Push, Pull or Push/Pull?

It occurred to me that I ought to write a tutorial on this topic after seeing an Craigslist add for a Corsair H60 with "536CFM". The radiator merely had eight fans modded onto it-that is two on each of the four spots where fans can be mounted. The radiator was, of course, in push pull configuration. This add made me burst out in laughter, because the concept behind the "536CFM" radiator was entirely flawed. Considering this is a relatively small topic, there seems to be a LOT of confusion about how fans and cooling work. The popular, and incorrect belief is that running a radiator or CPU cooler with more fans equates directly to better cooling performance. Unfortunately, this is not so. Want to know why? Keep reading to find out.

The first, and largest single misconception with adding more fans is that strapping fans together increases the cubic feet of air they can move in a minute. However, bolting two fans together and attaching them to your radiator or CPU cooler will air no faster than one of said fans will (presuming you use the same fan). This is because CFM (cubic feet per minute) cannot be increased by the addition of another fan which has the same CFM. They cannot be added! In other words, a radiator in push/pull will have the same thermal effectiveness as a radiator in push, or pull. The only benefit you may see is an increase in static pressure, the addition of a second fan increases a fans ability to push air through some sort of restricting object (e.g. a radiator). However, this benefit is, at least in my opinion, canceled out by the added noise of the extra fan. Not to mention, the entire problem of raising the static pressure can be solved by purchasing a fan with a higher static pressure.

Just to show you a video of some ridiculous setup that is a total load of crap, here is a link for your viewing pleasure:Stupid Cooling Idea
Knowing what you now know, your computer sixth sense should be telling you "What? What sort of nonsense is this?!" The answer: it is nonsense. I would assume that you noticed 1. The ridiculous amount of noise the rig in the video made. It's crazy! I can't imagine anyone who would want to listen to that. Second, some more observant people may have noticed that the CPU used in the video was running below ambient. This is not possible without some sort of water chiller. A fan cannot lower coolant temps below ambient, not to mention that below ambient temperatures would cause component killing condensation buildup. So how did the makers of the video get such low temperatures? The answer, which is said at the end of the video, is that the temps were faked.

The second fan misconception is that, if you can't run your radiator or CPU cooler in push/pull, push is the next best thing. Brace yourselves, because guess what- this isn't true either! A modern fan with tight blade spacing and acceptable static pressure will move the same amount of air when pulling through a radiator then when pushing through one. This is incredibly logical when you consider than the radiator will always have the same resistance, and that fans encounter the same resistance when pushing or pulling. Technically speaking, when a fan is pulling, more of the radiator will actually have air moving across it. The fan needs air, and it will pull it in through the smallest crevasses. A fan pushing will just cram air through a smaller area, with no air flowing under the frame of the fan or through the area where the fans motor is.

To sum it up, of performance, it matters not if you run push or pull, and push pull will only lead to a useless increase in motor noise.
Several tests have been conducted to support this consensus and if you would like to learn more you can look at this Linus Tech Tips video-LERN ABOUT COOLING!