Radiator Fans: Push or Pull through the rad?

S

SelRahc

Limp Gawd
Joined
Aug 12, 2004
Messages
389
Ok I tried doing a little search and couldn't find anything on it.

Is it best to Pull air through the rad, or Push air through? Does it even matter? I wasn't sure if there was a right or a wrong way to do it.
 
I would think on a radiator, it wouldn't really matter, since most are identical on both sides. It all depends I guess upon where you're mounting said radiator I suppose.
 
thelostrican said:
pull
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Ive read this time and time again, but I was wondering if there was raw data to back this up? I am about to order parts myself for a W/C Setup and have this same question.
 
Answered from my "Teh Uber L33t Aqua-Computer Thread"

I would have to say that it doesnt really matter if we place our fans in push or pull fashion on our small scale use of fan/radiator combos. On my Twisted AC rig I have the fans in intake pull form since I have space constraints between the side panel and the video card and the fittings would get in the way otherwise. The Sick Rig has them in intake push trim just because I only wanted cooler air to come in instead of exhausting the warm air from the case. I already have fans that do that anyways.

For those who would like a definition of what push and pull refer to in these cases.....

Push trim: The fan(s) suck in the air as if it/they were installed on top the radiator and "push" the air across the radiator fins.

Pull trim: the fan(s) suck in the air as if/they were installed below the radiator and "pull" the air across the radiator fins.

-Dan
 
My Gut instink is that the fans would be more effective pushing. Especially if you had a shroud that allowed and air gap between the fan and the radiator surface thus elimating the fan's dead spot.

From what I have seen computer fans are typicaly able to produce more pressure when pushing rather than pulling.

IMO :)
 
Steve said:
both.

120mm fan on each side of the rad.

just my $0.02 ;)
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You're right bro, I WOULD just go from the old blow/suck setup.....but not everyone ends up down that path. If I had to only have 1 fan I would have it sucking off the rad....I've seen nicer temps from this time and time again....and It'd be a hell of a lot easier to mount the fan/rad to the case panel and have it exhausting OUT of the card that way.....as opposed to have a fan blowing on the rad and possibly pushing some of that warm air back into and through the case....depending on where your rad is.
 
pHaestus from pro cooling did a little test and here are the results.
http://phaestus.procooling.com/shrouds-BIX.GIF

i personally went with a pull configuration, because it was more silent, at least for my ears, and it cooled better by about 2 degrees, this wasnt done in a very control enviroment, i recomend pull, with a shroud, but what better than to test yourself and go with what you think is better :)
 
Definitely use a pull configuration so any dust that enters the system does not get trapped between the radiator and the fans.
 
If I use a Push method how much impedence would some mesh filters over the fans hurt cooling?
 
Electric car fan manufacturers recomend pulling air.

From Summit FAQ

E-mail Answer What is more efficient a "pusher" or "puller" electric fan

Question
What is more efficient a "pusher" or "puller" electric fan?

Answer
A puller fan is more efficient. A pusher fan is generally only 80% as efficient as a puller fan.

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Related Answers
• Can an electric fan be installed as a pusher or as a puller?
• How do I activate the electric fan?
• What size electric fan do I need?
• Do I need a shroud on my Perma-Cool electric fan?
• Can I use more than one electric fan?
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Vette
 
Yea, pull is much better (especially with a shroud).
This way, you are pulling air thru/over the entire surface of the rad, not just pushing mainly at the "hot spot" of the fans airflow.

I have consistantly noticed a lower temp with a pull over a push (and I have tried this in many different setups).

D.
 
Definitely use a pull configuration so any dust that enters the system does not get trapped between the radiator and the fans.
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That's another thing with most ppl....I know how much dust enters my box due to my side 120mm intake.....and I'd hate to have that kind of buildup on my rad from time to time.

If I use a Push method how much impedence would some mesh filters over the fans hurt cooling?
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Well if you're gonna get filters that actually do a GOOD job then it IS gonna hurt the airflow a fair bit. Honestly dude, its not worth it......I'd just recommend you do a "pull" setup and not have to worry about the filters.

This way, you are pulling air thru/over the entire surface of the rad, not just pushing mainly at the "hot spot" of the fans airflow.
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And finally, yes, this is one of the key points to be made. Even with a shroud I would not call a blow setup perfect in terms of area of effect, but it is better. A pull setup with a shroud however is pretty hard to beat...as yes, air is forced over and through the entire rad to get to the fan and exhausted.

pull > push
 
Like another said, use both :D My small copper rad has a 92mm on each side, best of both worlds, and in low noise/low cfm applications like mine it does indeed make a 2c-3c difference in cooling versus a "push" only setup.
 
TheRapture said:
Like another said, use both :D My small copper rad has a 92mm on each side, best of both worlds, and in low noise/low cfm applications like mine it does indeed make a 2c-3c difference in cooling versus a "push" only setup.
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Which is just what I said earlier after Steve made the same comment. If you're looking at running a single fan setup then pull > push....but if you're willing too.....push+pull > pull.
 
i'm not too sure about rads...but on heatsinks pull is generally > push, and since a rad is like a giant heatsink...i'd say pull.
 
Compuer fans aren't made to overcome the backpressure of pushing. Pull is why their quieter, and flow more.
 
Pull for two reasons:

Backpressure created by the fan. the proximity of the fan to the radiator and the fan volume vs the radiator's throughput (not exactly the word I'm looking for, but the volume of free airspace a rad can pass) causes eddys of air to flow back against the fan, killing it's cfm.

Dirt buildup on the radiator. As more dust bunnies give their lives in the prevention of airflow, pusher fans will tend to clog the paths of least resistance. Most likely this will cause more backpressure.

A puller fan with shroud would be more efficient. the low pressure (vaccuum) created by the fan in the shroud will use more surface area of the radiator to equalize the pressure. As passages get full of dust bunnies, the vacuum will pull from other areas on the radiator not as plugged. Any air leaks in the shroud or fan housing don't hurt the fan's overall cfm (just the fan/radiator's cooling ability). I also prefer negative pressure cases for the same reason.

A green scratch pad should work well for an air cleaner. We're currently debating whether or not to use K&N's filter treatment on it, ir run as-is.
 
Cars have the fan behind the radiator with a fan shroud in between that pulls air from the front of the car, thru the radiator, and then exhausts into the front of the engine bay. I would assume this has come to acceptance through trial and error. Therefore, I would assume that the same applies for computer radiators. Although, computers dont normally move when they are turned on and most engine bays are fairly open to the elements, so maybe its just the best for that application.
 
well my two cents here, think about what is happening with the air in your system
since all my comp is water cooled (except the vid card) and uses otes to disperse the heat from the power rail, I opted to set my fans up pulling air from inside the case, through the top out of the case (koolance exos case)... since the water is keeping my case temps down it dropped the average load temp down a few degrees c, as opposed to the stock set-up which forced hot air into my case from the radiator .. whick upped the case temp and increased other temps

so yea, i would say its better to think how the radiator heat is goint to affect the rest of the temps more than whether or not its pushing air or pulling air
 
bmxerkrantz said:
so yea, i would say its better to think how the radiator heat is goint to affect the rest of the temps more than whether or not its pushing air or pulling air
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Or you could just mount your radiator outside of your case like me. ;)
 
It is better to pull through in a one fan setup because a fan has higher adabiatic efficiency when pulling through a restriction. This is a fancy way of saying that when a fan pushes air into a restriction, it creates turbulence at the point of the restriction which effectively reduces the volume of air able to flow through it. Less volume equals less cooling. I do not have any scientific data to back this up, but you should look up adabiatic efficiency for more info. Try thermo-/fluid-dynamics links on your local college's physics website.
 
lol ... external radiator ... too much stuff to deal with when throwing into the car to lan at friends houses ... i already thought how cool of a radiator an auto AC radiator would make .. but i thought it would just be way too much trouble
 
bmxerkrantz said:
lol ... external radiator ... too much stuff to deal with when throwing into the car to lan at friends houses ... i already thought how cool of a radiator an auto AC radiator would make .. but i thought it would just be way too much trouble
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Some people will go that route and some won't bother. It's what seperates the truely [H]ard modders and overclockers from the rest of us sometimes. :)
 
cornelious0_0 said:
Some people will go that route and some won't bother. It's what seperates the truely [H]ard modders and overclockers from the rest of us sometimes. :)
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the truly hardcore would find a way to have a seperate compartment in their case for their radiator setup.

;)
 
Giblet Plus! said:
the truly hardcore would find a way to have a seperate compartment in their case for their radiator setup.

;)
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Either or......some find joy in making the ugly look good. I cant say I'm up on that myself....but I love seeing when ppl are.
 
ill second the notion of a pull setup being quieter. I have a MCR220 on the top of my stacker and i have noticed that in a blowhole (push) setup it is louder than using the top as an intake(pull) through my radiator. I still dont have have too much negative with four 120 intakes (including the rad fans) since i use both my 120 exhausts (St810).

Go with pull for noise :D
 
uclajd said:
Or you could just mount your radiator outside of your case like me. ;)
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^Truth. Remove the exhaust problem alltogether. Took me no time to make a case top enclosure for the rad/fans setup. Oh , and yeah, its a PULL setup.

EDIT: yes, it is still portable. I dont Lan a lot but it has gone with me a few times. No biggie.
 
I'm looking into getting the Koolance Exos-2 and can't tell if the fans push or pull from the pics. I was wondering which way would be better for the fans since the whole enclosure is external. I might switch the fans around when I get it to see if affects the temps at all.
 
Amazed no-one's asked "which radiator" as that's the determining factor. For instance, Cathar tested the PA Series and found PUSH to work better on that particular range over pull.

So, it's all down to the particular rad in question.
 
interesting that Swiftech with the Apex kit installed the fans on the MCR220 in the push position. Should i go to the trouble of changing em?
 
I remember seeing a test of this done a few years back when I was researching my first build:

Pusher/puller set-ups dont gain a great deal of extra performance but they are a hella lot louder. The additional noise defeats one of the main purposes of WC'ing in the first place... it had the potential to be much quieter.

Pushers. As said in this thread: PC fans (most fans in reality) dont do well trying to push air through an impedance. The obstruction on the front of the fan just casuses the fan to draw less air as the air already drawn through "backwashes" into the fan and just creates a mess of turbulance. You'll also note this set-up is considerably louder because of the air turbulance... think about putting a finger guard over a fan, it gets louder. Now if you put spacers between the fan and the grill it's MUCH quieter.

Pullers: The best set-up IMO. You're basically creating negative pressure inside the radiator's cooling fins. This negative pressure is then filled with surrounding air trying to equalize that negative pressure. In effect, you're almost priming the fan with air moving into the radiator. I also like the idea of drawing heat off something as opposed to trying to blow it off. From my experience, this set-up is also the quietest.
 
I'm running my 80's on my rads as pullers and I've got proof that the deadspot in the center for the hub is B.S. on a pull through setup.

I'm not running anything but the 1/4" offset provided by the rads natively and on the inlet side of the rads I've taken some very porus filter foam and trimmed it to fit in the other offset. Guess what...there's always dust over the entire surface of the filter matterial unlike if there was a dead spot where air wasn't getting drawn though. If that was the case the middle of the filter matterial would be clean due to no airflow through that part of the medium.

That could explain why pull through tends to be more effective than push though. (In part at least)
 
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