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Discussion Starter · #1 ·
Heatsink fan guide

You just bought your Mugen, your Venomous X, or your Cogage Arrow. The metal is shiny, the heatpipes are well-curved. But there’s a problem: you need a fan. Im hoping this guide can help you pick a good fan for your heatsink ( or radiator )

I will first explain some things about fans and then explain how this should affect your fan choice. I would appreciate feedback, additions and corrections from you guys. I will edit and improve this guide as we go along.

A fan is a fan
Well, that’s not true. Fans differ by size, RPM, blade design and bearing. This affects the fans ability to push air and the noise it makes.

There is a big difference between choosing a case fan and a fan for your heatsink. A case fan doesn’t have any restriction, there is nothing blocking the air. Pushing air trough a dense radiator or a heatsink is a lot harder than pushing air trough a little mesh.
The amount of air that a fan can push is measured in CFM, cubic feet per minute. The number that tells you how hard the fan is pushing is static pressure.

Both CFM and static pressure depend on the RPM of the fan, but also on its blade design. That is why two fans with equal RPM can perform differently. Static pressure heavily depends on another factor: fan thickness. Fans are usually 25 mm thick, but some fans are 38 millimeters thick. These fans have great static pressure, but they can be loud.

There are a couple of sources of noise when a fan is working. First, there is the air going trough the heatsink. Second, there is the flow of the air around the blades. Blade design really affects this. The third important source of noise is the motor itself. Higher RPM means more noise offcourse, but the quality if the motor and the quality of the bearing really matters.
There are three types of bearings: sleeve, ball ( double ball ), and Fluid Dynamic Bearing ( aka fancy bearing ).
Sleeve bearings are the cheapest. They use a lubricant ( oil ) between the blades and the frame. I don’t think I need to explain ball bearings. Fancy bearings ( found on the Noctuas and the Scythe S-flex for instance ) use an advanced form of a sleeve bearing.
Sleeve bearings are good when new, but they wear out soon, especially when hanging horizontally. Ball bearings start out a bit louder, but they don’t wear out as soon. They are usually found on high performance fans ( 3k rpm 38 mm, or Delta’s ).
Fancy bearings are alien technology only affordable to some companies. They are really quiet, can work underwater ( youtube: nanoxia water ) and they last really long.

Types of fans
There are so many fans out there, I decided to categorize them to be able to cope with it all. I will start with the 120’s

Alien uber fans
These fans use FDB. They are generally very quiet, have decent static pressure and medium CFM. The Noctua U-12P, the S-Flex, some Enermax models.
Good for: They are quiet. They have decent static pressure so they can be used on all heatsinks. Dense heatsinks may require high-RPM versions for high end performance, or using two fans in a push-pull configuration. Radiators may require two fans in push-pull.
Don’t buy them because: They are expensive. If you really don’t mind noise don’t go with these.

Helicopter fans
The big bad boys. Kings of pressure. All are 38 millimeter and Medium to high RPM.
Im talking San Ace here, Delta offcourse ( these are loud ). Ultra Kaze is another one, but they have sleeve bearings and get mixed reviews. Panaflo has some good 38 millimeter fans, so does Papst.
Good for: High density sinks like the Megatron or the Venomous-x. Six Panaflo’s on a Black Ice is just absolute cooling madness. You could cool a Bugatti Veyron with that.
Don’t buy them because: they are LOUD and they eat fingers. You can undervolt them but only to a certain extent. Some of them don’t undervolt well. Only get this if you are sure you don’t mind the noise.

Ordinary Joe fan
These fans don’t have alien technology or uber powers. They are 120*25 mm and they generally use sleeve bearings. Excellent case fans. Im talking: scythe slipstream, gentle typhoon, most enermax fans, yate loons ( they are ball bearings and good build quality ), nexus, cooler master, the list is endless.
Some of them can be really good but make sure you check it before buying. The main advantage of these fans is that they are cheap.
Good for: Medium-low density heatsinks. For instance the Mugen 2, some Xiggy’s, coolers like the Cogage Arrow. These fans wont perform as good as the 38’s and they wont be as silent as the Noctuas but they will be a lot cheaper. On a Venomous-x the difference will be big ( let alone a Black Ice radiator ). On most heatsinks the difference will be small.

Bigger fan means more flow at the same RPM. If you can fit a 140, fit a 140. There aren’t a lot of high quality 140’s, or high quality 140*38 though. So if the fin density is very large, stick with a 120.

Choosing RPM.
Many fan models come in different types, each one with a different RPM. In this case my advice is to go with a model that can undervolt to about 800-1000 RPM. Around this RPM, most 120’s become really silent ( unless the motor makes noise ). Fans can undervolt but they cannot overvolt. So if you want 900 RPM when you are on your desktop; don’t go with the 900 RPM model of your favourite fan. Get the 1200 RPM and undervolt it. Or even the 1600 RPM. Its like hair: you can cut it off if its too long but you cannot grow it when you need it. Like when you want to make a rope.

You need to choose your fan based on your needs; do you have a TRUE or a Mugen. It makes a difference. Do you mind noise or not? Do you want a pretty fan or not?
I hope you now know what to look for in a fan ( if you didn’t already ).
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