View Full Version : Question about airflow/rpm of push/pull vs pull.
alacheesu
11-22-2009, 08:25 AM
How much more airflow do you get when going push/pull over just pull (or push)?
And a follow up, which is really what I'm interested in:
Say you run fans in push/pull at 1000rpm, what approximate rpm would give equal performance with just one set of fans?
TIA
millertime359
11-22-2009, 08:32 AM
How much more airflow do you get when going push/pull over just pull (or push)?
And a follow up, which is really what I'm interested in:
Say you run fans in push/pull at 1000rpm, what approximate rpm would give equal performance with just one set of fans?
TIA
This also depends on rads as high FPI rads perform worse on low speed fans than low FPI rads.
For the push pull, think you are looking for this (http://martin.skinneelabs.com/Radiator-Fan-Orientation-And-Shroud-Testing-Review.html).
alacheesu
11-22-2009, 08:46 PM
Bump. Anyone?
billb
11-22-2009, 11:19 PM
How much more airflow do you get when going push/pull over just pull (or push)?
And a follow up, which is really what I'm interested in:
Say you run , what approximate rpm would give equal performance with just one set of fans?
TIAFan performance depends on what fans you are using and what radiator they are pushing/pulling through.
And stating fan performance in RPM is useless. You need to know CFM.
For example, see this
(http://www.xtremesystems.org/forums/showpost.php?p=3733232&postcount=1)
terente0081
11-23-2009, 12:52 AM
I didn't read much on the subject, but I can guess that push/pull will give you about 50% more airflow through the rad.
A fan that's rated at 1000RPM and 40CFM in open air, will push just about 20-25CFM through a low FPI rad. If you push/pull, you will get about 30-35CFM through the rad.
If you just want push, you should get a fan that's at least 50% more powerful than the ones used at push/pull. Don't go cheap on fans; Choose fans from a reputable brand and check the RPM, CFM, noise and static pressure.
A good fan in push mode will create more airflow through the rad than a push/pull configuration with bad fans, while being more quiet as well.
Good fans to look at for push and/or pull are the Scythe GT's (I wouldn't use them without a shroud due to the enormous motor hub) and Noctua NF-P12's. There are other good fans, I just don't know about them. Generally, high static pressure is obtained from 38mm fans; Scythe Ultra Kaze for example.
millertime359
11-23-2009, 11:11 AM
Bump. Anyone?
This also depends on rads as high FPI rads perform worse on low speed fans than low FPI rads.
For the push pull, think you are looking for this (http://martin.skinneelabs.com/Radiator-Fan-Orientation-And-Shroud-Testing-Review.html).
Did you click on that link? That is Martin's review on the subject. :up:
alacheesu
11-23-2009, 11:17 PM
Did you click on that link? That is Martin's review on the subject. :up:
Yes, I've read it before, and it unfortunately doesn't answer my questions.
I know there is a lot of theory on axial fans out there, I just can't seem to find it. I was hoping someone knew the theory well and/or had done some experimenting with push/pull vs pull or pull. For pumps we know that running 2 pumps in serial gives around 30% more flow. We know this both from theory and real world testing. I don't see why we can't find an approximate relation for fans. Or if we can't, it would be nice to know why we can't.
millertime359
11-24-2009, 02:45 PM
Yes, I've read it before, and it unfortunately doesn't answer my questions.
I know there is a lot of theory on axial fans out there, I just can't seem to find it. I was hoping someone knew the theory well and/or had done some experimenting with push/pull vs pull or pull. For pumps we know that running 2 pumps in serial gives around 30% more flow. We know this both from theory and real world testing. I don't see why we can't find an approximate relation for fans. Or if we can't, it would be nice to know why we can't.
OIC, your looking for hard data. I took it as another which is better, not why is it better. ;)
BrokenArrow
11-24-2009, 05:40 PM
There does not seem to be much benefit of using push/pull configuration. I did a quick search and most posts said this as well.
http://www.xtremesystems.org/forums/showpost.php?p=1586049&postcount=5
http://www.xtremesystems.org/forums/showpost.php?p=2031759&postcount=9
http://www.xtremesystems.org/forums/showpost.php?p=2236463&postcount=21
You should try it yourself and report your findings. part of the fun of watercooling is testing different things.
Hondacity
11-24-2009, 05:51 PM
How much more airflow do you get when going push/pull over just pull (or push)?
And a follow up, which is really what I'm interested in:
Say you run fans in push/pull at 1000rpm, what approximate rpm would give equal performance with just one set of fans?
TIA
have a look at andreaBZ's estimator at the stickies... his numbers are based on testing...
be sure to read his thread too..there are lots of questions regarding what heatload(watts) to put etc...