Fan CFM and Watercooling

Push, Pull, and Push Pull CFM Realities

Steve Smith explains why there is no outstanding difference in push, pull, and push pull fan configurations on water cooling radiators.

Episode #4-46 released on August 7, 2014

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What do you think is better when trying to fan cool radiators?

This is a valid question, and normally you'd ask a person like myself in a computer store, and usually we could tell you why certain fans work better than others, why some are quieter, and much more. But the answer to that question when related to CFM is a trick question, and one I aim at clearing up for you.

First, CFM is short for cubic feet per minute. Its a number related to the amount of air that moves through the fan for every minute of operation.

Secondly, radiators are part of water cooling systems, and as such, are usually closed on the extremities, leading to only to facets where air can move. This gives us the ability to do one of three different types of cooling methods. These methods include push, pull, and push pull fan cooling. Most cars experience pull fan cooling, most computers are usually set up using push. In either case, a fan that outputs 100 CFM never outputs anything else higher whether installed in push or pull position.

Now, we would almost half expect that if we installed 2x 100 CFM fans, one in push and the other in pull, we would double the CFM. This is where it gets tricky for most people. Installing fans in computers is not as easy as adding all the CFM totals together. Your output and input subtracted from each other should be zero. What is known as a neutral build, which I have previously stated. The same holds true for radiators. The fan with the lowest CFM determines the CFM of the radiator, not the sum of the two fan's CFM.

Taking into account that there is no true difference in CFM input and output from the radiator, you can easily conclude that the difference between push, pull, and push pull fan cooling configurations through radiators comes out to the same thing.

Host : Steve Smith | Music : Jonny Lee Hart | Editor : Steve Smith | Producer : Zed Axis Productions

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