Anatomy of a PC fan: How does it really work?

Computer fans don't look like they've evolved much do they? Aside from the now-ubiquitous RGB, they basically look the same as they did 20 years ago. This, however, is not the case, as every physical aspect of a computer fan has an influence on the performance to the end user. So, we thought we'd go over the key design elements of a PC fan to understand what's really going on here.

Here we have the most immediately apparent part of a fan. The are the actual parts that scoop the air and push it through the parts of your PC. No blades = no airflow.

The goal here is twofold: Ideally we want maximum airflow, with minimum noise and turbulence. A fan that creates as much airflow as a jet engine could cool anything, but if it actually sounds like one, the performance gains would be useless, as people tend to sit close to their computers.

There's more to consider here than initially meets the eye. The shape, the angle, and the actual design of the airfoil all contribute to the aforementioned goals. It's not hard to make a fan push a lot of air, it's hard to make a fan push a lot of air while lasting for a meaningful amount of time, and retaining a respectable noise level.

Making the fan blades bigger could help, but PC cases are designed with tight tolerances to work with specific sizes of fans, so let's talk about that.

The radius of the fan blades directly impacts the amount of air moved. Larger blades (everything else being equal) move more air, so the overall fan construction matters as well.

The outside dimensions of a 120mm PC fan will always be 120mm, so the engineering performance race also depends on constructing the housing so that as much space as possible remains available for the blades. This creates a difficult engineering challenge to make the edges of the fan housing as thin as possible, without going too far and making them weak. This means that the choice of material matters a lot, just as it does for the other parts of a fan.

The material of the fan blades is important here. Thinner blades are lighter, meaning they can spin faster, but if you go too thin, problems can occur.

In scenarios requiring high static pressure, the choice of material becomes even more crucial. Strong, rigid materials ensure that blades do not flex under pressure, maintaining consistent performance. If the blade does flex or deform, this can lead to two issues. One is a lower effectiveness at scooping and pushing air as the aerodynamics of the fan change, and the other is that if the blades are known to flex, the tolerances must be increased to account for that to avoid the potential of a collision with the housing. Larger tolerances reduce blade size, and we’re back to lower effectiveness again. You're probably beginning to understand what a careful balancing act this can be.

Of course, blowing air really hard is only the beginning. The state of the air as it goes through and exits the fan must be correct. We mentioned turbulence earlier, and this is the crux of the next section.

First of all, you can hear turbulence. Turbulence of exhausted air contributes to fan noise, so if you’re comparing how well two fans perform at 40dB for example, the one with more turbulent exhaust will need to spin slower to meet the noise normalized levels.

The way a fan pushes air can also affect its interaction with radiator fins. A fan that creates less turbulence and has a well-designed exhaust cone can more effectively cover radiator fins, improving cooling efficiency and reducing noise.

The fan’s rotation creates a funnel of turbulence by design. This is why you’ll find AirGuide stator vanes on the back of some Corsair fans. These act to direct airflow in the direction opposite to fan spin. This reduces the wider cone to be something closer to a cylinder in shape. basically more accurately directing the exhausted air where you want it to go.

So let's say you manage to absolutely nail all that. The airflow is unreal, the turbulence is svelte, the noise levels are delightfully low. Perhaps now you should reconsider the bearing of the fan. The bearing sits at the very heart of the fan and cannot be overlooked.

The quality of a fan bearing is an often overlooked aspect of the design, but it's crucial. High-quality bearings reduce wobble and noise, contributing to better overall performance.

Just like the effect of turbulence noise above, a low-noise bearing allows the fan to spin at higher speeds and make the same level of noise as a fan whose bearing contributes to the noise more. If we use noise as a measure of discomfort you’re exposed to when using the PC, a quieter fan will deliver more performance at the same noise level than a noisy one.

Selecting the ideal fan for your PC is a blend of art and science. It requires an understanding of airflow dynamics, mechanical design, and material science.

But does this matter? Are you going to notice large changes in your CPU temperatures when using different fans? It depends. When comparing the top performance of flagship fans by leading brands, those differences will be fairly small. Perhaps not mathematically small, but differences of 5% to 10% lead to your cooling curve driving one fan 10% faster than another. And let’s be honest, you can’t really hear the difference between 900 and 1,000 RPM in your home.

When comparing these performance fans against lower performers on the market (either because engineering was forced to hit a low price point or when everything about the fan construction was prioritized for RGB and design), then yes, the differences can be significant. It’s not uncommon to see measured cooling performance deviate by 30% or more. And that’s where fans start getting really loud just to keep up with your regular PC use.

The best fan for you is not just about numbers; It needs to balance how much cooling your components need with how much noise you’re willing to tolerate. It might need to look good with RGB in your case, it might need to connect to some RGB hub you have in the old PC you’re rebuilding, and it might need to cost under a certain price. All of these other factors are up to you, but now, you can judge performance with a more informed eye.

Of course, even if this brief lesson hasn't awakened your inner engineer, you could just go with CORSAIR fans. You can believe that our people have obsessed over everything we've mentioned here and more in pursuit of top-tier fan design. Just take a look at our iCUE LINK RX and QX fans if you want to see how far our engineers are willing to go.