I have 4 Noctua NF-F12 PPC 2000 fans on the upper exhaust powered by a PWM dimmer turning the fans around 40%. That is enough flow to hold a piece of paper on the lower intake vent with ease. I also have an 80mm Noctua in the fridge blowing across the entire heat sink (those ones on eBay the blow across 3 fins is silly).
Why so many on the roof? No reason. But when in Palm Springs just shy of 100 degrees I had them running on high and the fridge never left the low 30's with no extra water swapping nor grazing the fridge limits. Once everything is cold soaked it seems to stay there. The whole point is to have zero temp delta between the intake air, and that being exhausted. These easily achieve that.
The NF-12 is around 55CFM IIRC, and they are DEAD SILENT... With all four running full out. There are other reasons for the Noctua: they are built to live in environments of 250 degrees, they are IP65 (extreme dust and moisture resistant), very low current draw for what you get out of them, and they run 3phase motors, just one more little thing to eliminate vibration. Did I say they are SILENT?
