Newbie question about fans

[overdog]

Ok this is a very basic question, but I had a hard time finding the answers I was looking for anywhere on the forums.

Could someone explain (or provide a link) the basics of fans?

Are CPU fans the same as case fans?

What is CFM? (My understanding is that the higher the better)

How does RPM affect cooling?

I see a lot of fans that are 60mm x 10mm. Is 60mm the width and 10 mm the thickness? What about 60mm x 25 mm? How would that fan differ?

 

[kly1222]

Fans are fans...they spin to push air. Size, CFM, RPM, dBa, etc...are what make each fan different.

A CPU fan is usually 60mm x 60mm square, and height may differ from 10 to 25mm.

A case fan is usually 80mm, 92mm, or 120mm square, and around 25mm thick. The larger the fan, the more likely it can push more air through.

CFM = cubic feet per minute....so it tells you how many cubic feet per minute it pushes through. In other words, the higher the cfm, the more airflow, the better.

RPM = rotations per min...this tells you how fast the fan is spinning. It doesn't tell you much, but the basic rule is that the faster it spins, the more likely it will have a higher CFM. Some motherboards allow you to monitor the RPM of your fans.


dBa = decibles...or in other words, it's how loud the fan is. The higher the RPMs, the more louder the fan will be. Also depends on the quality and construction of the fan.

 

[morriswindgate]

CFM or cubic feet per minute and RPM are interdependant. For a fan to move a large amount of air there are two ways to do it. The first is to increase the pitch of the fan blades (Angle of attack. This will move a lot of air but will be noisy and prone to vibration. The second way is to increase the number of blades, with less angle of attack, and increase speed but this can also be noisy. The thrid way is to reduce the angle of attack on the blades, shorten the blade lenght and increase the speed. This is what the best fans do.