A Guide to Case Fans

Case fans. They're the computing equivalent of napkins. Sure, a case fan is almost always necessary, but it is rarely considered exciting. It is just there, ready to fulfill its duty quietly. Most have little or no branding. Jump around computer review websites, and you'll see exactly what I mean - finding an extensive review about any particular case fan is very nearly impossible, and should you manage to find one, good luck on a second opinion.

But there are some important facts that you should know about case fans. Some fans are quieter than others, some fans push more air than others, and there are certain features you should consider before making a purchase.

The most common fan sizes are 80mm, 92mm, and 120mm. It is difficult to tell what the difference is between these fans simply by relying on consumer reviews and marketing blurbs, making it easy to come to the conclusion that the size of mount included simply has to do with the space available in the case.

But the size of fan you buy is important, and has a major effect on your computer. As you might expect, bigger fans are capable of pushing more air. The amount of air that a fan circulates is measured in cubic feet per minute (CFM), and larger fans nearly always move more air that smaller fans when rotating at the same RPM. The noise a fan generates - typically measured in decibels, or dB for short, it also reliant on fan size. Here, however, the opposite of intuition is is true. Small fans are not quieter. Because larger fans push more CFM than small fans, they don't have to spin as quickly to create useful airflow. This results in less noise.

As a result, there are two ways of looking at fan size when deciding which ones to buy. You can look at fans from a cooling perspective, in which case you'll simply want to buy the largest fans possible and run them at the fastest possible speed. But you can also look at them from the noise perspective, in which case you'll want to buy the largest fans possible and run them at a very low speed. Either way, large fans win. That said, you shouldn't write off a PC case simply because it won't let you mount 120mm fans. When operated at low speeds, the majority of 80mm and 92mm fans are nearly silent. It is only when running at full tilt that the noise from these smaller fans can become a problem.

The kind of bearing used by a case fan can have an impact on its characteristics, such as maximum speed and vibration noise. The kind of bearing used by a fan can also give you an indication of the fan's life expectancy. There are currently four common types of bearings available.

Ball Bearing: Ball bearing fans consist of metal balls which rotate against an axle. Lubricants aren't needed, making fans using a ball bearing very reliable over long periods of time. The fan's operation is not effected by heat, and most fans of this type remain relatively quiet in all conditions.

Sleeve Bearing: Sleeve bearings used lubricated surfaces that rotate around each other. As such, they're limited to the life-span of the lubricant, and as the lubricant drys up and decomposes, the fan will become noisier. Their only advantage is a low cost of production. Sleeve bearings are the most common bearing found in case fans.

Fluid Bearing: A fluid bearing uses a thin layer of liquid between the surfaces inside the bearing. Fans with this kind of bearing can be expected to have a long lifespan, because fluid bearings eliminate contact between rotating surface. This also means that fluid bearings are quiet. This kind of bearing isn't common,and is generally found in higher-end products.

Magnetic Bearing: This bearing works by using magnets to keep two surfaces out of contact which each other, allowing rotation. They are very quiet and have a very long life-span. Magnetic bearings are rare, but not necessarily limited to high-end products.