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General Information about Fans used on computers

To find CPU Cooling Fans go to this page. To find Computer Fans go to this page.

Computers have components inside the case which generate a large amount of heat. This heat has to be removed in order for the components to function properly.

Two methods are used for cooling.

One is the continuous movement of air from outside the room, through the inside of the computer and out the power supply fan.  The other is a localized cooling effect provided by smaller fans which are either attached to a device or are in close proximity of the device which needs cooling.

A third method is also available, THERMOELECTRIC COOLING (TEC) in which a special type of semiconductor has a low D.C. voltage applied causing heat to move in the direction of the current much like a heat pump. One face of the plate will be cold while the opposite face will be heated, and the effect is reversible. 

This is also known as the Peltier Effect. -

1. Cooling of the Whole Computer System

The heat is normally removed by having continuous air flow inside the case. Room temperature air is sucked in from openings in the case and it is pushed outside the case by fans.

There is always one fan inside the power supply which runs continuously to move the air and cool the components. As components are added, additional fans might be needed to move more air through the case.

Computers need to have air flow to move heat which is generated inside the case by the components.

Larger air flow can be generated by installing additional fans. Not all cases provide the space or mounting areas for adding fans.

Add-on fans have 4 screws that hold them in place on the inside of the computer case. Again, the case needs to have predrilled screw holes aligned with the fan installed.

The Fan is connected electrically to one of the power supply power connectors.  A Y-splitter can be used to tap into one of the drive power cables. Y-splitters have a single female plug on one end and two male plugs on the other end. All plugs use the standard 4 wire hard drive power configuration.

2. Local Component Cooling

Components which need individual cooling are

1) The CPU
2) Hard Disk Drives
3) several computer cards in close proximity to each other.

1) The CPU is cooled in one of two ways.

a) A Heat Sink is connected to the top of the flat surface of the CPU having a conductive gel like liquid placed between the top of the CPU and the Heat Sink. Heat is transferred from the CPU to the Heat Sink and dissipated to the inside of the case.

b) An electric fan is attached to the top of the CPU which blows air around the CPU to keep it cool.

Note: Better quality fans can have a built-in sensor, which will alert by emitting a sound when either the Fan speed drops too low or when there is an overheating of the attached CPU.

CPU Fans rotate at above 3000 rpm (revolutions per minute). They have  wires that come off the fan, and either connect to a small plug on the motherboard, or to a standard floppy or hard drive connector.

 

Technical Information about Fans

Rotational Speed - over 3000 rpm

Air Flow - measured in CFM (Cubic Feet Per Minute)

Noise Level - typically from 20dba to 40dba (decibels)

Size - 92MM x 92MM x 25MM, 80x80x25, 60x60x25, 52x52x15, 40x40x20, 40x40x10, 25x25x10, 50x50x10mm (2"x2"x.040")

Power - Source VDC (Volts Direct Current) or VAC (Volts Alternating Current) - typical 12VDC

Current Draw - typical .15 amps

Alarm availability - Some Fans can have an audible warning function to alert you in case of overheating or of lowering rotation of the Fan.

Heatsink Attachment - Screw Clamping, Lever Lock-On, pressure-fit with heat gel

Motor Type -  Typically DC Brushless,

Shaft support Type - Ball Bearing, Sleeve)

Mounting forms - 

Frame Mounting
Thermal Tape Mounting
Sprint Wire Mounting
Socket Clip Mounting

Connection Types -

1) a 4 pin plug identical to the hard drive power plug

2) a 3 pin small plug which connects to a plug on the motherboard

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