Why Fan Direction Matters For Your CPU Fan
When a computer is cooling down, the CPU fan direction of airflow usually changes. This results in the CPU fan being cooled in one direction, while the fans are blowing air in the other direction. When you take a look at the sticker that comes with the CPU, you should see a direction of operation sticker. The stickers on the front of the PC generally let you know what direction of airflow is used in the CPU fan.
Most modern CPU coolers have a built in fan direction switch. On some models, you will need to remove the rear plate before you can access the switch. Then you can simply flip the switch to the correct side. Some fans have two switches; a side switch that can be flipped to the "balanced" position (for the CPU to run at a stable speed) and a center switch that provide an alternate speed for the fan. Some models have three separate speed settings: low, medium and high.
Typically, a CPU fan has two or more copper wire coils wound onto a spring-tied assembly. When air is drawn across the fan blades, the coils expand and contract along with the air stream. The expansion and contraction of the coils produce turbulence which, as we have just described, brings a sudden flow of air into the case. If the fan blades are configured so that the rotation motion of the fan is the same, then there is no turbulence. If the rotation motion of the fan blades is different, the result is a slight breeze and a cooler atmosphere in the case.
CPU intake fans generally have a two-chambered design. The intake vent, which is near the front of the intake fan blade, pulls the heated air into the case. The two additional chambers near the rear of the fan blade push the cooled air out of the case. One intake vents can close completely while another intake vent may open slightly, allowing a small amount of warm air to enter the case.
CPU fan blades are usually labeled by their side plate. The side plates typically have a rectangular shape and a flat, smooth surface. The front side of the plate has a hexagon shaped slot for a cable to pass through. The back side of the plate has a slot for a standard 6-prong plug.
The number on the front of the plate indicates the number of blades on the fan. Blades are usually designated by a "D" through "Z" to indicate the diameter of the fan blade and the internal rotation speed. Each blade is typically made of a tough, lightweight aluminum plate. These fan blades can be mounted using either screws or nuts. Some fan blades are equipped with locking mechanisms to prevent rotation. This type of mechanism allows the user to lock the plate so that the fan blades cannot rotate, thus protecting the computer.
As with most fans, the air flow rate and the air ventilation capacity directly affect the performance and life of the fan. Typically, the higher the RPM (rate of rotation of the fan motor) and the CFM (cubic feet of air flow per minute) of the fan, the more efficient the airflow. For a properly sized fan, there should be no more air leaking from the intake port than there is coming in. Air leaking from the intake vents results in a hot spot, which can overheat an area. The fan blades help to draw the hot air out of a hot area and directs it into the air intake. Some intake vents are located at the top of the intake; others are located in the front of the intake vent.
The best place to install a CPU case fan is on the bottom of the case. This will provide the most air flow. Also, make sure that the holes for the case fan blade are pre-drilled and that the holes are drilled directly into the case itself. This will allow a good flow of air into the case fan blade and also help keep the blades from becoming clogged up.