Question How does a 2 fan heatsink actually work? I feel kinda stupid for asking this...

[Franknj229]

Am I just not understanding how this works, or am I overestimating how warm the air gets?

I'm looking at these huge dual tower heatsinks, like Noctual NH-DH15 G2 or the Thermalright Peerless Assassin 140... They have 2 towers and 2 fans. I've just been assuming that both fans direct air in the same direction (ie. air is drawn in through my front case fans, both heatsink fans continue the airflow in that direction, and the air is exhausted out the back of my case through the rear case fan.).

Right?

So isn't the first heatsink fan pushing warm air from the first tower into the second fan, which then pushes that warm air over the second tower? How much is that second tower really helping then?

I get that the warm air from the first tower is still probably cooler than the second tower itself, and therefore actually cooling the second tower...

Anyway, it must work better than 1 tower because the testing proves it, but do I have this line of thinking correct? Am I setting up the fans the right way?

 

[RAIDGoblin]

having the two fans moves the air faster, the faster the air moves the less it warms up on it's way through and the grater the cooling effect, the dual tower thing works because two towers has twice as much surface area to loose heat over, so it will loose the heat faster

 

[CountMike]

Am I just not understanding how this works, or am I overestimating how warm the air gets?

I'm looking at these huge dual tower heatsinks, like Noctual NH-DH15 G2 or the Thermalright Peerless Assassin 140... They have 2 towers and 2 fans. I've just been assuming that both fans direct air in the same direction (ie. air is drawn in through my front case fans, both heatsink fans continue the airflow in that direction, and the air is exhausted out the back of my case through the rear case fan.).

Right?

So isn't the first heatsink fan pushing warm air from the first tower into the second fan, which then pushes that warm air over the second tower? How much is that second tower really helping then?

I get that the warm air from the first tower is still probably cooler than the second tower itself, and therefore actually cooling the second tower...

Anyway, it must work better than 1 tower because the testing proves it, but do I have this line of thinking correct? Am I setting up the fans the right way?

It's total amount of airflow that counts. Both towers are connected thru heat pipes that transfer heat equally. Air temperatures from first tower are much lower than tower itself and even more so than CPU so it has minimal influence on second tower cooling.
Only advantage a dual tower has over same size single is that placing second fan in middle save some space.

 

[RAIDGoblin]

Only advantage a dual tower has over same size single is that placing second fan in middle save some space.

that's a good point, the dual tower coolers have two smaller towers, rather the single tower coolers have a bigger tower, so perhaps it doesn't make that much deference in terms of surface area

 

[Paperdoc]

^All above right. OP, one key to grasp here is that the air that has passed though the first tower has been warmed, but its temperature still is MUCH lower than the temp of the second tower, so that second tower and fan DO contribute a lot to overall cooling.

 

[Eximo]

Dual towers is for the increased surface area and, to some extent, ease of manufacturing.

It takes a lot of air pressure to get through the restrictions of the heatsinks. Solution 1) more powerful fan, result: louder. Solution 2) series fans, each running much slower, result: quieter.

So on the big dual tower coolers they go for oversized fans to maximize airflow and silence while still achieving enough static pressure to get air through the radiator.

Another more subtle effect is creating some turbulence where the center fan hubs are. These are dead zones. Having that transition from fan, to heatsink, to fan, to heatsink lessens that deadzone a little.

Take a look at server fans. Really thick, high RPM, but small diameter. Really loud, but extreme airflow performance.