Airflow

Placement of Fans and Airflow

Fans are usually placed at the front and rear of the case. In the last decade designs have had "blowholes" or, "top mounted" fans. These can be used to blast air out, or in less conventional cases, blast air in. The placement is usually to do with the individual system construction, or that of the case. If you have a lot of air in an area and believe you require more cooling, particularly in summer, you must decide if the air should be drawn out, or pushed in. Then you must work out where the additional airflow from the rest of the system will go. If you over or under supply air to the inside of the case and have no passive airflow (see Passive Airflow) to exhaust or intake additional air, you will create a vacuum, which can, and usually does, result in a horrible whistling noise. The result of a vacuum in a system CAN cause strain on intake and/or exhaust fans.

You must think of where the air can go or come from. For more information, refer to passive airflow.

Active Airflow

Active Airflow is airflow that is moved via fans or other devices. It is deliberately and/or unnaturally propelled. Active airflow in computers is usually from fans of various sizes. The fans force the air in a single direction, often disallowing the majority of air to attempt movement against the directional push. Active airflow is present in most systems and is advisable for all air cooled systems.

(Most) Passively cooled CPU's are cooled by Active Airflow of the case or rack unit. A fan is placed at the front or the back, blowing air over the CPU.

Passive Airflow

Passive Airflow refers to airflow that is not actively moved. Passive materials often used are meshes and breathable fabrics. These passive materials allow air to be inhaled or exhaled via the vacuum created by active and/or natural airflow. The advantage of having passive airflow aswell as active airflow is that if additional air is required, it can be obtained simply, easily and efficiently without causing strain on the intake fans. This prevents the stresses on fans and prolongs their lives. The disadvantage of course is dust. The filtration system can be applied to mesh, depending on size. The alternative is cleaning of components, heatsinks and fans on a regular basis. Also vacuum and/or sweep the areas around a passively cooled system.