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Is push/pull better than double-pull or double-push?

Last response: in Overclocking
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January 17, 2013 2:56:39 PM

Lots of debate around push vs pull vs push+pull, but I can't seem to find anything on doubling up.

Am particularly interested in double pulling, as it would make for easier radiator cleaning.

Atm I have an H100i with 2x noctua NF-F12's in a pull configuration with a vacuum seal using extruded butyl so that there is no leakage.

If it all has to do with air pressure and moving air through the radiator, is a push-pull superior to double pull?
a b K Overclocking
January 17, 2013 3:20:15 PM

a shroud is what you are looking for the best configuration would be fan shroud radiator shroud fan the fans would be in a push pull configuration i hope that helps
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a c 78 K Overclocking
January 18, 2013 12:22:34 AM

I tried two fans back to back on a heatsink and not a watercooling setup(in 2004), very stupid idea at the time and I learned not to do it since - you could ofc try it out and save yourself the need to wait for an answer and report of your temps.

If its a success you should post!
IF its a failure you should post!

^ however, either of the two will be added to the CLC subsection in the watercooling sticky.
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January 18, 2013 12:56:27 PM

Lutfij said:
I tried two fans back to back on a heatsink and not a watercooling setup(in 2004), very stupid idea at the time and I learned not to do it since - you could ofc try it out and save yourself the need to wait for an answer and report of your temps.

If its a success you should post!
IF its a failure you should post!

^ however, either of the two will be added to the CLC subsection in the watercooling sticky.


Thanks guys! You know, I had no idea that a shroud served any purpose other than to reduce out-noise, I did not know about deadzones! Apparently it is the deadzone that makes a pull flat up against a radiator worse than push.

I think what I will try is double shrouded pull.

My box is a Corsair 550D mid-tower so I can't do more than 50mm of cooling inside the rig, so I'm going to mod the case to be the radiator with 20mm shroud on top of it, that will touch the grill.
On top of the grill, outside of the case, a 10mm shroud ( giving about 30mm in total between radiator and first set of fans).
On top of those fans, another layer of shroud, this time a single 31mm shroud, followed by the second pair of fans.

As an added bonus I hope it also dampens the noise through the top of case significantly because that is where the most of the sound is escaping from atm.
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a b K Overclocking
January 18, 2013 1:24:26 PM

Bad idea, unless you have a really nice fan controller to time those fans to be in sync with each other.
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Best solution

a c 330 K Overclocking
January 18, 2013 1:46:15 PM

I'd think a nice pair of fans in push/pull would be your best bet over anything like double push or double pull unless you were very specific on how you setup the fans to build on one another. It would be difficult because if you had a higher performing fan pushing air into a lower performing fan, the lower fan would cause diminished performance overall and you'd get push-back to the higher fan. If you flip them around the lower performing fan might cause an issue with the amount of air the higher fan would pull and would cause excess resistance on the lower fan. It's worth a try I suppose, but you'd have to really know what you were doing to capitalize on airflow physics which I know absolutely nothing about.
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a b K Overclocking
January 18, 2013 2:14:34 PM

For someone who knows nothing about it that is a pretty good explanation of what needs to happen.
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a c 78 K Overclocking
January 18, 2013 2:20:20 PM

^ +5000!
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a c 330 K Overclocking
January 18, 2013 2:44:49 PM

Just some things I've seen when testing fan-into-fan results. You can tell there is a noticeable difference in fan RPM and airflow when doing either, even when fans are identical models...they never actually operate exactly the same and you don't achieve 1:1 movement of air.
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a c 78 K Overclocking
January 18, 2013 2:54:21 PM

Yeah, the rpm's on my fan, whether run off mobo header or fan controller's header, show a good 5% difference at least on 2~3 identical fans.
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January 18, 2013 8:05:21 PM

I have F12's as well and with those fans you really don't need a shroud as they are designed to minimize the dead spot anyways. I would do Push/Pull with 2 more NF-F12's and run them at the same speed. Its what I do and it works great and is completely silent.
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January 18, 2013 10:50:36 PM

Oh ok, well thanks for the heads up guys, I probably would have fried my cpu or something. :o 

As for the shrouds they are in the mail already. :\

Is there no use for them? I know that push/pull beats the hell out of a single shrouded push or pull but what about a push/shrouded-pull? Any benefit you think?

Obviously I have no idea what i'm doing I just look at the pretty graphs then go buy things. :( 

2 + 2 = 22 right?
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a c 78 K Overclocking
January 18, 2013 11:33:35 PM

A shroud could've been made from a fan that was lying around. Remove the mounts that hold the motor to the frame via a hacksaw...

And you clearly haven't visited the watrcooling sticky. Is scroll down to the CLC too much for your optical input device?

Please take time to read through the info(and the graphs) as reading is part of your growing up phase.
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January 19, 2013 6:52:17 AM

Best answer selected by hoki.
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a b K Overclocking
January 19, 2013 5:15:27 PM

the only way to really have an push-push setup is to have some ccw/cw fans.

same rotation will be wasted energy and only one fan will do 99% of the work.

the thing is it doesn't increase air flow that much, in increases pressure like mad.

http://db.sanyodenki.co.jp/product_db_e/coolingfan/dcfa...
vs
http://db.sanyodenki.co.jp/product_db_e/coolingfan/dcfa...

hard to find any hard data on a setup like this, but a single fan = 260 cfm, 340 PA static pressure, but the contra-rotation fan is 300 cfm with 480 pressure

Granted you don't want to use 6000 rpm fans, but thats the closest comparison I could find quickly, 64dba and 70dba ... lol.

Similar to this. http://en.wikipedia.org/wiki/Contra-rotating_propellers and http://en.wikipedia.org/wiki/Contra-rotating
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