noise overclocking) - but I'd be surprised if that translated into anything useful for your situation.
Either way, it's more important that you be drawing room air (not pc case air) into your rad - and that your case be as non-air-restrictive as you can make it.
And FWIW (and IMHO), stuff that "someone tells you" - unless they have the exact same setup you do - and can actually measure water temps and heat input - is less than useful.

[maxSaleen]

Just like everything here "it depends"... on a lot.

If it's for a traditional PC watercooling setup, which I assume it is, a little info can help us help you:

Where will the radiator be located?
What type of radiator is it and what are its demensions?
What type of fans will you be using?
What are your noise goals?

Push/pull config produces the most airflow.... but that should be pretty obvious.
IMHO, pull config, assuming it's drawing outside air, produces the best temps.

[Makubex_GB]

I see. Well in my case for example, what would be better?

Here are some pics:

That on top under the grill is the rad.



Those on the top are the two Sanyo Denki fans that are cooling the rad:


They are pulling air from in the case, pushing it through the rad and out the case.

As for noise, since I have 7 fans in my case (without counting the PSU fan and chipset fan) , you could say I can tolerate some noise. I do have them all controlled with 2 fan controllers. My room temps are usually on the 30~31C range, so I do need somewhat powerful fans.

My rad is a Swiftech MCR220 Dual 120mm

These are its dimensions:


What do you guys suggest?

[ricecrispi]

God damn vbb made me login and lost my post....Cliffnotes version

Anyways. Past experience or generalizations aren't always correct. Best way to find out is by testing configs.

I would bet money on pull config from past expereince. Also air intake from outside source instead of using inside warm 30C case air shows a good improvement but might not show any improvement in your setup. Testing will solve that problem

Too lazy or not motivated enough to test and want a shortcut.

Contact swiftech or Bill Adams here (if you get lucky he will reply) because they have radiator, fan config, and testing information and experience with this.

[Makubex_GB]

Very nice info there, thanks.

[pinetar]

My Picker medical systems pulls. The pic is in my sig. It seems to me that it makes sense to have the rad system external, otherwise the fan sucks hot air out thru the radiator first. Small and compact is not always good.

[RedViper]

I've tried both and I prefer pull. If for no other reason than this configuration allows me to hose my rad out with relative ease. Any difference you see in push/pull will be offset by this fact.

[thorilan]

pulling through dense finned rads and cores in general is slightly easyer than pushing due to leading edge rebound . the amount of diference it makes in a home cooling unit is not something that really makes much diference but when put together with other factors such as air from the outside coming into the case ( lowering your Dt) and fan pressure at low speeds ( you dont want your ears to bleed at max speed do you?) can all add up to a noticeable diference.

for instance pulling air from the outside of the case will usually be slightly cooler meaning your rad will get the cooler air and be more efficient.
then there is velocity. sealing the fans so that all the air has to come through the core/rad and not some cracks means more air per volume which would be the same as more flow inside your water cooling loop ( granted this is not a big deal).

but aside from all the scientific factors , it also comes down to personal preferance .

if you listen to your fan in push and then in pull its quite likely that you might hear a small diference in pitch / tone. this may be covered up by your case but in high powered cooling systems it can become noticeable

[SiGfever]

Originally Posted by thorilan

pulling through dense finned rads and cores in general is slightly easyer than pushing due to leading edge rebound . the amount of diference it makes in a home cooling unit is not something that really makes much diference but when put together with other factors such as air from the outside coming into the case ( lowering your Dt) and fan pressure at low speeds ( you dont want your ears to bleed at max speed do you?) can all add up to a noticeable diference.

for instance pulling air from the outside of the case will usually be slightly cooler meaning your rad will get the cooler air and be more efficient.
then there is velocity. sealing the fans so that all the air has to come through the core/rad and not some cracks means more air per volume which would be the same as more flow inside your water cooling loop ( granted this is not a big deal).

but aside from all the scientific factors , it also comes down to personal preferance .

if you listen to your fan in push and then in pull its quite likely that you might hear a small diference in pitch / tone. this may be covered up by your case but in high powered cooling systems it can become noticeable

thorilan,

Glad to see your post. I am getting ready to order a U2-UFO case and a PA120.3 rad with shroud to go inside. I am planning on drawing air from outside the case so would you recommend a push through the shroud to rad or pull?
Thanks,
John

[Makubex_GB]

Right now I have it drawing cool air from the outside and pulling it through the rad. But I also tested pulling air from outside and pushing through the rad and the temps and there was no temp difference. I suggest you test both and go with the one that makes less noise.

[mrastudent]

If your case air is hot enough to affect your water temps then you need to do something about it.

[bobkoure]

Originally Posted by mrastudent

If your case air is hot enough to affect your water temps then you need to do something about it.

You're kidding, right?
At a minimum, for every degree warmer than ambient your case air is - your water temps will also be warmer - and actually slightly more than degree for degree due to loss in efficiency (efficiency goes down as delta goes down).
If you mean hot enough to raise your processor temps to the point you care about it, well, sure - but wouldn't it be better to be able to turn your fans down just that much more and get a bit quieter machine?
Suit yourself, of course...

[ricecrispi]

Originally Posted by SiGfever

thorilan,

Glad to see your post. I am getting ready to order a U2-UFO case and a PA120.3 rad with shroud to go inside. I am planning on drawing air from outside the case so would you recommend a push through the shroud to rad or pull?
Thanks,
John

With the PA series rads I think it has FPI 14-16 so it isn't as restrictive as HE rad or older rads or heatercores.

Both push or pull should perform equally as well. Consider the difference in the amount of noise to be a key factor in you choice.

[SiGfever]

Thanks for the replies, I hope to get my U2-UFO ordered today.