Top fan as intake or exhaust

[Tech Reprise]

Suppose I have two fans on the top. Will putting one fan (the one nearer to the front, on top of the ram and cpu cooler) help in cooling the pc anymore efficiently? Or should I just lower its speed so that it doesn't exhaust the cold air that's coming from the front intakes. Or will it just make a negligible difference?

[WoodenMarker]

Depends on the system. If cooling is already good, adding another fan probably won't make a notable difference. 

[StDragon]

Just as with rack mounted servers, all my builds are designed to cool from front-to-back.

 

You don't want positive pressure with all fans blowing in, and you don't want to create negative pressure with all blowing out. You want to move ambient outside air into, through the case, and back out.

 

I've got a case with 2x 140mm fan in the front. Fans at the top are optional, but consider one at the rear if heat build-up under load is still an issue.

[SenKa]

I can tell you that in my define R6, I added 2 top fans and played around with them as intake and exhaust. This system is folding@home right now, and per my measurements its kicking out ~600w worth of heat. I have 2 140MM's in the front, and one in the back. Those are stock case fans, the top fans are silent wings 3.

 

Relevant specs are as follows: Ryzen 9 3900x, Stock cooler, RTX 2070, GTX 670

 

Top fans as intake: CPU temps never reached above ~75c, even while folding. Top GPU, the RTX 2070, was overheating even with the fans at full boar. Bottom GPU was uncomfortably hot, but more acceptable

 

Top fans as exhuast: With both GPU's loaded, and CPU at idle, the heat kicked off my GPU's is managing to make the CPU idle at ~55-65c. This is almost certainly the result of the down-firing stock cooler, but i felt it worth mentioning. CPU temps while folding are solid at 83c. GPU temps are MUCH lower. I'm having issues finding work units on my RTX 2070 right now, but it normally settles in around 80c, the GTX 670 (which has been folding all night) is sitting at 75c. Both cards are Gigabyte Windforce 3x. This is my recommended config.

 

But, in the end the only answer is the one you find for yourself with experimentation. You don't have a Define R6 as far as I can tell, so the above results may or may not be of use to you. Pick up a couple cheap fans, throw them in, load up prime 95, furmark, and HWInfo, and see what works best.

[Tostr4]

Physics : hot air rises, so you'll get better results 'going with the flow'. Try to redirect the intake from the front fans with some tubing to the hottest heat sources, rather than inverting the upward hot air flow. 

[WoodenMarker]

5 hours ago, Tostr4 said:

Physics : hot air rises, so you'll get better results 'going with the flow'.

Warm air rising is negligible when there's any active airflow.