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Push or pull air across radiator fins?

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post #1 of 28 (permalink) Old 01-10-2018, 10:34 AM - Thread Starter
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I have a general question.....

Is it more efficient an effective for cooling performance to have a fan push air into a radiator or pull air out of a radiator ?

This is assuming the fan being used is a static pressure fan, since those are supposed to have a more focused flow for restricted air flow situations, like a radiator.

But, the question is independent of where it the radiator is located or any other heat related issues.

Anybody know ?
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post #2 of 28 (permalink) Old 01-10-2018, 10:40 AM
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Some fans are less effective in pull configuration versus push. The difference in temps would likely be only a few degrees either way though.

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post #3 of 28 (permalink) Old 01-10-2018, 10:46 AM
 
 
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Push is better. But fans pulling or pushing cool air into the rad is ideal. Not having the hot air from the case going through the rad and out.

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post #4 of 28 (permalink) Old 01-10-2018, 10:49 AM
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Quote:
Originally Posted by stillsurfn View Post

I have a general question.....

Is it more efficient an effective for cooling performance to have a fan push air into a radiator or pull air out of a radiator ?

This is assuming the fan being used is a static pressure fan, since those are supposed to have a more focused flow for restricted air flow situations, like a radiator.

But, the question is independent of where it the radiator is located or any other heat related issues.

Anybody know ?
While what MNMadman said might be true in rare cases, fan airflow is basically the result of the pressure differential between intake and exhaust sides of impeller, .. and as such impeller has no idea if radiator is in front or behind it. But .. and it's a big 'BUT' .. the exhaust side of a fan has impellers 4-5mm farther away from fan mounting surface (fan housing) then on intake side. This is because exhaust side of fan has the framework from surrounding housing to center where motor is. This 4-5mm difference can mean fan will be much noisier and sometimes does is not able to pull air into itself as well and it can push it out. This is true regardless of where fans being mounted and used .. be it on case vents, cooler or radiator.

As for the difference in temperature of air coming out of radiator and into a fan versus being a few degrees cooler going through fan before going into radiator, it's not enough of a temperature difference to make much if any difference to fan or fan bearing life.
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Push is better. But fans pulling or pushing cool air into the rad is ideal. Not having the hot air from the case going through the rad and out.
So you suggest using pre-heated air coming out of radiator to cool components inside of case instead of cool air coming in? Radiators are effected less by the temperature of air going into them than air cooled components are, therefore it's better to have air a few degrees warmer feed a radiator instead of air cooled components.

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post #5 of 28 (permalink) Old 01-10-2018, 10:51 AM
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If you're doing low speed fans pull is usually better, high speed favors pushing. But saying that it's a tiny amount of difference.
You shouldn't have any issues and the best setup is whatever works in the build normally.

Some fans like eloops have been bad for pull setups as they catch on the radiator in some cases though.
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post #6 of 28 (permalink) Old 01-10-2018, 11:01 AM
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The best thing about a pull configuration is that the dust tends to accumulate on the accessible side of the radiator. On a push configuration dust builds up between the radiator and fan, making it a little more difficult to clean.

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post #7 of 28 (permalink) Old 01-10-2018, 11:03 AM
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Quote:
Originally Posted by doyll View Post

...fan airflow is basically the result of the pressure differential between intake and exhaust sides of impeller, .. and as such impeller has no idea if radiator is in front or behind it. But .. and it's a big 'BUT' .. the exhaust side of a fan has impellers 4-5mm farther away from fan mounting surface (fan housing) then on intake side. This is because exhaust side of fan has the framework from surrounding housing to center where motor is. This 4-5mm difference can mean fan will be much noiser and sometimes does is not able to pull air into itself as well and it can push it out.
Good explanation. So, like I said, some fans are less effective at pull configs. The CPU/GPU temperature difference as a result would only be a small one -- a few degrees maybe.

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post #8 of 28 (permalink) Old 01-10-2018, 11:08 AM - Thread Starter
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Thanks guys,

The reason I'm asking is that I have a somewhat unique situation.

I don't use a computer case, so I have no "heat buildup" or GPU heat transfer issues to the CPU area.

I don't worry about case intake or exhaust because there is no case.

I do use a noctua d15 and one thing that i've always wondered about it the "stock" configuration of the d15 with the center fan.

In stock configuration, one of the radiator fin stacks is always going to be using hot exhaust air from the other fin stack. One stack gets fresh air .... the other gets heated air.

So, I was wondering if it would be better to mount the 2 fans on the outside of the fin stacks, with no fan in the center.

Then the choice is wether to push air into each the fin stacks or pull air out of the fin stacks......

Any thoughts and opinions ??
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post #9 of 28 (permalink) Old 01-10-2018, 11:09 AM
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Quote:
Originally Posted by scientist View Post

The best thing about a pull configuration is that the dust tends to accumulate on the accessible side of the radiator. On a push configuration dust builds up between the radiator and fan, making it a little more difficult to clean.
This is the reason I run my fans in pull config. On my Thermaltake Core P5, the fans pull the air through a dust filter first so the rad doesn't even get dusty.

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post #10 of 28 (permalink) Old 01-10-2018, 11:10 AM
 
 
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Quote:
Originally Posted by doyll View Post

So you suggest using pre-heated air coming out of radiator to cool components inside of case instead of cool air coming in? Radiators are effected less by the temperature of air going into them than air cooled components are, therefore it's better to have air a few degrees warmer feed a radiator instead of air cooled components.

I suggest taking cool air from outside of the case into the rad then going into the case then out the exhaust.

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