Rad intake Pull or Push Better?

Karadjgne

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Ok. I explain.

Fans work by creating a vacuum when the blades spin, the byproduct is the exhaust out the rear. Vacuum is pretty much uniform across the entire front of the fan. So in pull config, you get even airflow across the entire circle where the fan connects to the rad. Basically a solid flow.

With push, the exhaust of that fan comes out directly from the blades. If you have 30cfm intake, you get 30cfm exhaust. But coming from the blades, it's almost 90° to start with. Unfortunately, there's this big chunk of motor sitting right in the middle and that sees exactly 0cfm. So you end up with a donut shape of flow through the rad. Same airflow, less area across the fins. To combat this, you'll need higher rpm to get the same results as pull. That's why at @1200-1500rpm for most fans, you've reached equilibrium, enough donut flow at speed to equal the solid flow at lower speed.

If you've ever looked at a dirty aio in push, the dust donut is quite obvious, whereas in pull it'll be a more even coating of dust across the entire fan area.
 

Darkbreeze

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I think mostly, it doesn't really matter. Whatever best fits the configuration and necessities of your case design. I've tested different heatsinks using the exact same fans, on the exact same heatsink, in both push and pull configurations and have never seen a difference in temps so long as there is sufficient airflow into and out of the case.

On a radiator I suppose there COULD be slight differences, but I really doubt it. Restrictions are restrictions, regardless if it's the fins on a radiator or the fins on a heatsink, AND, since I've seen plenty of radiators using fans in either configuration with no complaints regarding wild temperature differences I would assume it also holds true for them as well.

Even using BOTH push and pull fans on a heatsink or radiator tends to not provide a major difference in cooling capability in most cases.
 
Aug 3, 2018
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that's good to head because I really want the pull config purely for aesthetic purposes so I can have led fans and they were viewable thanks for the
 

Karadjgne

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Depends on fan speeds. Generally low rpm fans (@1200 or less) are more affective in pull. Fans above 1500 are better in push. Between is negligible differences. But you are only talking about a 4-5°C total spread between the 2,so a slower fan in push is only going to see @2° difference from pull.

Leds/rgbs have the lights on the top, the pretty side, (the ugly side being the backside of the motor) which is intake, so the fan will need to be in push for best viewing. If used in pull on a rad, the lighting gets sandwiched between the fan and radiator. Some Led fans it doesn't make much difference, the clear blades passing light either direction.

<--R|F|L is push, <--F|L|R is pull.
 

Darkbreeze

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Aerocool's DS fans have the lighting smack dab in the middle. Lights look the same whether mounted push or pull. LOL.

Not big on lighted fans anyhow. I'd rather have fans that are really good at what they are supposed to be doing, which is moving as much air as quietly as possible.
 
Aug 3, 2018
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I just find it hard to believe that pulling air is just as good as pushing air.to make it clear I am talking about a front mounted rad (intake so air going into the case) is better for the fans to be behind the rad and pushing air through it OR the fans in front of the rad pulling air through
 

Karadjgne

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Ok. I explain.

Fans work by creating a vacuum when the blades spin, the byproduct is the exhaust out the rear. Vacuum is pretty much uniform across the entire front of the fan. So in pull config, you get even airflow across the entire circle where the fan connects to the rad. Basically a solid flow.

With push, the exhaust of that fan comes out directly from the blades. If you have 30cfm intake, you get 30cfm exhaust. But coming from the blades, it's almost 90° to start with. Unfortunately, there's this big chunk of motor sitting right in the middle and that sees exactly 0cfm. So you end up with a donut shape of flow through the rad. Same airflow, less area across the fins. To combat this, you'll need higher rpm to get the same results as pull. That's why at @1200-1500rpm for most fans, you've reached equilibrium, enough donut flow at speed to equal the solid flow at lower speed.

If you've ever looked at a dirty aio in push, the dust donut is quite obvious, whereas in pull it'll be a more even coating of dust across the entire fan area.
 

Darkbreeze

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Moderator


This is a thinking error.

If the fans on a front mounted radiator are in FRONT of the radiator, that means they are closer to the outside than the radiator and will be pushing air through the radiator. If they are BEHIND the radiator, they will be pulling air through the radiator. You do not ever push air through the radiator from behind the radiator when the radiator is mounted in front or you would have an exhaust configuration and you don't ever have exhaust configurations at the front of the case.

Everything in front should, by common design, be going into the case whether by pushing or pulling. Any bottom mounted fans should be pulling air into the case as well. Fans mounted at the top of the case or the rear should be blowing OUT of the case in most configurations, as exhaust. Anything that differs from that scenario is a specialty configuration and should probably only be done by somebody with a good amount of experience who knows exactly what they are doing and why they are doing it, or not done at all.

Top mounted radiators in intake configurations are self defeating as that leaves only one location to expel out through the exhaust at the rear of the case. Not conducive to a well performing cooling system IMO. It also makes little sense to draw air into the case from where all the heat is.
 
Aug 3, 2018
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Thank you for the very descriptive analysis I appreciate it a lot
 
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